设计模式之责任链模式
2015-10-12 15:41
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1、核心
将能够处理同一类请求的对象连成一条链,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。2、应用场景
-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语言中,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
3、代码示例
问题场景:公司里面,请假条的审批过程:
如果请假天数小于3天,主任审批;
如果请假天数大于等于3天,小于10天,经理审批;
如果大于等于10天,小于30天,总经理审批;
如果大于等于30天,提示拒绝。
/** * 请假条类:封装请假信息 * @author ly1 * */ public class LeaveRequest { /** * 请假者姓名 */ private String name; /** * 请假天数 */ private int leaveOfDays; /** * 请假原因 */ private String reason; public LeaveRequest(String name, int leaveOfDays, String reason) { super(); this.name = name; this.leaveOfDays = leaveOfDays; this.reason = reason; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getLeaveOfDays() { return leaveOfDays; } public void setLeaveOfDays(int leaveOfDays) { this.leaveOfDays = leaveOfDays; } public String getReason() { return reason; } public void setReason(String reason) { this.reason = reason; } }
/** * 领导抽象类 * @author ly1 * */ public abstract class Leader { protected String name; protected Leader nextLeader; public Leader(String name) { super(); this.name = name; } public void setNextLeader(Leader nextLeader) { this.nextLeader = nextLeader; } public abstract void handleRequest(LeaveRequest request); }
/** * 主任类 * @author ly1 * */ public class Director extends Leader{ public Director(String name) { super(name); } @Override public void handleRequest(LeaveRequest request) { if(request.getLeaveOfDays() < 3){ System.out.println("员工:" + request.getName() + "请假,天数:" + request.getLeaveOfDays() + ",理由" + request.getReason()); System.out.println("主任:" + this.name + ",审批通过!"); }else{ this.nextLeader.handleRequest(request); } } }
/** * 经理类 * @author ly1 * */ public class Manager extends Leader{ public Manager(String name) { super(name); } @Override public void handleRequest(LeaveRequest request) { if(request.getLeaveOfDays() < 10){ System.out.println("员工:" + request.getName() + "请假,天数:" + request.getLeaveOfDays() + ",理由" + request.getReason()); System.out.println("经理:" + this.name + ",审批通过!"); }else{ this.nextLeader.handleRequest(request); } } }
/** * 总经理类 * @author ly1 * */ public class GeneralManager extends Leader{ public GeneralManager(String name) { super(name); } @Override public void handleRequest(LeaveRequest request) { if(request.getLeaveOfDays() < 30){ System.out.println("员工:" + request.getName() + "请假,天数:" + request.getLeaveOfDays() + ",理由" + request.getReason()); System.out.println("总经理:" + this.name + ",审批通过!"); }else{ System.out.println(request.getName()+",你是不想干了吧!"); } } }
/** * 客户端调用 * @author ly1 * */ public class Client { public static void main(String[] args) { Leader director = new Director("李主任"); Leader manager = new Manager("王经理"); Leader gManager = new GeneralManager("刘总经理"); director.setNextLeader(manager); manager.setNextLeader(gManager); LeaveRequest request1 = new LeaveRequest("Bob", 1, "休息"); director.handleRequest(request1); LeaveRequest request2 = new LeaveRequest("Alice", 6, "十一黄金周"); director.handleRequest(request2); LeaveRequest request3 = new LeaveRequest("Tom", 17, "出国旅游"); director.handleRequest(request3); } } 结果: 员工:Bob请假,天数:1,理由休息 主任:李主任,审批通过! 员工:Alice请假,天数:6,理由十一黄金周 经理:王经理,审批通过! 员工:Tom请假,天数:17,理由出国旅游 总经理:刘总经理,审批通过!
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