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Merge pull request iluwatar#546 from Crossy147/converter
Converter
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‎api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java

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* An adapter to communicate with the Image microservice
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*/
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@Component
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public class ImageClientImpl implements ImageClient{
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public class ImageClientImpl implements ImageClient {
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/**
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* Makes a simple HTTP Get request to the Image microservice
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* @return The path to the image

‎api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java

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* An adapter to communicate with the Price microservice
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*/
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@Component
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public class PriceClientImpl implements PriceClient{
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public class PriceClientImpl implements PriceClient {
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/**
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* Makes a simple HTTP Get request to the Price microservice
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* @return The price of the product

‎converter/README.md

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---
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layout: pattern
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title: Converter
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folder: converter
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permalink: /patterns/converter/
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categories:
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tags:
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- Java
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- Difficulty-Beginner
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---
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## Intent
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The purpose of the Converter Pattern is to provide a generic, common way of bidirectional
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conversion between corresponding types, allowing a clean implementation in which the types do not
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need to be aware of each other. Moreover, the Converter Pattern introduces bidirectional collection
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mapping, reducing a boilerplate code to minimum.
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![alt text](./etc/converter.png "Converter Pattern")
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## Applicability
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Use the Converter Pattern in the following situations:
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* When you have types that logically correspond which other and you need to convert entities between them
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* When you want to provide different ways of types conversions depending on a context
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* Whenever you introduce a DTO (Data transfer object), you will probably need to convert it into the domain equivalence
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## Credits
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* [Converter](http://www.xsolve.pl/blog/converter-pattern-in-java-8/)

‎converter/etc/Converter.png

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‎converter/etc/Converter.ucls

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<?xml version="1.0" encoding="UTF-8"?>
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<class-diagram version="1.1.14" icons="true" automaticImage="PNG" always-add-relationships="false"
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generalizations="true" realizations="true" associations="true" dependencies="false" nesting-relationships="true"
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router="FAN">
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<class id="1" language="java" name="com.iluwatar.converter.Converter" project="converter"
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file="/converter/src/main/java/com/iluwatar/converter/Converter.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="189" width="226" x="41" y="37"/>
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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.converter.UserConverter" project="converter"
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file="/converter/src/main/java/com/iluwatar/converter/UserConverter.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="81" width="107" x="41" y="356"/>
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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.converter.User" project="converter"
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file="/converter/src/main/java/com/iluwatar/converter/User.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="279" width="188" x="307" y="37"/>
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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="4" language="java" name="com.iluwatar.converter.UserDto" project="converter"
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file="/converter/src/main/java/com/iluwatar/converter/UserDto.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="279" width="204" x="535" y="37"/>
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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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<generalization id="5">
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<end type="SOURCE" refId="2"/>
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<end type="TARGET" refId="1"/>
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</generalization>
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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>

‎converter/pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<artifactId>java-design-patterns</artifactId>
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<groupId>com.iluwatar</groupId>
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<version>1.15.0-SNAPSHOT</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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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>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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</dependency>
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</dependencies>
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<artifactId>converter</artifactId>
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</project>

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

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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* <p>
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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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* <p>
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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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* <p>
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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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package com.iluwatar.converter;
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import com.google.common.collect.Lists;
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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 Converter pattern is a behavioral design pattern which allows a common way of bidirectional
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* conversion between corresponding types (e.g. DTO and domain representations of the logically
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* isomorphic types). Moreover, the pattern introduces a common way of converting a collection of
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* objects between types.
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*/
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public class App {
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/**
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* Program entry point
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*
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* @param args command line args
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*/
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public static void main(String[] args) {
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Converter<UserDto, User> userConverter = new Converter<>(
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userDto -> new User(userDto.getFirstName(), userDto.getLastName(), userDto.isActive(),
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userDto.getEmail()),
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user -> new UserDto(user.getFirstName(), user.getLastName(), user.isActive(), user.getUserId()));
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UserDto dtoUser = new UserDto("John", "Doe", true, "whatever[at]wherever.com");
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User user = userConverter.convertFromDto(dtoUser);
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System.out.println("Entity converted from DTO:" + user);
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ArrayList<User> users = Lists.newArrayList(new User("Camile", "Tough", false, "124sad"),
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new User("Marti", "Luther", true, "42309fd"), new User("Kate", "Smith", true, "if0243"));
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System.out.println("Domain entities:");
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users.forEach(System.out::println);
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System.out.println("DTO entities converted from domain:");
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List<UserDto> dtoEntities = userConverter.createFromEntities(users);
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dtoEntities.forEach(System.out::println);
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}
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}

‎converter/src/main/java/com/iluwatar/converter/Converter.java

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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* <p>
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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
7+
* 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
9+
* copies of the Software, and to permit persons to whom the Software is
10+
* furnished to do so, subject to the following conditions:
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* <p>
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* The above copyright notice and this permission notice shall be included in
13+
* all copies or substantial portions of the Software.
14+
* <p>
15+
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16+
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17+
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18+
* 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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package com.iluwatar.converter;
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import java.util.Collection;
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import java.util.List;
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import java.util.function.Function;
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import java.util.stream.Collectors;
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/**
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* Generic converter, thanks to Java8 features not only provides a way of generic bidirectional
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* conversion between coresponding types, but also a common way of converting a collection of objects
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* of the same type, reducing boilerplate code to the absolute minimum.
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* @param <T> DTO representation's type
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* @param <U> Domain representation's type
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*/
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public class Converter<T, U> {
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private final Function<T, U> fromDto;
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private final Function<U, T> fromEntity;
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/**
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* @param fromDto Function that converts given dto entity into the domain entity.
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* @param fromEntity Function that converts given domain entity into the dto entity.
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*/
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public Converter(final Function<T, U> fromDto, final Function<U, T> fromEntity) {
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this.fromDto = fromDto;
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this.fromEntity = fromEntity;
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}
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/**
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* @param userDto DTO entity
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* @return The domain representation - the result of the converting function application on dto entity.
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*/
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public final U convertFromDto(final T userDto) {
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return fromDto.apply(userDto);
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}
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/**
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* @param user domain entity
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* @return The DTO representation - the result of the converting function application on domain entity.
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*/
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public final T convertFromEntity(final U user) {
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return fromEntity.apply(user);
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}
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/**
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* @param dtoUsers collection of DTO entities
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* @return List of domain representation of provided entities retrieved by
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* mapping each of them with the convertion function
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*/
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public final List<U> createFromDtos(final Collection<T> dtoUsers) {
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return dtoUsers.stream().map(this::convertFromDto).collect(Collectors.toList());
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}
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/**
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* @param users collection of domain entities
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* @return List of domain representation of provided entities retrieved by
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* mapping each of them with the convertion function
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*/
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public final List<T> createFromEntities(final Collection<U> users) {
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return users.stream().map(this::convertFromEntity).collect(Collectors.toList());
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}
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}

‎converter/src/main/java/com/iluwatar/converter/User.java

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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* <p>
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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
7+
* in the Software without restriction, including without limitation the rights
8+
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9+
* copies of the Software, and to permit persons to whom the Software is
10+
* furnished to do so, subject to the following conditions:
11+
* <p>
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* The above copyright notice and this permission notice shall be included in
13+
* all copies or substantial portions of the Software.
14+
* <p>
15+
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16+
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17+
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18+
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19+
* 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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package com.iluwatar.converter;
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import java.util.Objects;
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public class User {
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private String firstName;
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private String lastName;
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private boolean isActive;
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private String userId;
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/**
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* @param firstName user's first name
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* @param lastName user's last name
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* @param isActive flag indicating whether the user is active
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* @param userId user's identificator
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*/
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public User(String firstName, String lastName, boolean isActive, String userId) {
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this.firstName = firstName;
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this.lastName = lastName;
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this.isActive = isActive;
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this.userId = userId;
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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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public boolean isActive() {
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return isActive;
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}
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public String getUserId() {
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return userId;
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}
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@Override public boolean equals(Object o) {
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if (this == o) {
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return true;
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}
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if (o == null || getClass() != o.getClass()) {
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return false;
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}
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User user = (User) o;
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return isActive == user.isActive && Objects.equals(firstName, user.firstName) && Objects
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.equals(lastName, user.lastName) && Objects.equals(userId, user.userId);
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}
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@Override public int hashCode() {
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return Objects.hash(firstName, lastName, isActive, userId);
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}
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@Override public String toString() {
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return "User{" + "firstName='" + firstName + '\'' + ", lastName='" + lastName + '\''
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+ ", isActive=" + isActive + ", userId='" + userId + '\'' + '}';
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}
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}

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