责任链模式的官方定义:很多对象由每一个对象对其下家的引用而连接起来形成一条链。请求在这个链上传递,直到链上的某一个对象决定处理此请求。
责任链模式的角色:
1.Handler:抽象处理者,定义出一个处理请求的接口。
2.ConcreteHandler:具体处理者,具体处理者接到请求后,可以选择将请求处理掉,或者将请求传给下家。
3.Request:抽象请求者,定义请求接口。
4.ConcreteRequest:具体请求者,继承抽象请求,实现具体的请求。
Handler(抽象处理者)
package com.exanple.command; /** * 抽象处理者 * @author zeng * */ public abstract class Handler { Handler nextHandler; public void handleRequest(Request request){ if (request.getHandlerLevel() == getHandlerLevel()) { handle(request); }else { if (nextHandler != null) { nextHandler.handleRequest(request); } } } public abstract int getHandlerLevel(); public abstract void handle(Request request); }
具体处理者一
package com.exanple.command; public class ConcoreteHandler01 extends Handler{ @Override public int getHandlerLevel() { return 1; } @Override public void handle(Request request) { System.out.println("处理请求: " + request.getHandlerLevel()); } }
具体处理者二
package com.exanple.command; public class ConcoreteHandler02 extends Handler{ @Override public int getHandlerLevel() { return 2; } @Override public void handle(Request request) { System.out.println("处理请求: " + request.getHandlerLevel()); } }
具体处理者三
package com.exanple.command; public class ConcoreteHandler03 extends Handler{ @Override public int getHandlerLevel() { return 3; } @Override public void handle(Request request) { System.out.println("处理请求: " + request.getHandlerLevel()); } }
抽象请求者
package com.exanple.command; public abstract class Request { public abstract int getHandlerLevel(); }
具体请求者
package com.exanple.command; public class ConcoreteRequest extends Request{ @Override public int getHandlerLevel() { return 2; } }
客户类
package com.exanple.command; public class Client { public static void main(String[] args) { Handler handler01 = new ConcoreteHandler01(); Handler handler02 = new ConcoreteHandler02(); Handler handler03 = new ConcoreteHandler03(); handler01.nextHandler = handler02; handler02.nextHandler = handler03; Request request = new ConcoreteRequest(); //第一个处理者开始分发请求 handler01.handleRequest(request); } }