12.责任链模式(设计模式笔记)

行为型模式关注系统中对象之间的相互交互，研究系统在运行时对象之间的相互通信和协作，
进一步明确对象的职责
创建型模式关注对象的创建过程

结构型模式关注对象和类的组织

定义：
将能够处理同一类请求的对象连城一条链，所提交的请求沿着链传递，
链上的对象逐个判断是否有能力处理该请求，如果能则处理，如果不能则
传递给链上的下一个对象。




场景：
打牌时，轮流出牌
接力赛跑
大学中，奖学金审批
公司中，公文审批


开发中常见的场景:
-java中，异常机制就是一种责任链模式。一个try可以对应多个catch，
当第一个catch不匹配类型，则自动跳到第二个catch。
-javascript语言中，事件的冒泡和捕获机制。java语音中，事件的处理采用观察者模式。
-Servlet开发中，过滤器的链式处理
-struts2中，拦截器的调用也是典型的责任链模式。

/** * 封装请假的基本信息 * @author Administrator * */public class LeaveRequest {private String empName;private int leaveDays;private String reason;public LeaveRequest(String empName, int leaveDays, String reason) {super();this.empName = empName;this.leaveDays = leaveDays;this.reason = reason;}public String getEmpName() {return empName;}public void setEmpName(String empName) {this.empName = empName;}public int getLeaveDays() {return leaveDays;}public void setLeaveDays(int leaveDays) {this.leaveDays = leaveDays;}public String getReason() {return reason;}public void setReason(String reason) {this.reason = reason;}}

/** * 抽象类 * @author Administrator * */public abstract class Leader {protected String name;protected Leader nextLeader; //责任链下一级对象public Leader(String name) {super();this.name = name;}//设置责任链的后续对象public void setNextLeader(Leader nextLeader) {this.nextLeader = nextLeader;}/** * 处理请求的核心的业务方法 * @param request */public abstract void handleRequest(LeaveRequest request);}

/** * 主任(审批请假天数小于三天) * @author Administrator * */public class Director extends Leader{public Director(String name) {super(name);}@Overridepublic void handleRequest(LeaveRequest request) {if(request.getLeaveDays() < 3) {System.out.println("主任"+this.name+"审批-" + "员工"+request.getEmpName()+"请假"+request.getLeaveDays()+"天,理由:" + request.getReason());} else {if(this.nextLeader != null) {this.nextLeader.handleRequest(request);}}}}

/** * 经理(审批请假天数小于10天大于三天) * @author Administrator * */public class Manager extends Leader{public Manager(String name) {super(name);}@Overridepublic void handleRequest(LeaveRequest request) {if(request.getLeaveDays() < 10 && request.getLeaveDays() > 3) {System.out.println("经理"+this.name+"审批-" + "员工"+request.getEmpName()+"请假"+request.getLeaveDays()+"天,理由:" + request.getReason());} else {if(this.nextLeader != null) {this.nextLeader.handleRequest(request);}}}}

/** * 总经理(审批请假天数大于) * @author Administrator * */public class GeneralManager extends Leader{public GeneralManager(String name) {super(name);}@Overridepublic void handleRequest(LeaveRequest request) {if(request.getLeaveDays() > 10 && request.getLeaveDays() < 30) {System.out.println("总经理"+this.name+"审批-" + "员工"+request.getEmpName()+"请假"+request.getLeaveDays()+"天,理由:" + request.getReason());} else {System.out.println("莫非:" + request.getEmpName() + "想辞职，居然请假"+request.getLeaveDays() + "天");}}}

public class Client {public static void main(String[] args) {Leader a = new Director("张三");Leader b = new Manager("李四");Leader c = new GeneralManager("王五");//组织责任链对象之间的关系a.setNextLeader(b);b.setNextLeader(c);//开始请假操作LeaveRequest req1 = new LeaveRequest("甜瓜", 200, "想去旅游");a.handleRequest(req1);}}