职责链模式（Chain of Responsibility）

**定义：**避免请求的发送者和接收者耦合在一起，让多个对象都有可能接收请求，将这些对象连接成一条链，沿着这条链传递请求，直到有对象处理它为止。

角色：

• 抽象处理者：Handler
• 具体处理者：ConcreteHandler
• 客户类：Client

模式分析：

关键在于抽象处理者类的设计：很多对象由每一个对象对其下家的引用而连接在一起。

抽象处理者典型代码：

//审批者类：抽象处理者abstract class Approver {protected Approver successor; //定义后继对象protected String name; //审批者姓名public Approver(String name) {this.name = name;}//设置后继者public void setSuccessor(Approver successor) {this.successor = successor;}//抽象请求处理方法public abstract void processRequest(PurchaseRequest request);}

具体处理者典型代码：

//董事长类：具体处理者class ViceManager extends Approver {public ViceManager(String name) {super(name);}//具体请求处理方法public void processRequest(PurchaseRequest request) {if (request.getAmount() < 100000) {System.out.println("副总经理" + this.name + "审批采购单：" + request.getNumber() + "，金额：" + 				request.getAmount() + "元，采购目的：" + request.getPurpose() + "。");  //处理请求}else {this.successor.processRequest(request);  //转发请求}}}

客户端调用典型代码：轮流设置下家

position1.setSuccessor(position2);position2.setSuccessor(position3);position3.setSuccessor(position4);position4.setSuccessor(meeting);

package com.c015;public class Client {public static void main(String[] args) {Approver position1,position2,position3,position4,meeting;  // 多个处理者position1 = new Director("甲");position2 = new PartManager("乙");position3 = new ViceManager("丙");position4 = new Manager("丁");meeting = new Congress("职工大会");//创建职责链position1.setSuccessor(position2);position2.setSuccessor(position3);position3.setSuccessor(position4);position4.setSuccessor(meeting);//创建采购单PurchaseRequest pr1 = new PurchaseRequest(5000,10001,"XXX");position1.processRequest(pr1);PurchaseRequest pr2 = new PurchaseRequest(45000,10002,"XXX");position1.processRequest(pr2);PurchaseRequest pr3 = new PurchaseRequest(77000,10003,"XXX");position1.processRequest(pr3);PurchaseRequest pr4 = new PurchaseRequest(150000,10004,"XXX");position1.processRequest(pr4);PurchaseRequest pr5 = new PurchaseRequest(800000,10005,"XXX");position1.processRequest(pr5);}}

核心理解

职责链模式关键在于设置职责的下家！

抽象处理者类要有一个自身的对象作为成员属性变量，并通过一个set方法完成赋值，之后要提供一个具体处理的方法接口供子类重写！

后续的子类重写具体的处理办法，如果处理不了，再次调用父类的处理方法直接把请求交给下家来完成！