#1298 Added the resources for Identity Field Design Pattern

identity-field/README.md

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+---
+title: Identity Field
+category: Structural
+language: en
+tag:
+- Enterprise Integration Pattern
+---
+
+## Also known as
+
+> P of EAA
+
+## Intent
+
+> Saves a database ID field in an object to maintain an identity between an in-memory object and a database row.
+
+## Explanation
+
+>The Identity Field design pattern is a structural design pattern that allows you to maintain the identity of an object between the application and the database. It is also known as P of EAA, which stands for Primary Key of Entity-Attribute-Association.
+
+>The Identity Field design pattern works by adding a field to your object that matches the primary key of the corresponding database table. This field is then used to identify the object in the database.
+
+## Class diagram
+![alt text](./etc/identity-field.urm.png "Identity-Field design pattern class diagram")
+
+## Applicability
+
+> Use Identity Field when there’s a mapping between objects in memory and rows in a database.
+
+## Credits
+
+* [P of EAA](https://martinfowler.com/eaaCatalog/identityField.html)
+* [Identity field design pattern](https://www.sourcecodeexamples.net/2018/05/identity-field-pattern.html)

identity-field/etc/identity-field.urm.puml

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+@startuml
+
+class Person {
+    + id : long
+    + name : String
+    + age : int
+}
+
+Person <|-- Person
+
+@enduml

identity-field/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.iluwatar</groupId>
+        <artifactId>java-design-patterns</artifactId>
+        <version>1.26.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>identity-field</artifactId>
+
+
+</project>

identity-field/src/main/java/com/iluwatar/Person.java

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+package com.iluwatar;
+
+public class Person {
+
+    // The identity of the person.
+    private long id;
+
+    // The name of the person.
+    private String name;
+
+    // The age of the person.
+    private int age;
+
+    public Person() {}
+
+    public Person(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+}

pom.xml

@@ -207,6 +207,7 @@
     <module>context-object</module>
     <module>thread-local-storage</module>
     <module>optimistic-offline-lock</module>
+      <module>identity-field</module>
   </modules>
   <repositories>
     <repository>