docs: update .all-contributorsrc [skip ci]

* Resolve Sonar Code Smell: Define a constant instead of duplicating this literal 'Space rocket <' 4 times.

* Resolve Sonar Critical Code Smell: Define a constant instead of duplicating this literal 'Error connecting to MongoDB' 4 times.

* Fix checkstyle violation.

* Resolve Sonar Critical Code Smell: Define a constant instead of duplicating this literal 'LITERAL 0' 4 times.

Co-authored-by: Subhrodip Mohanta <hello@subho.xyz>

.all-contributorsrc

@@ -1631,6 +1631,15 @@
       "contributions": [
         "translation"
       ]
+    },
+    {
+      "login": "sims-keshri",
+      "name": "Simran Keshri",
+      "avatar_url": "https://avatars.githubusercontent.com/u/62168475?v=4",
+      "profile": "https://github.com/sims-keshri",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 4,

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-179-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-180-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 <br/>
@@ -343,6 +343,7 @@ This project is licensed under the terms of the MIT license.
     <td align="center"><a href="https://github.com/Conhan93"><img src="https://avatars.githubusercontent.com/u/71334757?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Conny Hansson</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Conhan93" title="Documentation">📖</a></td>
     <td align="center"><a href="http://muklasr.medium.com"><img src="https://avatars.githubusercontent.com/u/43443753?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Muklas Rahmanto</b></sub></a><br /><a href="#translation-muklasr" title="Translation">🌍</a></td>
     <td align="center"><a href="https://github.com/VxDxK"><img src="https://avatars.githubusercontent.com/u/38704817?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Vadim</b></sub></a><br /><a href="#translation-VxDxK" title="Translation">🌍</a></td>
+    <td align="center"><a href="https://github.com/sims-keshri"><img src="https://avatars.githubusercontent.com/u/62168475?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Simran Keshri</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sims-keshri" title="Code">💻</a></td>
   </tr>
 </table>
 

abstract-document/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Abstract Document
-category: Structural
+folder: abstract-document
+permalink: /patterns/abstract-document/
+categories: Structural
 language: en
 tags: 
  - Extensibility

abstract-factory/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Abstract Factory
-category: Creational
+folder: abstract-factory
+permalink: /patterns/abstract-factory/
+categories: Creational
 language: en
 tags:
  - Gang of Four

active-object/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Active Object
-category: Concurrency
+folder: active-object
+permalink: /patterns/active-object/
+categories: Concurrency
 language: en
 tags:
  - Performance

acyclic-visitor/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Acyclic Visitor
-category: Behavioral
+folder: acyclic-visitor
+permalink: /patterns/acyclic-visitor/
+categories: Behavioral
 language: en
 tags:
  - Extensibility

adapter/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Adapter
-category: Structural
+folder: adapter
+permalink: /patterns/adapter/
+categories: Structural
 language: en
 tags:
  - Gang of Four

aggregator-microservices/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Aggregator Microservices
-category: Architectural
+folder: aggregator-microservices
+permalink: /patterns/aggregator-microservices/
+categories: Architectural
 language: en
 tags:
 - Cloud distributed

ambassador/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Ambassador
-category: Structural
+folder: ambassador
+permalink: /patterns/ambassador/
+categories: Structural
 language: en
 tags:
   - Decoupling

api-gateway/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: API Gateway
-category: Architectural
+folder: api-gateway
+permalink: /patterns/api-gateway/
+categories: Architectural
 language: en
 tags:
   - Cloud distributed

arrange-act-assert/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Arrange/Act/Assert
-category: Idiom
+folder: arrange-act-assert
+permalink: /patterns/arrange-act-assert/
+categories: Idiom
 language: en
 tags:
  - Testing

async-method-invocation/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Async Method Invocation
-category: Concurrency
+folder: async-method-invocation
+permalink: /patterns/async-method-invocation/
+categories: Concurrency
 language: en
 tags:
  - Reactive

async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/App.java

@@ -59,9 +59,12 @@ import lombok.extern.slf4j.Slf4j;
 @Slf4j
 public class App {
 
+  private static final String ROCKET_LAUNCH_LOG_PATTERN = "Space rocket <%s> launched successfully";
+
   /**
    * Program entry point.
    */
+
   public static void main(String[] args) throws Exception {
     // construct a new executor that will run async tasks
     var executor = new ThreadAsyncExecutor();
@@ -87,9 +90,9 @@ public class App {
     asyncResult5.await();
 
     // log the results of the tasks, callbacks log immediately when complete
-    log("Space rocket <" + result1 + "> launch complete");
+    log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result1));
-    log("Space rocket <" + result2 + "> launch complete");
+    log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result2));
-    log("Space rocket <" + result3 + "> launch complete");
+    log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result3));
   }
 
   /**
@@ -102,7 +105,7 @@ public class App {
   private static <T> Callable<T> lazyval(T value, long delayMillis) {
     return () -> {
       Thread.sleep(delayMillis);
-      log("Space rocket <" + value + "> launched successfully");
+      log(String.format(ROCKET_LAUNCH_LOG_PATTERN, value));
       return value;
     };
   }

balking/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Balking
-category: Concurrency
+folder: balking
+permalink: /patterns/balking/
+categories: Concurrency
 language: en
 tags:
  - Decoupling

bridge/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Bridge
-category: Structural
+folder: bridge
+permalink: /patterns/bridge/
+categories: Structural
 language: en
 tags:
  - Gang of Four

builder/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Builder
-category: Creational
+folder: builder
+permalink: /patterns/builder/
+categories: Creational
 language: en
 tags:
  - Gang of Four

business-delegate/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Business Delegate
-category: Structural
+folder: business-delegate
+permalink: /patterns/business-delegate/
+categories: Structural
 language: en
 tags:
  - Decoupling

bytecode/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Bytecode
-category: Behavioral
+folder: bytecode
+permalink: /patterns/bytecode/
+categories: Behavioral
 language: en
 tags:
  - Game programming

bytecode/src/main/java/com/iluwatar/bytecode/App.java

@@ -42,6 +42,14 @@ import lombok.extern.slf4j.Slf4j;
 @Slf4j
 public class App {
 
+  private static final String LITERAL_0 = "LITERAL 0";
+  private static final String HEALTH_PATTERN = "%s_HEALTH";
+  private static final String GET_AGILITY = "GET_AGILITY";
+  private static final String GET_WISDOM = "GET_WISDOM";
+  private static final String ADD = "ADD";
+  private static final String LITERAL_2 = "LITERAL 2";
+  private static final String DIVIDE = "DIVIDE";
+
   /**
    * Main app method.
    *
@@ -53,17 +61,17 @@ public class App {
         new Wizard(45, 7, 11, 0, 0),
         new Wizard(36, 18, 8, 0, 0));
 
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(LITERAL_0));
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(LITERAL_0));
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_HEALTH"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(String.format(HEALTH_PATTERN, "GET")));
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(LITERAL_0));
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_AGILITY"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(GET_AGILITY));
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(LITERAL_0));
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_WISDOM"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(GET_WISDOM));
-    vm.execute(InstructionConverterUtil.convertToByteCode("ADD"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(ADD));
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 2"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(LITERAL_2));
-    vm.execute(InstructionConverterUtil.convertToByteCode("DIVIDE"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(DIVIDE));
-    vm.execute(InstructionConverterUtil.convertToByteCode("ADD"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(ADD));
-    vm.execute(InstructionConverterUtil.convertToByteCode("SET_HEALTH"));
+    vm.execute(InstructionConverterUtil.convertToByteCode(String.format(HEALTH_PATTERN, "SET")));
   }
 }

caching/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Caching
-category: Behavioral
+folder: caching
+permalink: /patterns/caching/
+categories: Behavioral
 language: en
 tags:
   - Performance
@@ -40,29 +43,39 @@ Wikipedia says:
 **Programmatic Example**
 
 Let's first look at the data layer of our application. The interesting classes are `UserAccount`
-which is a simple Java object containing the user account details, and `DbManager` interface which handles
+which is a simple Java object containing the user account details, and `DbManager` which handles
-reading and writing of these objects to/from database.
+reading and writing of these objects to/from MongoDB database.
 
 ```java
-@Data
+@Setter
+@Getter
 @AllArgsConstructor
 @ToString
-@EqualsAndHashCode
 public class UserAccount {
   private String userId;
   private String userName;
   private String additionalInfo;
 }
 
-public interface DbManager {
+@Slf4j
+public final class DbManager {
 
-  void connect();
+  private static MongoClient mongoClient;
-  void disconnect();
+  private static MongoDatabase db;
 
-  UserAccount readFromDb(String userId);
+  private DbManager() { /*...*/ }
-  UserAccount writeToDb(UserAccount userAccount);
+
-  UserAccount updateDb(UserAccount userAccount);
+  public static void createVirtualDb() { /*...*/ }
-  UserAccount upsertDb(UserAccount userAccount);
+
+  public static void connect() throws ParseException { /*...*/ }
+
+  public static UserAccount readFromDb(String userId) { /*...*/ }
+
+  public static void writeToDb(UserAccount userAccount) { /*...*/ }
+
+  public static void updateDb(UserAccount userAccount) { /*...*/ }
+
+  public static void upsertDb(UserAccount userAccount) { /*...*/ }
 }
 ```
 
@@ -158,43 +171,30 @@ strategies.
 @Slf4j
 public class CacheStore {
 
-  private static final int CAPACITY = 3;
   private static LruCache cache;
-  private final DbManager dbManager;
 
   /* ... details omitted ... */
 
-  public UserAccount readThrough(final String userId) {
+  public static UserAccount readThrough(String userId) {
     if (cache.contains(userId)) {
-      LOGGER.info("# Found in Cache!");
+      LOGGER.info("# Cache Hit!");
       return cache.get(userId);
     }
-    LOGGER.info("# Not found in cache! Go to DB!!");
+    LOGGER.info("# Cache Miss!");
-    UserAccount userAccount = dbManager.readFromDb(userId);
+    UserAccount userAccount = DbManager.readFromDb(userId);
     cache.set(userId, userAccount);
     return userAccount;
   }
 
-  public void writeThrough(final UserAccount userAccount) {
+  public static void writeThrough(UserAccount userAccount) {
     if (cache.contains(userAccount.getUserId())) {
-      dbManager.updateDb(userAccount);
+      DbManager.updateDb(userAccount);
     } else {
-      dbManager.writeToDb(userAccount);
+      DbManager.writeToDb(userAccount);
     }
     cache.set(userAccount.getUserId(), userAccount);
   }
 
-  public void writeAround(final UserAccount userAccount) {
-    if (cache.contains(userAccount.getUserId())) {
-      dbManager.updateDb(userAccount);
-      // Cache data has been updated -- remove older
-      cache.invalidate(userAccount.getUserId());
-      // version from cache.
-    } else {
-      dbManager.writeToDb(userAccount);
-    }
-  }
-
   public static void clearCache() {
     if (cache != null) {
       cache.clear();
@@ -225,39 +225,34 @@ class.
 public final class AppManager {
 
   private static CachingPolicy cachingPolicy;
-  private final DbManager dbManager;
-  private final CacheStore cacheStore;
 
   private AppManager() {
   }
 
-  public void initDb() { /* ... */ }
+  public static void initDb(boolean useMongoDb) { /* ... */ }
 
   public static void initCachingPolicy(CachingPolicy policy) { /* ... */ }
 
   public static void initCacheCapacity(int capacity) { /* ... */ }
 
-  public UserAccount find(final String userId) {
+  public static UserAccount find(String userId) {
-    LOGGER.info("Trying to find {} in cache", userId);
+    if (cachingPolicy == CachingPolicy.THROUGH || cachingPolicy == CachingPolicy.AROUND) {
-    if (cachingPolicy == CachingPolicy.THROUGH
+      return CacheStore.readThrough(userId);
-            || cachingPolicy == CachingPolicy.AROUND) {
-      return cacheStore.readThrough(userId);
     } else if (cachingPolicy == CachingPolicy.BEHIND) {
-      return cacheStore.readThroughWithWriteBackPolicy(userId);
+      return CacheStore.readThroughWithWriteBackPolicy(userId);
     } else if (cachingPolicy == CachingPolicy.ASIDE) {
       return findAside(userId);
     }
     return null;
   }
 
-  public void save(final UserAccount userAccount) {
+  public static void save(UserAccount userAccount) {
-    LOGGER.info("Save record!");
     if (cachingPolicy == CachingPolicy.THROUGH) {
-      cacheStore.writeThrough(userAccount);
+      CacheStore.writeThrough(userAccount);
     } else if (cachingPolicy == CachingPolicy.AROUND) {
-      cacheStore.writeAround(userAccount);
+      CacheStore.writeAround(userAccount);
     } else if (cachingPolicy == CachingPolicy.BEHIND) {
-      cacheStore.writeBehind(userAccount);
+      CacheStore.writeBehind(userAccount);
     } else if (cachingPolicy == CachingPolicy.ASIDE) {
       saveAside(userAccount);
     }
@@ -277,35 +272,24 @@ Here is what we do in the main class of the application.
 @Slf4j
 public class App {
 
-  public static void main(final String[] args) {
+  public static void main(String[] args) {
-    boolean isDbMongo = isDbMongo(args);
+    AppManager.initDb(false);
-    if(isDbMongo){
+    AppManager.initCacheCapacity(3);
-      LOGGER.info("Using the Mongo database engine to run the application.");
+    var app = new App();
-    } else {
-      LOGGER.info("Using the 'in Memory' database to run the application.");
-    }
-    App app = new App(isDbMongo);
     app.useReadAndWriteThroughStrategy();
-    String splitLine = "==============================================";
-    LOGGER.info(splitLine);
     app.useReadThroughAndWriteAroundStrategy();
-    LOGGER.info(splitLine);
     app.useReadThroughAndWriteBehindStrategy();
-    LOGGER.info(splitLine);
     app.useCacheAsideStategy();
-    LOGGER.info(splitLine);
   }
 
   public void useReadAndWriteThroughStrategy() {
     LOGGER.info("# CachingPolicy.THROUGH");
-    appManager.initCachingPolicy(CachingPolicy.THROUGH);
+    AppManager.initCachingPolicy(CachingPolicy.THROUGH);
-
     var userAccount1 = new UserAccount("001", "John", "He is a boy.");
-
+    AppManager.save(userAccount1);
-    appManager.save(userAccount1);
+    LOGGER.info(AppManager.printCacheContent());
-    LOGGER.info(appManager.printCacheContent());
+    AppManager.find("001");
-    appManager.find("001");
+    AppManager.find("001");
-    appManager.find("001");
   }
 
   public void useReadThroughAndWriteAroundStrategy() { /* ... */ }
@@ -316,6 +300,16 @@ public class App {
 }
 ```
 
+Finally, here is some of the console output from the program.
+
+```
+12:32:53.845 [main] INFO com.iluwatar.caching.App - # CachingPolicy.THROUGH
+12:32:53.900 [main] INFO com.iluwatar.caching.App - 
+--CACHE CONTENT--
+UserAccount(userId=001, userName=John, additionalInfo=He is a boy.)
+----
+```
+
 ## Class diagram
 
 ![alt text](./etc/caching.png "Caching")

caching/docker-compose.yml

@@ -1,11 +0,0 @@
-version: '3.7'
-services:
-  mongodb_container:
-    image: mongo:latest
-    environment:
-      MONGO_INITDB_ROOT_USERNAME: root
-      MONGO_INITDB_ROOT_PASSWORD: rootpassword
-    ports:
-      - 27017:27017
-    volumes:
-      - ./mongo-data/:/data/db

caching/pom.xml

@@ -39,21 +39,19 @@
       <scope>test</scope>
     </dependency>
     <dependency>
-      <groupId>org.mockito</groupId>
+      <groupId>org.mongodb</groupId>
-      <artifactId>mockito-junit-jupiter</artifactId>
+      <artifactId>mongodb-driver</artifactId>
-      <version>3.12.4</version>
+      <version>3.12.1</version>
-      <scope>test</scope>
-    </dependency>
-    <dependency>
-      <groupId>org.mockito</groupId>
-      <artifactId>mockito-all</artifactId>
-      <version>1.10.19</version>
-      <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>org.mongodb</groupId>
-      <artifactId>mongo-java-driver</artifactId>
+      <artifactId>mongodb-driver-core</artifactId>
-      <version>3.4.1</version>
+      <version>3.0.4</version>
+    </dependency>
+    <dependency>
+      <groupId>org.mongodb</groupId>
+      <artifactId>bson</artifactId>
+      <version>3.0.4</version>
     </dependency>
   </dependencies>
   <!--

caching/src/main/java/com/iluwatar/caching/App.java

@@ -1,62 +1,58 @@
+/*
+ * 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.caching;
 
-import com.iluwatar.caching.database.DbManager;
-import com.iluwatar.caching.database.DbManagerFactory;
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * The Caching pattern describes how to avoid expensive re-acquisition of
+ * The Caching pattern describes how to avoid expensive re-acquisition of resources by not releasing
- * resources by not releasing the resources immediately after their use.
+ * the resources immediately after their use. The resources retain their identity, are kept in some
- * The resources retain their identity, are kept in some fast-access storage,
+ * fast-access storage, and are re-used to avoid having to acquire them again. There are four main
- * and are re-used to avoid having to acquire them again. There are four main
+ * caching strategies/techniques in this pattern; each with their own pros and cons. They are;
- * caching strategies/techniques in this pattern; each with their own pros and
+ * <code>write-through</code> which writes data to the cache and DB in a single transaction,
- * cons. They are <code>write-through</code> which writes data to the cache and
+ * <code>write-around</code> which writes data immediately into the DB instead of the cache,
- * DB in a single transaction, <code>write-around</code> which writes data
+ * <code>write-behind</code> which writes data into the cache initially whilst the data is only
- * immediately into the DB instead of the cache, <code>write-behind</code>
+ * written into the DB when the cache is full, and <code>cache-aside</code> which pushes the
- * which writes data into the cache initially whilst the data is only
+ * responsibility of keeping the data synchronized in both data sources to the application itself.
- * written into the DB when the cache is full, and <code>cache-aside</code>
+ * The <code>read-through</code> strategy is also included in the mentioned four strategies --
- * which pushes the responsibility of keeping the data synchronized in both
+ * returns data from the cache to the caller <b>if</b> it exists <b>else</b> queries from DB and
- * data sources to the application itself. The <code>read-through</code>
+ * stores it into the cache for future use. These strategies determine when the data in the cache
- * strategy is also included in the mentioned four strategies --
+ * should be written back to the backing store (i.e. Database) and help keep both data sources
- * returns data from the cache to the caller <b>if</b> it exists <b>else</b>
+ * synchronized/up-to-date. This pattern can improve performance and also helps to maintain
- * queries from DB and stores it into the cache for future use. These strategies
+ * consistency between data held in the cache and the data in the underlying data store.
- * determine when the data in the cache should be written back to the backing
- * store (i.e. Database) and help keep both data sources
- * synchronized/up-to-date. This pattern can improve performance and also helps
- * to maintainconsistency between data held in the cache and the data in
- * the underlying data store.
  *
- * <p>In this example, the user account ({@link UserAccount}) entity is used
+ * <p>In this example, the user account ({@link UserAccount}) entity is used as the underlying
- * as the underlying application data. The cache itself is implemented as an
+ * application data. The cache itself is implemented as an internal (Java) data structure. It adopts
- * internal (Java) data structure. It adopts a Least-Recently-Used (LRU)
+ * a Least-Recently-Used (LRU) strategy for evicting data from itself when its full. The four
- * strategy for evicting data from itself when its full. The four
+ * strategies are individually tested. The testing of the cache is restricted towards saving and
- * strategies are individually tested. The testing of the cache is restricted
+ * querying of user accounts from the underlying data store ( {@link DbManager}). The main class (
- * towards saving and querying of user accounts from the
+ * {@link App} is not aware of the underlying mechanics of the application (i.e. save and query) and
- * underlying data store( {@link DbManager}). The main class ( {@link App}
+ * whether the data is coming from the cache or the DB (i.e. separation of concern). The AppManager
- * is not aware of the underlying mechanics of the application
+ * ({@link AppManager}) handles the transaction of data to-and-from the underlying data store
- * (i.e. save and query) and whether the data is coming from the cache or the
+ * (depending on the preferred caching policy/strategy).
- * DB (i.e. separation of concern). The AppManager ({@link AppManager}) handles
- * the transaction of data to-and-from the underlying data store (depending on
- * the preferred caching policy/strategy).
  * <p>
- * <i>{@literal App --> AppManager --> CacheStore/LRUCache/CachingPolicy -->
+ * <i>{@literal App --> AppManager --> CacheStore/LRUCache/CachingPolicy --> DBManager} </i>
- * DBManager} </i>
- * </p>
- *
- * <p>
- * There are 2 ways to launch the application.
- *  - to use "in Memory" database.
- *  - to use the MongoDb as a database
- *
- * To run the application with "in Memory" database, just launch it without parameters
- * Example: 'java -jar app.jar'
- *
- * To run the application with MongoDb you need to be installed the MongoDb
- * in your system, or to launch it in the docker container.
- * You may launch docker container from the root of current module with command:
- * 'docker-compose up'
- * Then you can start the application with parameter --mongo
- * Example: 'java -jar app.jar --mongo'
  * </p>
  *
  * @see CacheStore
@@ -65,67 +61,23 @@ import lombok.extern.slf4j.Slf4j;
  */
 @Slf4j
 public class App {
-  /**
-   * Constant parameter name to use mongoDB.
-   */
-  private static final String USE_MONGO_DB = "--mongo";
-  /**
-   * Application manager.
-   */
-  private final AppManager appManager;
-
-  /**
-   * Constructor of current App.
-   *
-   * @param isMongo boolean
-   */
-  public App(final boolean isMongo) {
-    DbManager dbManager = DbManagerFactory.initDb(isMongo);
-    appManager = new AppManager(dbManager);
-    appManager.initDb();
-  }
 
   /**
    * Program entry point.
    *
    * @param args command line args
    */
-  public static void main(final String[] args) {
+  public static void main(String[] args) {
-    // VirtualDB (instead of MongoDB) was used in running the JUnit tests
+    AppManager.initDb(false); // VirtualDB (instead of MongoDB) was used in running the JUnit tests
     // and the App class to avoid Maven compilation errors. Set flag to
     // true to run the tests with MongoDB (provided that MongoDB is
     // installed and socket connection is open).
-    boolean isDbMongo = isDbMongo(args);
+    AppManager.initCacheCapacity(3);
-    if (isDbMongo) {
+    var app = new App();
-      LOGGER.info("Using the Mongo database engine to run the application.");
-    } else {
-      LOGGER.info("Using the 'in Memory' database to run the application.");
-    }
-    App app = new App(isDbMongo);
     app.useReadAndWriteThroughStrategy();
-    String splitLine = "==============================================";
-    LOGGER.info(splitLine);
     app.useReadThroughAndWriteAroundStrategy();
-    LOGGER.info(splitLine);
     app.useReadThroughAndWriteBehindStrategy();
-    LOGGER.info(splitLine);
     app.useCacheAsideStategy();
-    LOGGER.info(splitLine);
-  }
-
-  /**
-   * Check the input parameters. if
-   *
-   * @param args input params
-   * @return true if there is "--mongo" parameter in arguments
-   */
-  private static boolean isDbMongo(final String[] args) {
-    for (String arg : args) {
-      if (arg.equals(USE_MONGO_DB)) {
-        return true;
-      }
-    }
-    return false;
   }
 
   /**
@@ -133,14 +85,14 @@ public class App {
    */
   public void useReadAndWriteThroughStrategy() {
     LOGGER.info("# CachingPolicy.THROUGH");
-    appManager.initCachingPolicy(CachingPolicy.THROUGH);
+    AppManager.initCachingPolicy(CachingPolicy.THROUGH);
 
     var userAccount1 = new UserAccount("001", "John", "He is a boy.");
 
-    appManager.save(userAccount1);
+    AppManager.save(userAccount1);
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.find("001");
+    AppManager.find("001");
-    appManager.find("001");
+    AppManager.find("001");
   }
 
   /**
@@ -148,21 +100,21 @@ public class App {
    */
   public void useReadThroughAndWriteAroundStrategy() {
     LOGGER.info("# CachingPolicy.AROUND");
-    appManager.initCachingPolicy(CachingPolicy.AROUND);
+    AppManager.initCachingPolicy(CachingPolicy.AROUND);
 
     var userAccount2 = new UserAccount("002", "Jane", "She is a girl.");
 
-    appManager.save(userAccount2);
+    AppManager.save(userAccount2);
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.find("002");
+    AppManager.find("002");
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    userAccount2 = appManager.find("002");
+    userAccount2 = AppManager.find("002");
     userAccount2.setUserName("Jane G.");
-    appManager.save(userAccount2);
+    AppManager.save(userAccount2);
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.find("002");
+    AppManager.find("002");
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.find("002");
+    AppManager.find("002");
   }
 
   /**
@@ -170,31 +122,23 @@ public class App {
    */
   public void useReadThroughAndWriteBehindStrategy() {
     LOGGER.info("# CachingPolicy.BEHIND");
-    appManager.initCachingPolicy(CachingPolicy.BEHIND);
+    AppManager.initCachingPolicy(CachingPolicy.BEHIND);
 
-    var userAccount3 = new UserAccount("003",
+    var userAccount3 = new UserAccount("003", "Adam", "He likes food.");
-            "Adam",
+    var userAccount4 = new UserAccount("004", "Rita", "She hates cats.");
-            "He likes food.");
+    var userAccount5 = new UserAccount("005", "Isaac", "He is allergic to mustard.");
-    var userAccount4 = new UserAccount("004",
-            "Rita",
-            "She hates cats.");
-    var userAccount5 = new UserAccount("005",
-            "Isaac",
-            "He is allergic to mustard.");
 
-    appManager.save(userAccount3);
+    AppManager.save(userAccount3);
-    appManager.save(userAccount4);
+    AppManager.save(userAccount4);
-    appManager.save(userAccount5);
+    AppManager.save(userAccount5);
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.find("003");
+    AppManager.find("003");
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    UserAccount userAccount6 = new UserAccount("006",
+    UserAccount userAccount6 = new UserAccount("006", "Yasha", "She is an only child.");
-            "Yasha",
+    AppManager.save(userAccount6);
-            "She is an only child.");
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.save(userAccount6);
+    AppManager.find("004");
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.find("004");
-    LOGGER.info(appManager.printCacheContent());
   }
 
   /**
@@ -202,26 +146,20 @@ public class App {
    */
   public void useCacheAsideStategy() {
     LOGGER.info("# CachingPolicy.ASIDE");
-    appManager.initCachingPolicy(CachingPolicy.ASIDE);
+    AppManager.initCachingPolicy(CachingPolicy.ASIDE);
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
 
-    var userAccount3 = new UserAccount("003",
+    var userAccount3 = new UserAccount("003", "Adam", "He likes food.");
-            "Adam",
+    var userAccount4 = new UserAccount("004", "Rita", "She hates cats.");
-            "He likes food.");
+    var userAccount5 = new UserAccount("005", "Isaac", "He is allergic to mustard.");
-    var userAccount4 = new UserAccount("004",
+    AppManager.save(userAccount3);
-            "Rita",
+    AppManager.save(userAccount4);
-            "She hates cats.");
+    AppManager.save(userAccount5);
-    var userAccount5 = new UserAccount("005",
-            "Isaac",
-            "He is allergic to mustard.");
-    appManager.save(userAccount3);
-    appManager.save(userAccount4);
-    appManager.save(userAccount5);
 
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.find("003");
+    AppManager.find("003");
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
-    appManager.find("004");
+    AppManager.find("004");
-    LOGGER.info(appManager.printCacheContent());
+    LOGGER.info(AppManager.printCacheContent());
   }
 }

caching/src/main/java/com/iluwatar/caching/AppManager.java

@@ -23,80 +23,65 @@
 
 package com.iluwatar.caching;
 
-import com.iluwatar.caching.database.DbManager;
+import java.text.ParseException;
-
 import java.util.Optional;
-
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * AppManager helps to bridge the gap in communication between the main class
+ * AppManager helps to bridge the gap in communication between the main class and the application's
- * and the application's back-end. DB connection is initialized through this
+ * back-end. DB connection is initialized through this class. The chosen caching strategy/policy is
- * class. The chosen  caching strategy/policy is also initialized here.
+ * also initialized here. Before the cache can be used, the size of the cache has to be set.
- * Before the cache can be used, the size of the  cache has to be set.
+ * Depending on the chosen caching policy, AppManager will call the appropriate function in the
- * Depending on the chosen caching policy, AppManager will call the
+ * CacheStore class.
- * appropriate function in the CacheStore class.
  */
 @Slf4j
-public class AppManager {
+public final class AppManager {
-  /**
-   * Caching Policy.
-   */
-  private CachingPolicy cachingPolicy;
-  /**
-   * Database Manager.
-   */
-  private final DbManager dbManager;
-  /**
-   * Cache Store.
-   */
-  private final CacheStore cacheStore;
 
-  /**
+  private static CachingPolicy cachingPolicy;
-   * Constructor.
+
-   *
+  private AppManager() {
-   * @param newDbManager database manager
-   */
-  public AppManager(final DbManager newDbManager) {
-    this.dbManager = newDbManager;
-    this.cacheStore = new CacheStore(newDbManager);
   }
 
   /**
-   * Developer/Tester is able to choose whether the application should use
+   * Developer/Tester is able to choose whether the application should use MongoDB as its underlying
-   * MongoDB as its underlying data storage or a simple Java data structure
+   * data storage or a simple Java data structure to (temporarily) store the data/objects during
-   * to (temporarily) store the data/objects during runtime.
+   * runtime.
    */
-  public void initDb() {
+  public static void initDb(boolean useMongoDb) {
-    dbManager.connect();
+    if (useMongoDb) {
+      try {
+        DbManager.connect();
+      } catch (ParseException e) {
+        LOGGER.error("Error connecting to MongoDB", e);
+      }
+    } else {
+      DbManager.createVirtualDb();
+    }
   }
 
   /**
    * Initialize caching policy.
-   *
-   * @param policy is a {@link CachingPolicy}
    */
-  public void initCachingPolicy(final CachingPolicy policy) {
+  public static void initCachingPolicy(CachingPolicy policy) {
     cachingPolicy = policy;
     if (cachingPolicy == CachingPolicy.BEHIND) {
-      Runtime.getRuntime().addShutdownHook(new Thread(cacheStore::flushCache));
+      Runtime.getRuntime().addShutdownHook(new Thread(CacheStore::flushCache));
     }
-    cacheStore.clearCache();
+    CacheStore.clearCache();
+  }
+
+  public static void initCacheCapacity(int capacity) {
+    CacheStore.initCapacity(capacity);
   }
 
   /**
    * Find user account.
-   *
-   * @param userId String
-   * @return {@link UserAccount}
    */
-  public UserAccount find(final String userId) {
+  public static UserAccount find(String userId) {
-    LOGGER.info("Trying to find {} in cache", userId);
+    if (cachingPolicy == CachingPolicy.THROUGH || cachingPolicy == CachingPolicy.AROUND) {
-    if (cachingPolicy == CachingPolicy.THROUGH
+      return CacheStore.readThrough(userId);
-            || cachingPolicy == CachingPolicy.AROUND) {
-      return cacheStore.readThrough(userId);
     } else if (cachingPolicy == CachingPolicy.BEHIND) {
-      return cacheStore.readThroughWithWriteBackPolicy(userId);
+      return CacheStore.readThroughWithWriteBackPolicy(userId);
     } else if (cachingPolicy == CachingPolicy.ASIDE) {
       return findAside(userId);
     }
@@ -105,55 +90,41 @@ public class AppManager {
 
   /**
    * Save user account.
-   *
-   * @param userAccount {@link UserAccount}
    */
-  public void save(final UserAccount userAccount) {
+  public static void save(UserAccount userAccount) {
-    LOGGER.info("Save record!");
     if (cachingPolicy == CachingPolicy.THROUGH) {
-      cacheStore.writeThrough(userAccount);
+      CacheStore.writeThrough(userAccount);
     } else if (cachingPolicy == CachingPolicy.AROUND) {
-      cacheStore.writeAround(userAccount);
+      CacheStore.writeAround(userAccount);
     } else if (cachingPolicy == CachingPolicy.BEHIND) {
-      cacheStore.writeBehind(userAccount);
+      CacheStore.writeBehind(userAccount);
     } else if (cachingPolicy == CachingPolicy.ASIDE) {
       saveAside(userAccount);
     }
   }
 
-  /**
+  public static String printCacheContent() {
-   * Returns String.
+    return CacheStore.print();
-   *
-   * @return String
-   */
-  public String printCacheContent() {
-    return cacheStore.print();
   }
 
   /**
    * Cache-Aside save user account helper.
-   *
-   * @param userAccount {@link UserAccount}
    */
-  private void saveAside(final UserAccount userAccount) {
+  private static void saveAside(UserAccount userAccount) {
-    dbManager.updateDb(userAccount);
+    DbManager.updateDb(userAccount);
-    cacheStore.invalidate(userAccount.getUserId());
+    CacheStore.invalidate(userAccount.getUserId());
   }
 
   /**
    * Cache-Aside find user account helper.
-   *
-   * @param userId String
-   * @return {@link UserAccount}
    */
-  private UserAccount findAside(final String userId) {
+  private static UserAccount findAside(String userId) {
-    return Optional.ofNullable(cacheStore.get(userId))
+    return Optional.ofNullable(CacheStore.get(userId))
-            .or(() -> {
+        .or(() -> {
-              Optional<UserAccount> userAccount =
+          Optional<UserAccount> userAccount = Optional.ofNullable(DbManager.readFromDb(userId));
-                      Optional.ofNullable(dbManager.readFromDb(userId));
+          userAccount.ifPresent(account -> CacheStore.set(userId, account));
-              userAccount.ifPresent(account -> cacheStore.set(userId, account));
+          return userAccount;
-              return userAccount;
+        })
-            })
+        .orElse(null);
-            .orElse(null);
   }
 }

caching/src/main/java/com/iluwatar/caching/CacheStore.java

@@ -23,11 +23,9 @@
 
 package com.iluwatar.caching;
 
-import com.iluwatar.caching.database.DbManager;
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Collectors;
-
 import lombok.extern.slf4j.Slf4j;
 
 /**
@@ -35,34 +33,16 @@ import lombok.extern.slf4j.Slf4j;
  */
 @Slf4j
 public class CacheStore {
-  /**
-   * Cache capacity.
-   */
-  private static final int CAPACITY = 3;
 
-  /**
+  private static LruCache cache;
-   * Lru cache see {@link LruCache}.
-   */
-  private LruCache cache;
-  /**
-   * DbManager.
-   */
-  private final DbManager dbManager;
 
-  /**
+  private CacheStore() {
-   * Cache Store.
-   * @param dataBaseManager {@link DbManager}
-   */
-  public CacheStore(final DbManager dataBaseManager) {
-    this.dbManager = dataBaseManager;
-    initCapacity(CAPACITY);
   }
 
   /**
    * Init cache capacity.
-   * @param capacity int
    */
-  public void initCapacity(final int capacity) {
+  public static void initCapacity(int capacity) {
     if (cache == null) {
       cache = new LruCache(capacity);
     } else {
@@ -72,64 +52,57 @@ public class CacheStore {
 
   /**
    * Get user account using read-through cache.
-   * @param userId {@link String}
-   * @return {@link UserAccount}
    */
-  public UserAccount readThrough(final String userId) {
+  public static UserAccount readThrough(String userId) {
     if (cache.contains(userId)) {
-      LOGGER.info("# Found in Cache!");
+      LOGGER.info("# Cache Hit!");
       return cache.get(userId);
     }
-    LOGGER.info("# Not found in cache! Go to DB!!");
+    LOGGER.info("# Cache Miss!");
-    UserAccount userAccount = dbManager.readFromDb(userId);
+    UserAccount userAccount = DbManager.readFromDb(userId);
     cache.set(userId, userAccount);
     return userAccount;
   }
 
   /**
    * Get user account using write-through cache.
-   * @param userAccount {@link UserAccount}
    */
-  public void writeThrough(final UserAccount userAccount) {
+  public static void writeThrough(UserAccount userAccount) {
     if (cache.contains(userAccount.getUserId())) {
-      dbManager.updateDb(userAccount);
+      DbManager.updateDb(userAccount);
     } else {
-      dbManager.writeToDb(userAccount);
+      DbManager.writeToDb(userAccount);
     }
     cache.set(userAccount.getUserId(), userAccount);
   }
 
   /**
    * Get user account using write-around cache.
-   * @param userAccount {@link UserAccount}
    */
-  public void writeAround(final UserAccount userAccount) {
+  public static void writeAround(UserAccount userAccount) {
     if (cache.contains(userAccount.getUserId())) {
-      dbManager.updateDb(userAccount);
+      DbManager.updateDb(userAccount);
-      // Cache data has been updated -- remove older
+      cache.invalidate(userAccount.getUserId()); // Cache data has been updated -- remove older
-      cache.invalidate(userAccount.getUserId());
       // version from cache.
     } else {
-      dbManager.writeToDb(userAccount);
+      DbManager.writeToDb(userAccount);
     }
   }
 
   /**
    * Get user account using read-through cache with write-back policy.
-   * @param userId {@link String}
-   * @return {@link UserAccount}
    */
-  public UserAccount readThroughWithWriteBackPolicy(final String userId) {
+  public static UserAccount readThroughWithWriteBackPolicy(String userId) {
     if (cache.contains(userId)) {
-      LOGGER.info("# Found in cache!");
+      LOGGER.info("# Cache Hit!");
       return cache.get(userId);
     }
-    LOGGER.info("# Not found in Cache!");
+    LOGGER.info("# Cache Miss!");
-    UserAccount userAccount = dbManager.readFromDb(userId);
+    UserAccount userAccount = DbManager.readFromDb(userId);
     if (cache.isFull()) {
       LOGGER.info("# Cache is FULL! Writing LRU data to DB...");
       UserAccount toBeWrittenToDb = cache.getLruData();
-      dbManager.upsertDb(toBeWrittenToDb);
+      DbManager.upsertDb(toBeWrittenToDb);
     }
     cache.set(userId, userAccount);
     return userAccount;
@@ -137,13 +110,12 @@ public class CacheStore {
 
   /**
    * Set user account.
-   * @param userAccount {@link UserAccount}
    */
-  public void writeBehind(final UserAccount userAccount) {
+  public static void writeBehind(UserAccount userAccount) {
     if (cache.isFull() && !cache.contains(userAccount.getUserId())) {
       LOGGER.info("# Cache is FULL! Writing LRU data to DB...");
       UserAccount toBeWrittenToDb = cache.getLruData();
-      dbManager.upsertDb(toBeWrittenToDb);
+      DbManager.upsertDb(toBeWrittenToDb);
     }
     cache.set(userAccount.getUserId(), userAccount);
   }
@@ -151,7 +123,7 @@ public class CacheStore {
   /**
    * Clears cache.
    */
-  public void clearCache() {
+  public static void clearCache() {
     if (cache != null) {
       cache.clear();
     }
@@ -160,51 +132,44 @@ public class CacheStore {
   /**
    * Writes remaining content in the cache into the DB.
    */
-  public void flushCache() {
+  public static void flushCache() {
     LOGGER.info("# flushCache...");
     Optional.ofNullable(cache)
         .map(LruCache::getCacheDataInListForm)
         .orElse(List.of())
-        .forEach(dbManager::updateDb);
+        .forEach(DbManager::updateDb);
-    dbManager.disconnect();
   }
 
   /**
    * Print user accounts.
-   * @return {@link String}
    */
-  public String print() {
+  public static String print() {
     return Optional.ofNullable(cache)
         .map(LruCache::getCacheDataInListForm)
         .orElse(List.of())
         .stream()
         .map(userAccount -> userAccount.toString() + "\n")
-        .collect(Collectors.joining("", "\n--CACHE CONTENT--\n", "----"));
+        .collect(Collectors.joining("", "\n--CACHE CONTENT--\n", "----\n"));
   }
 
   /**
    * Delegate to backing cache store.
-   * @param userId {@link String}
-   * @return {@link UserAccount}
    */
-  public UserAccount get(final String userId) {
+  public static UserAccount get(String userId) {
     return cache.get(userId);
   }
 
   /**
    * Delegate to backing cache store.
-   * @param userId {@link String}
-   * @param userAccount {@link UserAccount}
    */
-  public void set(final String userId, final UserAccount userAccount) {
+  public static void set(String userId, UserAccount userAccount) {
     cache.set(userId, userAccount);
   }
 
   /**
    * Delegate to backing cache store.
-   * @param userId {@link String}
    */
-  public void invalidate(final String userId) {
+  public static void invalidate(String userId) {
     cache.invalidate(userId);
   }
 }

caching/src/main/java/com/iluwatar/caching/CachingPolicy.java

@@ -32,25 +32,10 @@ import lombok.Getter;
 @AllArgsConstructor
 @Getter
 public enum CachingPolicy {
-  /**
-   * Through.
-   */
   THROUGH("through"),
-  /**
-   * AROUND.
-   */
   AROUND("around"),
-  /**
-   * BEHIND.
-   */
   BEHIND("behind"),
-  /**
-   * ASIDE.
-   */
   ASIDE("aside");
 
-  /**
-   * Policy value.
-   */
   private final String policy;
 }

caching/src/main/java/com/iluwatar/caching/DbManager.java

@@ -0,0 +1,172 @@
+/*
+ * 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.caching;
+
+import com.iluwatar.caching.constants.CachingConstants;
+import com.mongodb.MongoClient;
+import com.mongodb.client.MongoDatabase;
+import com.mongodb.client.model.UpdateOptions;
+import java.text.ParseException;
+import java.util.HashMap;
+import java.util.Map;
+import lombok.extern.slf4j.Slf4j;
+import org.bson.Document;
+
+/**
+ * <p>DBManager handles the communication with the underlying data store i.e. Database. It contains
+ * the implemented methods for querying, inserting, and updating data. MongoDB was used as the
+ * database for the application.</p>
+ *
+ * <p>Developer/Tester is able to choose whether the application should use MongoDB as its
+ * underlying data storage (connect()) or a simple Java data structure to (temporarily) store the
+ * data/objects during runtime (createVirtualDB()).</p>
+ */
+@Slf4j
+public final class DbManager {
+
+  private static MongoClient mongoClient;
+  private static MongoDatabase db;
+  private static boolean useMongoDB;
+
+  private static Map<String, UserAccount> virtualDB;
+  private static final String ERROR_MESSAGE_LOG = "Error connecting to MongoDB";
+
+  private DbManager() {
+  }
+
+  /**
+   * Create DB.
+   */
+  public static void createVirtualDb() {
+    useMongoDB = false;
+    virtualDB = new HashMap<>();
+  }
+
+  /**
+   * Connect to DB.
+   */
+  public static void connect() throws ParseException {
+    useMongoDB = true;
+    mongoClient = new MongoClient();
+    db = mongoClient.getDatabase("test");
+  }
+
+  /**
+   * Read user account from DB.
+   */
+  public static UserAccount readFromDb(String userId) {
+    if (!useMongoDB) {
+      if (virtualDB.containsKey(userId)) {
+        return virtualDB.get(userId);
+      }
+      return null;
+    }
+    if (db == null) {
+      try {
+        connect();
+      } catch (ParseException e) {
+        LOGGER.error(ERROR_MESSAGE_LOG, e);
+      }
+    }
+    var iterable = db
+        .getCollection(CachingConstants.USER_ACCOUNT)
+        .find(new Document(CachingConstants.USER_ID, userId));
+    if (iterable == null) {
+      return null;
+    }
+    Document doc = iterable.first();
+    String userName = doc.getString(CachingConstants.USER_NAME);
+    String appInfo = doc.getString(CachingConstants.ADD_INFO);
+    return new UserAccount(userId, userName, appInfo);
+  }
+
+  /**
+   * Write user account to DB.
+   */
+  public static void writeToDb(UserAccount userAccount) {
+    if (!useMongoDB) {
+      virtualDB.put(userAccount.getUserId(), userAccount);
+      return;
+    }
+    if (db == null) {
+      try {
+        connect();
+      } catch (ParseException e) {
+        LOGGER.error(ERROR_MESSAGE_LOG, e);
+      }
+    }
+    db.getCollection(CachingConstants.USER_ACCOUNT).insertOne(
+        new Document(CachingConstants.USER_ID, userAccount.getUserId())
+            .append(CachingConstants.USER_NAME, userAccount.getUserName())
+            .append(CachingConstants.ADD_INFO, userAccount.getAdditionalInfo())
+    );
+  }
+
+  /**
+   * Update DB.
+   */
+  public static void updateDb(UserAccount userAccount) {
+    if (!useMongoDB) {
+      virtualDB.put(userAccount.getUserId(), userAccount);
+      return;
+    }
+    if (db == null) {
+      try {
+        connect();
+      } catch (ParseException e) {
+        LOGGER.error(ERROR_MESSAGE_LOG, e);
+      }
+    }
+    db.getCollection(CachingConstants.USER_ACCOUNT).updateOne(
+        new Document(CachingConstants.USER_ID, userAccount.getUserId()),
+        new Document("$set", new Document(CachingConstants.USER_NAME, userAccount.getUserName())
+            .append(CachingConstants.ADD_INFO, userAccount.getAdditionalInfo())));
+  }
+
+  /**
+   * Insert data into DB if it does not exist. Else, update it.
+   */
+  public static void upsertDb(UserAccount userAccount) {
+    if (!useMongoDB) {
+      virtualDB.put(userAccount.getUserId(), userAccount);
+      return;
+    }
+    if (db == null) {
+      try {
+        connect();
+      } catch (ParseException e) {
+        LOGGER.error(ERROR_MESSAGE_LOG, e);
+      }
+    }
+    db.getCollection(CachingConstants.USER_ACCOUNT).updateOne(
+        new Document(CachingConstants.USER_ID, userAccount.getUserId()),
+        new Document("$set",
+            new Document(CachingConstants.USER_ID, userAccount.getUserId())
+                .append(CachingConstants.USER_NAME, userAccount.getUserName())
+                .append(CachingConstants.ADD_INFO, userAccount.getAdditionalInfo())
+        ),
+        new UpdateOptions().upsert(true)
+    );
+  }
+}

caching/src/main/java/com/iluwatar/caching/LruCache.java

@@ -29,83 +29,41 @@ import java.util.List;
 import java.util.Map;
 import lombok.extern.slf4j.Slf4j;
 
-
 /**
- * Data structure/implementation of the application's cache. The data structure
+ * Data structure/implementation of the application's cache. The data structure consists of a hash
- * consists of a hash table attached with a doubly linked-list. The linked-list
+ * table attached with a doubly linked-list. The linked-list helps in capturing and maintaining the
- * helps in capturing and maintaining the LRU data in the cache. When a data is
+ * LRU data in the cache. When a data is queried (from the cache), added (to the cache), or updated,
- * queried (from the cache), added (to the cache), or updated, the data is
+ * the data is moved to the front of the list to depict itself as the most-recently-used data. The
- * moved to the front of the list to depict itself as the most-recently-used
+ * LRU data is always at the end of the list.
- * data. The LRU data is always at the end of the list.
  */
 @Slf4j
 public class LruCache {
-  /**
-   * Static class Node.
-   */
-  static class Node {
-    /**
-     * user id.
-     */
-    private final String userId;
-    /**
-     * User Account.
-     */
-    private UserAccount userAccount;
-    /**
-     * previous.
-     */
-    private Node previous;
-    /**
-     * next.
-     */
-    private Node next;
 
-    /**
+  static class Node {
-     * Node definition.
+    String userId;
-     *
+    UserAccount userAccount;
-     * @param id      String
+    Node previous;
-     * @param account {@link UserAccount}
+    Node next;
-     */
+
-    Node(final String id, final UserAccount account) {
+    public Node(String userId, UserAccount userAccount) {
-      this.userId = id;
+      this.userId = userId;
-      this.userAccount = account;
+      this.userAccount = userAccount;
     }
   }
 
-  /**
+  int capacity;
-   * Capacity of Cache.
+  Map<String, Node> cache = new HashMap<>();
-   */
+  Node head;
-  private int capacity;
+  Node end;
-  /**
-   * Cache {@link HashMap}.
-   */
-  private Map<String, Node> cache = new HashMap<>();
-  /**
-   * Head.
-   */
-  private Node head;
-  /**
-   * End.
-   */
-  private Node end;
 
-  /**
+  public LruCache(int capacity) {
-   * Constructor.
+    this.capacity = capacity;
-   *
-   * @param cap Integer.
-   */
-  public LruCache(final int cap) {
-    this.capacity = cap;
   }
 
   /**
    * Get user account.
-   *
-   * @param userId String
-   * @return {@link UserAccount}
    */
-  public UserAccount get(final String userId) {
+  public UserAccount get(String userId) {
     if (cache.containsKey(userId)) {
       var node = cache.get(userId);
       remove(node);
@@ -117,10 +75,8 @@ public class LruCache {
 
   /**
    * Remove node from linked list.
-   *
-   * @param node {@link Node}
    */
-  public void remove(final Node node) {
+  public void remove(Node node) {
     if (node.previous != null) {
       node.previous.next = node.next;
     } else {
@@ -135,10 +91,8 @@ public class LruCache {
 
   /**
    * Move node to the front of the list.
-   *
-   * @param node {@link Node}
    */
-  public void setHead(final Node node) {
+  public void setHead(Node node) {
     node.next = head;
     node.previous = null;
     if (head != null) {
@@ -152,11 +106,8 @@ public class LruCache {
 
   /**
    * Set user account.
-   *
-   * @param userAccount {@link UserAccount}
-   * @param userId      {@link String}
    */
-  public void set(final String userId, final UserAccount userAccount) {
+  public void set(String userId, UserAccount userAccount) {
     if (cache.containsKey(userId)) {
       var old = cache.get(userId);
       old.userAccount = userAccount;
@@ -176,43 +127,25 @@ public class LruCache {
     }
   }
 
-  /**
+  public boolean contains(String userId) {
-   * Check if Cache contains the userId.
-   *
-   * @param userId {@link String}
-   * @return boolean
-   */
-  public boolean contains(final String userId) {
     return cache.containsKey(userId);
   }
 
   /**
    * Invalidate cache for user.
-   *
-   * @param userId {@link String}
    */
-  public void invalidate(final String userId) {
+  public void invalidate(String userId) {
     var toBeRemoved = cache.remove(userId);
     if (toBeRemoved != null) {
-      LOGGER.info("# {} has been updated! "
+      LOGGER.info("# {} has been updated! Removing older version from cache...", userId);
-              + "Removing older version from cache...", userId);
       remove(toBeRemoved);
     }
   }
 
-  /**
-   * Check if the cache is full.
-   * @return boolean
-   */
   public boolean isFull() {
     return cache.size() >= capacity;
   }
 
-  /**
-   * Get LRU data.
-   *
-   * @return {@link UserAccount}
-   */
   public UserAccount getLruData() {
     return end.userAccount;
   }
@@ -228,8 +161,6 @@ public class LruCache {
 
   /**
    * Returns cache data in list form.
-   *
-   * @return {@link List}
    */
   public List<UserAccount> getCacheDataInListForm() {
     var listOfCacheData = new ArrayList<UserAccount>();
@@ -243,14 +174,10 @@ public class LruCache {
 
   /**
    * Set cache capacity.
-   *
-   * @param newCapacity int
    */
-  public void setCapacity(final int newCapacity) {
+  public void setCapacity(int newCapacity) {
     if (capacity > newCapacity) {
-      // Behavior can be modified to accommodate
+      clear(); // Behavior can be modified to accommodate for decrease in cache size. For now, we'll
-      // for decrease in cache size. For now, we'll
-      clear();
       // just clear the cache.
     } else {
       this.capacity = newCapacity;

caching/src/main/java/com/iluwatar/caching/UserAccount.java

@@ -24,28 +24,19 @@
 package com.iluwatar.caching;
 
 import lombok.AllArgsConstructor;
-import lombok.Data;
+import lombok.Getter;
-import lombok.EqualsAndHashCode;
+import lombok.Setter;
 import lombok.ToString;
 
 /**
  * Entity class (stored in cache and DB) used in the application.
  */
-@Data
+@Setter
+@Getter
 @AllArgsConstructor
 @ToString
-@EqualsAndHashCode
 public class UserAccount {
-  /**
-   * User Id.
-   */
   private String userId;
-  /**
-   * User Name.
-   */
   private String userName;
-  /**
-   * Additional Info.
-   */
   private String additionalInfo;
 }

caching/src/main/java/com/iluwatar/caching/constants/CachingConstants.java

@@ -26,27 +26,11 @@ package com.iluwatar.caching.constants;
 /**
  * Constant class for defining constants.
  */
-public final class CachingConstants {
+public class CachingConstants {
-  /**
+
-   * User Account.
-   */
   public static final String USER_ACCOUNT = "user_accounts";
-  /**
-   * User ID.
-   */
   public static final String USER_ID = "userID";
-  /**
-   * User Name.
-   */
   public static final String USER_NAME = "userName";
-  /**
-   * Additional Info.
-   */
   public static final String ADD_INFO = "additionalInfo";
 
-  /**
-   * Constructor.
-   */
-  private CachingConstants() {
-  }
 }

caching/src/main/java/com/iluwatar/caching/constants/package-info.java

@@ -1,4 +0,0 @@
-/**
- * Constants.
- */
-package com.iluwatar.caching.constants;

caching/src/main/java/com/iluwatar/caching/database/DbManager.java

@@ -1,52 +0,0 @@
-package com.iluwatar.caching.database;
-
-import com.iluwatar.caching.UserAccount;
-
-/**
- * <p>DBManager handles the communication with the underlying data store i.e.
- * Database. It contains the implemented methods for querying, inserting,
- * and updating data. MongoDB was used as the database for the application.</p>
- */
-public interface DbManager {
-  /**
-   * Connect to DB.
-   */
-  void connect();
-
-  /**
-   * Disconnect from DB.
-   */
-  void disconnect();
-
-  /**
-   * Read from DB.
-   *
-   * @param userId {@link String}
-   * @return {@link UserAccount}
-   */
-  UserAccount readFromDb(String userId);
-
-  /**
-   * Write to DB.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  UserAccount writeToDb(UserAccount userAccount);
-
-  /**
-   * Update record.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  UserAccount updateDb(UserAccount userAccount);
-
-  /**
-   * Update record or Insert if not exists.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  UserAccount upsertDb(UserAccount userAccount);
-}

caching/src/main/java/com/iluwatar/caching/database/DbManagerFactory.java

@@ -1,25 +0,0 @@
-package com.iluwatar.caching.database;
-
-/**
- * Creates the database connection accroding the input parameter.
- */
-public final class DbManagerFactory {
-  /**
-   * Private constructor.
-   */
-  private DbManagerFactory() {
-  }
-
-  /**
-   * Init database.
-   *
-   * @param isMongo boolean
-   * @return {@link DbManager}
-   */
-  public static DbManager initDb(final boolean isMongo) {
-    if (isMongo) {
-      return new MongoDb();
-    }
-    return new VirtualDb();
-  }
-}

caching/src/main/java/com/iluwatar/caching/database/MongoDb.java

@@ -1,128 +0,0 @@
-package com.iluwatar.caching.database;
-
-import static com.iluwatar.caching.constants.CachingConstants.ADD_INFO;
-import static com.iluwatar.caching.constants.CachingConstants.USER_ACCOUNT;
-import static com.iluwatar.caching.constants.CachingConstants.USER_ID;
-import static com.iluwatar.caching.constants.CachingConstants.USER_NAME;
-
-import com.iluwatar.caching.UserAccount;
-import com.iluwatar.caching.constants.CachingConstants;
-import com.mongodb.MongoClient;
-import com.mongodb.MongoClientOptions;
-import com.mongodb.MongoCredential;
-import com.mongodb.ServerAddress;
-import com.mongodb.client.MongoDatabase;
-import com.mongodb.client.model.UpdateOptions;
-import java.util.List;
-import lombok.extern.slf4j.Slf4j;
-import org.bson.Document;
-
-/**
- * Implementation of DatabaseManager.
- * implements base methods to work with MongoDb.
- */
-@Slf4j
-public class MongoDb implements DbManager {
-  private static final String DATABASE_NAME = "admin";
-  private static final String MONGO_USER = "root";
-  private static final String MONGO_PASSWORD = "rootpassword";
-  private MongoClient client;
-  private MongoDatabase db;
-
-  /**
-   * Connect to Db. Check th connection
-   */
-  @Override
-  public void connect() {
-    MongoCredential mongoCredential = MongoCredential.createCredential(MONGO_USER,
-                    DATABASE_NAME,
-                    MONGO_PASSWORD.toCharArray());
-    MongoClientOptions options = MongoClientOptions.builder().build();
-    client = new MongoClient(new ServerAddress(), List.of(mongoCredential), options);
-    db = client.getDatabase(DATABASE_NAME);
-  }
-
-  @Override
-  public void disconnect() {
-    client.close();
-  }
-
-  /**
-   * Read data from DB.
-   *
-   * @param userId {@link String}
-   * @return {@link UserAccount}
-   */
-  @Override
-  public UserAccount readFromDb(final String userId) {
-    var iterable = db
-            .getCollection(CachingConstants.USER_ACCOUNT)
-            .find(new Document(USER_ID, userId));
-    if (iterable.first() == null) {
-      return null;
-    }
-    Document doc = iterable.first();
-    if (doc != null) {
-      String userName = doc.getString(USER_NAME);
-      String appInfo = doc.getString(ADD_INFO);
-      return new UserAccount(userId, userName, appInfo);
-    } else {
-      return null;
-    }
-  }
-
-  /**
-   * Write data to DB.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  @Override
-  public UserAccount writeToDb(final UserAccount userAccount) {
-    db.getCollection(USER_ACCOUNT).insertOne(
-            new Document(USER_ID, userAccount.getUserId())
-                    .append(USER_NAME, userAccount.getUserName())
-                    .append(ADD_INFO, userAccount.getAdditionalInfo())
-    );
-    return userAccount;
-  }
-
-  /**
-   * Update DB.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  @Override
-  public UserAccount updateDb(final UserAccount userAccount) {
-    Document id = new Document(USER_ID, userAccount.getUserId());
-    Document dataSet = new Document(USER_NAME, userAccount.getUserName())
-            .append(ADD_INFO, userAccount.getAdditionalInfo());
-    db.getCollection(CachingConstants.USER_ACCOUNT)
-            .updateOne(id, new Document("$set", dataSet));
-    return userAccount;
-  }
-
-  /**
-   * Update data if exists.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  @Override
-  public UserAccount upsertDb(final UserAccount userAccount) {
-    String userId = userAccount.getUserId();
-    String userName = userAccount.getUserName();
-    String additionalInfo = userAccount.getAdditionalInfo();
-    db.getCollection(CachingConstants.USER_ACCOUNT).updateOne(
-            new Document(USER_ID, userId),
-            new Document("$set",
-                    new Document(USER_ID, userId)
-                            .append(USER_NAME, userName)
-                            .append(ADD_INFO, additionalInfo)
-            ),
-            new UpdateOptions().upsert(true)
-    );
-    return userAccount;
-  }
-}

caching/src/main/java/com/iluwatar/caching/database/VirtualDb.java

@@ -1,78 +0,0 @@
-package com.iluwatar.caching.database;
-
-import com.iluwatar.caching.UserAccount;
-
-import java.util.HashMap;
-import java.util.Map;
-
-/**
- * Implementation of DatabaseManager.
- * implements base methods to work with hashMap as database.
- */
-public class VirtualDb implements DbManager {
-  /**
-   * Virtual DataBase.
-   */
-  private Map<String, UserAccount> db;
-
-  /**
-   * Creates new HashMap.
-   */
-  @Override
-  public void connect() {
-    db = new HashMap<>();
-  }
-
-  @Override
-  public void disconnect() {
-    db = null;
-  }
-
-  /**
-   * Read from Db.
-   *
-   * @param userId {@link String}
-   * @return {@link UserAccount}
-   */
-  @Override
-  public UserAccount readFromDb(final String userId) {
-    if (db.containsKey(userId)) {
-      return db.get(userId);
-    }
-    return null;
-  }
-
-  /**
-   * Write to DB.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  @Override
-  public UserAccount writeToDb(final UserAccount userAccount) {
-    db.put(userAccount.getUserId(), userAccount);
-    return userAccount;
-  }
-
-  /**
-   * Update reecord in DB.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  @Override
-  public UserAccount updateDb(final UserAccount userAccount) {
-    return writeToDb(userAccount);
-  }
-
-  /**
-   * Update.
-   *
-   * @param userAccount {@link UserAccount}
-   * @return {@link UserAccount}
-   */
-  @Override
-  public UserAccount upsertDb(final UserAccount userAccount) {
-    return updateDb(userAccount);
-  }
-}

caching/src/main/java/com/iluwatar/caching/database/package-info.java

@@ -1,4 +0,0 @@
-/**
- * Database classes.
- */
-package com.iluwatar.caching.database;

caching/src/main/java/com/iluwatar/caching/package-info.java

@@ -1,20 +0,0 @@
-/**
- * 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.caching;

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

@@ -25,21 +25,25 @@ package com.iluwatar.caching;
 
 import org.junit.jupiter.api.Test;
 
+import java.io.IOException;
+
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
 /**
  * Tests that Caching example runs without errors.
  */
 class AppTest {
+
   /**
    * Issue: Add at least one assertion to this test case.
-   * <p>
+   *
    * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
    * throws an exception.
    */
 
   @Test
   void shouldExecuteApplicationWithoutException() {
+
     assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

caching/src/test/java/com/iluwatar/caching/CachingTest.java

@@ -23,11 +23,11 @@
 
 package com.iluwatar.caching;
 
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertNotNull;
-
 /**
  * Application test
  */
@@ -43,30 +43,32 @@ class CachingTest {
     // to avoid Maven compilation errors. Set flag to true to run the
     // tests with MongoDB (provided that MongoDB is installed and socket
     // connection is open).
-    app = new App(false);
+    AppManager.initDb(false);
+    AppManager.initCacheCapacity(3);
+    app = new App();
   }
 
   @Test
   void testReadAndWriteThroughStrategy() {
-    assertNotNull(app);
+	assertNotNull(app);
     app.useReadAndWriteThroughStrategy();
   }
 
   @Test
   void testReadThroughAndWriteAroundStrategy() {
-    assertNotNull(app);
+	assertNotNull(app);
     app.useReadThroughAndWriteAroundStrategy();
   }
 
   @Test
   void testReadThroughAndWriteBehindStrategy() {
-    assertNotNull(app);
+	assertNotNull(app);
     app.useReadThroughAndWriteBehindStrategy();
   }
 
   @Test
   void testCacheAsideStrategy() {
-    assertNotNull(app);
+	assertNotNull(app);
     app.useCacheAsideStategy();
   }
 }

caching/src/test/java/com/iluwatar/caching/database/MongoDbTest.java

@@ -1,84 +0,0 @@
-package com.iluwatar.caching.database;
-
-import com.iluwatar.caching.UserAccount;
-import com.iluwatar.caching.constants.CachingConstants;
-import com.mongodb.client.FindIterable;
-import com.mongodb.client.MongoCollection;
-import com.mongodb.client.MongoDatabase;
-import org.bson.Document;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-import org.mockito.Mock;
-import org.mockito.internal.util.reflection.Whitebox;
-
-import static com.iluwatar.caching.constants.CachingConstants.ADD_INFO;
-import static com.iluwatar.caching.constants.CachingConstants.USER_ID;
-import static com.iluwatar.caching.constants.CachingConstants.USER_NAME;
-import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.Mockito.*;
-
-class MongoDbTest {
-  private static final String ID = "123";
-  private static final String NAME = "Some user";
-  private static final String ADDITIONAL_INFO = "Some app Info";
-
-  @Mock
-  MongoDatabase db;
-  private MongoDb mongoDb = new MongoDb();
-
-  private UserAccount userAccount;
-
-  @BeforeEach
-  void init() {
-    db = mock(MongoDatabase.class);
-    Whitebox.setInternalState(mongoDb, "db", db);
-    userAccount = new UserAccount(ID, NAME, ADDITIONAL_INFO);
-
-
-  }
-
-  @Test
-  void connect() {
-    assertDoesNotThrow(() -> mongoDb.connect());
-  }
-
-  @Test
-  void readFromDb() {
-    Document document = new Document(USER_ID, ID)
-            .append(USER_NAME, NAME)
-            .append(ADD_INFO, ADDITIONAL_INFO);
-    MongoCollection<Document> mongoCollection = mock(MongoCollection.class);
-    when(db.getCollection(CachingConstants.USER_ACCOUNT)).thenReturn(mongoCollection);
-
-    FindIterable<Document> findIterable = mock(FindIterable.class);
-    when(mongoCollection.find(any(Document.class))).thenReturn(findIterable);
-
-    when(findIterable.first()).thenReturn(document);
-
-    assertEquals(mongoDb.readFromDb(ID),userAccount);
-  }
-
-  @Test
-  void writeToDb() {
-    MongoCollection<Document> mongoCollection = mock(MongoCollection.class);
-    when(db.getCollection(CachingConstants.USER_ACCOUNT)).thenReturn(mongoCollection);
-    doNothing().when(mongoCollection).insertOne(any(Document.class));
-    assertDoesNotThrow(()-> {mongoDb.writeToDb(userAccount);});
-  }
-
-  @Test
-  void updateDb() {
-    MongoCollection<Document> mongoCollection = mock(MongoCollection.class);
-    when(db.getCollection(CachingConstants.USER_ACCOUNT)).thenReturn(mongoCollection);
-    assertDoesNotThrow(()-> {mongoDb.updateDb(userAccount);});
-  }
-
-  @Test
-  void upsertDb() {
-    MongoCollection<Document> mongoCollection = mock(MongoCollection.class);
-    when(db.getCollection(CachingConstants.USER_ACCOUNT)).thenReturn(mongoCollection);
-    assertDoesNotThrow(()-> {mongoDb.upsertDb(userAccount);});
-  }
-}

callback/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Callback
-category: Idiom
+folder: callback
+permalink: /patterns/callback/
+categories: Idiom
 language: en
 tags:
  - Reactive

chain-of-responsibility/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Chain of responsibility
-category: Behavioral
+folder: chain-of-responsibility
+permalink: /patterns/chain-of-responsibility/
+categories: Behavioral
 language: en
 tags:
  - Gang of Four

circuit-breaker/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Circuit Breaker
-category: Behavioral
+folder: circuit-breaker
+permalink: /patterns/circuit-breaker/
+categories: Behavioral
 language: en
 tags:
   - Performance

cloud-static-content-hosting/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Static Content Hosting
-category: Cloud
+folder: cloud-static-content-hosting
+permalink: /patterns/cloud-static-content-hosting/
+categories: Cloud
 language: en
 tags:
 - Cloud distributed

collection-pipeline/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Collection Pipeline
-category: Functional
+folder: collection-pipeline
+permalink: /patterns/collection-pipeline/
+categories: Functional
 language: en
 tags:
  - Reactive

combinator/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Combinator
-category: Idiom
+folder: combinator
+permalink: /patterns/combinator/
+categories: Idiom
 language: en
 tags:
  - Reactive

command/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Command
-category: Behavioral
+folder: command
+permalink: /patterns/command/
+categories: Behavioral
 language: en
 tags:
  - Gang of Four

commander/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Commander
-category: Concurrency
+folder: commander
+permalink: /patterns/commander/
+categories: Concurrency
 language: en
 tags:
  - Cloud distributed

composite-entity/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Composite Entity
-category: Structural
+folder: composite-entity
+permalink: /patterns/composite-entity/
+categories: Structural
 language: en
 tags:
  - Enterprise Integration Pattern

composite/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Composite
-category: Structural
+folder: composite
+permalink: /patterns/composite/
+categories: Structural
 language: en
 tags:
  - Gang of Four

converter/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Converter
-category: Creational
+folder: converter
+permalink: /patterns/converter/
+categories: Creational
 language: en
 tags:
  - Decoupling

cqrs/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: CQRS
-category: Architectural
+folder: cqrs
+permalink: /patterns/cqrs/
+categories: Architectural
 language: en
 tags:
   - Performance

dao/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Data Access Object
-category: Architectural
+folder: dao
+permalink: /patterns/dao/
+categories: Architectural
 language: en
 tags:
  - Data access

data-bus/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Data Bus
-category: Architectural
+folder: data-bus
+permalink: /patterns/data-bus/
+categories: Architectural
 language: en
 tags:
  - Decoupling

data-locality/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Data Locality
-category: Behavioral
+folder: data-locality
+permalink: /patterns/data-locality/
+categories: Behavioral
 language: en
 tags:
  - Game programming

data-mapper/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Data Mapper
-category: Architectural
+folder: data-mapper
+permalink: /patterns/data-mapper/
+categories: Architectural
 language: en
 tags:
  - Decoupling

data-transfer-object/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Data Transfer Object
-category: Architectural
+folder: data-transfer-object
+permalink: /patterns/data-transfer-object/
+categories: Architectural
 language: en
 tags:
  - Performance

decorator/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Decorator
-category: Structural
+folder: decorator
+permalink: /patterns/decorator/
+categories: Structural
 language: en
 tags:
  - Gang of Four

delegation/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Delegation
-category: Structural
+folder: delegation
+permalink: /patterns/delegation/
+categories: Structural
 language: en
 tags:
  - Decoupling

dependency-injection/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Dependency Injection
-category: Creational
+folder: dependency-injection
+permalink: /patterns/dependency-injection/
+categories: Creational
 language: en
 tags:
  - Decoupling

dirty-flag/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Dirty Flag
-category: Behavioral
+folder: dirty-flag
+permalink: /patterns/dirty-flag/
+categories: Behavioral
 language: en
 tags:
  - Game programming

domain-model/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Domain Model
-category: Architectural
+folder: domain-model
+permalink: /patterns/domain-model/
+categories: Architectural
 language: en
 tags:
  - Domain

double-buffer/README.md

@@ -1,6 +1,9 @@
 ---  
+layout: pattern  
 title: Double Buffer 
-category: Behavioral
+folder:  double-buffer  
+permalink: /patterns/double-buffer/  
+categories: Behavioral
 language: en
 tags:  
  - Performance

double-checked-locking/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Double Checked Locking
-category: Idiom
+folder: double-checked-locking
+permalink: /patterns/double-checked-locking/
+categories: Idiom
 language: en
 tags:
  - Performance

double-dispatch/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Double Dispatch
-category: Idiom
+folder: double-dispatch
+permalink: /patterns/double-dispatch/
+categories: Idiom
 language: en
 tags:
  - Extensibility

eip-aggregator/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: EIP Aggregator
-category: Integration
+folder: eip-aggregator
+permalink: /patterns/eip-aggregator/
+categories: Integration
 language: en
 tags:
  - Enterprise Integration Pattern

eip-message-channel/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: EIP Message Channel
-category: Integration
+folder: eip-message-channel
+permalink: /patterns/eip-message-channel/
+categories: Integration
 language: en
 tags:
  - Enterprise Integration Pattern

eip-publish-subscribe/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: EIP Publish Subscribe
-category: Integration
+folder: eip-publish-subscribe
+permalink: /patterns/eip-publish-subscribe/
+categories: Integration
 language: en
 tags:
  - Enterprise Integration Pattern

eip-splitter/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: EIP Splitter
-category: Integration
+folder: eip-splitter
+permalink: /patterns/eip-splitter/
+categories: Integration
 language: en
 tags:
  - Enterprise Integration Pattern

eip-wire-tap/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: EIP Wire Tap
-category: Integration
+folder: eip-wire-tap
+permalink: /patterns/eip-wire-tap/
+categories: Integration
 language: en
 tags:
  - Enterprise Integration Pattern

event-aggregator/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Event Aggregator
-category: Structural
+folder: event-aggregator
+permalink: /patterns/event-aggregator/
+categories: Structural
 language: en
 tags:
  - Reactive

event-asynchronous/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Event-based Asynchronous
-category: Concurrency
+folder: event-asynchronous
+permalink: /patterns/event-asynchronous/
+categories: Concurrency
 language: en
 tags:
  - Reactive

event-driven-architecture/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Event Driven Architecture
-category: Architectural
+folder: event-driven-architecture
+permalink: /patterns/event-driven-architecture/
+categories: Architectural
 language: en
 tags:
  - Reactive

event-queue/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Event Queue
-category: Concurrency
+folder: event-queue
+permalink: /patterns/event-queue/
+categories: Concurrency
 language: en
 tags:
  - Game programming

event-sourcing/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Event Sourcing
-category: Architectural
+folder: event-sourcing
+permalink: /patterns/event-sourcing/
+categories: Architectural
 language: en
 tags:
   - Performance

execute-around/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Execute Around
-category: Idiom
+folder: execute-around
+permalink: /patterns/execute-around/
+categories: Idiom
 language: en
 tags:
  - Extensibility

extension-objects/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Extension objects
-category: Behavioral
+folder: extension-objects
+permalink: /patterns/extension-objects/
+categories: Behavioral
 language: en
 tags:
  - Extensibility

facade/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Facade
-category: Structural
+folder: facade
+permalink: /patterns/facade/
+categories: Structural
 language: en
 tags:
  - Gang Of Four

factory-kit/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Factory Kit
-category: Creational
+folder: factory-kit
+permalink: /patterns/factory-kit/
+categories: Creational
 language: en
 tags:
  - Extensibility

factory-method/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Factory Method
-category: Creational
+folder: factory-method
+permalink: /patterns/factory-method/
+categories: Creational
 language: en
 tags:
  - Extensibility

factory/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Factory
-category: Creational
+folder: factory
+permalink: /patterns/factory/
+categories: Creational
 language: en
 tags:
  - Gang of Four

fanout-fanin/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Fan-Out/Fan-In
-category: Integration
+folder: fanout-fanin
+permalink: /patterns/fanout-fanin/
+categories: Integration
 language: en
 tags:
 - Microservices

feature-toggle/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Feature Toggle
-category: Behavioral
+folder: feature-toggle
+permalink: /patterns/feature-toggle/
+categories: Behavioral
 language: en
 tags:
  - Extensibility

filterer/README.md

@@ -1,8 +1,10 @@
 ---
+layout: pattern
 title: Filterer
-description: Design pattern that helps container-like objects to return filtered version of themselves.# short meta description that shows in Google search results
+folder: filterer
+permalink: /patterns/filterer/
 language: en
-category: Functional
+categories: Functional
 tags:
  - Extensibility
 ---

fluentinterface/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Fluent Interface
-category: Functional
+folder: fluentinterface
+permalink: /patterns/fluentinterface/
+categories: Functional
 language: en
 tags: 
  - Reactive

flux/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Flux
-category: Structural
+folder: flux
+permalink: /patterns/flux/
+categories: Structural
 language: en
 tags:
  - Decoupling

flyweight/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Flyweight
-category: Structural
+folder: flyweight
+permalink: /patterns/flyweight/
+categories: Structural
 language: en
 tags:
  - Gang of Four

front-controller/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Front Controller
-category: Structural
+folder: front-controller
+permalink: /patterns/front-controller/
+categories: Structural
 language: en
 tags:
  - Decoupling

game-loop/README.md

@@ -1,6 +1,9 @@
 ---  
+layout: pattern  
 title: Game Loop 
-category: Behavioral
+folder:  game-loop  
+permalink: /patterns/game-loop/  
+categories: Behavioral
 language: en
 tags:  
  - Game programming

guarded-suspension/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Guarded Suspension
-category: Concurrency
+folder: guarded-suspension
+permalink: /patterns/guarded-suspension/
+categories: Concurrency
 language: en
 tags:
  - Decoupling

half-sync-half-async/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Half-Sync/Half-Async
-category: Concurrency
+folder: half-sync-half-async
+permalink: /patterns/half-sync-half-async/
+categories: Concurrency
 language: en
 tags:
  - Performance

hexagonal/README.md

@@ -1,6 +1,10 @@
 ---
+layout: pattern
 title: Hexagonal Architecture
-category: Architectural
+folder: hexagonal
+permalink: /patterns/hexagonal/
+pumlformat: svg
+categories: Architectural
 language: en
 tags:
  - Decoupling

index.md

@@ -1,147 +0,0 @@
-| Pattern                                                                              | Category               | Tags                              |
-| :---                                                                                 | :---                   | :---                              |
-| [Abstract Document](abstract-document)                                               | Structural             | Extensibility                     |
-| [Abstract Factory](abstract-factory)                                                 | Creational             | Gang of Four                      |
-| [Active Object](active-object)                                                       | Concurrency            | Performance                       |
-| [Acyclic Visitor](acyclic-visitor)                                                   | Behavioral             | Extensibility                     |
-| [Adapter](adapter)                                                                   | Structural             | Gang of Four                      |
-| [Aggregator Microservices](aggregator-microservices)                                 | Architectural          | Cloud distributed                 |
-| [Ambassador](ambassador)                                                             | Structural             | Decoupling                        |
-| [API Gateway](api-gateway)                                                           | Architectural          | Cloud distributed, Decoupling     |
-| [Arrange/Act/Assert](arrange-act-assert)                                             | Idiom                  | Testing                           |
-| [Async Method Invocation](async-method-invocation)                                   | Concurrency            | Reactive                          |
-| [Balking](balking)                                                                   | Concurrency            | Decoupling                        |
-| [Bridge](bridge)                                                                     | Structural             | Gang of Four                      |
-| [Builder](builder)                                                                   | Creational             | Gang of Four                      |
-| [Business Delegate](business-delegate)                                               | Structural             | Decoupling                        |
-| [Bytecode](bytecode)                                                                 | Behavioral             | Game programming                  |
-| [Caching](caching)                                                                   | Behavioral             | Performance                       |
-| [Callback](callback)                                                                 | Idiom                  | Reactive                          |
-| [Chain of Responsibility](chain-of-responsibility)                                   | Behavioral             | Gang of Four                      |
-| [Circuit Breaker](circuit-breaker)                                                   | Behavioral             | Performance, Decoupling           |
-| [Cloud Static Content Hosting](cloud-static-content-hosting)                         | Cloud                  | Cloud distributed                 |
-| [Collection Pipeline](collection-pipeline)                                           | Functional             | Reactive                          |
-| [Combinator](combinator)                                                             | Idiom                  | Reactive                          |
-| [Command](command)                                                                   | Behavioral             | Gang of Four                      |
-| [Commander](commander)                                                               | Concurrency            | Cloud distributed                 |
-| [Composite](composite)                                                               | Structural             | Gang of Four                      |
-| [Composite Entity](composite-entity)                                                 | Structural             | Enterprise Integration Pattern    |
-| [Converter](converter)                                                               | Creational             | Decoupling                        |
-| [Command Query Responsibility Segregation](command-query-responsibility-segregation) | Architectural          | Performance, Cloud distributed    |
-| [Data Access Object](data-access-object)                                             | Architectural          | Data access                       |
-| [Data Bus](data-bus)                                                                 | Architectural          | Decoupling                        |
-| [Data Locality](data-locality)                                                       | Behavioral             | Performance, Game programming     |
-| [Data Mapper](data-mapper)                                                           | Architectural          | Decoupling                        |
-| [Data Transfer Object](data-transfer-object)                                         | Architectural          | Performance                       |
-| [Decorator](decorator)                                                               | Structural             | Gang of Four, Extensibility       |
-| [Delegation](delegation)                                                             | Structural             | Decoupling                        |
-| [Dependency Injection](dependency-injection)                                         | Creational             | Decoupling                        |
-| [Dirty Flag](dirty-flag)                                                             | Behavioral             | Performance, Game programming     |
-| [Double Buffer](double-buffer)                                                       | Behavioral             | Performance, Game programming     |
-| [Double Checked Locking](double-checked-locking)                                     | Idiom                  | Performance                       |
-| [Double Dispatch](double-dispatch)                                                   | Idiom                  | Extensibility                     |
-| [EIP Aggregator](eip-aggregator)                                                     | Integration            | Enterprise Integration Pattern    |
-| [EIP Message Channel](eip-message-channel)                                           | Integration            | Enterprise Integration Pattern    |
-| [EIP Publish and Subscribe](eip-publish-and-subscribe)                               | Integration            | Enterprise Integration Pattern    |
-| [EIP Splitter](eip-splitter)                                                         | Integration            | Enterprise Integration Pattern    |
-| [EIP Wire Tap](eip-wire-tap)                                                         | Integration            | Enterprise Integration Pattern    |
-| [Event Aggregator](event-aggregator)                                                 | Structural             | Reactive                          |
-| [Event Based Asynchronous](event-based-asynchronous)                                 | Concurrency            | Reactive                          |
-| [Event Driven Architecture](event-driven-architecture)                               | Architectural          | Reactive                          |
-| [Event Queue](event-queue)                                                           | Concurrency            | Game programming                  |
-| [Event Sourcing](event-sourcing)                                                     | Architectural          | Performance                       |
-| [Execute Around](execute-around)                                                     | Idiom                  | Extensibility                     |
-| [Extension Objects](extension-objects)                                               | Behavioral             | Extensibility                     |
-| [Facade](facade)                                                                     | Structural             | Gang of Four, Decoupling          |
-| [Factory](factory)                                                                   | Creational             | Gang of Four                      |
-| [Factory kit](factory-kit)                                                           | Creational             | Extensibility                     |
-| [Factory Method](factory-method)                                                     | Creational             | Gang of Four, Extensibility       |
-| [Fan-Out/Fan-In](fanout-fanin)                                                       | Integration            | Microservices                     |
-| [Feature Toggle](feature-toggle)                                                     | Behavioral             | Extensibility                     |
-| [Filterer](filterer)                                                                 | Functional             | Extensibility                     |
-| [Fluent Interface](fluent-interface)                                                 | Functional             | Reactive                          |
-| [Flux](flux)                                                                         | Structural             | Decoupling                        |
-| [Flyweight](flyweight)                                                               | Structural             | Gang of Four, Performance         |
-| [Front Controller](front-controller)                                                 | Structural             | Decoupling                        |
-| [Game Loop](game-loop)                                                               | Behavioral             | Game programming                  |
-| [Guarded Suspension](guarded-suspension)                                             | Concurrency            | Decoupling                        |
-| [Half-Sync Half-Async](half-sync-half-async)                                         | Concurrency            | Performance                       |
-| [Hexagonal](hexagonal)                                                               | Architectural          | Decoupling                        |
-| [Intercepting Filter](intercepting-filter)                                           | Behavioral             | Decoupling                        |
-| [Interpreter](interpreter)                                                           | Behavioral             | Gang of Four                      |
-| [Iterator](iterator)                                                                 | Behavioral             | Gang of Four                      |
-| [Layers](layers)                                                                     | Architectural          | Decoupling                        |
-| [Lazy Loading](lazy-loading)                                                         | Idiom                  | Performance                       |
-| [Leader Election](leader-election)                                                   | Behavioral             | Cloud distributed                 |
-| [Leader Followers](leader-followers)                                                 | Concurrency            | Performance                       |
-| [Lockable Object](lockable-object)                                                   | Concurrency            | Performance                       |
-| [Marker Interface](marker-interface)                                                 | Structural             | Decoupling                        |
-| [Master Worker](master-worker)                                                       | Concurrency            | Performance                       |
-| [Mediator](mediator)                                                                 | Behavioral             | Gang of Four, Decoupling          |
-| [Memento](memento)                                                                   | Behavioral             | Gang of Four                      |
-| [Model View Controller](model-view-controller)                                       | Architectural          | Decoupling                        |
-| [Model View Presenter](model-view-presenter)                                         | Architectural          | Decoupling                        |
-| [Model View ViewModel](model-view-viewmodel)                                         | Architectural          | Decoupling                        |
-| [Module](module)                                                                     | Structural             | Decoupling                        |
-| [Monad](monad)                                                                       | Functional             | Reactive                          |
-| [Monostate](monostate)                                                               | Creational             | Instantiation                     |
-| [Multiton](multiton)                                                                 | Creational             | Instantiation                     |
-| [Mute Idiom](mute-idiom)                                                             | Idiom                  | Decoupling                        |
-| [Naked Objects](naked-objects)                                                       | Architectural          | Decoupling                        |
-| [Null Object](null-object)                                                           | Behavioral             | Extensibility                     |
-| [Object Mother](object-mother)                                                       | Creational             | Instantiation                     |
-| [Object Pool](object-pool)                                                           | Creational             | Performance, Game programming     |
-| [Observer](observer)                                                                 | Behavioral             | Gang of Four, Reactive            |
-| [Page Object](page-object)                                                           | Structural             | Decoupling                        |
-| [Parameter Object](parameter-object)                                                 | Behavioral             | Extensibility                     |
-| [Partial Response](partial-response)                                                 | Behavioral             | Decoupling                        |
-| [Pipeline](pipeline)                                                                 | Behavioral             | Decoupling                        |
-| [Poison Pill](poison-pill)                                                           | Behavioral             | Cloud distributed, Reactive       |
-| [Presentation Model](presentation-model)                                             | Behavioral             | Decoupling                        |
-| [Priority Queue](priority-queue)                                                     | Behavioral             | Decoupling                        |
-| [Private Class Data](private-class-data)                                             | Idiom                  | Data access                       |
-| [Producer Consumer](producer-consumer)                                               | Concurrency            | Reactive                          |
-| [Promise](promise)                                                                   | Concurrency            | Reactive                          |
-| [Property](property)                                                                 | Creational             | Instantiation                     |
-| [Prototype](prototype)                                                               | Creational             | Gang of Four, Instantiation       |
-| [Proxy](proxy)                                                                       | Structural             | Gang of Four, Decoupling          |
-| [Queue Based Load Leveling](queue-based-load-leveling)                               | Concurrency            | Performance, Decoupling           |
-| [Reactor](reactor)                                                                   | Concurrency            | Performance, Reactive             |
-| [Reader Writer Lock](reader-writer-lock)                                             | Concurrency            | Performance                       |
-| [Registry](registry)                                                                 | Creational             | Instantiation                     |
-| [Repository](repository)                                                             | Architectural          | Data access                       |
-| [Resource Acquisition Is Initialization](resource-acquisition-is-initialization)     | Idiom                  | Data access                       |
-| [Retry](retry)                                                                       | Behavioral             | Performance                       |
-| [Role Object](role-object)                                                           | Structural             | Extensibility                     |
-| [Saga](saga)                                                                         | Concurrency            | Cloud distributed                 |
-| [Semaphore](semaphore)                                                               | Concurrency            | Performance                       |
-| [Separated Interface](separated-interface)                                           | Structural             | Decoupling                        |
-| [Servant](servant)                                                                   | Behavioral             | Decoupling                        |
-| [Serverless](serverless)                                                             | Architectural          | Cloud distributed                 |
-| [Service Layer](service-layer)                                                       | Architectural          | Data access                       |
-| [Service Locator](service-locator)                                                   | Architectural          | Performance, Game programming     |
-| [Sharding](sharding)                                                                 | Behavioral             | Performance, Cloud distributed    |
-| [Singleton](singleton)                                                               | Creational             | Gang of Four                      |
-| [Spatial Partition](spatial-partition)                                               | Behavioral             | Performance, Game programming     |
-| [Special Case](special-case)                                                         | Behavioral             | Extensibility                     |
-| [Specification](specification)                                                       | Behavioral             | Data access                       |
-| [State](state)                                                                       | Behavioral             | Gang of Four                      |
-| [Step Builder](step-builder)                                                         | Creational             | Instantiation                     |
-| [Strangler](strangler)                                                               | Structural             | Cloud distributed, Extensibility  |
-| [Strategy](strategy)                                                                 | Behavioral             | Gang of Four                      |
-| [Subclass Sandbox](subclass-sandbox)                                                 | Behavioral             | Game programming                  |
-| [Table Module](table-module)                                                         | Structural             | Data access                       |
-| [Template Method](table-module)                                                      | Behavioral             | Gang of Four                      |
-| [Thread Pool](thread-pool)                                                           | Concurrency            | Performance                       |
-| [Throttling](throttling)                                                             | Behavioral             | Performance                       |
-| [Thread Local Storage](thread-local-storage)                                         | Idiom                  | Performance                       |
-| [Tolerant Reader](tolerant-reader)                                                   | Integration            | Decoupling                        |
-| [Trampoline](trampoline)                                                             | Behavioral             | Performance                       |
-| [Transaction Script](transaction-script)                                             | Behavioral             | Data access                       |
-| [Twin](twin)                                                                         | Structural             | Extensibility                     |
-| [Type Object](type-object)                                                           | Behavioral             | Game programming, Extensibility   |
-| [Unit of Work](unit-of-work)                                                         | Architectural          | Data access                       |
-| [Update Method](update-method)                                                       | Behavioral             | Game programming                  |
-| [Value Object](value-object)                                                         | Creational             | Instantiation                     |
-| [Version Number](version-number)                                                     | Concurrency            | Data access, Microservices        |
-| [Visitor](visitor)                                                                   | Behavioral             | Gang of Four                      |

intercepting-filter/README.md

@@ -1,5 +1,8 @@
 ---
+layout: pattern
 title: Intercepting Filter
+folder: intercepting-filter
+permalink: /patterns/intercepting-filter/
 categories: Behavioral
 language: en
 tags:

interpreter/README.md

@@ -1,5 +1,8 @@
 ---
+layout: pattern
 title: Interpreter
+folder: interpreter
+permalink: /patterns/interpreter/
 categories: Behavioral
 language: en
 tags:

iterator/README.md

@@ -1,5 +1,8 @@
 ---
+layout: pattern
 title: Iterator
+folder: iterator
+permalink: /patterns/iterator/
 categories: Behavioral
 language: en
 tags:

layers/README.md

@@ -1,6 +1,10 @@
 ---
+layout: pattern
 title: Layers
-category: Architectural
+folder: layers
+permalink: /patterns/layers/
+pumlformat: svg
+categories: Architectural
 language: en
 tags:
  - Decoupling

lazy-loading/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Lazy Loading
-category: Idiom
+folder: lazy-loading
+permalink: /patterns/lazy-loading/
+categories: Idiom
 language: en
 tags:
  - Performance

leader-election/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Leader Election
-category: Behavioral
+folder: leader-election
+permalink: /patterns/leader-election/
+categories: Behavioral
 language: en
 tags:
  - Cloud distributed

leader-followers/README.md

@@ -1,6 +1,9 @@
 ---
+layout: pattern
 title: Leader/Followers
-category: Concurrency
+folder: leader-followers
+permalink: /patterns/leader-followers/
+categories: Concurrency
 language: en
 tags:
  - Performance