Merge pull request #608 from gopinath-langote/master

#348 Data Transfer Object design pattern

data-transfer-object/README.md

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+---
+layout: pattern
+title: Data Transfer Object
+folder: data-transfer-object
+permalink: /patterns/data-transfer-object/
+categories: Architectural
+tags:
+ - Java
+ - KISS
+ - YAGNI
+ - Difficulty-Beginner
+---
+
+## Intent
+Pass data with multiple attributes in one shot from client to server,
+to avoid multiple calls to remote server. 
+
+![alt text](./etc/data-transfer-object.urm.png "data-transfer-object")
+
+## Applicability
+Use the Data Transfer Object pattern when
+
+* The client is asking for multiple information. And the information is related.
+* When you want to boost the performance to get resources.
+* You want reduced number of remote calls.
+
+## Credits
+
+* [Design Pattern - Transfer Object Pattern](https://www.tutorialspoint.com/design_pattern/transfer_object_pattern.htm)
+* [Data Transfer Object](https://msdn.microsoft.com/en-us/library/ff649585.aspx)

data-transfer-object/etc/data-transfer-object.ucls

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+<?xml version="1.0" encoding="UTF-8"?>
+<class-diagram version="1.2.0" icons="true" always-add-relationships="false" generalizations="true" realizations="true" 
+  associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
+  <class id="1" language="java" name="com.iluwatar.datatransfer.CustomerClientApp" project="data-transfer-object" 
+    file="/data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerClientApp.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="145" y="93"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="2" language="java" name="com.iluwatar.datatransfer.CustomerDto" project="data-transfer-object" 
+    file="/data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerDto.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="386" y="329"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="3" language="java" name="com.iluwatar.datatransfer.CustomerResource" project="data-transfer-object" 
+    file="/data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerResource.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="677" y="93"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <association id="4">    
+    <end type="SOURCE" refId="3" navigable="false">      
+      <attribute id="5" name="customers"/>      
+      <multiplicity id="6" minimum="0" maximum="2147483647"/>    
+    </end>    
+    <end type="TARGET" refId="2" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+    sort-features="false" accessors="true" visibility="true">    
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
+    <operations public="true" package="true" protected="true" private="true" static="true"/>  
+  </classifier-display>  
+  <association-display labels="true" multiplicity="true"/>
+</class-diagram>

data-transfer-object/etc/data-transfer-object.urm.puml

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+@startuml
+package com.iluwatar.datatransfer {
+  class CustomerClientApp {
+    + CustomerClientApp()
+    + main(args : String[]) {static}
+    - printCustomerDetails(allCustomers : List<CustomerDto>) {static}
+  }
+  class CustomerDto {
+    - firstName : String
+    - id : String
+    - lastName : String
+    + CustomerDto(id : String, firstName : String, lastName : String)
+    + getFirstName() : String
+    + getId() : String
+    + getLastName() : String
+  }
+  class CustomerResource {
+    - customers : List<CustomerDto>
+    + CustomerResource(customers : List<CustomerDto>)
+    + delete(customerId : String)
+    + getAllCustomers() : List<CustomerDto>
+    + save(customer : CustomerDto)
+  }
+}
+CustomerResource -->  "-customers" CustomerDto
+@enduml

data-transfer-object/pom.xml

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+<?xml version="1.0"?>
+<!--
+
+    The MIT License
+    Copyright (c) 2016 Gopinath Langote
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.iluwatar</groupId>
+        <artifactId>java-design-patterns</artifactId>
+        <version>1.17.0-SNAPSHOT</version>
+    </parent>
+    <artifactId>data-transfer-object</artifactId>
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+        </dependency>
+    </dependencies>
+</project>

data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerClientApp.java

@@ -0,0 +1,84 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Gopinath Langote
+ *
+ * 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.datatransfer;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * The Data Transfer Object pattern is a design pattern in which an data transfer object is used to serve related
+ * information together to avoid multiple call for each piece of information.
+ * <p>
+ * In this example, ({@link CustomerClientApp}) as as customer details consumer i.e. client to request for
+ * customer details to server.
+ * <p>
+ * CustomerResource ({@link CustomerResource}) act as server to serve customer information.
+ * And The CustomerDto ({@link CustomerDto} is data transfer object to share customer information.
+ */
+public class CustomerClientApp {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(CustomerClientApp.class);
+
+  /**
+   * Method as act client and request to server for details.
+   *
+   * @param args program argument.
+   */
+  public static void main(String[] args) {
+    List<CustomerDto> customers = new ArrayList<>();
+    CustomerDto customerOne = new CustomerDto("1", "Kelly", "Brown");
+    CustomerDto customerTwo = new CustomerDto("2", "Alfonso", "Bass");
+    customers.add(customerOne);
+    customers.add(customerTwo);
+
+    CustomerResource customerResource = new CustomerResource(customers);
+
+    LOGGER.info("All customers:-");
+    List<CustomerDto> allCustomers = customerResource.getAllCustomers();
+    printCustomerDetails(allCustomers);
+
+    LOGGER.info("----------------------------------------------------------");
+
+    LOGGER.info("Deleting customer with id {1}");
+    customerResource.delete(customerOne.getId());
+    allCustomers = customerResource.getAllCustomers();
+    printCustomerDetails(allCustomers);
+
+    LOGGER.info("----------------------------------------------------------");
+
+    LOGGER.info("Adding customer three}");
+    CustomerDto customerThree = new CustomerDto("3", "Lynda", "Blair");
+    customerResource.save(customerThree);
+    allCustomers = customerResource.getAllCustomers();
+    printCustomerDetails(allCustomers);
+  }
+
+  private static void printCustomerDetails(List<CustomerDto> allCustomers) {
+    allCustomers.forEach(customer -> LOGGER.info(customer.getFirstName()));
+  }
+}

data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerDto.java

@@ -0,0 +1,60 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Gopinath Langote
+ *
+ * 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.datatransfer;
+
+/**
+ * {@link CustomerDto} is a data transfer object POJO. Instead of sending individual information to client
+ * We can send related information together in POJO.
+ * <p>
+ * Dto will not have any business logic in it.
+ */
+public class CustomerDto {
+  private final String id;
+  private final String firstName;
+  private final String lastName;
+
+  /**
+   * @param id        customer id
+   * @param firstName customer first name
+   * @param lastName  customer last name
+   */
+  public CustomerDto(String id, String firstName, String lastName) {
+    this.id = id;
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
+  public String getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public String getLastName() {
+    return lastName;
+  }
+}

data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerResource.java

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+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Gopinath Langote
+ *
+ * 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.datatransfer;
+
+import java.util.List;
+
+/**
+ * The resource class which serves customer information.
+ * This class act as server in the demo. Which has all customer details.
+ */
+public class CustomerResource {
+  private List<CustomerDto> customers;
+
+  /**
+   * @param customers initialize resource with existing customers. Act as database.
+   */
+  public CustomerResource(List<CustomerDto> customers) {
+    this.customers = customers;
+  }
+
+  /**
+   * @return : all customers in list.
+   */
+  public List<CustomerDto> getAllCustomers() {
+    return customers;
+  }
+
+  /**
+   * @param customer save new customer to list.
+   */
+  public void save(CustomerDto customer) {
+    customers.add(customer);
+  }
+
+  /**
+   * @param customerId delete customer with id {@code customerId}
+   */
+  public void delete(String customerId) {
+    customers.removeIf(customer -> customer.getId().equals(customerId));
+  }
+}

data-transfer-object/src/test/java/com/iluwatar/datatransfer/CustomerResourceTest.java

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+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Gopinath Langote
+ *
+ * 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.datatransfer;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * tests {@link CustomerResource}.
+ */
+public class CustomerResourceTest {
+  @Test
+  public void shouldGetAllCustomers() {
+    CustomerDto customer = new CustomerDto("1", "Melody", "Yates");
+    List<CustomerDto> customers = new ArrayList<>();
+    customers.add(customer);
+
+    CustomerResource customerResource = new CustomerResource(customers);
+
+    List<CustomerDto> allCustomers = customerResource.getAllCustomers();
+
+    assertEquals(allCustomers.size(), 1);
+    assertEquals(allCustomers.get(0).getId(), "1");
+    assertEquals(allCustomers.get(0).getFirstName(), "Melody");
+    assertEquals(allCustomers.get(0).getLastName(), "Yates");
+  }
+
+  @Test
+  public void shouldSaveCustomer() {
+    CustomerDto customer = new CustomerDto("1", "Rita", "Reynolds");
+    CustomerResource customerResource = new CustomerResource(new ArrayList<>());
+
+    customerResource.save(customer);
+
+    List<CustomerDto> allCustomers = customerResource.getAllCustomers();
+    assertEquals(allCustomers.get(0).getId(), "1");
+    assertEquals(allCustomers.get(0).getFirstName(), "Rita");
+    assertEquals(allCustomers.get(0).getLastName(), "Reynolds");
+  }
+
+  @Test
+  public void shouldDeleteCustomer() {
+    CustomerDto customer = new CustomerDto("1", "Terry", "Nguyen");
+    List<CustomerDto> customers = new ArrayList<>();
+    customers.add(customer);
+
+    CustomerResource customerResource = new CustomerResource(customers);
+
+    customerResource.delete(customer.getId());
+
+    List<CustomerDto> allCustomers = customerResource.getAllCustomers();
+    assertEquals(allCustomers.size(), 0);
+  }
+
+}

pom.xml

@@ -143,6 +143,7 @@
         <module>extension-objects</module>
         <module>marker</module>
         <module>cqrs</module>
+        <module>data-transfer-object</module>
 
     </modules>