data transfer hash(issue 1269)

Data_Transfer_Hash/etc/dataTransferHash.puml

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+@startuml
+
+Class data_transfer_hash {
+    +key
+    -value
+    +getVelue(key)
+}
+class Business_objects
+class Presentation_tier_objects
+data_transfer_hash<--Business_objects : create or use
+data_transfer_hash<--Presentation_tier_objects : create or use
+@enduml

Data_Transfer_Hash/java-design-patterns.iml

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+<?xml version="1.0" encoding="UTF-8"?>
+<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_7">
+    <output url="file://$MODULE_DIR$/target/classes" />
+    <output-test url="file://$MODULE_DIR$/target/test-classes" />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src/main/java" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/test/java" isTestSource="true" />
+      <excludeFolder url="file://$MODULE_DIR$/target" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" scope="TEST" name="Maven: junit:junit:4.11" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
+  </component>
+</module>

Data_Transfer_Hash/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>
+
+ <groupId>com.iluwatar</groupId>
+ <artifactId>java-design-patterns</artifactId>
+ <version>1.24.0-SNAPSHOT</version>
+
+  <name>Data_Transfer_Hash</name>
+  <!-- FIXME change it to the project's website -->
+  <url>http://www.example.com</url>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>1.7</maven.compiler.source>
+    <maven.compiler.target>1.7</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.11</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
+      <plugins>
+        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
+        <plugin>
+          <artifactId>maven-clean-plugin</artifactId>
+          <version>3.1.0</version>
+        </plugin>
+        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
+        <plugin>
+          <artifactId>maven-resources-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.0</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-surefire-plugin</artifactId>
+          <version>2.22.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-jar-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-install-plugin</artifactId>
+          <version>2.5.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-deploy-plugin</artifactId>
+          <version>2.8.2</version>
+        </plugin>
+        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
+        <plugin>
+          <artifactId>maven-site-plugin</artifactId>
+          <version>3.7.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-project-info-reports-plugin</artifactId>
+          <version>3.0.0</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+  </build>
+</project>

Data_Transfer_Hash/readme.md

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+---
+layout: pattern
+title: data transfer hash
+folder: Data_Transfer_Hash
+permalink: /patterns/Data_Transfer_Hash/
+categories: Architectural
+tags:
+ - Performance
+---
+
+## Also known as
+
+* data transfer hash
+
+## Intent
+
+Providing a  class called data transfer hash, in order to send message between other class.
+
+## Explanation
+
+
+> Data transfer hashes may be implemented as simple hash tables (or HashMaps). 
+A more robust implementation uses a container object to hold the hash, as well as identifying information, type-safe data retrieval methods, and well-known keys.
+> https://www.oreilly.com/library/view/j2ee-design-patterns/0596004273/re12.html
+
+**Programmatic Example**
+
+We have an function `create` and `get`.
+
+```java
+public static void main( String[] args )
+    {
+        Hash hash= new Hash();
+        Business business=new Business();
+        Presentation presentation=new Presentation();
+        business.create("a", "aaa", hash);
+        System.out.println("Business create "+"aaa");
+        business.create("b", "bbb", hash);
+        System.out.println("Business create "+"bbb");
+        business.create("c", "ccc", hash);
+        System.out.println("Business create "+"ccc");
+
+        presentation.get("a", hash);
+        System.out.println("Presentation heard "+presentation.get("a", hash));
+        presentation.get("b", hash);
+        System.out.println("Presentation heard "+presentation.get("b", hash));
+    }
+
+```
+
+
+
+
+
+Program output:
+
+```java
+Business create aaa
+Business create bbb
+Business create ccc
+Presentation heard aaa
+Presentation heard bbb
+```
+
+## Class Diagram
+
+![alt text](./etc/dataTransferHash.png "data Transfer Hash pattern class diagram")
+
+## Applicability
+
+Use the data transfer hash pattern when you only care about the creation of a object, not how to create 
+and manage it.
+
+* Not only string but other types canbe value but key must be string
+

Data_Transfer_Hash/src/main/java/Data_Transfer_Hash/App.java

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+package Data_Transfer_Hash;
+/*
+Data transfer hashes may be implemented as simple hash tables (or HashMaps). 
+A more robust implementation uses a container object to hold the hash, as well as identifying information, type-safe data retrieval methods, and well-known keys.
+*/
+
+public class App 
+{
+    public static void main( String[] args )
+    {
+        Hash hash= new Hash();
+        Business business=new Business();
+        Presentation presentation=new Presentation();
+        business.create("a", "aaa", hash);
+        System.out.println("Business create "+"aaa");
+        business.create("b", "bbb", hash);
+        System.out.println("Business create "+"bbb");
+        business.create("c", "ccc", hash);
+        System.out.println("Business create "+"ccc");
+
+        presentation.get("a", hash);
+        System.out.println("Presentation heard "+presentation.get("a", hash));
+        presentation.get("b", hash);
+        System.out.println("Presentation heard "+presentation.get("b", hash));
+
+
+
+    }
+
+
+}

Data_Transfer_Hash/src/main/java/Data_Transfer_Hash/Business.java

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+package Data_Transfer_Hash;
+/*Business objects
+Create hashes for sending data, or use values in received hashes.*/
+public class Business {
+    public void create(String k,Object v,Hash hash)
+    {
+        hash.create(k, v);
+
+    }
+    public Object get(String k,Hash hash)
+    {
+
+
+        return  hash.get(k);
+    }
+}

Data_Transfer_Hash/src/main/java/Data_Transfer_Hash/Hash.java

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+package Data_Transfer_Hash;
+
+import java.util.Hashtable;
+/*Data transfer hash
+Stores data for transport between layers as a set of values associated with well-known keys.*/
+public class Hash {
+    private Hashtable hash;
+    Hash()
+    {hash=new Hashtable();}
+    public void create(String k,Object v)
+    {
+        this.hash.put(k, v);
+    }
+    public Object get(String k)
+    {
+        return  this.hash.get(k);
+    }
+
+}

Data_Transfer_Hash/src/main/java/Data_Transfer_Hash/Presentation.java

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+package Data_Transfer_Hash;
+/*Presentation tier objects
+Create hashes for sending data, or use values in received hashes. */
+public class Presentation {
+    public void create(String k,Object v,Hash hash)
+    {
+        hash.create(k, v);
+
+    }
+    public Object get(String k,Hash hash)
+    {
+
+        return  hash.get(k);
+
+    }
+
+}

Data_Transfer_Hash/src/test/java/Data_Transfer_Hash/AppTest.java

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+package Data_Transfer_Hash;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class AppTest 
+{
+    @Test
+    public void getTrueCvreate()
+    {
+        Hash hash= new Hash();
+        Business business=new Business();
+        business.create("a", "aaa", hash);
+
+    }
+    @Test
+    public void getTrueAnswer()
+    {
+        Hash hash= new Hash();
+        Business business=new Business();
+        Presentation presentation=new Presentation();
+        business.create("a", "aaa", hash);
+        business.create("b", "bbb", hash);
+        business.create("c", "ccc", hash);
+
+        assertEquals(presentation.get("a", hash),"aaa");
+        assertEquals(presentation.get("b", hash),"bbb");
+
+    }
+    @Test
+    public void getTrueAnswerAfterChange()
+    {
+        Hash hash= new Hash();
+        Business business=new Business();
+        Presentation presentation=new Presentation();
+        business.create("a", "aaa", hash);
+        business.create("b", "bbb", hash);
+        business.create("c", "ccc", hash);
+
+        assertEquals(presentation.get("a", hash),"aaa");
+        assertEquals(presentation.get("b", hash),"bbb");
+        business.create("a", "abc", hash);
+        assertEquals(presentation.get("a", hash),"abc");
+    }
+}