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Merge pull request iluwatar#608 from gopinath-langote/master
iluwatar#348 Data Transfer Object design pattern
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‎data-transfer-object/README.md

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---
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layout: pattern
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title: Data Transfer Object
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folder: data-transfer-object
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permalink: /patterns/data-transfer-object/
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categories: Architectural
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tags:
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- Java
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- KISS
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- YAGNI
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- Difficulty-Beginner
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---
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## Intent
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Pass data with multiple attributes in one shot from client to server,
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to avoid multiple calls to remote server.
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![alt text](./etc/data-transfer-object.urm.png "data-transfer-object")
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## Applicability
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Use the Data Transfer Object pattern when
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* The client is asking for multiple information. And the information is related.
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* When you want to boost the performance to get resources.
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* You want reduced number of remote calls.
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## Credits
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* [Design Pattern - Transfer Object Pattern](https://www.tutorialspoint.com/design_pattern/transfer_object_pattern.htm)
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* [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"?>
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<class-diagram version="1.2.0" icons="true" always-add-relationships="false" generalizations="true" realizations="true"
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associations="true" dependencies="false" nesting-relationships="true" router="FAN">
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<class id="1" language="java" name="com.iluwatar.datatransfer.CustomerClientApp" project="data-transfer-object"
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file="/data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerClientApp.java" binary="false"
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corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="145" y="93"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="2" language="java" name="com.iluwatar.datatransfer.CustomerDto" project="data-transfer-object"
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file="/data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerDto.java" binary="false"
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corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="386" y="329"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="3" language="java" name="com.iluwatar.datatransfer.CustomerResource" project="data-transfer-object"
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file="/data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerResource.java" binary="false"
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corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="677" y="93"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<association id="4">
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<end type="SOURCE" refId="3" navigable="false">
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<attribute id="5" name="customers"/>
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<multiplicity id="6" minimum="0" maximum="2147483647"/>
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</end>
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<end type="TARGET" refId="2" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</classifier-display>
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<association-display labels="true" multiplicity="true"/>
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</class-diagram>

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

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

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

‎data-transfer-object/pom.xml

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

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

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/*
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* The MIT License (MIT)
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*
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* Copyright (c) 2017 Gopinath Langote
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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package com.iluwatar.datatransfer;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* The Data Transfer Object pattern is a design pattern in which an data transfer object is used to serve related
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* information together to avoid multiple call for each piece of information.
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* <p>
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* In this example, ({@link CustomerClientApp}) as as customer details consumer i.e. client to request for
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* customer details to server.
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* <p>
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* CustomerResource ({@link CustomerResource}) act as server to serve customer information.
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* And The CustomerDto ({@link CustomerDto} is data transfer object to share customer information.
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*/
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public class CustomerClientApp {
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private static final Logger LOGGER = LoggerFactory.getLogger(CustomerClientApp.class);
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/**
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* Method as act client and request to server for details.
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*
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* @param args program argument.
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*/
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public static void main(String[] args) {
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List<CustomerDto> customers = new ArrayList<>();
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CustomerDto customerOne = new CustomerDto("1", "Kelly", "Brown");
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CustomerDto customerTwo = new CustomerDto("2", "Alfonso", "Bass");
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customers.add(customerOne);
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customers.add(customerTwo);
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CustomerResource customerResource = new CustomerResource(customers);
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LOGGER.info("All customers:-");
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List<CustomerDto> allCustomers = customerResource.getAllCustomers();
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printCustomerDetails(allCustomers);
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LOGGER.info("----------------------------------------------------------");
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LOGGER.info("Deleting customer with id {1}");
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customerResource.delete(customerOne.getId());
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allCustomers = customerResource.getAllCustomers();
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printCustomerDetails(allCustomers);
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LOGGER.info("----------------------------------------------------------");
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LOGGER.info("Adding customer three}");
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CustomerDto customerThree = new CustomerDto("3", "Lynda", "Blair");
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customerResource.save(customerThree);
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allCustomers = customerResource.getAllCustomers();
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printCustomerDetails(allCustomers);
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}
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private static void printCustomerDetails(List<CustomerDto> allCustomers) {
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allCustomers.forEach(customer -> LOGGER.info(customer.getFirstName()));
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}
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}

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

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/*
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* The MIT License (MIT)
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*
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* Copyright (c) 2017 Gopinath Langote
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIAB 10000 LE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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package com.iluwatar.datatransfer;
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/**
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* {@link CustomerDto} is a data transfer object POJO. Instead of sending individual information to client
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* We can send related information together in POJO.
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* <p>
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* Dto will not have any business logic in it.
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*/
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public class CustomerDto {
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private final String id;
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private final String firstName;
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private final String lastName;
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/**
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* @param id customer id
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* @param firstName customer first name
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* @param lastName customer last name
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*/
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public CustomerDto(String id, String firstName, String lastName) {
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this.id = id;
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this.firstName = firstName;
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this.lastName = lastName;
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}
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public String getId() {
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return id;
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}
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public String getFirstName() {
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return firstName;
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}
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public String getLastName() {
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return lastName;
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}
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}

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

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/*
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* The MIT License (MIT)
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*
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* Copyright (c) 2017 Gopinath Langote
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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package com.iluwatar.datatransfer;
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import java.util.List;
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/**
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* The resource class which serves customer information.
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* This class act as server in the demo. Which has all customer details.
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*/
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public class CustomerResource {
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private List<CustomerDto> customers;
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/**
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* @param customers initialize resource with existing customers. Act as database.
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*/
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public CustomerResource(List<CustomerDto> customers) {
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this.customers = customers;
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}
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/**
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* @return : all customers in list.
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*/
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public List<CustomerDto> getAllCustomers() {
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return customers;
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}
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/**
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* @param customer save new customer to list.
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*/
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public void save(CustomerDto customer) {
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customers.add(customer);
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}
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/**
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* @param customerId delete customer with id {@code customerId}
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*/
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public void delete(String customerId) {
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customers.removeIf(customer -> customer.getId().equals(customerId));
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}
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}

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