设计模式 - 责任链
优质
小牛编辑
129浏览
2023-12-01
责任链(Chain Of Responsibility)
Intent
使多个对象都有机会处理请求,从而避免请求的发送者和接收者之间的耦合关系。将这些对象连成一条链,并沿着这条链发送该请求,直到有一个对象处理它为止。
Class Diagram
Handler:定义处理请求的接口,并且实现后继链(successor)
Implementation
// java public abstract class Handler { protected Handler successor; public Handler(Handler successor) { this.successor = successor; } protected abstract void handleRequest(Request request); }
// java public class ConcreteHandler1 extends Handler { public ConcreteHandler1(Handler successor) { super(successor); } @Override protected void handleRequest(Request request) { if (request.getType() == RequestType.TYPE1) { System.out.println(request.getName() + " is handle by ConcreteHandler1"); return; } if (successor != null) { successor.handleRequest(request); } } }
// java public class ConcreteHandler2 extends Handler { public ConcreteHandler2(Handler successor) { super(successor); } @Override protected void handleRequest(Request request) { if (request.getType() == RequestType.TYPE2) { System.out.println(request.getName() + " is handle by ConcreteHandler2"); return; } if (successor != null) { successor.handleRequest(request); } } }
// java public class Request { private RequestType type; private String name; public Request(RequestType type, String name) { this.type = type; this.name = name; } public RequestType getType() { return type; } public String getName() { return name; } }
// java public enum RequestType { TYPE1, TYPE2 }
// java public class Client { public static void main(String[] args) { Handler handler1 = new ConcreteHandler1(null); Handler handler2 = new ConcreteHandler2(handler1); Request request1 = new Request(RequestType.TYPE1, "request1"); handler2.handleRequest(request1); Request request2 = new Request(RequestType.TYPE2, "request2"); handler2.handleRequest(request2); } }
// html request1 is handle by ConcreteHandler1 request2 is handle by ConcreteHandler2