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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");
}
}








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