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Merged
merged 3 commits into from
Nov 28, 2019
Merged

Adding Proxy Design Pattern #1178

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5d79026
adds proxy design pattern.
ali4j Nov 3, 2019
e30d115
removes the Citizen class in src directory.
ali4j Nov 28, 2019
45fee18
adds commit to the President class.
ali4j Nov 28, 2019
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31 changes: 31 additions & 0 deletions src/main/java/com/designpatterns/structural/proxy/president/President.java
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package com.designpatterns.structural.proxy.president;

import com.designpatterns.creational.singleton.Singleton;

/**
* This is a class which is gonna be proxied by PresidentSecretary.
* Whenever any citizen decides to contact the President, they have to talk to the Secretary.
*/
public class President {

private volatile static President instance = null;

private President() {}

static President getInstance() {
if (instance == null) {
synchronized (Singleton.class) {
if (instance == null) {
instance = new President();
}
}
}
return instance;
}



void talkToThePresident(String message){
System.out.println("President: I have received the message:" + message);
}
}
25 changes: 25 additions & 0 deletions src/main/java/com/designpatterns/structural/proxy/president/PresidentSecretary.java
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package com.designpatterns.structural.proxy.president;

public class PresidentSecretary {

private President president;

public PresidentSecretary() {
this.president = President.getInstance();
}

public void leaveValidMessageForPresident(String message){

if(!isMessageValid(message))
throw new RuntimeException("invalid message");

System.out.println("Secretary: message is being sent to the President...");
president.talkToThePresident(message);
System.out.println("Secretary: message is sent to the President.");

}

private boolean isMessageValid(String message) {
return message != null && !message.isEmpty() && message.length() >= 10 && message.length() <= 100;
}
}
39 changes: 39 additions & 0 deletions src/test/java/com/designpatterns/structural/proxy/Citizen.java
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package com.designpatterns.structural.proxy;

import com.designpatterns.structural.proxy.president.PresidentSecretary;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

public class Citizen {


private PresidentSecretary presidentSecretary = new PresidentSecretary();

@Test
public void talkToPresident_secretaryShouldRejectTooShortMessage() {
String message = "Hi there.";

Assertions.assertThrows(RuntimeException.class, () -> {
presidentSecretary.leaveValidMessageForPresident(message);
});
}

@Test
public void talkToPresident_secretaryShouldRejectTooLongMessage() {
String message = "Hi there. this is a message about some personal issue which I have decided to share with Mr.President.";

Assertions.assertThrows(RuntimeException.class, () -> {
presidentSecretary.leaveValidMessageForPresident(message);
});
}

@Test
public void talkToPresident_secretaryShouldAcceptTheMessage() {
String message = "Hello Mr.President";

presidentSecretary.leaveValidMessageForPresident(message);
Assertions.assertTrue(true);
}


}