Design Patterns in Java (Behavioral) - Chain of Responsability

Chain of Responsibility

• Decoupling sender from receiver
• Promote loose coupling

Example

This example pass a request to be approved and validate if that position can approve it or need to be passed to the next level.

Main

 public static void main(String[] args) {

  

  Manager m = new Manager();

  Director d = new Director();

  CEO c = new CEO();

  

  m.setSuccesor(d);

  d.setSuccesor(c);

  

  Request r1 = new Request(1, 500);

  m.handleRequest(r1);

  

  

  Request r2 = new Request(2, 500);

  m.handleRequest(r2);

  


























 }

Handle

public abstract class Handler {



 protected Handler succesor;

 

 public void setSuccesor(Handler succesor){

  this.succesor = succesor;

 }

 

 public abstract void handleRequest(Request r);



}

Request

public class Request {



 private int requestType;

 private int amount;

 

 public Request(int requestType, int amount){

  this.requestType = requestType;

  this.amount = amount;

 }

 

 public int getRequestType() {

  return requestType;

 }

 public double getAmount() {

  return amount;

 }

 

 




























}

 

Manager

public class Manager extends Handler {



 @Override

 public void handleRequest(Request r) {

  if(r.getRequestType() == 3){

   System.out.println(" Manager can approve this request");

  }else{

   succesor.handleRequest(r);

  }



 }
























} 

Director

public class Director extends Handler {



 @Override

 public void handleRequest(Request r) {

  if(r.getRequestType() == 2){

   System.out.println(" Director can approve this request");

  }else{

   succesor.handleRequest(r);

  }

  

 } 
























}

 

CEO

public class CEO extends Handler {



 @Override

 public void handleRequest(Request r) {

  System.out.println("CEO can approve everything");



 }


















}