refactor unit of work

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

.all-contributorsrc

@@ -1730,6 +1730,61 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "Kevinyl3",
+      "name": "Kevin",
+      "avatar_url": "https://avatars.githubusercontent.com/u/47126749?v=4",
+      "profile": "http://no website",
+      "contributions": [
+        "review"
+      ]
+    },
+    {
+      "login": "Shrirang97",
+      "name": "Shrirang",
+      "avatar_url": "https://avatars.githubusercontent.com/u/28738668?v=4",
+      "profile": "https://github.com/Shrirang97",
+      "contributions": [
+        "review",
+        "code"
+      ]
+    },
+    {
+      "login": "interactwithankush",
+      "name": "interactwithankush",
+      "avatar_url": "https://avatars.githubusercontent.com/u/18613127?v=4",
+      "profile": "https://github.com/interactwithankush",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "yuhangbin",
+      "name": "CharlieYu",
+      "avatar_url": "https://avatars.githubusercontent.com/u/17566866?v=4",
+      "profile": "https://github.com/yuhangbin",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "Leisterbecker",
+      "name": "Leisterbecker",
+      "avatar_url": "https://avatars.githubusercontent.com/u/20650323?v=4",
+      "profile": "https://github.com/Leisterbecker",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "castleKing1997",
+      "name": "DragonDreamer",
+      "avatar_url": "https://avatars.githubusercontent.com/u/35420129?v=4",
+      "profile": "http://rosaecrucis.cn",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -10,7 +10,7 @@
 [![Coverage](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=coverage)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
 [![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-190-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-196-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 <br/>
@@ -320,6 +320,12 @@ This project is licensed under the terms of the MIT license.
   </tr>
   <tr>
     <td align="center"><a href="https://www.linkedin.com/in/abhinav-vashisth-06613b208/"><img src="https://avatars.githubusercontent.com/u/89785800?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Abhinav Vashisth</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vashisthabhinav" title="Documentation">📖</a></td>
+    <td align="center"><a href="http://no website"><img src="https://avatars.githubusercontent.com/u/47126749?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kevin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AKevinyl3" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://github.com/Shrirang97"><img src="https://avatars.githubusercontent.com/u/28738668?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Shrirang</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AShrirang97" title="Reviewed Pull Requests">👀</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=Shrirang97" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/interactwithankush"><img src="https://avatars.githubusercontent.com/u/18613127?v=4?s=100" width="100px;" alt=""/><br /><sub><b>interactwithankush</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=interactwithankush" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/yuhangbin"><img src="https://avatars.githubusercontent.com/u/17566866?v=4?s=100" width="100px;" alt=""/><br /><sub><b>CharlieYu</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yuhangbin" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Leisterbecker"><img src="https://avatars.githubusercontent.com/u/20650323?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Leisterbecker</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Leisterbecker" title="Code">💻</a></td>
+    <td align="center"><a href="http://rosaecrucis.cn"><img src="https://avatars.githubusercontent.com/u/35420129?v=4?s=100" width="100px;" alt=""/><br /><sub><b>DragonDreamer</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=castleKing1997" title="Code">💻</a></td>
   </tr>
 </table>
 

adapter/README.md

@@ -18,10 +18,10 @@ couldn't otherwise because of incompatible interfaces.
 
 ## Explanation
 
-Real world example
+Real-world example
 
-> Consider that you have some pictures in your memory card and you need to transfer them to your computer. In order to transfer them you need some kind of adapter that is compatible with your computer ports so that you can attach memory card to your computer. In this case card reader is an adapter.
-> Another example would be the famous power adapter; a three legged plug can't be connected to a two pronged outlet, it needs to use a power adapter that makes it compatible with the two pronged outlet.
+> Consider that you have some pictures on your memory card and you need to transfer them to your computer. To transfer them, you need some kind of adapter that is compatible with your computer ports so that you can attach a memory card to your computer. In this case card reader is an adapter.
+> Another example would be the famous power adapter; a three-legged plug can't be connected to a two-pronged outlet, it needs to use a power adapter that makes it compatible with the two-pronged outlets.
 > Yet another example would be a translator translating words spoken by one person to another
 
 In plain words
@@ -36,7 +36,7 @@ Wikipedia says
 
 Consider a captain that can only use rowing boats and cannot sail at all.
 
-First we have interfaces `RowingBoat` and `FishingBoat`
+First, we have interfaces `RowingBoat` and `FishingBoat`
 
 ```java
 public interface RowingBoat {
@@ -68,7 +68,7 @@ public class Captain {
 }
 ```
 
-Now let's say the pirates are coming and our captain needs to escape but there is only fishing boat available. We need to create an adapter that allows the captain to operate the fishing boat with his rowing boat skills.
+Now let's say the pirates are coming and our captain needs to escape but there is only a fishing boat available. We need to create an adapter that allows the captain to operate the fishing boat with his rowing boat skills.
 
 ```java
 @Slf4j
@@ -100,10 +100,10 @@ captain.row();
 ## Applicability
 Use the Adapter pattern when
 
-* you want to use an existing class, and its interface does not match the one you need
-* you want to create a reusable class that cooperates with unrelated or unforeseen classes, that is, classes that don't necessarily have compatible interfaces
-* you need to use several existing subclasses, but it's impractical to adapt their interface by subclassing every one. An object adapter can adapt the interface of its parent class.
-* most of the applications using third party libraries use adapters as a middle layer between the application and the 3rd party library to decouple the application from the library. If another library has to be used only an adapter for the new library is required without having to change the application code.
+* You want to use an existing class, and its interface does not match the one you need
+* You want to create a reusable class that cooperates with unrelated or unforeseen classes, that is, classes that don't necessarily have compatible interfaces
+* You need to use several existing subclasses, but it's impractical to adapt their interface by subclassing everyone. An object adapter can adapt the interface of its parent class.
+* Most of the applications using third-party libraries use adapters as a middle layer between the application and the 3rd party library to decouple the application from the library. If another library has to be used only an adapter for the new library is required without having to change the application code.
 
 ## Tutorials
 
@@ -114,17 +114,17 @@ Use the Adapter pattern when
 ## Consequences
 Class and object adapters have different trade-offs. A class adapter
 
-*	adapts Adaptee to Target by committing to a concrete Adaptee class. As a consequence, a class adapter won’t work when we want to adapt a class and all its subclasses.
-*	let’s Adapter override some of Adaptee’s behavior, since Adapter is a subclass of Adaptee.
-*	introduces only one object, and no additional pointer indirection is needed to get to the adaptee.
+*	Adapts Adaptee to Target by committing to a concrete Adaptee class. As a consequence, a class adapter won’t work when we want to adapt a class and all its subclasses.
+*	Let’s Adapter override some of Adaptee’s behavior since Adapter is a subclass of Adaptee.
+*	Introduces only one object, and no additional pointer indirection is needed to get to the adaptee.
 
 An object adapter	
 
-*	let’s a single Adapter work with many Adaptees—that is, the Adaptee itself and all of its subclasses (if any). The Adapter can also add functionality to all Adaptees at once.
-*	makes it harder to override Adaptee behavior. It will require subclassing Adaptee and making Adapter refer to the subclass rather than the Adaptee itself.
+*	Lets a single Adapter work with many Adaptees—that is, the Adaptee itself and all of its subclasses (if any). The Adapter can also add functionality to all Adaptees at once.
+*	Makes it harder to override Adaptee behavior. It will require subclassing Adaptee and making the Adapter refer to the subclass rather than the Adaptee itself.
 
 
-## Known uses
+## Real-world examples
 
 * [java.util.Arrays#asList()](http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#asList%28T...%29)
 * [java.util.Collections#list()](https://docs.oracle.com/javase/8/docs/api/java/util/Collections.html#list-java.util.Enumeration-)

adapter/src/test/java/com/iluwatar/adapter/AdapterPatternTest.java

@@ -33,7 +33,7 @@ import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 
 /**
- * Test class
+ * Tests for the adapter pattern.
  */
 class AdapterPatternTest {
 

adapter/src/test/java/com/iluwatar/adapter/AppTest.java

@@ -33,9 +33,7 @@ import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 class AppTest {
 
   /**
-   * Issue: Add at least one assertion to this test case.
-   *
-   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * Check whether the execution of the main method in {@link App}
    * throws an exception.
    */
 

cloud-claim-check-pattern/.gitignore

@@ -0,0 +1,38 @@
+# Build output
+target/
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# IDE
+.idea/
+*.iml
+.settings/
+.project
+.classpath
+
+# macOS
+.DS_Store
+
+# Azure Functions
+local.settings.json
+bin/
+obj/

cloud-claim-check-pattern/README.md

@@ -0,0 +1,83 @@
+---
+layout: pattern
+title: Claim Check Pattern
+folder: cloud-claim-check-pattern
+permalink: /patterns/cloud-claim-check-pattern/
+categories: Cloud
+language: en
+tags:
+  - Cloud distributed
+  - Microservices
+---
+
+## Name
+
+[Claim Check Pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/claim-check)
+
+## Also known as
+
+[Reference-Based Messaging](https://www.enterpriseintegrationpatterns.com/patterns/messaging/StoreInLibrary.html)
+
+## Intent
+
+- Reduce the load of data transfer through the Internet. Instead of sending actual data directly, just send the message reference.
+- Improve data security. As only message reference is shared, no data is exposed to the Internet.
+
+## Explanation
+
+Real-World Example
+
+> Suppose if you want to build a photo processing system. A photo processing system takes an image as input, processes it, and outputs a different set of images. Consider system has one persistent storage, one input component, ten processing components, messaging platform. Once a photo is given to the input component, it stores that image on persistent storage. It then creates ten different messages/events with the same image location and publishes them to the messaging platform. The messaging platform triggers ten different processing components. The ten processing components extract information about image location from the received event and then read an image from persistent storage. They generate ten different images from the original image and drop these images again to persistent storage.
+
+In Plain words
+
+> Split a large message into a claim check and a payload. Send the claim check to the messaging platform and store the payload to an external service. This pattern allows large messages to be processed while protecting the message bus and the client from being overwhelmed or slowed down. This pattern also helps to reduce costs, as storage is usually cheaper than resource units used by the messaging platform.([ref](https://docs.microsoft.com/en-us/azure/architecture/patterns/claim-check))
+
+## Architecture Diagram
+
+![alt text](./etc/Claim-Check-Pattern.png "Claim Check Pattern")
+
+## Applicability
+
+Use the Claim Check Pattern when
+
+- Huge processing data causes a lot of bandwidth consumption to transfer data through the Internet.
+- To secure your data transfer by storing in common persistent storage.
+- Using a cloud platform - Azure Functions or AWS Lambda, Azure EventGrid or AWS Event Bridge, Azure Blob Storage or AWS S3 Bucket.
+- Each service must be independent and idempotent. Output data is dropped to persistent storage by the service.
+- Publish-subscribe messaging pattern needs to be used.
+
+## Consequences
+
+- This pattern is stateless. Any compute API will not store any data.
+- You must have persistent storage and a reliable messaging platform.
+
+## Tutorials
+
+### Workflow
+
+Suppose a telecom company wants to build call cost calculator system which generate the call cost daily. At the end of each day, details of the calls made by the consumers are stored somewhere. The call calculator system will read this data and generate call cost data for each user. Consumers will be billed using this generated data in case of postpaid service.
+
+Producer class( `UsageDetailPublisherFunction` Azure Function) will generate call usage details (here we are generating call data in producer class itself. In real world scenario, it will read from storage). `UsageDetailPublisherFunction` creates a message. Message consists of message header and message body. Message header is basically an event grid event or claim or message reference. Message body contains actual data. `UsageDetailPublisherFunction` sends a message header to Event Grid topic `usage-detail` and drops an entire message to the blob storage. Event Grid then sent this message header to the `UsageCostProcessorFunction` Azure function. It will read the entire message from blob storage with the help of the header, will calculate call cost and drop the result to the blob storage.
+
+### Class Diagrams
+
+![alt text](./etc/class-diagram.png "Claim-Check-Class-Diagram")
+
+### Setup
+
+- Any operating system can be used macOS, Windows, Linux as everything is deployed on Azure.
+- Install Java JDK 11 and set up Java environmental variables.
+- Install Git.
+- Install Visual Studio Code.
+- Install [ Azure Functions extension](https://marketplace.visualstudio.com/items?itemName=ms-azuretools.vscode-azurefunctions) to be able to deploy using Visual studio.
+
+### Storage Data
+
+The data is stored in the Azure blob storage in the container `callusageapp`. For every trigger, one GUID is created. Under the `GUID folder`, 2 files will be created `input.json` and `output.json`.
+`Input.json` is dropped `producer` azure function which contains call usage details.` Output.json` contains call cost details which are dropped by the `consumer` azure function.
+
+## Credits
+
+- [Messaging Pattern - Claim Check](https://www.enterpriseintegrationpatterns.com/patterns/messaging/StoreInLibrary.html)
+- [Azure Architecture Pattern - Claim Check Pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/claim-check)

cloud-claim-check-pattern/call-usage-app/.gitignore

@@ -0,0 +1,38 @@
+# Build output
+target/
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# IDE
+.idea/
+*.iml
+.settings/
+.project
+.classpath
+
+# macOS
+.DS_Store
+
+# Azure Functions
+local.settings.json
+bin/
+obj/

cloud-claim-check-pattern/call-usage-app/etc/call-usage-app.urm.puml

@@ -0,0 +1,117 @@
+@startuml
+package com.iluwatar.claimcheckpattern.producer.calldetails.functions {
+  class UsageDetailPublisherFunction {
+    - eventHandlerUtility : EventHandlerUtility<MessageHeader>
+    - messageHandlerUtility : MessageHandlerUtility<UsageDetail>
+    + UsageDetailPublisherFunction()
+    + UsageDetailPublisherFunction(messageHandlerUtility : MessageHandlerUtility<UsageDetail>, eventHandlerUtility : EventHandlerUtility<MessageHeader>)
+    + run(request : HttpRequestMessage<Optional<String>>, context : ExecutionContext) : HttpResponseMessage
+  }
+}
+package com.iluwatar.claimcheckpattern.domain {
+  class Message<T> {
+    - messageBody : MessageBody<T>
+    - messageHeader : MessageHeader
+    + Message<T>()
+    + getMessageBody() : MessageBody<T>
+    + getMessageHeader() : MessageHeader
+    + setMessageBody(messageBody : MessageBody<T>)
+    + setMessageHeader(messageHeader : MessageHeader)
+  }
+  class MessageBody<T> {
+    - data : List<T>
+    + MessageBody<T>()
+    + getData() : List<T>
+    + setData(data : List<T>)
+  }
+  class MessageHeader {
+    - data : Object
+    - dataVersion : String
+    - eventTime : String
+    - eventType : String
+    - id : String
+    - subject : String
+    - topic : String
+    + MessageHeader()
+    + getData() : Object
+    + getDataVersion() : String
+    + getEventTime() : String
+    + getEventType() : String
+    + getId() : String
+    + getSubject() : String
+    + getTopic() : String
+    + setData(data : Object)
+    + setDataVersion(dataVersion : String)
+    + setEventTime(eventTime : String)
+    + setEventType(eventType : String)
+    + setId(id : String)
+    + setSubject(subject : String)
+    + setTopic(topic : String)
+  }
+  class MessageReference {
+    - dataFileName : String
+    - dataLocation : String
+    + MessageReference()
+    + MessageReference(dataLocation : String, dataFileName : String)
+    + getDataFileName() : String
+    + getDataLocation() : String
+    + setDataFileName(dataFileName : String)
+    + setDataLocation(dataLocation : String)
+  }
+  class UsageCostDetail {
+    - callCost : double
+    - dataCost : double
+    - userId : String
+    + UsageCostDetail()
+    + getCallCost() : double
+    + getDataCost() : double
+    + getUserId() : String
+    + setCallCost(callCost : double)
+    + setDataCost(dataCost : double)
+    + setUserId(userId : String)
+  }
+  class UsageDetail {
+    - data : int
+    - duration : int
+    - userId : String
+    + UsageDetail()
+    + getData() : int
+    + getDuration() : int
+    + getUserId() : String
+    + setData(data : int)
+    + setDuration(duration : int)
+    + setUserId(userId : String)
+  }
+}
+package com.iluwatar.claimcheckpattern.utility {
+  class EventHandlerUtility<T> {
+    - customEventClient : EventGridPublisherClient<BinaryData>
+    + EventHandlerUtility<T>()
+    + EventHandlerUtility<T>(customEventClient : EventGridPublisherClient<BinaryData>)
+    + publishEvent(customEvent : T, logger : Logger)
+  }
+  class MessageHandlerUtility<T> {
+    - blobServiceClient : BlobServiceClient
+    + MessageHandlerUtility<T>()
+    + MessageHandlerUtility<T>(blobServiceClient : BlobServiceClient)
+    + dropToPersistantStorage(message : Message<T>, logger : Logger)
+    + readFromPersistantStorage(messageReference : MessageReference, logger : Logger) : Message<T>
+  }
+}
+package com.iluwatar.claimcheckpattern.consumer.callcostprocessor.functions {
+  class UsageCostProcessorFunction {
+    - messageHandlerUtilityForUsageCostDetail : MessageHandlerUtility<UsageCostDetail>
+    - messageHandlerUtilityForUsageDetail : MessageHandlerUtility<UsageDetail>
+    + UsageCostProcessorFunction()
+    + UsageCostProcessorFunction(messageHandlerUtilityForUsageDetail : MessageHandlerUtility<UsageDetail>, messageHandlerUtilityForUsageCostDetail : MessageHandlerUtility<UsageCostDetail>)
+    - calculateUsageCostDetails(usageDetailsList : List<UsageDetail>) : List<UsageCostDetail>
+    + run(request : HttpRequestMessage<Optional<String>>, context : ExecutionContext) : HttpResponseMessage
+  }
+}
+UsageCostProcessorFunction -->  "-messageHandlerUtilityForUsageDetail" MessageHandlerUtility
+Message -->  "-messageBody" MessageBody
+UsageDetailPublisherFunction -->  "-eventHandlerUtility" EventHandlerUtility
+Builder ..+ HttpResponseMessage
+UsageDetailPublisherFunction -->  "-messageHandlerUtility" MessageHandlerUtility
+Message -->  "-messageHeader" MessageHeader
+@enduml

cloud-claim-check-pattern/call-usage-app/host.json

@@ -0,0 +1,7 @@
+{
+  "version": "2.0",
+  "extensionBundle": {
+    "id": "Microsoft.Azure.Functions.ExtensionBundle",
+    "version": "[1.*, 2.0.0)"
+  } 
+}

cloud-claim-check-pattern/call-usage-app/pom.xml

@@ -0,0 +1,150 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!--
+
+    The MIT License
+    Copyright © 2014-2021 Ilkka Seppälä
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+
+    <parent>
+	    <groupId>com.iluwatar</groupId>
+	    <artifactId>claim-check-pattern</artifactId>
+	    <version>1.25.0-SNAPSHOT</version>		
+	 </parent>
+    
+    <artifactId>call-usage-app</artifactId>
+    <name>call-usage-app</name>
+    <packaging>jar</packaging>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <azure.functions.maven.plugin.version>1.14.0</azure.functions.maven.plugin.version>
+        <azure.functions.java.library.version>1.4.2</azure.functions.java.library.version>
+        <functionAppName>CallUsageApp</functionAppName>
+    </properties>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>com.azure</groupId>
+                <artifactId>azure-sdk-bom</artifactId>
+                <version>1.0.4</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.microsoft.azure.functions</groupId>
+            <artifactId>azure-functions-java-library</artifactId>
+            <version>${azure.functions.java.library.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>com.azure</groupId>
+            <artifactId>azure-messaging-eventgrid</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.azure</groupId>
+            <artifactId>azure-storage-blob</artifactId>
+            <version>12.13.0</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-simple</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <!-- Test -->
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>com.microsoft.azure</groupId>
+                <artifactId>azure-functions-maven-plugin</artifactId>
+                <version>${azure.functions.maven.plugin.version}</version>
+                <configuration>
+                    <!-- function app name -->
+                    <appName>${functionAppName}</appName>
+                    <!-- function app resource group -->
+                    <resourceGroup>java-functions-group</resourceGroup>
+                    <!-- function app service plan name -->
+                    <appServicePlanName>java-functions-app-service-plan</appServicePlanName>
+                    <!-- function app region-->
+                    <!-- refers https://github.com/microsoft/azure-maven-plugins/wiki/Azure-Functions:-Configuration-Details#supported-regions for all valid values -->
+                    <region>westus</region>
+                    <!-- function pricingTier, default to be consumption if not specified -->
+                    <!-- refers https://github.com/microsoft/azure-maven-plugins/wiki/Azure-Functions:-Configuration-Details#supported-pricing-tiers for all valid values -->
+                    <!-- <pricingTier></pricingTier> -->
+                    <!-- Whether to disable application insights, default is false -->
+                    <!-- refers https://github.com/microsoft/azure-maven-plugins/wiki/Azure-Functions:-Configuration-Details for all valid configurations for application insights-->
+                    <!-- <disableAppInsights></disableAppInsights> -->
+                    <runtime>
+                        <!-- runtime os, could be windows, linux or docker-->
+                        <os>windows</os>
+                        <javaVersion>11</javaVersion>
+                    </runtime>
+                    <appSettings>
+                        <property>
+                            <name>FUNCTIONS_EXTENSION_VERSION</name>
+                            <value>~3</value>
+                        </property>
+                    </appSettings>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>package-functions</id>
+                        <goals>
+                            <goal>package</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <!--Remove obj folder generated by .NET SDK in maven clean-->
+            <plugin>
+                <artifactId>maven-clean-plugin</artifactId>
+                <version>3.1.0</version>
+                <configuration>
+                    <filesets>
+                        <fileset>
+                            <directory>obj</directory>
+                        </fileset>
+                    </filesets>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/consumer/callcostprocessor/functions/UsageCostProcessorFunction.java

@@ -0,0 +1,168 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.consumer.callcostprocessor.functions;
+
+import com.azure.core.util.BinaryData;
+import com.azure.core.util.serializer.TypeReference;
+import com.azure.messaging.eventgrid.EventGridEvent;
+import com.azure.messaging.eventgrid.systemevents.SubscriptionValidationEventData;
+import com.azure.messaging.eventgrid.systemevents.SubscriptionValidationResponse;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.MessageBody;
+import com.iluwatar.claimcheckpattern.domain.MessageHeader;
+import com.iluwatar.claimcheckpattern.domain.MessageReference;
+import com.iluwatar.claimcheckpattern.domain.UsageCostDetail;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+import com.microsoft.azure.functions.ExecutionContext;
+import com.microsoft.azure.functions.HttpMethod;
+import com.microsoft.azure.functions.HttpRequestMessage;
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import com.microsoft.azure.functions.annotation.AuthorizationLevel;
+import com.microsoft.azure.functions.annotation.FunctionName;
+import com.microsoft.azure.functions.annotation.HttpTrigger;
+import java.time.OffsetDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Azure Functions with HTTP Trigger.
+ * This is Consumer class.
+ */
+public class UsageCostProcessorFunction {
+
+  private MessageHandlerUtility<UsageDetail> messageHandlerUtilityForUsageDetail;
+  private MessageHandlerUtility<UsageCostDetail> messageHandlerUtilityForUsageCostDetail;
+
+  public UsageCostProcessorFunction() {
+    this.messageHandlerUtilityForUsageDetail = new MessageHandlerUtility<>();
+    this.messageHandlerUtilityForUsageCostDetail = new MessageHandlerUtility<>();
+  }
+
+  public UsageCostProcessorFunction(
+      MessageHandlerUtility<UsageDetail> messageHandlerUtilityForUsageDetail,
+      MessageHandlerUtility<UsageCostDetail> messageHandlerUtilityForUsageCostDetail) {
+    this.messageHandlerUtilityForUsageDetail = messageHandlerUtilityForUsageDetail;
+    this.messageHandlerUtilityForUsageCostDetail = messageHandlerUtilityForUsageCostDetail;
+  }
+
+  /**
+   * Azure function which gets triggered when event grid event send event to it.
+   * After receiving event, it read input file from blob storage, calculate call cost details.
+   * It creates new message with cost details and drop message to blob storage.
+   * @param request represents HttpRequestMessage
+   * @param context represents ExecutionContext
+   * @return HttpResponseMessage
+   */
+  @FunctionName("UsageCostProcessorFunction")
+  public HttpResponseMessage run(@HttpTrigger(name = "req", methods = { HttpMethod.GET,
+      HttpMethod.POST }, authLevel = AuthorizationLevel.ANONYMOUS)
+                                       HttpRequestMessage<Optional<String>> request,
+                                 final ExecutionContext context) {
+    try {
+      var eventGridEvents = EventGridEvent.fromString(request.getBody().get());
+      for (var eventGridEvent : eventGridEvents) {
+        // Handle system events
+        if (eventGridEvent.getEventType()
+            .equals("Microsoft.EventGrid.SubscriptionValidationEvent")) {
+          SubscriptionValidationEventData subscriptionValidationEventData = eventGridEvent.getData()
+              .toObject(SubscriptionValidationEventData.class);
+          // Handle the subscription validation event
+          var responseData = new SubscriptionValidationResponse();
+          responseData.setValidationResponse(subscriptionValidationEventData.getValidationCode());
+          return request.createResponseBuilder(HttpStatus.OK).body(responseData).build();
+
+        } else if (eventGridEvent.getEventType().equals("UsageDetail")) {
+          // Get message header and reference
+          var messageReference = eventGridEvent.getData()
+              .toObject(MessageReference.class);
+
+          // Read message from persistent storage
+          var message = this.messageHandlerUtilityForUsageDetail
+              .readFromPersistantStorage(messageReference, context.getLogger());
+
+          // Get Data and generate cost details
+          List<UsageDetail> usageDetailsList = BinaryData.fromObject(
+              message.getMessageBody().getData())
+              .toObject(new TypeReference<>() {
+              });
+          var usageCostDetailsList = calculateUsageCostDetails(usageDetailsList);
+
+          // Create message body
+          var newMessageBody = new MessageBody<UsageCostDetail>();
+          newMessageBody.setData(usageCostDetailsList);
+
+          // Create message header
+          var newMessageReference = new MessageReference("callusageapp",
+              eventGridEvent.getId() + "/output.json");
+          var newMessageHeader = new MessageHeader();
+          newMessageHeader.setId(eventGridEvent.getId());
+          newMessageHeader.setSubject("UsageCostProcessor");
+          newMessageHeader.setTopic("");
+          newMessageHeader.setEventType("UsageCostDetail");
+          newMessageHeader.setEventTime(OffsetDateTime.now().toString());
+          newMessageHeader.setData(newMessageReference);
+          newMessageHeader.setDataVersion("v1.0");
+
+          // Create entire message
+          var newMessage = new Message<UsageCostDetail>();
+          newMessage.setMessageHeader(newMessageHeader);
+          newMessage.setMessageBody(newMessageBody);
+
+          // Drop data to persistent storage
+          this.messageHandlerUtilityForUsageCostDetail.dropToPersistantStorage(newMessage,
+              context.getLogger());
+
+          context.getLogger().info("Message is dropped successfully");
+          return request.createResponseBuilder(HttpStatus.OK)
+              .body("Message is dropped successfully").build();
+        }
+      }
+    } catch (Exception e) {
+      context.getLogger().warning(e.getMessage());
+    }
+
+    return request.createResponseBuilder(HttpStatus.INTERNAL_SERVER_ERROR).body(null).build();
+  }
+
+  private List<UsageCostDetail> calculateUsageCostDetails(List<UsageDetail> usageDetailsList) {
+    if (usageDetailsList == null) {
+      return null;
+    }
+    var usageCostDetailsList = new ArrayList<UsageCostDetail>();
+
+    usageDetailsList.forEach(usageDetail -> {
+      var usageCostDetail = new UsageCostDetail();
+      usageCostDetail.setUserId(usageDetail.getUserId());
+      usageCostDetail.setCallCost(usageDetail.getDuration() * 0.30); // 0.30₹ per minute
+      usageCostDetail.setDataCost(usageDetail.getData() * 0.20); // 0.20₹ per MB
+
+      usageCostDetailsList.add(usageCostDetail);
+    });
+
+    return usageCostDetailsList;
+  }
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/Message.java

@@ -0,0 +1,43 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * It is the message which gets dropped or read by Producer or Consumer Azure functions.
+ * It is stored in the json format.
+ * @param <T> represents UsageDetail or UsageCostDetail
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class Message<T> {
+  private MessageHeader messageHeader;
+
+  private MessageBody<T> messageBody;
+
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageBody.java

@@ -0,0 +1,43 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.domain;
+
+import java.util.List;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * It is message body of the message.
+ * It stores actual data in our case UsageCostDetail or UsageDetail.
+ * @param <T> represents UsageDetail or UsageCostDetail
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class MessageBody<T> {
+
+  private List<T> data;
+
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageHeader.java

@@ -0,0 +1,47 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * This is message header or event which is sent to Event Grid.
+ * Its structure is same as Azure Event Grid Event Class.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class MessageHeader {
+
+  private String id;
+  private String subject;
+  private String topic;
+  private String eventType;
+  private String eventTime;
+  private Object data;
+  private String dataVersion;
+
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageReference.java

@@ -0,0 +1,45 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * This is claim/message reference class.
+ * It contains the information about data where it is stored in persistent storage
+ * and file name.
+ * dataLocation is blob storage container name.
+ * dataFileName is file name in above container.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class MessageReference {
+
+  private String dataLocation;
+  private String dataFileName;
+
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/UsageCostDetail.java

@@ -0,0 +1,43 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * This is call cost details class.
+ * It stores userId of the caller, call duration cost and data cost.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class UsageCostDetail {
+
+  private String userId;
+  private double callCost;
+  private double dataCost;
+
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/UsageDetail.java

@@ -0,0 +1,44 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * This is call usage detail calls.
+ * It stores userId of the caller, call duration and data used.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class UsageDetail {
+
+  private String userId;
+
+  private int duration;
+
+  private int data;
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/producer/calldetails/functions/UsageDetailPublisherFunction.java

@@ -0,0 +1,146 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.producer.calldetails.functions;
+
+import com.azure.messaging.eventgrid.EventGridEvent;
+import com.azure.messaging.eventgrid.systemevents.SubscriptionValidationEventData;
+import com.azure.messaging.eventgrid.systemevents.SubscriptionValidationResponse;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.MessageBody;
+import com.iluwatar.claimcheckpattern.domain.MessageHeader;
+import com.iluwatar.claimcheckpattern.domain.MessageReference;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import com.iluwatar.claimcheckpattern.utility.EventHandlerUtility;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+import com.microsoft.azure.functions.ExecutionContext;
+import com.microsoft.azure.functions.HttpMethod;
+import com.microsoft.azure.functions.HttpRequestMessage;
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import com.microsoft.azure.functions.annotation.AuthorizationLevel;
+import com.microsoft.azure.functions.annotation.FunctionName;
+import com.microsoft.azure.functions.annotation.HttpTrigger;
+import java.time.OffsetDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.Random;
+import java.util.UUID;
+
+/**
+ * Azure Functions with HTTP Trigger.
+ * This is Producer class.
+ */
+public class UsageDetailPublisherFunction {
+
+  private MessageHandlerUtility<UsageDetail> messageHandlerUtility;
+  private EventHandlerUtility<MessageHeader> eventHandlerUtility;
+
+  public UsageDetailPublisherFunction() {
+    this.messageHandlerUtility = new MessageHandlerUtility<>();
+    this.eventHandlerUtility = new EventHandlerUtility<>();
+  }
+
+  public UsageDetailPublisherFunction(MessageHandlerUtility<UsageDetail> messageHandlerUtility,
+      EventHandlerUtility<MessageHeader> eventHandlerUtility) {
+    this.messageHandlerUtility = messageHandlerUtility;
+    this.eventHandlerUtility = eventHandlerUtility;
+  }
+
+  /**
+   * Azure function which create message, drop it in persistent storage
+   * and publish the event to Event Grid topic.
+   * @param request represents HttpRequestMessage
+   * @param context represents ExecutionContext
+   * @return HttpResponseMessage
+   */
+  @FunctionName("UsageDetailPublisherFunction")
+  public HttpResponseMessage run(@HttpTrigger(name = "req", methods = {
+      HttpMethod.POST }, authLevel = AuthorizationLevel.ANONYMOUS)
+      HttpRequestMessage<Optional<String>> request,
+      final ExecutionContext context) {
+    try {
+
+      var eventGridEvents = EventGridEvent.fromString(request.getBody().get());
+
+      for (EventGridEvent eventGridEvent : eventGridEvents) {
+        // Handle system events
+        if (eventGridEvent.getEventType()
+            .equals("Microsoft.EventGrid.SubscriptionValidationEvent")) {
+          SubscriptionValidationEventData subscriptionValidationEventData = eventGridEvent.getData()
+              .toObject(SubscriptionValidationEventData.class);
+          // Handle the subscription validation event
+          var responseData = new SubscriptionValidationResponse();
+          responseData.setValidationResponse(subscriptionValidationEventData.getValidationCode());
+          return request.createResponseBuilder(HttpStatus.OK).body(responseData).build();
+
+        } else if (eventGridEvent.getEventType().equals("UsageDetail")) {
+          // Create message body
+          var messageBody = new MessageBody<UsageDetail>();
+          var usageDetailsList = new ArrayList<UsageDetail>();
+          var random = new Random();
+          for (int i = 0; i < 51; i++) {
+            var usageDetail = new UsageDetail();
+            usageDetail.setUserId("userId" + i);
+            usageDetail.setData(random.nextInt(500));
+            usageDetail.setDuration(random.nextInt(500));
+
+            usageDetailsList.add(usageDetail);
+          }
+          messageBody.setData(usageDetailsList);
+
+          // Create message header
+          var messageHeader = new MessageHeader();
+          messageHeader.setId(UUID.randomUUID().toString());
+          messageHeader.setSubject("UsageDetailPublisher");
+          messageHeader.setTopic("usagecostprocessorfunction-topic");
+          messageHeader.setEventType("UsageDetail");
+          messageHeader.setEventTime(OffsetDateTime.now().toString());
+          var messageReference = new MessageReference("callusageapp",
+              messageHeader.getId() + "/input.json");
+          messageHeader.setData(messageReference);
+          messageHeader.setDataVersion("v1.0");
+
+          // Create entire message
+          var message = new Message<UsageDetail>();
+          message.setMessageHeader(messageHeader);
+          message.setMessageBody(messageBody);
+
+          // Drop data to persistent storage
+          this.messageHandlerUtility.dropToPersistantStorage(message, context.getLogger());
+
+          // Publish event to event grid topic
+          eventHandlerUtility.publishEvent(messageHeader, context.getLogger());
+
+          context.getLogger().info("Message is dropped and event is published successfully");
+          return request.createResponseBuilder(HttpStatus.OK).body(message).build();
+        }
+      }
+    } catch (Exception e) {
+      context.getLogger().warning(e.getMessage());
+    }
+
+    return request.createResponseBuilder(HttpStatus.OK).body(null).build();
+  }
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/utility/EventHandlerUtility.java

@@ -0,0 +1,66 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.utility;
+
+import com.azure.core.credential.AzureKeyCredential;
+import com.azure.core.util.BinaryData;
+import com.azure.messaging.eventgrid.EventGridPublisherClient;
+import com.azure.messaging.eventgrid.EventGridPublisherClientBuilder;
+import java.util.logging.Logger;
+
+/**
+ * This class is event publisher utility which published message header to Event Grid topic.
+ * @param <T> represents UsageDetail or UsageCostDetail
+ */
+public class EventHandlerUtility<T> {
+
+  private EventGridPublisherClient<BinaryData> customEventClient;
+
+  /** Default constructor.
+   */
+  public EventHandlerUtility() {
+    this.customEventClient = new EventGridPublisherClientBuilder()
+            .endpoint(System.getenv("EventGridURL"))
+        .credential(new AzureKeyCredential(System.getenv("EventGridKey")))
+            .buildCustomEventPublisherClient();
+  }
+
+  /**
+  Parameterized constructor.
+   */
+  public EventHandlerUtility(EventGridPublisherClient<BinaryData> customEventClient) {
+    this.customEventClient = customEventClient;
+  }
+
+  /**
+  Method for publishing event to Event Grid Topic.
+   */
+  public void publishEvent(T customEvent, Logger logger) {
+    try {
+      customEventClient.sendEvent(BinaryData.fromObject(customEvent));
+    } catch (Exception e) {
+      logger.info(e.getMessage());
+    }
+  }
+}

cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/utility/MessageHandlerUtility.java

@@ -0,0 +1,127 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.utility;
+
+import com.azure.core.util.BinaryData;
+import com.azure.core.util.serializer.TypeReference;
+import com.azure.storage.blob.BlobClient;
+import com.azure.storage.blob.BlobContainerClient;
+import com.azure.storage.blob.BlobServiceClient;
+import com.azure.storage.blob.BlobServiceClientBuilder;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.MessageReference;
+import java.util.logging.Logger;
+
+/**
+ * This class read and drop message from Azure blob storage.
+ * @param <T> represents UsageDetail or UsageCostDetail
+ */
+public class MessageHandlerUtility<T> {
+
+  private BlobServiceClient blobServiceClient;
+
+  /**
+   * Parameterized constructor.
+   * @param blobServiceClient represents BlobServiceClient
+   */
+  public MessageHandlerUtility(BlobServiceClient blobServiceClient) {
+    this.blobServiceClient = blobServiceClient;
+  }
+
+  /**
+   * Default constructor.
+   */
+  public MessageHandlerUtility() {
+    // Create a BlobServiceClient object which will be used to create a container
+    // client
+    this.blobServiceClient = new BlobServiceClientBuilder()
+        .connectionString(System.getenv("BlobStorageConnectionString")).buildClient();
+
+  }
+
+  /**
+   * Read message from blob storage.
+   * @param messageReference represents MessageReference
+   * @param logger represents Logger
+   * @return Message
+   */
+  public Message<T> readFromPersistantStorage(MessageReference messageReference, Logger logger) {
+    Message<T> message = null;
+    try {
+
+      // Get container name from message reference
+      String containerName = messageReference.getDataLocation();
+
+      // Get blob name from message reference
+      String blobName = messageReference.getDataFileName();
+
+      // Get container client
+      BlobContainerClient containerClient = blobServiceClient.getBlobContainerClient(containerName);
+
+      // Get a reference to a blob
+      BlobClient blobClient = containerClient.getBlobClient(blobName);
+
+      // download the blob
+      message = blobClient.downloadContent().toObject(new TypeReference<Message<T>>() {
+      });
+    } catch (Exception e) {
+      logger.info(e.getMessage());
+    }
+    return message;
+
+  }
+
+  /**
+   * Drop message to blob storage.
+   * @param message represents Message
+   * @param logger represents Logger
+   */
+  public void dropToPersistantStorage(Message<T> message, Logger logger) {
+    try {
+
+      // Get message reference
+      MessageReference messageReference = (MessageReference) message.getMessageHeader().getData();
+
+      // Create a unique name for the container
+      String containerName = messageReference.getDataLocation();
+
+      // Create the container and return a container client object
+      BlobContainerClient containerClient = this.blobServiceClient
+          .getBlobContainerClient(containerName);
+      if (!containerClient.exists()) {
+        containerClient.create();
+      }
+
+      // Get a reference to a blob
+      BlobClient blobClient = containerClient.getBlobClient(messageReference.getDataFileName());
+
+      // Upload the blob
+      blobClient.upload(BinaryData.fromObject(message));
+    } catch (Exception e) {
+      logger.info(e.getMessage());
+    }
+
+  }
+
+}

cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/HttpResponseMessageMock.java

@@ -0,0 +1,105 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern;
+
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import com.microsoft.azure.functions.HttpStatusType;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * The mock for HttpResponseMessage, can be used in unit tests to verify if the
+ * returned response by HTTP trigger function is correct or not.
+ */
+public class HttpResponseMessageMock implements HttpResponseMessage {
+    private int httpStatusCode;
+    private HttpStatusType httpStatus;
+    private Object body;
+    private Map<String, String> headers;
+
+    public HttpResponseMessageMock(HttpStatusType status, Map<String, String> headers, Object body) {
+        this.httpStatus = status;
+        this.httpStatusCode = status.value();
+        this.headers = headers;
+        this.body = body;
+    }
+
+    @Override
+    public HttpStatusType getStatus() {
+        return this.httpStatus;
+    }
+
+    @Override
+    public int getStatusCode() {
+        return httpStatusCode;
+    }
+
+    @Override
+    public String getHeader(String key) {
+        return this.headers.get(key);
+    }
+
+    @Override
+    public Object getBody() {
+        return this.body;
+    }
+
+    public static class HttpResponseMessageBuilderMock implements HttpResponseMessage.Builder {
+        private Object body;
+        private int httpStatusCode;
+        private Map<String, String> headers = new HashMap<>();
+        private HttpStatusType httpStatus;
+
+        public Builder status(HttpStatus status) {
+            this.httpStatusCode = status.value();
+            this.httpStatus = status;
+            return this;
+        }
+
+        @Override
+        public Builder status(HttpStatusType httpStatusType) {
+            this.httpStatusCode = httpStatusType.value();
+            this.httpStatus = httpStatusType;
+            return this;
+        }
+
+        @Override
+        public HttpResponseMessage.Builder header(String key, String value) {
+            this.headers.put(key, value);
+            return this;
+        }
+
+        @Override
+        public HttpResponseMessage.Builder body(Object body) {
+            this.body = body;
+            return this;
+        }
+
+        @Override
+        public HttpResponseMessage build() {
+            return new HttpResponseMessageMock(this.httpStatus, this.headers, this.body);
+        }
+    }
+}

cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/consumer/callcostprocessor/functions/UsageCostProcessorFunctionTest.java

@@ -0,0 +1,181 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.consumer.callcostprocessor.functions;
+
+import com.iluwatar.claimcheckpattern.HttpResponseMessageMock;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.MessageBody;
+import com.iluwatar.claimcheckpattern.domain.MessageHeader;
+import com.iluwatar.claimcheckpattern.domain.MessageReference;
+import com.iluwatar.claimcheckpattern.domain.UsageCostDetail;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+import com.microsoft.azure.functions.ExecutionContext;
+import com.microsoft.azure.functions.HttpRequestMessage;
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.mockito.stubbing.Answer;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.time.OffsetDateTime;
+import java.util.*;
+import java.util.logging.Logger;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+/**
+ * Unit test for Function class.
+ */
+@ExtendWith(MockitoExtension.class)
+public class UsageCostProcessorFunctionTest {
+
+    @Mock
+    MessageHandlerUtility<UsageDetail> mockMessageHandlerUtilityForUsageADetail;
+    @Mock
+    MessageHandlerUtility<UsageCostDetail> mockMessageHandlerUtilityForUsageCostDetail;
+    @Mock
+    ExecutionContext context;
+
+    Message<UsageCostDetail> messageToDrop;
+    Message<UsageDetail> messageToRead;
+    MessageReference messageReference;
+    @InjectMocks
+    UsageCostProcessorFunction usageCostProcessorFunction;
+
+    @BeforeEach
+    public void setUp() {
+        var messageBodyUsageDetail = new MessageBody<UsageDetail>();
+        var usageDetailsList = new ArrayList<UsageDetail>();
+
+        var messageBodyUsageCostDetail = new MessageBody<UsageCostDetail>();
+        var usageCostDetailsList = new ArrayList<UsageCostDetail>();
+        for (int i = 0; i < 2; i++) {
+            var usageDetail = new UsageDetail();
+            usageDetail.setUserId("userId" + i);
+            usageDetail.setData(i + 1);
+            usageDetail.setDuration(i + 1);
+            usageDetailsList.add(usageDetail);
+
+            var usageCostDetail = new UsageCostDetail();
+            usageCostDetail.setUserId(usageDetail.getUserId());
+            usageCostDetail.setDataCost(usageDetail.getData() * 0.20);
+            usageCostDetail.setCallCost(usageDetail.getDuration() * 0.30);
+            usageCostDetailsList.add(usageCostDetail);
+        }
+        messageBodyUsageDetail.setData(usageDetailsList);
+        messageBodyUsageCostDetail.setData(usageCostDetailsList);
+
+        // Create message header
+        var messageHeader = new MessageHeader();
+        messageHeader.setId(UUID.randomUUID().toString());
+        messageHeader.setSubject("UsageDetailPublisher");
+        messageHeader.setTopic("usagecostprocessorfunction-topic");
+        messageHeader.setEventType("UsageDetail");
+        messageHeader.setEventTime(OffsetDateTime.now().toString());
+        this.messageReference = new MessageReference("callusageapp", "d8284456-dfff-4bd4-9cef-ea99f70f4835/input.json");
+        messageHeader.setData(messageReference);
+        messageHeader.setDataVersion("v1.0");
+
+        // Create entire message
+        messageToRead = new Message<>();
+        messageToRead.setMessageHeader(messageHeader);
+        messageToRead.setMessageBody(messageBodyUsageDetail);
+
+        messageToDrop = new Message<>();
+        messageToDrop.setMessageHeader(messageHeader);
+        messageToDrop.setMessageBody(messageBodyUsageCostDetail);
+
+    }
+
+    /**
+     * Unit test for HttpTriggerJava method.
+     */
+    @Test
+    public void shouldTriggerHttpAzureFunctionJavaWithSubscriptionValidationEventType() throws Exception {
+
+        // Setup
+        @SuppressWarnings("unchecked")
+        final HttpRequestMessage<Optional<String>> req = mock(HttpRequestMessage.class);
+        String fileAbsolutePath = getClass().getResource("/subscriptionValidationEvent.json").getPath()
+                .replaceAll("%20", " "), jsonBody = Files.readString(Paths.get(fileAbsolutePath)).replaceAll("\n", " ");
+        doReturn(Optional.of(jsonBody)).when(req).getBody();
+        doAnswer(new Answer<HttpResponseMessage.Builder>() {
+            @Override
+            public HttpResponseMessage.Builder answer(InvocationOnMock invocation) {
+                HttpStatus status = (HttpStatus) invocation.getArguments()[0];
+                return new HttpResponseMessageMock.HttpResponseMessageBuilderMock().status(status);
+            }
+        }).when(req).createResponseBuilder(any(HttpStatus.class));
+
+        final ExecutionContext context = mock(ExecutionContext.class);
+
+        // Invoke
+        final HttpResponseMessage ret = this.usageCostProcessorFunction.run(req, context);
+
+        // Verify
+        assertEquals(ret.getStatus(), HttpStatus.OK);
+    }
+
+    @Test
+    public void shouldTriggerHttpAzureFunctionJavaWithUsageDetailEventType() throws Exception {
+        // Setup
+        @SuppressWarnings("unchecked")
+        final HttpRequestMessage<Optional<String>> req = mock(HttpRequestMessage.class);
+        String fileAbsolutePath = getClass().getResource("/usageDetailEvent.json").getPath().replaceAll("%20", " "),
+                jsonBody = Files.readString(Paths.get(fileAbsolutePath)).replaceAll("\n", " ");
+        doReturn(Optional.of(jsonBody)).when(req).getBody();
+        doReturn(Logger.getGlobal()).when(context).getLogger();
+
+        when(this.mockMessageHandlerUtilityForUsageADetail.readFromPersistantStorage(any(MessageReference.class),
+                eq(Logger.getGlobal()))).thenReturn(messageToRead);
+        doAnswer(new Answer<HttpResponseMessage.Builder>() {
+            @Override
+            public HttpResponseMessage.Builder answer(InvocationOnMock invocation) {
+                HttpStatus status = (HttpStatus) invocation.getArguments()[0];
+                return new HttpResponseMessageMock.HttpResponseMessageBuilderMock().status(status);
+            }
+        }).when(req).createResponseBuilder(any(HttpStatus.class));
+
+        assertNotNull(this.mockMessageHandlerUtilityForUsageADetail);
+        assertEquals(this.messageToRead, this.mockMessageHandlerUtilityForUsageADetail
+                .readFromPersistantStorage(this.messageReference, Logger.getGlobal()));
+
+        // Invoke
+        final HttpResponseMessage ret = this.usageCostProcessorFunction.run(req, context);
+
+        // Verify
+        assertEquals(HttpStatus.OK, ret.getStatus());
+        assertEquals("Message is dropped successfully", ret.getBody());
+    }
+
+}

cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/producer/calldetails/functions/UsageDetailPublisherFunctionTest.java

@@ -0,0 +1,119 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.producer.calldetails.functions;
+
+import com.iluwatar.claimcheckpattern.HttpResponseMessageMock;
+import com.iluwatar.claimcheckpattern.domain.MessageHeader;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import com.iluwatar.claimcheckpattern.utility.EventHandlerUtility;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+import com.microsoft.azure.functions.ExecutionContext;
+import com.microsoft.azure.functions.HttpRequestMessage;
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.mockito.stubbing.Answer;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.*;
+import java.util.logging.Logger;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+/**
+ * Unit test for Function class.
+ */
+@ExtendWith(MockitoExtension.class)
+public class UsageDetailPublisherFunctionTest {
+    @Mock
+    MessageHandlerUtility<UsageDetail> mockMessageHandlerUtility;
+    @Mock
+    EventHandlerUtility<MessageHeader> mockEventHandlerUtility;
+
+    @InjectMocks
+    UsageDetailPublisherFunction usageDetailPublisherFunction;
+
+    /**
+     * Unit test for HttpTriggerJava method.
+     */
+    @Test
+    public void shouldTriggerHttpAzureFunctionJavaWithSubscriptionValidationEventType() throws Exception {
+
+        // Setup
+        @SuppressWarnings("unchecked")
+        final HttpRequestMessage<Optional<String>> req = mock(HttpRequestMessage.class);
+        String fileAbsolutePath = getClass().getResource("/subscriptionValidationEvent.json").getPath()
+                .replaceAll("%20", " "), jsonBody = Files.readString(Paths.get(fileAbsolutePath)).replaceAll("\n", " ");
+        doReturn(Optional.of(jsonBody)).when(req).getBody();
+        doAnswer(new Answer<HttpResponseMessage.Builder>() {
+            @Override
+            public HttpResponseMessage.Builder answer(InvocationOnMock invocation) {
+                HttpStatus status = (HttpStatus) invocation.getArguments()[0];
+                return new HttpResponseMessageMock.HttpResponseMessageBuilderMock().status(status);
+            }
+        }).when(req).createResponseBuilder(any(HttpStatus.class));
+
+        final ExecutionContext context = mock(ExecutionContext.class);
+
+        // Invoke
+        final HttpResponseMessage ret = this.usageDetailPublisherFunction.run(req, context);
+
+        // Verify
+        assertEquals(ret.getStatus(), HttpStatus.OK);
+    }
+
+    @Test
+    public void shouldTriggerHttpAzureFunctionJavaWithUsageDetailEventType() throws Exception {
+
+        // Setup
+        @SuppressWarnings("unchecked")
+        final HttpRequestMessage<Optional<String>> req = mock(HttpRequestMessage.class);
+        String fileAbsolutePath = getClass().getResource("/usageDetailEvent.json").getPath().replaceAll("%20", " "),
+                jsonBody = Files.readString(Paths.get(fileAbsolutePath)).replaceAll("\n", " ");
+        doReturn(Optional.of(jsonBody)).when(req).getBody();
+        doAnswer(new Answer<HttpResponseMessage.Builder>() {
+            @Override
+            public HttpResponseMessage.Builder answer(InvocationOnMock invocation) {
+                HttpStatus status = (HttpStatus) invocation.getArguments()[0];
+                return new HttpResponseMessageMock.HttpResponseMessageBuilderMock().status(status);
+            }
+        }).when(req).createResponseBuilder(any(HttpStatus.class));
+
+        final ExecutionContext context = mock(ExecutionContext.class);
+        doReturn(Logger.getGlobal()).when(context).getLogger();
+
+        // Invoke
+        final HttpResponseMessage ret = this.usageDetailPublisherFunction.run(req, context);
+
+        // Verify
+        assertEquals(ret.getStatus(), HttpStatus.OK);
+    }
+
+}

cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/utility/EventHandlerUtilityTest.java

@@ -0,0 +1,70 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.utility;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+import com.azure.core.util.BinaryData;
+import com.azure.messaging.eventgrid.EventGridPublisherClient;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import java.util.logging.Logger;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+public class EventHandlerUtilityTest {
+
+    @Mock
+    EventGridPublisherClient<BinaryData> mockCustomEventClient;
+
+    @InjectMocks
+    EventHandlerUtility<Message<UsageDetail>> eventHandlerUtility;
+
+    @BeforeEach
+    public void setUp() {
+
+        System.setProperty("EventGridURL", "https://www.dummyEndpoint.com/api/events");
+        System.setProperty("EventGridKey", "EventGridURL");
+    }
+
+    @Test
+    void shouldPublishEvent() {
+        doNothing().when(mockCustomEventClient).sendEvent(any(BinaryData.class));
+        eventHandlerUtility.publishEvent(null, Logger.getLogger("logger"));
+        verify(mockCustomEventClient, times(1)).sendEvent(any(BinaryData.class));
+
+    }
+
+    @Test
+    void shouldPublishEventWithNullLogger() {
+        eventHandlerUtility.publishEvent(null, null);
+        verify(mockCustomEventClient, times(1)).sendEvent(any(BinaryData.class));
+    }
+}

cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/utility/MessageHandlerUtilityTest.java

@@ -0,0 +1,114 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.claimcheckpattern.utility;
+
+import com.azure.storage.blob.BlobClient;
+import com.azure.storage.blob.BlobContainerClient;
+import com.azure.storage.blob.BlobServiceClient;
+import com.iluwatar.claimcheckpattern.domain.*;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import java.time.OffsetDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.UUID;
+import java.util.logging.Logger;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.*;
+
+@ExtendWith(MockitoExtension.class)
+public class MessageHandlerUtilityTest {
+    @Mock
+    private BlobClient mockBlobClient;
+
+    @Mock
+    private BlobContainerClient mockContainerClient;
+
+    @Mock
+    private BlobServiceClient mockBlobServiceClient;
+
+    @InjectMocks
+    private MessageHandlerUtility<UsageDetail> messageHandlerUtility;
+
+    private Message<UsageDetail> messageToPublish;
+    private MessageReference messageReference;
+
+    @BeforeEach
+    public void setUp() {
+        System.setProperty("BlobStorageConnectionString", "https://www.dummyEndpoint.com/api/blobs");
+
+        var messageBody = new MessageBody<UsageDetail>();
+        var usageDetailsList = new ArrayList<UsageDetail>();
+        var random = new Random();
+        for (int i = 0; i < 51; i++) {
+            var usageDetail = new UsageDetail();
+            usageDetail.setUserId("userId" + i);
+            usageDetail.setData(random.nextInt(500));
+            usageDetail.setDuration(random.nextInt(500));
+
+            usageDetailsList.add(usageDetail);
+        }
+        messageBody.setData(usageDetailsList);
+
+        // Create message header
+        var messageHeader = new MessageHeader();
+        messageHeader.setId(UUID.randomUUID().toString());
+        messageHeader.setSubject("UsageDetailPublisher");
+        messageHeader.setTopic("usagecostprocessorfunction-topic");
+        messageHeader.setEventType("UsageDetail");
+        messageHeader.setEventTime(OffsetDateTime.now().toString());
+        this.messageReference = new MessageReference("callusageapp", messageHeader.getId() + "/input.json");
+        messageHeader.setData(messageReference);
+        messageHeader.setDataVersion("v1.0");
+
+        // Create entire message
+        this.messageToPublish = new Message<>();
+        this.messageToPublish.setMessageHeader(messageHeader);
+        this.messageToPublish.setMessageBody(messageBody);
+
+        when(mockContainerClient.getBlobClient(anyString())).thenReturn(mockBlobClient);
+        when(mockBlobServiceClient.getBlobContainerClient(anyString())).thenReturn(mockContainerClient);
+    }
+
+    @Test
+    void shouldDropMessageToPersistantStorage() {
+        messageHandlerUtility.dropToPersistantStorage(messageToPublish, Logger.getLogger("logger"));
+        verify(mockBlobServiceClient, times(1)).getBlobContainerClient(anyString());
+        // verify(mockContainerClient, times(0)).exists();
+    }
+
+    @Test
+    void shouldReadMessageFromPersistantStorage() {
+
+        messageHandlerUtility.readFromPersistantStorage(messageReference, Logger.getLogger("logger"));
+        verify(mockBlobServiceClient, times(1)).getBlobContainerClient(anyString());
+    }
+}

cloud-claim-check-pattern/call-usage-app/src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker

@@ -0,0 +1 @@
+mock-maker-inline

cloud-claim-check-pattern/call-usage-app/src/test/resources/subscriptionValidationEvent.json

@@ -0,0 +1,15 @@
+[
+  {
+    "data": {
+      "validationCode": "C12F266E-79D9-4C0A-9922-5EF6201A34C2",
+      "validationUrl": "https://rp-centralindia.eventgrid.azure.net:553/eventsubscriptions/usagedetailpublisherfunction-subscription/validate?idu003dC12F266E-79D9-4C0A-9922-5EF6201A34C2u0026tu003d2021-10-26T08:10:52.4999377Zu0026apiVersionu003d2020-10-15-previewu0026tokenu003d30kEVoL8rAOWzQv0buurhrKnbP%2bGMtHObbA%2bax6wb4Y%3d"
+    },
+    "dataVersion": "2",
+    "eventTime": "2021-10-26T08:10:52.4999377Z",
+    "eventType": "Microsoft.EventGrid.SubscriptionValidationEvent",
+    "id": "e2a8466b-3dc0-46b7-bb7d-b999e51a2848",
+    "metadataVersion": "1",
+    "subject": "",
+    "topic": "/subscriptions/0fef643d-a6b1-48f9-a256-53fbd0d22f48/resourceGroups/resource-group-ccp/providers/Microsoft.EventGrid/domains/event-grid-domains-ccp/topics/usagedetailpublisherfunction-topic"
+  }
+]

cloud-claim-check-pattern/call-usage-app/src/test/resources/usageDetailEvent.json

@@ -0,0 +1,15 @@
+[
+  {
+    "data": {
+      "dataFileName": "d8284456-dfff-4bd4-9cef-ea99f70f4835/input.json",
+      "dataLocation": "callusageapp"
+    },
+    "dataVersion": "v1.0",
+    "eventTime": "2021-10-25T19:17:15.7468501Z",
+    "eventType": "UsageDetail",
+    "id": "d8284456-dfff-4bd4-9cef-ea99f70f4835",
+    "metadataVersion": "1",
+    "subject": "UsageDetailPublisher",
+    "topic": "/subscriptions/0fef643d-a6b1-48f9-a256-ea99f70f4835/resourceGroups/resource-group-ccp/providers/Microsoft.EventGrid/domains/event-grid-domains-ccp/topics/usagecostprocessorfunction-topic"
+  }
+]

cloud-claim-check-pattern/etc/claim-check-pattern.urm.puml

@@ -0,0 +1,117 @@
+@startuml
+class UsageDetailPublisherFunction [[java:com.iluwatar.producer.calldetails.functions]] {
+	-messageHandlerUtility: MessageHandlerUtility<UsageDetail>
+	-eventHandlerUtility: EventHandlerUtility<MessageHeader>
+	+run(): HttpResponseMessage
+}
+
+class UsageCostProcessorFunction [[java:com.iluwatar.consumer.callcostprocessor.functions]] {
+	-messageHandlerUtilityForUsageDetail: MessageHandlerUtility<UsageDetail>
+        -messageHandlerUtilityForUsageCostDetail: MessageHandlerUtility<UsageCostDetail>
+	+run(): HttpResponseMessage
+}
+
+class "MessageHandlerUtility<T>" as MessageHandlerUtility_T [[java:com.iluwatar.claimcheckpattern.utility]] {
+	+readFromPersistantStorage(messageReference: MessageReference, logger: Logger): Message
+	+dropToPersistantStorage(message: Message, logger: Logger): void
+}
+
+class "EventHandlerUtility<T>" as EventHandlerUtility_T [[java:com.callusage.utility.PersistentLocalStorageUtility]] {
+	+publishEvent(customEvent: T, logger: Logger): void
+}
+
+class "Message<T>" as Message_T [[java:com.iluwatar.claimcheckpattern.domain]] {
+	-messageHeader: MessageHeader
+	-messageData: MessageData<T>
+	+Message(messageHeader: MessageHeader, messageData: MessageData<T>)
+	+getMessageData(): MessageData<T>
+	+getMessageHeader(): MessageHeader
+}
+
+
+class MessageHeader [[java:com.iluwatar.claimcheckpattern.domain]] {
+	-id: String
+	-subject: String
+	-topic: String
+	-eventType: String
+	-eventTime: String
+	-data: Object
+	-dataVersion: String
+	+getId(): String
+	+setId(id: String): void
+	+getSubject(): String
+	+setSubject(subject: String): void
+	+getTopic(): String
+	+setTopic(topic: String): void
+	+getEventType(): String
+        +setEventType(eventType: String): void
+        +getEventTime(): String
+	+setEventTime(eventTime: String): void
+        +getData(): Object
+	+setData(data: Object): void
+        +getDataVersion(): String
+	+setDataVersion(dataVersion:String): void
+
+}
+
+
+class "MessageBody<T>" as MessageBody_T [[java:com.iluwatar.claimcheckpattern.domain]] {
+	-data: List[] T
+	+getData(): List[] T
+	+setData(data:List[] T): void
+}
+
+class MessageReference [[java:com.iluwatar.claimcheckpattern.domain]] {
+	-dataLocation: String
+	-dataFileName: String
+	+getDataLocation(): String
+	+setDataLocation(dataLocation:String): void
+	+getDataFileName(): String
+	+setDataFileName(dataFileName:String): void
+}
+
+class UsageDetail [[java:com.iluwatar.claimcheckpattern.domain]] {
+	-userId: String
+	-duration: int
+	-data: int
+	+getUserId(): String
+	+setUserId(userId: String): void
+	+getDuration(): long
+	+setDuration(duration: long): void
+	+getData(): long
+	+setData(data: long): void
+}
+
+class UsageCostDetail [[java:com.iluwatar.claimcheckpattern.domain]] {
+	-userId: String
+	-callCost: double
+	-dataCost: double
+	+getUserId(): String
+	+setUserId(userId: String): void
+	+getCallCost(): double
+	+setCallCost(callCost:double): void
+	+getDataCost(): double
+	+setDataCost(dataCost:double) : void
+}
+
+
+
+
+
+
+
+Message_T "1" *-- "1" MessageHeader : has
+Message_T "1" *-- "1" MessageBody_T : has
+MessageHeader "1" *-- "1" MessageReference : has as data object
+MessageBody_T "1" *-- "1" UsageDetail: has
+MessageBody_T "1" *-- "1" UsageCostDetail: has
+
+EventHandlerUtility_T "1" *-- "1" MessageHeader: has
+MessageHandlerUtility_T "1" *-- "1" Message_T: has
+
+UsageDetailPublisherFunction "1" *-- "1" MessageHandlerUtility_T : has
+UsageDetailPublisherFunction "1" *-- "1" EventHandlerUtility_T : has
+
+UsageCostProcessorFunction "1" *-- "1" MessageHandlerUtility_T : has
+UsageCostProcessorFunction "1" *-- "1" MessageHandlerUtility_T : has
+@enduml

cloud-claim-check-pattern/pom.xml

@@ -0,0 +1,69 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    The MIT License
+    Copyright © 2014-2021 Ilkka Seppälä
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+	 <parent>
+	    <groupId>com.iluwatar</groupId>
+	    <artifactId>java-design-patterns</artifactId>
+	    <version>1.25.0-SNAPSHOT</version>		
+	 </parent>
+    
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>claim-check-pattern</artifactId>
+    <packaging>pom</packaging>
+
+    <modules>
+        <module>call-usage-app</module>
+    </modules>
+    <dependencies>
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <version>2.8.8</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.8.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-junit-jupiter</artifactId>
+            <version>4.0.0</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-inline</artifactId>
+            <version>4.0.0</version>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+    </project>

command/src/main/java/com/iluwatar/command/Wizard.java

@@ -36,9 +36,6 @@ public class Wizard {
   private final Deque<Runnable> undoStack = new LinkedList<>();
   private final Deque<Runnable> redoStack = new LinkedList<>();
 
-  public Wizard() {
-  }
-
   /**
    * Cast spell.
    */

commander/src/main/java/com/iluwatar/commander/Commander.java

@@ -90,6 +90,13 @@ public class Commander {
   private static final Logger LOG = LoggerFactory.getLogger(Commander.class);
   //we could also have another db where it stores all orders
 
+  private static final String ORDER_ID = "Order {}";
+  private static final String REQUEST_ID = " request Id: {}";
+  private static final String ERROR_CONNECTING_MSG_SVC =
+          ": Error in connecting to messaging service ";
+  private static final String TRY_CONNECTING_MSG_SVC =
+          ": Trying to connect to messaging service..";
+
   Commander(EmployeeHandle empDb, PaymentService paymentService, ShippingService shippingService,
             MessagingService messagingService, QueueDatabase qdb, int numOfRetries,
             long retryDuration, long queueTime, long queueTaskTime, long paymentTime,
@@ -118,17 +125,17 @@ public class Commander {
     Retry.Operation op = (l) -> {
       if (!l.isEmpty()) {
         if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-          LOG.debug("Order " + order.id + ": Error in connecting to shipping service, "
-              + "trying again..");
+          LOG.debug(ORDER_ID + ": Error in connecting to shipping service, "
+              + "trying again..", order.id);
         } else {
-          LOG.debug("Order " + order.id + ": Error in creating shipping request..");
+          LOG.debug(ORDER_ID + ": Error in creating shipping request..", order.id);
         }
         throw l.remove(0);
       }
       String transactionId = shippingService.receiveRequest(order.item, order.user.address);
       //could save this transaction id in a db too
-      LOG.info("Order " + order.id + ": Shipping placed successfully, transaction id: "
-          + transactionId);
+      LOG.info(ORDER_ID + ": Shipping placed successfully, transaction id: {}",
+              order.id, transactionId);
       LOG.info("Order has been placed and will be shipped to you. Please wait while we make your"
           + " payment... ");
       sendPaymentRequest(order);
@@ -138,19 +145,19 @@ public class Commander {
         LOG.info("Shipping is currently not possible to your address. We are working on the problem"
             + " and will get back to you asap.");
         finalSiteMsgShown = true;
-        LOG.info("Order " + order.id + ": Shipping not possible to address, trying to add problem "
-            + "to employee db..");
+        LOG.info(ORDER_ID + ": Shipping not possible to address, trying to add problem "
+            + "to employee db..", order.id);
         employeeHandleIssue(o);
       } else if (ItemUnavailableException.class.isAssignableFrom(err.getClass())) {
         LOG.info("This item is currently unavailable. We will inform you as soon as the item "
             + "becomes available again.");
         finalSiteMsgShown = true;
-        LOG.info("Order " + order.id + ": Item " + order.item + " unavailable, trying to add "
-            + "problem to employee handle..");
+        LOG.info(ORDER_ID + ": Item {}" + " unavailable, trying to add "
+            + "problem to employee handle..", order.id, order.item);
         employeeHandleIssue(o);
       } else {
         LOG.info("Sorry, there was a problem in creating your order. Please try later.");
-        LOG.error("Order " + order.id + ": Shipping service unavailable, order not placed..");
+        LOG.error(ORDER_ID + ": Shipping service unavailable, order not placed..", order.id);
         finalSiteMsgShown = true;
       }
     };
@@ -164,7 +171,7 @@ public class Commander {
       if (order.paid.equals(PaymentStatus.TRYING)) {
         order.paid = PaymentStatus.NOT_DONE;
         sendPaymentFailureMessage(order);
-        LOG.error("Order " + order.id + ": Payment time for order over, failed and returning..");
+        LOG.error(ORDER_ID + ": Payment time for order over, failed and returning..", order.id);
       } //if succeeded or failed, would have been dequeued, no attempt to make payment     
       return;
     }
@@ -173,17 +180,18 @@ public class Commander {
       Retry.Operation op = (l) -> {
         if (!l.isEmpty()) {
           if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-            LOG.debug("Order " + order.id + ": Error in connecting to payment service,"
-                + " trying again..");
+            LOG.debug(ORDER_ID + ": Error in connecting to payment service,"
+                + " trying again..", order.id);
           } else {
-            LOG.debug("Order " + order.id + ": Error in creating payment request..");
+            LOG.debug(ORDER_ID + ": Error in creating payment request..", order.id);
           }
           throw l.remove(0);
         }
         if (order.paid.equals(PaymentStatus.TRYING)) {
           var transactionId = paymentService.receiveRequest(order.price);
           order.paid = PaymentStatus.DONE;
-          LOG.info("Order " + order.id + ": Payment successful, transaction Id: " + transactionId);
+          LOG.info(ORDER_ID + ": Payment successful, transaction Id: {}",
+                  order.id, transactionId);
           if (!finalSiteMsgShown) {
             LOG.info("Payment made successfully, thank you for shopping with us!!");
             finalSiteMsgShown = true;
@@ -199,7 +207,7 @@ public class Commander {
                 + "Meanwhile, your order has been converted to COD and will be shipped.");
             finalSiteMsgShown = true;
           }
-          LOG.error("Order " + order.id + ": Payment details incorrect, failed..");
+          LOG.error(ORDER_ID + ": Payment details incorrect, failed..", order.id);
           o.paid = PaymentStatus.NOT_DONE;
           sendPaymentFailureMessage(o);
         } else {
@@ -209,7 +217,7 @@ public class Commander {
                   + "asap. Don't worry, your order has been placed and will be shipped.");
               finalSiteMsgShown = true;
             }
-            LOG.warn("Order " + order.id + ": Payment error, going to queue..");
+            LOG.warn(ORDER_ID + ": Payment error, going to queue..", order.id);
             sendPaymentPossibleErrorMsg(o);
           }
           if (o.paid.equals(PaymentStatus.TRYING) && System
@@ -234,7 +242,7 @@ public class Commander {
     if (System.currentTimeMillis() - qt.order.createdTime >= this.queueTime) {
       // since payment time is lesser than queuetime it would have already failed..
       // additional check not needed
-      LOG.trace("Order " + qt.order.id + ": Queue time for order over, failed..");
+      LOG.trace(ORDER_ID + ": Queue time for order over, failed..", qt.order.id);
       return;
     } else if (qt.taskType.equals(TaskType.PAYMENT) && !qt.order.paid.equals(PaymentStatus.TRYING)
         || qt.taskType.equals(TaskType.MESSAGING) && (qt.messageType == 1
@@ -242,30 +250,30 @@ public class Commander {
         || qt.order.messageSent.equals(MessageSent.PAYMENT_FAIL)
         || qt.order.messageSent.equals(MessageSent.PAYMENT_SUCCESSFUL))
         || qt.taskType.equals(TaskType.EMPLOYEE_DB) && qt.order.addedToEmployeeHandle) {
-      LOG.trace("Order " + qt.order.id + ": Not queueing task since task already done..");
+      LOG.trace(ORDER_ID + ": Not queueing task since task already done..", qt.order.id);
       return;
     }
     var list = queue.exceptionsList;
     Thread t = new Thread(() -> {
       Retry.Operation op = (list1) -> {
         if (!list1.isEmpty()) {
-          LOG.warn("Order " + qt.order.id + ": Error in connecting to queue db, trying again..");
+          LOG.warn(ORDER_ID + ": Error in connecting to queue db, trying again..", qt.order.id);
           throw list1.remove(0);
         }
         queue.add(qt);
         queueItems++;
-        LOG.info("Order " + qt.order.id + ": " + qt.getType() + " task enqueued..");
+        LOG.info(ORDER_ID + ": {}" + " task enqueued..", qt.order.id, qt.getType());
         tryDoingTasksInQueue();
       };
       Retry.HandleErrorIssue<QueueTask> handleError = (qt1, err) -> {
         if (qt1.taskType.equals(TaskType.PAYMENT)) {
           qt1.order.paid = PaymentStatus.NOT_DONE;
           sendPaymentFailureMessage(qt1.order);
-          LOG.error("Order " + qt1.order.id + ": Unable to enqueue payment task,"
-              + " payment failed..");
+          LOG.error(ORDER_ID + ": Unable to enqueue payment task,"
+              + " payment failed..", qt1.order.id);
         }
-        LOG.error("Order " + qt1.order.id + ": Unable to enqueue task of type " + qt1.getType()
-            + ", trying to add to employee handle..");
+        LOG.error(ORDER_ID + ": Unable to enqueue task of type {}"
+                + ", trying to add to employee handle..", qt1.order.id, qt1.getType());
         employeeHandleIssue(qt1.order);
       };
       var r = new Retry<>(op, handleError, numOfRetries, retryDuration,
@@ -328,7 +336,7 @@ public class Commander {
 
   private void sendSuccessMessage(Order order) {
     if (System.currentTimeMillis() - order.createdTime >= this.messageTime) {
-      LOG.trace("Order " + order.id + ": Message time for order over, returning..");
+      LOG.trace(ORDER_ID + ": Message time for order over, returning..", order.id);
       return;
     }
     var list = messagingService.exceptionsList;
@@ -354,8 +362,8 @@ public class Commander {
         && System.currentTimeMillis() - o.createdTime < messageTime) {
       var qt = new QueueTask(order, TaskType.MESSAGING, 2);
       updateQueue(qt);
-      LOG.info("Order " + order.id + ": Error in sending Payment Success message, trying to"
-          + " queue task and add to employee handle..");
+      LOG.info(ORDER_ID + ": Error in sending Payment Success message, trying to"
+          + " queue task and add to employee handle..", order.id);
       employeeHandleIssue(order);
     }
   }
@@ -364,11 +372,11 @@ public class Commander {
     return (l) -> {
       if (!l.isEmpty()) {
         if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-          LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
-              + "(Payment Success msg), trying again..");
+          LOG.debug(ORDER_ID + ERROR_CONNECTING_MSG_SVC
+              + "(Payment Success msg), trying again..", order.id);
         } else {
-          LOG.debug("Order " + order.id + ": Error in creating Payment Success"
-              + " messaging request..");
+          LOG.debug(ORDER_ID + ": Error in creating Payment Success"
+              + " messaging request..", order.id);
         }
         throw l.remove(0);
       }
@@ -376,15 +384,15 @@ public class Commander {
           && !order.messageSent.equals(MessageSent.PAYMENT_SUCCESSFUL)) {
         var requestId = messagingService.receiveRequest(2);
         order.messageSent = MessageSent.PAYMENT_SUCCESSFUL;
-        LOG.info("Order " + order.id + ": Payment Success message sent,"
-            + " request Id: " + requestId);
+        LOG.info(ORDER_ID + ": Payment Success message sent,"
+            + REQUEST_ID, order.id, requestId);
       }
     };
   }
 
   private void sendPaymentFailureMessage(Order order) {
     if (System.currentTimeMillis() - order.createdTime >= this.messageTime) {
-      LOG.trace("Order " + order.id + ": Message time for order over, returning..");
+      LOG.trace(ORDER_ID + ": Message time for order over, returning..", order.id);
       return;
     }
     var list = messagingService.exceptionsList;
@@ -412,8 +420,8 @@ public class Commander {
         && System.currentTimeMillis() - o.createdTime < messageTime) {
       var qt = new QueueTask(order, TaskType.MESSAGING, 0);
       updateQueue(qt);
-      LOG.warn("Order " + order.id + ": Error in sending Payment Failure message, "
-          + "trying to queue task and add to employee handle..");
+      LOG.warn(ORDER_ID + ": Error in sending Payment Failure message, "
+              + "trying to queue task and add to employee handle..", order.id);
       employeeHandleIssue(o);
     }
   }
@@ -421,11 +429,11 @@ public class Commander {
   private void handlePaymentFailureRetryOperation(Order order, List<Exception> l) throws Exception {
     if (!l.isEmpty()) {
       if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-        LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
-            + "(Payment Failure msg), trying again..");
+        LOG.debug(ORDER_ID + ERROR_CONNECTING_MSG_SVC
+            + "(Payment Failure msg), trying again..", order.id);
       } else {
-        LOG.debug("Order " + order.id + ": Error in creating Payment Failure"
-            + " message request..");
+        LOG.debug(ORDER_ID + ": Error in creating Payment Failure"
+            + " message request..", order.id);
       }
       throw l.remove(0);
     }
@@ -433,8 +441,8 @@ public class Commander {
         && !order.messageSent.equals(MessageSent.PAYMENT_SUCCESSFUL)) {
       var requestId = messagingService.receiveRequest(0);
       order.messageSent = MessageSent.PAYMENT_FAIL;
-      LOG.info("Order " + order.id + ": Payment Failure message sent successfully,"
-          + " request Id: " + requestId);
+      LOG.info(ORDER_ID + ": Payment Failure message sent successfully,"
+          + REQUEST_ID, order.id, requestId);
     }
   }
 
@@ -469,7 +477,7 @@ public class Commander {
       var qt = new QueueTask(order, TaskType.MESSAGING, 1);
       updateQueue(qt);
       LOG.warn("Order " + order.id + ": Error in sending Payment Error message, "
-          + "trying to queue task and add to employee handle..");
+              + "trying to queue task and add to employee handle..");
       employeeHandleIssue(o);
     }
   }
@@ -478,11 +486,11 @@ public class Commander {
       throws Exception {
     if (!l.isEmpty()) {
       if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-        LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
-            + "(Payment Error msg), trying again..");
+        LOG.debug(ORDER_ID + ERROR_CONNECTING_MSG_SVC
+            + "(Payment Error msg), trying again..", order.id);
       } else {
-        LOG.debug("Order " + order.id + ": Error in creating Payment Error"
-            + " messaging request..");
+        LOG.debug(ORDER_ID + ": Error in creating Payment Error"
+            + " messaging request..", order.id);
       }
       throw l.remove(0);
     }
@@ -490,28 +498,28 @@ public class Commander {
         .equals(MessageSent.NONE_SENT)) {
       var requestId = messagingService.receiveRequest(1);
       order.messageSent = MessageSent.PAYMENT_TRYING;
-      LOG.info("Order " + order.id + ": Payment Error message sent successfully,"
-          + " request Id: " + requestId);
+      LOG.info(ORDER_ID + ": Payment Error message sent successfully,"
+          + REQUEST_ID, order.id, requestId);
     }
   }
 
   private void employeeHandleIssue(Order order) {
     if (System.currentTimeMillis() - order.createdTime >= this.employeeTime) {
-      LOG.trace("Order " + order.id + ": Employee handle time for order over, returning..");
+      LOG.trace(ORDER_ID + ": Employee handle time for order over, returning..", order.id);
       return;
     }
     var list = employeeDb.exceptionsList;
     var t = new Thread(() -> {
       Retry.Operation op = (l) -> {
         if (!l.isEmpty()) {
-          LOG.warn("Order " + order.id + ": Error in connecting to employee handle,"
-              + " trying again..");
+          LOG.warn(ORDER_ID + ": Error in connecting to employee handle,"
+              + " trying again..", order.id);
           throw l.remove(0);
         }
         if (!order.addedToEmployeeHandle) {
           employeeDb.receiveRequest(order);
           order.addedToEmployeeHandle = true;
-          LOG.info("Order " + order.id + ": Added order to employee database");
+          LOG.info(ORDER_ID + ": Added order to employee database", order.id);
         }
       };
       Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
@@ -519,8 +527,8 @@ public class Commander {
             .currentTimeMillis() - order.createdTime < employeeTime) {
           var qt = new QueueTask(order, TaskType.EMPLOYEE_DB, -1);
           updateQueue(qt);
-          LOG.warn("Order " + order.id + ": Error in adding to employee db,"
-              + " trying to queue task..");
+          LOG.warn(ORDER_ID + ": Error in adding to employee db,"
+              + " trying to queue task..", order.id);
         }
       };
       var r = new Retry<>(op, handleError, numOfRetries, retryDuration,
@@ -538,51 +546,51 @@ public class Commander {
     if (queueItems != 0) {
       var qt = queue.peek(); //this should probably be cloned here
       //this is why we have retry for doTasksInQueue
-      LOG.trace("Order " + qt.order.id + ": Started doing task of type " + qt.getType());
+      LOG.trace(ORDER_ID + ": Started doing task of type {}", qt.order.id, qt.getType());
       if (qt.getFirstAttemptTime() == -1) {
         qt.setFirstAttemptTime(System.currentTimeMillis());
       }
       if (System.currentTimeMillis() - qt.getFirstAttemptTime() >= queueTaskTime) {
         tryDequeue();
-        LOG.trace("Order " + qt.order.id + ": This queue task of type " + qt.getType()
-            + " does not need to be done anymore (timeout), dequeue..");
+        LOG.trace(ORDER_ID + ": This queue task of type {}"
+            + " does not need to be done anymore (timeout), dequeue..", qt.order.id, qt.getType());
       } else {
         if (qt.taskType.equals(TaskType.PAYMENT)) {
           if (!qt.order.paid.equals(PaymentStatus.TRYING)) {
             tryDequeue();
-            LOG.trace("Order " + qt.order.id + ": This payment task already done, dequeueing..");
+            LOG.trace(ORDER_ID + ": This payment task already done, dequeueing..", qt.order.id);
           } else {
             sendPaymentRequest(qt.order);
-            LOG.debug("Order " + qt.order.id + ": Trying to connect to payment service..");
+            LOG.debug(ORDER_ID + ": Trying to connect to payment service..", qt.order.id);
           }
         } else if (qt.taskType.equals(TaskType.MESSAGING)) {
           if (qt.order.messageSent.equals(MessageSent.PAYMENT_FAIL)
               || qt.order.messageSent.equals(MessageSent.PAYMENT_SUCCESSFUL)) {
             tryDequeue();
-            LOG.trace("Order " + qt.order.id + ": This messaging task already done, dequeue..");
+            LOG.trace(ORDER_ID + ": This messaging task already done, dequeue..", qt.order.id);
           } else if (qt.messageType == 1 && (!qt.order.messageSent.equals(MessageSent.NONE_SENT)
               || !qt.order.paid.equals(PaymentStatus.TRYING))) {
             tryDequeue();
-            LOG.trace("Order " + qt.order.id + ": This messaging task does not need to be done,"
-                + " dequeue..");
+            LOG.trace(ORDER_ID + ": This messaging task does not need to be done,"
+                + " dequeue..", qt.order.id);
           } else if (qt.messageType == 0) {
             sendPaymentFailureMessage(qt.order);
-            LOG.debug("Order " + qt.order.id + ": Trying to connect to messaging service..");
+            LOG.debug(ORDER_ID + TRY_CONNECTING_MSG_SVC, qt.order.id);
           } else if (qt.messageType == 1) {
             sendPaymentPossibleErrorMsg(qt.order);
-            LOG.debug("Order " + qt.order.id + ": Trying to connect to messaging service..");
+            LOG.debug(ORDER_ID + TRY_CONNECTING_MSG_SVC, qt.order.id);
           } else if (qt.messageType == 2) {
             sendSuccessMessage(qt.order);
-            LOG.debug("Order " + qt.order.id + ": Trying to connect to messaging service..");
+            LOG.debug(ORDER_ID + TRY_CONNECTING_MSG_SVC, qt.order.id);
           }
         } else if (qt.taskType.equals(TaskType.EMPLOYEE_DB)) {
           if (qt.order.addedToEmployeeHandle) {
             tryDequeue();
-            LOG.trace("Order " + qt.order.id + ": This employee handle task already done,"
-                + " dequeue..");
+            LOG.trace(ORDER_ID + ": This employee handle task already done,"
+                + " dequeue..", qt.order.id);
           } else {
             employeeHandleIssue(qt.order);
-            LOG.debug("Order " + qt.order.id + ": Trying to connect to employee handle..");
+            LOG.debug(ORDER_ID + ": Trying to connect to employee handle..", qt.order.id);
           }
         }
       }

commander/src/test/java/com/iluwatar/commander/CommanderTest.java

@@ -0,0 +1,526 @@
+package com.iluwatar.commander;
+
+import com.iluwatar.commander.employeehandle.EmployeeDatabase;
+import com.iluwatar.commander.employeehandle.EmployeeHandle;
+import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
+import com.iluwatar.commander.exceptions.ItemUnavailableException;
+import com.iluwatar.commander.exceptions.PaymentDetailsErrorException;
+import com.iluwatar.commander.exceptions.ShippingNotPossibleException;
+import com.iluwatar.commander.messagingservice.MessagingDatabase;
+import com.iluwatar.commander.messagingservice.MessagingService;
+import com.iluwatar.commander.paymentservice.PaymentDatabase;
+import com.iluwatar.commander.paymentservice.PaymentService;
+import com.iluwatar.commander.queue.QueueDatabase;
+import com.iluwatar.commander.shippingservice.ShippingDatabase;
+import com.iluwatar.commander.shippingservice.ShippingService;
+
+import org.junit.jupiter.api.Test;
+import org.junit.platform.commons.util.StringUtils;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+class CommanderTest {
+
+    private final int numOfRetries = 1;
+    private final long retryDuration = 1_000;
+    private long queueTime = 1_00;
+    private long queueTaskTime = 1_000;
+    private long paymentTime = 6_000;
+    private long messageTime = 5_000;
+    private long employeeTime = 2_000;
+
+    private static final List<Exception> exceptionList = new ArrayList<>();
+
+    static {
+        exceptionList.add(new DatabaseUnavailableException());
+        exceptionList.add(new ShippingNotPossibleException());
+        exceptionList.add(new ItemUnavailableException());
+        exceptionList.add(new PaymentDetailsErrorException());
+        exceptionList.add(new IllegalStateException());
+    }
+
+    private Commander buildCommanderObject() {
+        return buildCommanderObject(false);
+    }
+
+    private Commander buildCommanderObject(boolean nonPaymentException) {
+        PaymentService paymentService = new PaymentService
+                (new PaymentDatabase(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException());
+
+        ShippingService shippingService;
+        MessagingService messagingService;
+        if (nonPaymentException) {
+            shippingService = new ShippingService(new ShippingDatabase(), new DatabaseUnavailableException());
+            messagingService = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
+
+        } else {
+            shippingService = new ShippingService(new ShippingDatabase(), new DatabaseUnavailableException());
+            messagingService = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
+
+        }
+        var employeeHandle = new EmployeeHandle
+                (new EmployeeDatabase(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException());
+        var qdb = new QueueDatabase
+                (new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException());
+        return new Commander(employeeHandle, paymentService, shippingService,
+                messagingService, qdb, numOfRetries, retryDuration,
+                queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
+    }
+
+    private Commander buildCommanderObjectVanilla() {
+        PaymentService paymentService = new PaymentService
+                (new PaymentDatabase(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException());
+        var shippingService = new ShippingService(new ShippingDatabase());
+        var messagingService = new MessagingService(new MessagingDatabase());
+        var employeeHandle = new EmployeeHandle
+                (new EmployeeDatabase(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException());
+        var qdb = new QueueDatabase
+                (new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+                        new DatabaseUnavailableException(), new DatabaseUnavailableException());
+        return new Commander(employeeHandle, paymentService, shippingService,
+                messagingService, qdb, numOfRetries, retryDuration,
+                queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
+    }
+
+    private Commander buildCommanderObjectUnknownException() {
+        PaymentService paymentService = new PaymentService
+                (new PaymentDatabase(), new IllegalStateException());
+        var shippingService = new ShippingService(new ShippingDatabase());
+        var messagingService = new MessagingService(new MessagingDatabase());
+        var employeeHandle = new EmployeeHandle
+                (new EmployeeDatabase(), new IllegalStateException());
+        var qdb = new QueueDatabase
+                (new DatabaseUnavailableException(), new IllegalStateException());
+        return new Commander(employeeHandle, paymentService, shippingService,
+                messagingService, qdb, numOfRetries, retryDuration,
+                queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
+    }
+
+    private Commander buildCommanderObjectNoPaymentException1() {
+        PaymentService paymentService = new PaymentService
+                (new PaymentDatabase());
+        var shippingService = new ShippingService(new ShippingDatabase());
+        var messagingService = new MessagingService(new MessagingDatabase());
+        var employeeHandle = new EmployeeHandle
+                (new EmployeeDatabase(), new IllegalStateException());
+        var qdb = new QueueDatabase
+                (new DatabaseUnavailableException(), new IllegalStateException());
+        return new Commander(employeeHandle, paymentService, shippingService,
+                messagingService, qdb, numOfRetries, retryDuration,
+                queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
+    }
+
+    private Commander buildCommanderObjectNoPaymentException2() {
+        PaymentService paymentService = new PaymentService
+                (new PaymentDatabase());
+        var shippingService = new ShippingService(new ShippingDatabase());
+        var messagingService = new MessagingService(new MessagingDatabase(), new IllegalStateException());
+        var employeeHandle = new EmployeeHandle
+                (new EmployeeDatabase(), new IllegalStateException());
+        var qdb = new QueueDatabase
+                (new DatabaseUnavailableException(), new IllegalStateException());
+        return new Commander(employeeHandle, paymentService, shippingService,
+                messagingService, qdb, numOfRetries, retryDuration,
+                queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
+    }
+
+    private Commander buildCommanderObjectNoPaymentException3() {
+        PaymentService paymentService = new PaymentService
+                (new PaymentDatabase());
+        var shippingService = new ShippingService(new ShippingDatabase());
+        var messagingService = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
+        var employeeHandle = new EmployeeHandle
+                (new EmployeeDatabase(), new IllegalStateException());
+        var qdb = new QueueDatabase
+                (new DatabaseUnavailableException(), new IllegalStateException());
+        return new Commander(employeeHandle, paymentService, shippingService,
+                messagingService, qdb, numOfRetries, retryDuration,
+                queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
+    }
+
+    private Commander buildCommanderObjectWithDB() {
+        return buildCommanderObjectWithoutDB(false, false, new IllegalStateException());
+    }
+
+    private Commander buildCommanderObjectWithDB(boolean includeException, boolean includeDBException, Exception e) {
+        var l = includeDBException ? new DatabaseUnavailableException() : e;
+        PaymentService paymentService;
+        ShippingService shippingService;
+        MessagingService messagingService;
+        EmployeeHandle employeeHandle;
+        if (includeException) {
+            paymentService = new PaymentService
+                    (new PaymentDatabase(), l);
+            shippingService = new ShippingService(new ShippingDatabase(), l);
+            messagingService = new MessagingService(new MessagingDatabase(), l);
+            employeeHandle = new EmployeeHandle
+                    (new EmployeeDatabase(), l);
+        } else {
+            paymentService = new PaymentService
+                    (null);
+            shippingService = new ShippingService(null);
+            messagingService = new MessagingService(null);
+            employeeHandle = new EmployeeHandle
+                    (null);
+        }
+
+
+        return new Commander(employeeHandle, paymentService, shippingService,
+                messagingService, null, numOfRetries, retryDuration,
+                queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
+    }
+
+    private Commander buildCommanderObjectWithoutDB() {
+        return buildCommanderObjectWithoutDB(false, false, new IllegalStateException());
+    }
+
+    private Commander buildCommanderObjectWithoutDB(boolean includeException, boolean includeDBException, Exception e) {
+        var l = includeDBException ? new DatabaseUnavailableException() : e;
+        PaymentService paymentService;
+        ShippingService shippingService;
+        MessagingService messagingService;
+        EmployeeHandle employeeHandle;
+        if (includeException) {
+            paymentService = new PaymentService
+                    (null, l);
+            shippingService = new ShippingService(null, l);
+            messagingService = new MessagingService(null, l);
+            employeeHandle = new EmployeeHandle
+                    (null, l);
+        } else {
+            paymentService = new PaymentService
+                    (null);
+            shippingService = new ShippingService(null);
+            messagingService = new MessagingService(null);
+            employeeHandle = new EmployeeHandle
+                    (null);
+        }
+
+
+        return new Commander(employeeHandle, paymentService, shippingService,
+                messagingService, null, numOfRetries, retryDuration,
+                queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
+    }
+
+    @Test
+    void testPlaceOrderVanilla() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            Commander c = buildCommanderObjectVanilla();
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrder() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            Commander c = buildCommanderObject(true);
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrder2() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            Commander c = buildCommanderObject(false);
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderNoException1() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            Commander c = buildCommanderObjectNoPaymentException1();
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderNoException2() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            Commander c = buildCommanderObjectNoPaymentException2();
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderNoException3() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            Commander c = buildCommanderObjectNoPaymentException3();
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderNoException4() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            Commander c = buildCommanderObjectNoPaymentException3();
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                c.placeOrder(order);
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderUnknownException() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+            Commander c = buildCommanderObjectUnknownException();
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderShortDuration() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+            Commander c = buildCommanderObject(true);
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderShortDuration2() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+            Commander c = buildCommanderObject(false);
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderNoExceptionShortMsgDuration() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+            Commander c = buildCommanderObjectNoPaymentException1();
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderNoExceptionShortQueueDuration() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+            Commander c = buildCommanderObjectUnknownException();
+            var order = new Order(new User("K", "J"), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderWithDatabase() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+            Commander c = buildCommanderObjectWithDB();
+            var order = new Order(new User("K", null), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderWithDatabaseAndExceptions() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+
+            for (Exception e : exceptionList) {
+
+                Commander c = buildCommanderObjectWithDB(true, true, e);
+                var order = new Order(new User("K", null), "pen", 1f);
+                for (Order.MessageSent ms : Order.MessageSent.values()) {
+                    c.placeOrder(order);
+                    assertFalse(StringUtils.isBlank(order.id));
+                }
+
+                c = buildCommanderObjectWithDB(true, false, e);
+                order = new Order(new User("K", null), "pen", 1f);
+                for (Order.MessageSent ms : Order.MessageSent.values()) {
+                    c.placeOrder(order);
+                    assertFalse(StringUtils.isBlank(order.id));
+                }
+
+                c = buildCommanderObjectWithDB(false, false, e);
+                order = new Order(new User("K", null), "pen", 1f);
+                for (Order.MessageSent ms : Order.MessageSent.values()) {
+                    c.placeOrder(order);
+                    assertFalse(StringUtils.isBlank(order.id));
+                }
+
+                c = buildCommanderObjectWithDB(false, true, e);
+                order = new Order(new User("K", null), "pen", 1f);
+                for (Order.MessageSent ms : Order.MessageSent.values()) {
+                    c.placeOrder(order);
+                    assertFalse(StringUtils.isBlank(order.id));
+                }
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderWithoutDatabase() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+            Commander c = buildCommanderObjectWithoutDB();
+            var order = new Order(new User("K", null), "pen", 1f);
+            for (Order.MessageSent ms : Order.MessageSent.values()) {
+                c.placeOrder(order);
+                assertFalse(StringUtils.isBlank(order.id));
+            }
+        }
+    }
+
+    @Test
+    void testPlaceOrderWithoutDatabaseAndExceptions() throws Exception {
+        for (double d = 0.1; d < 2; d = d + 0.1) {
+            paymentTime *= d;
+            queueTaskTime *= d;
+            messageTime *= d;
+            employeeTime *= d;
+            queueTime *= d;
+
+            for (Exception e : exceptionList) {
+
+                Commander c = buildCommanderObjectWithoutDB(true, true, e);
+                var order = new Order(new User("K", null), "pen", 1f);
+                for (Order.MessageSent ms : Order.MessageSent.values()) {
+                    c.placeOrder(order);
+                    assertFalse(StringUtils.isBlank(order.id));
+                }
+
+                c = buildCommanderObjectWithoutDB(true, false, e);
+                order = new Order(new User("K", null), "pen", 1f);
+                for (Order.MessageSent ms : Order.MessageSent.values()) {
+                    c.placeOrder(order);
+                    assertFalse(StringUtils.isBlank(order.id));
+                }
+
+                c = buildCommanderObjectWithoutDB(false, false, e);
+                order = new Order(new User("K", null), "pen", 1f);
+                for (Order.MessageSent ms : Order.MessageSent.values()) {
+                    c.placeOrder(order);
+                    assertFalse(StringUtils.isBlank(order.id));
+                }
+
+                c = buildCommanderObjectWithoutDB(false, true, e);
+                order = new Order(new User("K", null), "pen", 1f);
+                for (Order.MessageSent ms : Order.MessageSent.values()) {
+                    c.placeOrder(order);
+                    assertFalse(StringUtils.isBlank(order.id));
+                }
+            }
+        }
+    }
+
+}

event-aggregator/src/main/java/com/iluwatar/event/aggregator/App.java

@@ -49,13 +49,28 @@ public class App {
   public static void main(String[] args) {
 
     var kingJoffrey = new KingJoffrey();
-    var kingsHand = new KingsHand(kingJoffrey);
+
+    var kingsHand = new KingsHand();
+    kingsHand.registerObserver(kingJoffrey, Event.TRAITOR_DETECTED);
+    kingsHand.registerObserver(kingJoffrey, Event.STARK_SIGHTED);
+    kingsHand.registerObserver(kingJoffrey, Event.WARSHIPS_APPROACHING);
+    kingsHand.registerObserver(kingJoffrey, Event.WHITE_WALKERS_SIGHTED);
+
+    var varys = new LordVarys();
+    varys.registerObserver(kingsHand, Event.TRAITOR_DETECTED);
+    varys.registerObserver(kingsHand, Event.WHITE_WALKERS_SIGHTED);
+
+    var scout = new Scout();
+    scout.registerObserver(kingsHand, Event.WARSHIPS_APPROACHING);
+    scout.registerObserver(varys, Event.WHITE_WALKERS_SIGHTED);
+
+    var baelish = new LordBaelish(kingsHand, Event.STARK_SIGHTED);
 
     var emitters = List.of(
         kingsHand,
-        new LordBaelish(kingsHand),
-        new LordVarys(kingsHand),
-        new Scout(kingsHand)
+        baelish,
+        varys,
+        scout
     );
 
     Arrays.stream(Weekday.values())

event-aggregator/src/main/java/com/iluwatar/event/aggregator/Event.java

@@ -31,6 +31,7 @@ import lombok.RequiredArgsConstructor;
 @RequiredArgsConstructor
 public enum Event {
 
+  WHITE_WALKERS_SIGHTED("White walkers sighted"),
   STARK_SIGHTED("Stark sighted"),
   WARSHIPS_APPROACHING("Warships approaching"),
   TRAITOR_DETECTED("Traitor detected");

event-aggregator/src/main/java/com/iluwatar/event/aggregator/EventEmitter.java

@@ -23,31 +23,48 @@
 
 package com.iluwatar.event.aggregator;
 
+import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
 
 /**
  * EventEmitter is the base class for event producers that can be observed.
  */
 public abstract class EventEmitter {
 
-  private final List<EventObserver> observers;
+  private final Map<Event, List<EventObserver>> observerLists;
 
   public EventEmitter() {
-    observers = new LinkedList<>();
+    observerLists = new HashMap<>();
   }
 
-  public EventEmitter(EventObserver obs) {
+  public EventEmitter(EventObserver obs, Event e) {
     this();
-    registerObserver(obs);
+    registerObserver(obs, e);
   }
 
-  public final void registerObserver(EventObserver obs) {
-    observers.add(obs);
+  /**
+  * Registers observer for specific event in the related list.
+  *
+  * @param obs the observer that observers this emitter
+  * @param e the specific event for that observation occurs
+  * */
+  public final void registerObserver(EventObserver obs, Event e) {
+    if (!observerLists.containsKey(e)) {
+      observerLists.put(e, new LinkedList<>());
+    }
+    if (!observerLists.get(e).contains(obs)) {
+      observerLists.get(e).add(obs);
+    }
   }
 
   protected void notifyObservers(Event e) {
-    observers.forEach(obs -> obs.onEvent(e));
+    if (observerLists.containsKey(e)) {
+      observerLists
+        .get(e)
+        .forEach(observer -> observer.onEvent(e));
+    }
   }
 
   public abstract void timePasses(Weekday day);

event-aggregator/src/main/java/com/iluwatar/event/aggregator/KingsHand.java

@@ -31,8 +31,8 @@ public class KingsHand extends EventEmitter implements EventObserver {
   public KingsHand() {
   }
 
-  public KingsHand(EventObserver obs) {
-    super(obs);
+  public KingsHand(EventObserver obs, Event e) {
+    super(obs, e);
   }
 
   @Override
@@ -42,6 +42,5 @@ public class KingsHand extends EventEmitter implements EventObserver {
 
   @Override
   public void timePasses(Weekday day) {
-    // NOP
   }
 }

event-aggregator/src/main/java/com/iluwatar/event/aggregator/LordBaelish.java

@@ -31,8 +31,8 @@ public class LordBaelish extends EventEmitter {
   public LordBaelish() {
   }
 
-  public LordBaelish(EventObserver obs) {
-    super(obs);
+  public LordBaelish(EventObserver obs, Event e) {
+    super(obs, e);
   }
 
   @Override

event-aggregator/src/main/java/com/iluwatar/event/aggregator/LordVarys.java

@@ -23,16 +23,19 @@
 
 package com.iluwatar.event.aggregator;
 
+import lombok.extern.slf4j.Slf4j;
+
 /**
  * LordVarys produces events.
  */
-public class LordVarys extends EventEmitter {
+@Slf4j
+public class LordVarys extends EventEmitter implements EventObserver {
 
   public LordVarys() {
   }
 
-  public LordVarys(EventObserver obs) {
-    super(obs);
+  public LordVarys(EventObserver obs, Event e) {
+    super(obs, e);
   }
 
   @Override
@@ -41,4 +44,10 @@ public class LordVarys extends EventEmitter {
       notifyObservers(Event.TRAITOR_DETECTED);
     }
   }
+
+
+  @Override
+  public void onEvent(Event e) {
+    notifyObservers(e);
+  }
 }

event-aggregator/src/main/java/com/iluwatar/event/aggregator/Scout.java

@@ -31,8 +31,8 @@ public class Scout extends EventEmitter {
   public Scout() {
   }
 
-  public Scout(EventObserver obs) {
-    super(obs);
+  public Scout(EventObserver obs, Event e) {
+    super(obs, e);
   }
 
   @Override
@@ -40,5 +40,8 @@ public class Scout extends EventEmitter {
     if (day == Weekday.TUESDAY) {
       notifyObservers(Event.WARSHIPS_APPROACHING);
     }
+    if (day == Weekday.WEDNESDAY) {
+      notifyObservers(Event.WHITE_WALKERS_SIGHTED);
+    }
   }
 }

event-aggregator/src/test/java/com/iluwatar/event/aggregator/EventEmitterTest.java

@@ -31,6 +31,7 @@ import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.verifyZeroInteractions;
 
 import java.util.Objects;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.Supplier;
 import org.junit.jupiter.api.Test;
@@ -46,7 +47,7 @@ abstract class EventEmitterTest<E extends EventEmitter> {
   /**
    * Factory used to create a new instance of the test object with a default observer
    */
-  private final Function<EventObserver, E> factoryWithDefaultObserver;
+  private final BiFunction<EventObserver, Event, E> factoryWithDefaultObserver;
 
   /**
    * Factory used to create a new instance of the test object without passing a default observer
@@ -67,7 +68,7 @@ abstract class EventEmitterTest<E extends EventEmitter> {
    * Create a new event emitter test, using the given test object factories, special day and event
    */
   EventEmitterTest(final Weekday specialDay, final Event event,
-                   final Function<EventObserver, E> factoryWithDefaultObserver,
+                   final BiFunction<EventObserver, Event, E> factoryWithDefaultObserver,
                    final Supplier<E> factoryWithoutDefaultObserver) {
 
     this.specialDay = specialDay;
@@ -129,8 +130,8 @@ abstract class EventEmitterTest<E extends EventEmitter> {
     final var observer2 = mock(EventObserver.class);
 
     final var emitter = this.factoryWithoutDefaultObserver.get();
-    emitter.registerObserver(observer1);
-    emitter.registerObserver(observer2);
+    emitter.registerObserver(observer1, event);
+    emitter.registerObserver(observer2, event);
 
     testAllDays(specialDay, event, emitter, observer1, observer2);
   }
@@ -146,9 +147,9 @@ abstract class EventEmitterTest<E extends EventEmitter> {
     final var observer1 = mock(EventObserver.class);
     final var observer2 = mock(EventObserver.class);
 
-    final var emitter = this.factoryWithDefaultObserver.apply(defaultObserver);
-    emitter.registerObserver(observer1);
-    emitter.registerObserver(observer2);
+    final var emitter = this.factoryWithDefaultObserver.apply(defaultObserver, event);
+    emitter.registerObserver(observer1, event);
+    emitter.registerObserver(observer2, event);
 
     testAllDays(specialDay, event, emitter, defaultObserver, observer1, observer2);
   }

event-aggregator/src/test/java/com/iluwatar/event/aggregator/KingsHandTest.java

@@ -55,7 +55,11 @@ class KingsHandTest extends EventEmitterTest<KingsHand> {
   @Test
   void testPassThrough() throws Exception {
     final var observer = mock(EventObserver.class);
-    final var kingsHand = new KingsHand(observer);
+    final var kingsHand = new KingsHand();
+    kingsHand.registerObserver(observer, Event.STARK_SIGHTED);
+    kingsHand.registerObserver(observer, Event.WARSHIPS_APPROACHING);
+    kingsHand.registerObserver(observer, Event.TRAITOR_DETECTED);
+    kingsHand.registerObserver(observer, Event.WHITE_WALKERS_SIGHTED);
 
     // The kings hand should not pass any events before he received one
     verifyZeroInteractions(observer);

event-aggregator/src/test/java/com/iluwatar/event/aggregator/ScoutTest.java

@@ -34,7 +34,9 @@ class ScoutTest extends EventEmitterTest<Scout> {
    * Create a new test instance, using the correct object factory
    */
   public ScoutTest() {
-    super(Weekday.TUESDAY, Event.WARSHIPS_APPROACHING, Scout::new, Scout::new);
+
+      super(Weekday.TUESDAY, Event.WARSHIPS_APPROACHING, Scout::new, Scout::new);
+
   }
 
 }

metadata-mapping/README.md

@@ -0,0 +1,182 @@
+---
+layout: pattern
+title: Metadata Mapping
+folder: metadata-mapping
+permalink: /patterns/metadata-mapping/
+categories: Architectural
+language: en
+tags:
+ - Data access
+---
+
+## Intent
+
+Holds details of object-relational mapping in the metadata.
+
+## Explanation
+
+Real world example
+
+> Hibernate ORM Tool uses Metadata Mapping Pattern to specify the mapping between classes and tables either using XML or annotations in code. 
+
+In plain words
+
+> Metadata Mapping specifies the mapping between classes and tables so that we could treat a table of any database like a Java class.
+
+Wikipedia says
+
+> Create a "virtual [object database](https://en.wikipedia.org/wiki/Object_database)" that can be used from within the programming language.
+
+**Programmatic Example**
+
+We give an example about visiting the information of `USER` table in `h2` database. Firstly, we create `USER` table with `h2`:
+
+```java
+@Slf4j
+public class DatabaseUtil {
+  private static final String DB_URL = "jdbc:h2:mem:metamapping";
+  private static final String CREATE_SCHEMA_SQL = "DROP TABLE IF EXISTS `user`;"
+      + "CREATE TABLE `user` (\n"
+      + "  `id` int(11) NOT NULL AUTO_INCREMENT,\n"
+      + "  `username` varchar(255) NOT NULL,\n"
+      + "  `password` varchar(255) NOT NULL,\n"
+      + "  PRIMARY KEY (`id`)\n"
+      + ");";
+    
+  /**
+   * Create database.
+   */
+  static {
+    LOGGER.info("create h2 database");
+    var source = new JdbcDataSource();
+    source.setURL(DB_URL);
+    try (var statement = source.getConnection().createStatement()) {
+      statement.execute(CREATE_SCHEMA_SQL);
+    } catch (SQLException e) {
+      LOGGER.error("unable to create h2 data source", e);
+    }
+  }
+}
+```
+
+Correspondingly, here's the basic `User` entity.
+
+```java
+@Setter
+@Getter
+@ToString
+public class User {
+  private Integer id;
+  private String username;
+  private String password;
+    
+  /**
+   * Get a user.
+   * @param username user name
+   * @param password user password
+   */
+  public User(String username, String password) {
+    this.username = username;
+    this.password = password;
+  }
+}
+```
+
+Then we write a `xml` file to show the mapping between the table and the object:
+
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE hibernate-mapping PUBLIC
+    "-//Hibernate/Hibernate Mapping DTD//EN"
+    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
+
+<hibernate-mapping>
+  <class name="com.iluwatar.metamapping.model.User" table="user">
+    <id name="id" type="java.lang.Integer" column="id">
+      <generator class="native"/>
+    </id>
+    <property name="username" column="username" type="java.lang.String"/>
+    <property name="password" column="password" type="java.lang.String"/>
+  </class>
+</hibernate-mapping>
+```
+
+We use `Hibernate` to resolve the mapping and connect to our database, here's its configuration:
+
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE hibernate-configuration PUBLIC
+    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
+    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
+<hibernate-configuration>
+  <session-factory>
+    <!-- JDBC Database connection settings -->
+    <property name="connection.url">jdbc:h2:mem:metamapping</property>
+    <property name="connection.driver_class">org.h2.Driver</property>
+    <!-- JDBC connection pool settings ... using built-in test pool -->
+    <property name="connection.pool_size">1</property>
+    <!-- Select our SQL dialect -->
+    <property name="dialect">org.hibernate.dialect.H2Dialect</property>
+    <!-- Echo the SQL to stdout -->
+    <property name="show_sql">false</property>
+    <!-- Drop and re-create the database schema on startup -->
+    <property name="hbm2ddl.auto">create-drop</property>
+    <mapping resource="com/iluwatar/metamapping/model/User.hbm.xml" />
+  </session-factory>
+</hibernate-configuration>
+```
+
+Then we can get access to the table just like an object with `Hibernate`, here's some CRUDs:
+
+```java
+@Slf4j
+public class UserService {
+  private static final SessionFactory factory = HibernateUtil.getSessionFactory();
+
+  /**
+   * List all users.
+   * @return list of users
+   */
+  public List<User> listUser() {
+    LOGGER.info("list all users.");
+    List<User> users = new ArrayList<>();
+    try (var session = factory.openSession()) {
+      var tx = session.beginTransaction();
+      List<User> userIter = session.createQuery("FROM User").list();
+      for (var iterator = userIter.iterator(); iterator.hasNext();) {
+        users.add(iterator.next());
+      }
+      tx.commit();
+    } catch (HibernateException e) {
+      LOGGER.debug("fail to get users", e);
+    }
+    return users;
+  }
+  
+  // other CRUDs ->
+  ...
+    
+  public void close() {
+    HibernateUtil.shutdown();
+  }
+}
+```
+
+## Class diagram
+
+![metamapping](etc/metamapping.png)
+
+## Applicability
+
+Use the Metadata Mapping when:
+
+- you want reduce the amount of work needed to handle database mapping.
+
+## Known uses
+
+[Hibernate](https://hibernate.org/), [EclipseLink](https://www.eclipse.org/eclipselink/), [MyBatis](https://blog.mybatis.org/)......
+
+## Credits
+
+- [J2EE Design Patterns](https://www.amazon.com/gp/product/0596004273/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596004273&linkCode=as2&tag=javadesignpat-20&linkId=48d37c67fb3d845b802fa9b619ad8f31)
+

metadata-mapping/etc/metamapping.puml

@@ -0,0 +1,32 @@
+@startuml
+interface com.iluwatar.metamapping.service.UserService {
++ List<User> listUser()
++ int createUser(User)
++ void updateUser(Integer,User)
++ void deleteUser(Integer)
++ User getUser(Integer)
++ void close()
+}
+class com.iluwatar.metamapping.utils.DatabaseUtil {
++ {static} void createDataSource()
+}
+class com.iluwatar.metamapping.model.User {
+- Integer id
+- String username
+- String password
++ User(String username, String password)
+}
+class com.iluwatar.metamapping.utils.HibernateUtil {
++ {static} SessionFactory getSessionFactory()
++ {static} void shutdown()
+}
+class com.iluwatar.metamapping.App {
++ {static} void main(String[])
++ {static} List<User> generateSampleUsers()
+}
+
+com.iluwatar.metamapping.service.UserService <.. com.iluwatar.metamapping.App
+com.iluwatar.metamapping.model.User <.. com.iluwatar.metamapping.service.UserService
+com.iluwatar.metamapping.utils.HibernateUtil <.. com.iluwatar.metamapping.service.UserService
+com.iluwatar.metamapping.utils.DatabaseUtil <-- com.iluwatar.metamapping.utils.HibernateUtil
+@enduml

metadata-mapping/pom.xml

@@ -0,0 +1,87 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+  The MIT License
+  Copyright © 2014-2021 Ilkka Seppälä
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files (the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+  THE SOFTWARE.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <parent>
+    <artifactId>java-design-patterns</artifactId>
+    <groupId>com.iluwatar</groupId>
+    <version>1.26.0-SNAPSHOT</version>
+  </parent>
+  <modelVersion>4.0.0</modelVersion>
+
+  <artifactId>metadata-mapping</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-engine</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.h2database</groupId>
+      <artifactId>h2</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.hibernate</groupId>
+      <artifactId>hibernate-core</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>com.h2database</groupId>
+      <artifactId>h2</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>javax.xml.bind</groupId>
+      <artifactId>jaxb-api</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>com.sun.xml.bind</groupId>
+      <artifactId>jaxb-impl</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>com.sun.istack</groupId>
+      <artifactId>istack-commons-runtime</artifactId>
+    </dependency>
+  </dependencies>
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.metamapping.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>

metadata-mapping/src/main/java/com/iluwatar/metamapping/App.java

@@ -0,0 +1,72 @@
+package com.iluwatar.metamapping;
+
+import com.iluwatar.metamapping.model.User;
+import com.iluwatar.metamapping.service.UserService;
+import com.iluwatar.metamapping.utils.DatabaseUtil;
+import java.util.List;
+import lombok.extern.slf4j.Slf4j;
+import org.hibernate.service.ServiceRegistry;
+
+/**
+ * Metadata Mapping specifies the mapping
+ * between classes and tables so that
+ * we could treat a table of any database like a Java class.
+ *
+ * <p>With hibernate, we achieve list/create/update/delete/get operations:
+ * 1)Create the H2 Database in {@link DatabaseUtil}.
+ * 2)Hibernate resolve hibernate.cfg.xml and generate service like save/list/get/delete.
+ *    For learning metadata mapping pattern, we go deeper into Hibernate here:
+ * a)read properties from hibernate.cfg.xml and mapping from *.hbm.xml
+ * b)create session factory to generate session interacting with database
+ * c)generate session with factory pattern
+ * d)create query object or use basic api with session,
+ *      hibernate will convert all query to database query according to metadata
+ * 3)We encapsulate hibernate service in {@link UserService} for our use.
+ * @see org.hibernate.cfg.Configuration#configure(String)
+ * @see org.hibernate.cfg.Configuration#buildSessionFactory(ServiceRegistry)
+ * @see org.hibernate.internal.SessionFactoryImpl#openSession()
+ */
+@Slf4j
+public class App {
+  /**
+   * Program entry point.
+   *
+   * @param args command line args.
+   * @throws Exception if any error occurs.
+   */
+  public static void main(String[] args)  throws Exception {
+    // get service
+    var userService = new UserService();
+    // use create service to add users
+    for (var user: generateSampleUsers()) {
+      var id = userService.createUser(user);
+      LOGGER.info("Add user" + user + "at" + id + ".");
+    }
+    // use list service to get users
+    var users = userService.listUser();
+    LOGGER.info(String.valueOf(users));
+    // use get service to get a user
+    var user = userService.getUser(1);
+    LOGGER.info(String.valueOf(user));
+    // change password of user 1
+    user.setPassword("new123");
+    // use update service to update user 1
+    userService.updateUser(1, user);
+    // use delete service to delete user 2
+    userService.deleteUser(2);
+    // close service
+    userService.close();
+  }
+
+  /**
+   * Generate users.
+   *
+   * @return list of users.
+   */
+  public static List<User> generateSampleUsers() {
+    final var user1 = new User("ZhangSan", "zhs123");
+    final var user2 = new User("LiSi", "ls123");
+    final var user3 = new User("WangWu", "ww123");
+    return List.of(user1, user2, user3);
+  }
+}

metadata-mapping/src/main/java/com/iluwatar/metamapping/model/User.java

@@ -0,0 +1,29 @@
+package com.iluwatar.metamapping.model;
+
+import lombok.Getter;
+import lombok.Setter;
+import lombok.ToString;
+
+/**
+ * User Entity.
+ */
+@Setter
+@Getter
+@ToString
+public class User {
+  private Integer id;
+  private String username;
+  private String password;
+
+  public User() {}
+
+  /**
+   * Get a user.
+   * @param username user name
+   * @param password user password
+   */
+  public User(String username, String password) {
+    this.username = username;
+    this.password = password;
+  }
+}

metadata-mapping/src/main/java/com/iluwatar/metamapping/service/UserService.java

@@ -0,0 +1,114 @@
+package com.iluwatar.metamapping.service;
+
+import com.iluwatar.metamapping.model.User;
+import com.iluwatar.metamapping.utils.HibernateUtil;
+import java.util.ArrayList;
+import java.util.List;
+import lombok.extern.slf4j.Slf4j;
+import org.hibernate.HibernateException;
+import org.hibernate.SessionFactory;
+
+/**
+ * Service layer for user.
+ */
+@Slf4j
+public class UserService {
+  private static final SessionFactory factory = HibernateUtil.getSessionFactory();
+
+  /**
+   * List all users.
+   * @return list of users
+   */
+  public List<User> listUser() {
+    LOGGER.info("list all users.");
+    List<User> users = new ArrayList<>();
+    try (var session = factory.openSession()) {
+      var tx = session.beginTransaction();
+      List<User> userIter = session.createQuery("FROM User").list();
+      for (var iterator = userIter.iterator(); iterator.hasNext();) {
+        users.add(iterator.next());
+      }
+      tx.commit();
+    } catch (HibernateException e) {
+      LOGGER.debug("fail to get users", e);
+    }
+    return users;
+  }
+
+  /**
+   * Add a user.
+   * @param user user entity
+   * @return user id
+   */
+  public int createUser(User user) {
+    LOGGER.info("create user: " + user.getUsername());
+    var id = -1;
+    try (var session = factory.openSession()) {
+      var tx = session.beginTransaction();
+      id = (Integer) session.save(user);
+      tx.commit();
+    } catch (HibernateException e) {
+      LOGGER.debug("fail to create user", e);
+    }
+    LOGGER.info("create user " + user.getUsername() + " at " + id);
+    return id;
+  }
+
+  /**
+   * Update user.
+   * @param id user id
+   * @param user new user entity
+   */
+  public void updateUser(Integer id, User user) {
+    LOGGER.info("update user at " + id);
+    try (var session = factory.openSession()) {
+      var tx = session.beginTransaction();
+      user.setId(id);
+      session.update(user);
+      tx.commit();
+    } catch (HibernateException e) {
+      LOGGER.debug("fail to update user", e);
+    }
+  }
+
+  /**
+   * Delete user.
+   * @param id user id
+   */
+  public void deleteUser(Integer id) {
+    LOGGER.info("delete user at: " + id);
+    try (var session = factory.openSession()) {
+      var tx = session.beginTransaction();
+      var user = session.get(User.class, id);
+      session.delete(user);
+      tx.commit();
+    } catch (HibernateException e) {
+      LOGGER.debug("fail to delete user", e);
+    }
+  }
+
+  /**
+   * Get user.
+   * @param id user id
+   * @return deleted user
+   */
+  public User getUser(Integer id) {
+    LOGGER.info("get user at: " + id);
+    User user = null;
+    try (var session = factory.openSession()) {
+      var tx = session.beginTransaction();
+      user = session.get(User.class, id);
+      tx.commit();
+    } catch (HibernateException e) {
+      LOGGER.debug("fail to get user", e);
+    }
+    return user;
+  }
+
+  /**
+   * Close hibernate.
+   */
+  public void close() {
+    HibernateUtil.shutdown();
+  }
+}

metadata-mapping/src/main/java/com/iluwatar/metamapping/utils/DatabaseUtil.java

@@ -0,0 +1,39 @@
+package com.iluwatar.metamapping.utils;
+
+import java.sql.SQLException;
+import lombok.extern.slf4j.Slf4j;
+import org.h2.jdbcx.JdbcDataSource;
+
+/**
+ * Create h2 database.
+ */
+@Slf4j
+public class DatabaseUtil {
+  private static final String DB_URL = "jdbc:h2:mem:metamapping";
+  private static final String CREATE_SCHEMA_SQL = "DROP TABLE IF EXISTS `user`;"
+      + "CREATE TABLE `user` (\n"
+      + "  `id` int(11) NOT NULL AUTO_INCREMENT,\n"
+      + "  `username` varchar(255) NOT NULL,\n"
+      + "  `password` varchar(255) NOT NULL,\n"
+      + "  PRIMARY KEY (`id`)\n"
+      + ");";
+
+  /**
+   * Hide constructor.
+   */
+  private DatabaseUtil() {}
+
+  /**
+   * Create database.
+   */
+  static {
+    LOGGER.info("create h2 database");
+    var source = new JdbcDataSource();
+    source.setURL(DB_URL);
+    try (var statement = source.getConnection().createStatement()) {
+      statement.execute(CREATE_SCHEMA_SQL);
+    } catch (SQLException e) {
+      LOGGER.error("unable to create h2 data source", e);
+    }
+  }
+}

metadata-mapping/src/main/java/com/iluwatar/metamapping/utils/HibernateUtil.java

@@ -0,0 +1,45 @@
+package com.iluwatar.metamapping.utils;
+
+import lombok.extern.slf4j.Slf4j;
+import org.hibernate.SessionFactory;
+import org.hibernate.cfg.Configuration;
+
+/**
+ * Manage hibernate.
+ */
+@Slf4j
+public class HibernateUtil {
+
+  private static final SessionFactory sessionFactory = buildSessionFactory();
+
+  /**
+   * Hide constructor.
+   */
+  private HibernateUtil() {}
+
+  /**
+   * Build session factory.
+   * @return session factory
+   */
+  private static SessionFactory buildSessionFactory() {
+    // Create the SessionFactory from hibernate.cfg.xml
+    return new Configuration().configure().buildSessionFactory();
+  }
+
+  /**
+   * Get session factory.
+   * @return session factory
+   */
+  public static SessionFactory getSessionFactory() {
+    return sessionFactory;
+  }
+
+  /**
+   * Close session factory.
+   */
+  public static void shutdown() {
+    // Close caches and connection pools
+    getSessionFactory().close();
+  }
+
+}

metadata-mapping/src/main/resources/com/iluwatar/metamapping/model/User.hbm.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE hibernate-mapping PUBLIC
+    "-//Hibernate/Hibernate Mapping DTD//EN"
+    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
+
+<hibernate-mapping>
+  <class name="com.iluwatar.metamapping.model.User" table="user">
+    <id name="id" type="java.lang.Integer" column="id">
+      <generator class="native"/>
+    </id>
+    <property name="username" column="username" type="java.lang.String"/>
+    <property name="password" column="password" type="java.lang.String"/>
+  </class>
+</hibernate-mapping>

metadata-mapping/src/main/resources/hibernate.cfg.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE hibernate-configuration PUBLIC
+    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
+    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
+<hibernate-configuration>
+  <session-factory>
+    <!-- JDBC Database connection settings -->
+    <property name="connection.url">jdbc:h2:mem:metamapping</property>
+    <property name="connection.driver_class">org.h2.Driver</property>
+    <!-- JDBC connection pool settings ... using built-in test pool -->
+    <property name="connection.pool_size">1</property>
+    <!-- Select our SQL dialect -->
+    <property name="dialect">org.hibernate.dialect.H2Dialect</property>
+    <!-- Echo the SQL to stdout -->
+    <property name="show_sql">false</property>
+    <!-- Drop and re-create the database schema on startup -->
+    <property name="hbm2ddl.auto">create-drop</property>
+    <mapping resource="com/iluwatar/metamapping/model/User.hbm.xml" />
+  </session-factory>
+</hibernate-configuration>

metadata-mapping/src/test/java/com/iluwatar/metamapping/AppTest.java

@@ -0,0 +1,20 @@
+package com.iluwatar.metamapping;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+/**
+ * Tests that metadata mapping example runs without errors.
+ */
+class AppTest {
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+  @Test
+  void shouldExecuteMetaMappingWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
+  }
+}

pom.xml

@@ -75,6 +75,7 @@
     <license-maven-plugin.version>3.0</license-maven-plugin.version>
     <urm-maven-plugin.version>1.4.8</urm-maven-plugin.version>
     <commons-io.version>2.7</commons-io.version>
+    <istack-commons-runtime.version>4.0.1</istack-commons-runtime.version>
     <!-- SonarCloud -->
     <sonar.host.url>https://sonarcloud.io</sonar.host.url>
     <sonar.organization>iluwatar</sonar.organization>
@@ -227,6 +228,7 @@
     <module>lockable-object</module>
     <module>fanout-fanin</module>
     <module>domain-model</module>
+    <module>metadata-mapping</module>
   </modules>
   <repositories>
     <repository>
@@ -377,6 +379,11 @@
         <artifactId>commons-io</artifactId>
         <version>${commons-io.version}</version>
       </dependency>
+      <dependency>
+        <groupId>com.sun.istack</groupId>
+        <artifactId>istack-commons-runtime</artifactId>
+        <version>${istack-commons-runtime.version}</version>
+      </dependency>
     </dependencies>
   </dependencyManagement>
   <dependencies>

reactor/src/main/java/com/iluwatar/reactor/framework/NioReactor.java

@@ -96,9 +96,11 @@ public class NioReactor {
    * @throws IOException          if any I/O error occurs.
    */
   public void stop() throws InterruptedException, IOException {
-    reactorMain.shutdownNow();
+    reactorMain.shutdown();
     selector.wakeup();
-    reactorMain.awaitTermination(4, TimeUnit.SECONDS);
+    if (!reactorMain.awaitTermination(4, TimeUnit.SECONDS)) {
+      reactorMain.shutdownNow();
+    }
     selector.close();
     LOGGER.info("Reactor stopped");
   }

reactor/src/main/java/com/iluwatar/reactor/framework/ThreadPoolDispatcher.java

@@ -64,6 +64,8 @@ public class ThreadPoolDispatcher implements Dispatcher {
   @Override
   public void stop() throws InterruptedException {
     executorService.shutdown();
-    executorService.awaitTermination(4, TimeUnit.SECONDS);
+    if (executorService.awaitTermination(4, TimeUnit.SECONDS)) {
+      executorService.shutdownNow();
+    }
   }
 }

spatial-partition/src/main/java/com/iluwatar/spatialpartition/SpatialPartitionBubbles.java

@@ -34,11 +34,11 @@ import java.util.HashMap;
 public class SpatialPartitionBubbles extends SpatialPartitionGeneric<Bubble> {
 
   private final HashMap<Integer, Bubble> bubbles;
-  private final QuadTree quadTree;
+  private final QuadTree bubblesQuadTree;
 
-  SpatialPartitionBubbles(HashMap<Integer, Bubble> bubbles, QuadTree quadTree) {
+  SpatialPartitionBubbles(HashMap<Integer, Bubble> bubbles, QuadTree bubblesQuadTree) {
     this.bubbles = bubbles;
-    this.quadTree = quadTree;
+    this.bubblesQuadTree = bubblesQuadTree;
   }
 
   void handleCollisionsUsingQt(Bubble b) {
@@ -46,7 +46,7 @@ public class SpatialPartitionBubbles extends SpatialPartitionGeneric<Bubble> {
     // centre of bubble and length = radius of bubble
     var rect = new Rect(b.coordinateX, b.coordinateY, 2D * b.radius, 2D * b.radius);
     var quadTreeQueryResult = new ArrayList<Point>();
-    this.quadTree.query(rect, quadTreeQueryResult);
+    this.bubblesQuadTree.query(rect, quadTreeQueryResult);
     //handling these collisions
     b.handleCollision(quadTreeQueryResult, this.bubbles);
   }

unit-of-work/README.md

@@ -12,20 +12,20 @@ tags:
 
 ## Intent
 
-When a business transaction is completed, all the the updates are sent as one big unit of work to be 
+When a business transaction is completed, all the updates are sent as one big unit of work to be 
 persisted in one go to minimize database round-trips. 
 
 ## Explanation
 
-Real world example
+Real-world example
 
-> We have a database containing student information. Administrators all over the country are 
-> constantly updating this information and it causes high load on the database server. To make the 
+> Arms dealer has a database containing weapon information. Merchants all over the town are 
+> constantly updating this information and it causes a high load on the database server. To make the 
 > load more manageable we apply to Unit of Work pattern to send many small updates in batches.       
 
 In plain words
 
-> Unit of Work merges many small database updates in single batch to optimize the number of 
+> Unit of Work merges many small database updates in a single batch to optimize the number of 
 > round-trips. 
 
 [MartinFowler.com](https://martinfowler.com/eaaCatalog/unitOfWork.html) says
@@ -35,37 +35,20 @@ In plain words
 
 **Programmatic Example**
 
-Here's the `Student` entity that is being persisted to the database.
+Here's the `Weapon` entity that is being persisted in the database.
 
 ```java
-public class Student {
-  private final Integer id;
-  private final String name;
-  private final String address;
-
-  public Student(Integer id, String name, String address) {
-    this.id = id;
-    this.name = name;
-    this.address = address;
-  }
-
-  public String getName() {
-    return name;
-  }
-
-  public Integer getId() {
-    return id;
-  }
-
-  public String getAddress() {
-    return address;
-  }
+@Getter
+@RequiredArgsConstructor
+public class Weapon {
+    private final Integer id;
+    private final String name;
 }
 ```
 
-The essence of the implementation is the `StudentRepository` implementing the Unit of Work pattern. 
+The essence of the implementation is the `ArmsDealer` implementing the Unit of Work pattern. 
 It maintains a map of database operations (`context`) that need to be done and when `commit` is 
-called it applies them in single batch.
+called it applies them in a single batch.
 
 ```java
 public interface IUnitOfWork<T> {
@@ -84,96 +67,117 @@ public interface IUnitOfWork<T> {
 }
 
 @Slf4j
-public class StudentRepository implements IUnitOfWork<Student> {
+@RequiredArgsConstructor
+public class ArmsDealer implements IUnitOfWork<Weapon> {
 
-  private final Map<String, List<Student>> context;
-  private final StudentDatabase studentDatabase;
+    private final Map<String, List<Weapon>> context;
+    private final WeaponDatabase weaponDatabase;
 
-  public StudentRepository(Map<String, List<Student>> context, StudentDatabase studentDatabase) {
-    this.context = context;
-    this.studentDatabase = studentDatabase;
-  }
-
-  @Override
-  public void registerNew(Student student) {
-    LOGGER.info("Registering {} for insert in context.", student.getName());
-    register(student, IUnitOfWork.INSERT);
-  }
-
-  @Override
-  public void registerModified(Student student) {
-    LOGGER.info("Registering {} for modify in context.", student.getName());
-    register(student, IUnitOfWork.MODIFY);
-
-  }
-
-  @Override
-  public void registerDeleted(Student student) {
-    LOGGER.info("Registering {} for delete in context.", student.getName());
-    register(student, IUnitOfWork.DELETE);
-  }
-
-  private void register(Student student, String operation) {
-    var studentsToOperate = context.get(operation);
-    if (studentsToOperate == null) {
-      studentsToOperate = new ArrayList<>();
-    }
-    studentsToOperate.add(student);
-    context.put(operation, studentsToOperate);
-  }
-
-  @Override
-  public void commit() {
-    if (context == null || context.size() == 0) {
-      return;
-    }
-    LOGGER.info("Commit started");
-    if (context.containsKey(IUnitOfWork.INSERT)) {
-      commitInsert();
+    @Override
+    public void registerNew(Weapon weapon) {
+        LOGGER.info("Registering {} for insert in context.", weapon.getName());
+        register(weapon, UnitActions.INSERT.getActionValue());
     }
 
-    if (context.containsKey(IUnitOfWork.MODIFY)) {
-      commitModify();
-    }
-    if (context.containsKey(IUnitOfWork.DELETE)) {
-      commitDelete();
-    }
-    LOGGER.info("Commit finished.");
-  }
+    @Override
+    public void registerModified(Weapon weapon) {
+        LOGGER.info("Registering {} for modify in context.", weapon.getName());
+        register(weapon, UnitActions.MODIFY.getActionValue());
 
-  private void commitInsert() {
-    var studentsToBeInserted = context.get(IUnitOfWork.INSERT);
-    for (var student : studentsToBeInserted) {
-      LOGGER.info("Saving {} to database.", student.getName());
-      studentDatabase.insert(student);
     }
-  }
 
-  private void commitModify() {
-    var modifiedStudents = context.get(IUnitOfWork.MODIFY);
-    for (var student : modifiedStudents) {
-      LOGGER.info("Modifying {} to database.", student.getName());
-      studentDatabase.modify(student);
+    @Override
+    public void registerDeleted(Weapon weapon) {
+        LOGGER.info("Registering {} for delete in context.", weapon.getName());
+        register(weapon, UnitActions.DELETE.getActionValue());
     }
-  }
 
-  private void commitDelete() {
-    var deletedStudents = context.get(IUnitOfWork.DELETE);
-    for (var student : deletedStudents) {
-      LOGGER.info("Deleting {} to database.", student.getName());
-      studentDatabase.delete(student);
+    private void register(Weapon weapon, String operation) {
+        var weaponsToOperate = context.get(operation);
+        if (weaponsToOperate == null) {
+            weaponsToOperate = new ArrayList<>();
+        }
+        weaponsToOperate.add(weapon);
+        context.put(operation, weaponsToOperate);
+    }
+
+    /**
+     * All UnitOfWork operations are batched and executed together on commit only.
+     */
+    @Override
+    public void commit() {
+        if (context == null || context.size() == 0) {
+            return;
+        }
+        LOGGER.info("Commit started");
+        if (context.containsKey(UnitActions.INSERT.getActionValue())) {
+            commitInsert();
+        }
+
+        if (context.containsKey(UnitActions.MODIFY.getActionValue())) {
+            commitModify();
+        }
+        if (context.containsKey(UnitActions.DELETE.getActionValue())) {
+            commitDelete();
+        }
+        LOGGER.info("Commit finished.");
+    }
+
+    private void commitInsert() {
+        var weaponsToBeInserted = context.get(UnitActions.INSERT.getActionValue());
+        for (var weapon : weaponsToBeInserted) {
+            LOGGER.info("Inserting a new weapon {} to sales rack.", weapon.getName());
+            weaponDatabase.insert(weapon);
+        }
+    }
+
+    private void commitModify() {
+        var modifiedWeapons = context.get(UnitActions.MODIFY.getActionValue());
+        for (var weapon : modifiedWeapons) {
+            LOGGER.info("Scheduling {} for modification work.", weapon.getName());
+            weaponDatabase.modify(weapon);
+        }
+    }
+
+    private void commitDelete() {
+        var deletedWeapons = context.get(UnitActions.DELETE.getActionValue());
+        for (var weapon : deletedWeapons) {
+            LOGGER.info("Scrapping {}.", weapon.getName());
+            weaponDatabase.delete(weapon);
+        }
     }
-  }
 }
 ```
 
-Finally, here's how we use the `StudentRepository` and `commit` the transaction.
+Here is how the whole app is put together.
 
 ```java
-    studentRepository.registerNew(ram);
-    studentRepository.registerModified(shyam);
-    studentRepository.registerDeleted(gopi);
-    studentRepository.commit();
+// create some weapons
+var enchantedHammer = new Weapon(1, "enchanted hammer");
+var brokenGreatSword = new Weapon(2, "broken great sword");
+var silverTrident = new Weapon(3, "silver trident");
+
+// create repository
+var weaponRepository = new ArmsDealer(new HashMap<String, List<Weapon>>(), new WeaponDatabase());
+
+// perform operations on the weapons
+weaponRepository.registerNew(enchantedHammer);
+weaponRepository.registerModified(silverTrident);
+weaponRepository.registerDeleted(brokenGreatSword);
+weaponRepository.commit();
+```
+
+Here is the console output.
+
+```
+21:39:21.984 [main] INFO com.iluwatar.unitofwork.ArmsDealer - Registering enchanted hammer for insert in context.
+21:39:21.989 [main] INFO com.iluwatar.unitofwork.ArmsDealer - Registering silver trident for modify in context.
+21:39:21.989 [main] INFO com.iluwatar.unitofwork.ArmsDealer - Registering broken great sword for delete in context.
+21:39:21.989 [main] INFO com.iluwatar.unitofwork.ArmsDealer - Commit started
+21:39:21.989 [main] INFO com.iluwatar.unitofwork.ArmsDealer - Inserting a new weapon enchanted hammer to sales rack.
+21:39:21.989 [main] INFO com.iluwatar.unitofwork.ArmsDealer - Scheduling silver trident for modification work.
+21:39:21.989 [main] INFO com.iluwatar.unitofwork.ArmsDealer - Scrapping broken great sword.
+21:39:21.989 [main] INFO com.iluwatar.unitofwork.ArmsDealer - Commit finished.
 ```
 
 ## Class diagram
@@ -186,7 +190,7 @@ Use the Unit Of Work pattern when
 
 * To optimize the time taken for database transactions.
 * To send changes to database as a unit of work which ensures atomicity of the transaction.
-* To reduce number of database calls.
+* To reduce the number of database calls.
 
 ## Tutorials
 

unit-of-work/etc/unit-of-work.ucls

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <class-diagram version="1.2.1" icons="true" always-add-relationships="false" generalizations="true" realizations="true" 
   associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
-  <class id="1" language="java" name="com.iluwatar.unitofwork.StudentDatabase" project="unit-of-work" 
+  <class id="1" language="java" name="com.iluwatar.unitofwork.WeaponDatabase" project="unit-of-work"
     file="/unit-of-work/src/main/java/com/iluwatar/unitofwork/StudentDatabase.java" binary="false" corner="BOTTOM_RIGHT">    
     <position height="-1" width="-1" x="170" y="406"/>    
     <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
@@ -28,7 +28,7 @@
       <operations public="true" package="true" protected="true" private="true" static="true"/>    
     </display>  
   </class>  
-  <class id="4" language="java" name="com.iluwatar.unitofwork.StudentRepository" project="unit-of-work" 
+  <class id="4" language="java" name="com.iluwatar.unitofwork.ArmsDealer" project="unit-of-work"
     file="/unit-of-work/src/main/java/com/iluwatar/unitofwork/StudentRepository.java" binary="false" 
     corner="BOTTOM_RIGHT">    
     <position height="-1" width="-1" x="377" y="166"/>    
@@ -38,7 +38,7 @@
       <operations public="true" package="true" protected="true" private="true" static="true"/>    
     </display>  
   </class>  
-  <class id="5" language="java" name="com.iluwatar.unitofwork.Student" project="unit-of-work" 
+  <class id="5" language="java" name="com.iluwatar.unitofwork.Weapon" project="unit-of-work"
     file="/unit-of-work/src/main/java/com/iluwatar/unitofwork/Student.java" binary="false" corner="BOTTOM_RIGHT">    
     <position height="-1" width="-1" x="696" y="130"/>    
     <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 

unit-of-work/src/main/java/com/iluwatar/unitofwork/App.java

@@ -27,7 +27,7 @@ import java.util.HashMap;
 import java.util.List;
 
 /**
- * {@link App} Application for managing student data.
+ * {@link App} Application demonstrating unit of work pattern.
  */
 public class App {
   /**
@@ -37,17 +37,19 @@ public class App {
    */
 
   public static void main(String[] args) {
-    var ram = new Student(1, "Ram", "Street 9, Cupertino");
-    var shyam = new Student(2, "Shyam", "Z bridge, Pune");
-    var gopi = new Student(3, "Gopi", "Street 10, Mumbai");
+    // create some weapons
+    var enchantedHammer = new Weapon(1, "enchanted hammer");
+    var brokenGreatSword = new Weapon(2, "broken great sword");
+    var silverTrident = new Weapon(3, "silver trident");
 
-    var context = new HashMap<String, List<Student>>();
-    var studentDatabase = new StudentDatabase();
-    var studentRepository = new StudentRepository(context, studentDatabase);
+    // create repository
+    var weaponRepository = new ArmsDealer(new HashMap<String, List<Weapon>>(),
+            new WeaponDatabase());
 
-    studentRepository.registerNew(ram);
-    studentRepository.registerModified(shyam);
-    studentRepository.registerDeleted(gopi);
-    studentRepository.commit();
+    // perform operations on the weapons
+    weaponRepository.registerNew(enchantedHammer);
+    weaponRepository.registerModified(silverTrident);
+    weaponRepository.registerDeleted(brokenGreatSword);
+    weaponRepository.commit();
   }
 }

unit-of-work/src/main/java/com/iluwatar/unitofwork/ArmsDealer.java

@@ -30,41 +30,41 @@ import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * {@link StudentRepository} Student database repository. supports unit of work for student data.
+ * {@link ArmsDealer} Weapon repository that supports unit of work for weapons.
  */
 @Slf4j
 @RequiredArgsConstructor
-public class StudentRepository implements IUnitOfWork<Student> {
+public class ArmsDealer implements IUnitOfWork<Weapon> {
 
-  private final Map<String, List<Student>> context;
-  private final StudentDatabase studentDatabase;
+  private final Map<String, List<Weapon>> context;
+  private final WeaponDatabase weaponDatabase;
 
   @Override
-  public void registerNew(Student student) {
-    LOGGER.info("Registering {} for insert in context.", student.getName());
-    register(student, UnitActions.INSERT.getActionValue());
+  public void registerNew(Weapon weapon) {
+    LOGGER.info("Registering {} for insert in context.", weapon.getName());
+    register(weapon, UnitActions.INSERT.getActionValue());
   }
 
   @Override
-  public void registerModified(Student student) {
-    LOGGER.info("Registering {} for modify in context.", student.getName());
-    register(student, UnitActions.MODIFY.getActionValue());
+  public void registerModified(Weapon weapon) {
+    LOGGER.info("Registering {} for modify in context.", weapon.getName());
+    register(weapon, UnitActions.MODIFY.getActionValue());
 
   }
 
   @Override
-  public void registerDeleted(Student student) {
-    LOGGER.info("Registering {} for delete in context.", student.getName());
-    register(student, UnitActions.DELETE.getActionValue());
+  public void registerDeleted(Weapon weapon) {
+    LOGGER.info("Registering {} for delete in context.", weapon.getName());
+    register(weapon, UnitActions.DELETE.getActionValue());
   }
 
-  private void register(Student student, String operation) {
-    var studentsToOperate = context.get(operation);
-    if (studentsToOperate == null) {
-      studentsToOperate = new ArrayList<>();
+  private void register(Weapon weapon, String operation) {
+    var weaponsToOperate = context.get(operation);
+    if (weaponsToOperate == null) {
+      weaponsToOperate = new ArrayList<>();
     }
-    studentsToOperate.add(student);
-    context.put(operation, studentsToOperate);
+    weaponsToOperate.add(weapon);
+    context.put(operation, weaponsToOperate);
   }
 
   /**
@@ -90,26 +90,26 @@ public class StudentRepository implements IUnitOfWork<Student> {
   }
 
   private void commitInsert() {
-    var studentsToBeInserted = context.get(UnitActions.INSERT.getActionValue());
-    for (var student : studentsToBeInserted) {
-      LOGGER.info("Saving {} to database.", student.getName());
-      studentDatabase.insert(student);
+    var weaponsToBeInserted = context.get(UnitActions.INSERT.getActionValue());
+    for (var weapon : weaponsToBeInserted) {
+      LOGGER.info("Inserting a new weapon {} to sales rack.", weapon.getName());
+      weaponDatabase.insert(weapon);
     }
   }
 
   private void commitModify() {
-    var modifiedStudents = context.get(UnitActions.MODIFY.getActionValue());
-    for (var student : modifiedStudents) {
-      LOGGER.info("Modifying {} to database.", student.getName());
-      studentDatabase.modify(student);
+    var modifiedWeapons = context.get(UnitActions.MODIFY.getActionValue());
+    for (var weapon : modifiedWeapons) {
+      LOGGER.info("Scheduling {} for modification work.", weapon.getName());
+      weaponDatabase.modify(weapon);
     }
   }
 
   private void commitDelete() {
-    var deletedStudents = context.get(UnitActions.DELETE.getActionValue());
-    for (var student : deletedStudents) {
-      LOGGER.info("Deleting {} to database.", student.getName());
-      studentDatabase.delete(student);
+    var deletedWeapons = context.get(UnitActions.DELETE.getActionValue());
+    for (var weapon : deletedWeapons) {
+      LOGGER.info("Scrapping {}.", weapon.getName());
+      weaponDatabase.delete(weapon);
     }
   }
 }

unit-of-work/src/main/java/com/iluwatar/unitofwork/Weapon.java

@@ -27,14 +27,12 @@ import lombok.Getter;
 import lombok.RequiredArgsConstructor;
 
 /**
- * {@link Student} is an entity.
+ * {@link Weapon} is an entity.
  */
 @Getter
 @RequiredArgsConstructor
-public class Student {
+public class Weapon {
 
   private final Integer id;
   private final String name;
-  private final String address;
-
 }

unit-of-work/src/main/java/com/iluwatar/unitofwork/WeaponDatabase.java

@@ -24,19 +24,19 @@
 package com.iluwatar.unitofwork;
 
 /**
- * Act as Database for student records.
+ * Act as database for weapon records.
  */
-public class StudentDatabase {
+public class WeaponDatabase {
 
-  public void insert(Student student) {
+  public void insert(Weapon weapon) {
     //Some insert logic to DB
   }
 
-  public void modify(Student student) {
+  public void modify(Weapon weapon) {
     //Some modify logic to DB
   }
 
-  public void delete(Student student) {
+  public void delete(Weapon weapon) {
     //Some delete logic to DB
   }
 }

unit-of-work/src/test/java/com/iluwatar/unitofwork/ArmsDealerTest.java

@@ -36,102 +36,102 @@ import java.util.Map;
 import org.junit.jupiter.api.Test;
 
 /**
- * tests {@link StudentRepository}
+ * tests {@link ArmsDealer}
  */
 
-class StudentRepositoryTest {
-  private final Student student1 = new Student(1, "Ram", "street 9, cupertino");
-  private final Student student2 = new Student(1, "Sham", "Z bridge, pune");
+class ArmsDealerTest {
+  private final Weapon weapon1 = new Weapon(1, "battle ram");
+  private final Weapon weapon2 = new Weapon(1, "wooden lance");
 
-  private final Map<String, List<Student>> context = new HashMap<>();
-  private final StudentDatabase studentDatabase = mock(StudentDatabase.class);
-  private final StudentRepository studentRepository = new StudentRepository(context, studentDatabase);;
+  private final Map<String, List<Weapon>> context = new HashMap<>();
+  private final WeaponDatabase weaponDatabase = mock(WeaponDatabase.class);
+  private final ArmsDealer armsDealer = new ArmsDealer(context, weaponDatabase);;
 
   @Test
   void shouldSaveNewStudentWithoutWritingToDb() {
-    studentRepository.registerNew(student1);
-    studentRepository.registerNew(student2);
+    armsDealer.registerNew(weapon1);
+    armsDealer.registerNew(weapon2);
 
     assertEquals(2, context.get(UnitActions.INSERT.getActionValue()).size());
-    verifyNoMoreInteractions(studentDatabase);
+    verifyNoMoreInteractions(weaponDatabase);
   }
 
   @Test
   void shouldSaveDeletedStudentWithoutWritingToDb() {
-    studentRepository.registerDeleted(student1);
-    studentRepository.registerDeleted(student2);
+    armsDealer.registerDeleted(weapon1);
+    armsDealer.registerDeleted(weapon2);
 
     assertEquals(2, context.get(UnitActions.DELETE.getActionValue()).size());
-    verifyNoMoreInteractions(studentDatabase);
+    verifyNoMoreInteractions(weaponDatabase);
   }
 
   @Test
   void shouldSaveModifiedStudentWithoutWritingToDb() {
-    studentRepository.registerModified(student1);
-    studentRepository.registerModified(student2);
+    armsDealer.registerModified(weapon1);
+    armsDealer.registerModified(weapon2);
 
     assertEquals(2, context.get(UnitActions.MODIFY.getActionValue()).size());
-    verifyNoMoreInteractions(studentDatabase);
+    verifyNoMoreInteractions(weaponDatabase);
   }
 
   @Test
   void shouldSaveAllLocalChangesToDb() {
-    context.put(UnitActions.INSERT.getActionValue(), List.of(student1));
-    context.put(UnitActions.MODIFY.getActionValue(), List.of(student1));
-    context.put(UnitActions.DELETE.getActionValue(), List.of(student1));
+    context.put(UnitActions.INSERT.getActionValue(), List.of(weapon1));
+    context.put(UnitActions.MODIFY.getActionValue(), List.of(weapon1));
+    context.put(UnitActions.DELETE.getActionValue(), List.of(weapon1));
 
-    studentRepository.commit();
+    armsDealer.commit();
 
-    verify(studentDatabase, times(1)).insert(student1);
-    verify(studentDatabase, times(1)).modify(student1);
-    verify(studentDatabase, times(1)).delete(student1);
+    verify(weaponDatabase, times(1)).insert(weapon1);
+    verify(weaponDatabase, times(1)).modify(weapon1);
+    verify(weaponDatabase, times(1)).delete(weapon1);
   }
 
   @Test
   void shouldNotWriteToDbIfContextIsNull() {
-    var studentRepository = new StudentRepository(null, studentDatabase);
+    var weaponRepository = new ArmsDealer(null, weaponDatabase);
 
-    studentRepository.commit();
+    weaponRepository.commit();
 
-    verifyNoMoreInteractions(studentDatabase);
+    verifyNoMoreInteractions(weaponDatabase);
   }
 
   @Test
   void shouldNotWriteToDbIfNothingToCommit() {
-    var studentRepository = new StudentRepository(new HashMap<>(), studentDatabase);
+    var weaponRepository = new ArmsDealer(new HashMap<>(), weaponDatabase);
 
-    studentRepository.commit();
+    weaponRepository.commit();
 
-    verifyNoMoreInteractions(studentDatabase);
+    verifyNoMoreInteractions(weaponDatabase);
   }
 
   @Test
   void shouldNotInsertToDbIfNoRegisteredStudentsToBeCommitted() {
-    context.put(UnitActions.MODIFY.getActionValue(), List.of(student1));
-    context.put(UnitActions.DELETE.getActionValue(), List.of(student1));
+    context.put(UnitActions.MODIFY.getActionValue(), List.of(weapon1));
+    context.put(UnitActions.DELETE.getActionValue(), List.of(weapon1));
 
-    studentRepository.commit();
+    armsDealer.commit();
 
-    verify(studentDatabase, never()).insert(student1);
+    verify(weaponDatabase, never()).insert(weapon1);
   }
 
   @Test
   void shouldNotModifyToDbIfNotRegisteredStudentsToBeCommitted() {
-    context.put(UnitActions.INSERT.getActionValue(), List.of(student1));
-    context.put(UnitActions.DELETE.getActionValue(), List.of(student1));
+    context.put(UnitActions.INSERT.getActionValue(), List.of(weapon1));
+    context.put(UnitActions.DELETE.getActionValue(), List.of(weapon1));
 
-    studentRepository.commit();
+    armsDealer.commit();
 
-    verify(studentDatabase, never()).modify(student1);
+    verify(weaponDatabase, never()).modify(weapon1);
   }
 
   @Test
   void shouldNotDeleteFromDbIfNotRegisteredStudentsToBeCommitted() {
-    context.put(UnitActions.INSERT.getActionValue(), List.of(student1));
-    context.put(UnitActions.MODIFY.getActionValue(), List.of(student1));
+    context.put(UnitActions.INSERT.getActionValue(), List.of(weapon1));
+    context.put(UnitActions.MODIFY.getActionValue(), List.of(weapon1));
 
-    studentRepository.commit();
+    armsDealer.commit();
 
-    verify(studentDatabase, never()).delete(student1);
+    verify(weaponDatabase, never()).delete(weapon1);
   }
 }