责任链模式（Chain of Responsibility Pattern）为请求创建了一个接收者对象的链。这种模式给予请求的类型，对请求的发送者和接收者进行解耦。这种类型的设计模式属于行为型模式。
    就是每一个类只负责自己的模块的功能。

    应用实例： 1、红楼梦中的”击鼓传花”。 2、JS 中的事件冒泡。 3、JAVA WEB 中 Apache Tomcat 对 Encoding 的处理，Struts2 的拦截器，jsp servlet 的 Filter。

    请假请求类

    1. /**
    2.  * @author meikb
    3.  * @desc 请假请求类
    4.  * @date 2020-05-23 16:59
    5.  */
    6. public class LeaveRequest {
    7.     public LeaveRequest(int day){
    8.         this.day = day;
    9.     }
    11.     private int day;
    13.     public int getDay() {
    14.         return day;
    15.     }
    17.     public void setDay(int day) {
    18.         this.day = day;
    19.     }
    20. }

    抽象类

    1. /**
    2.  * @author meikb
    3.  * @desc    请假抽象类
    4.  * @date 2020-05-23 16:21
    5.  */
    6. public abstract class AbstractLeave {
    7.     public int min = 1;
    8.     public int middle = 3;
    9.     public int max = 5;
    11.     protected AbstractLeave nextHandler;
    13.     public void handLeave(LeaveRequest request){
    15.     }
    17.     public AbstractLeave getNextHandler() {
    18.         return nextHandler;
    19.     }
    21.     public void setNextHandler(AbstractLeave nextHandler) {
    22.         this.nextHandler = nextHandler;
    23.     }
    24. }

    一级审核人

    1. /**
    2.  * @author meikb
    3.  * @desc
    4.  * @date 2020-05-23 16:57
    5.  */
    6. public class FirstLeader extends AbstractLeave{
    7.     @Override
    8.     public void handLeave(LeaveRequest request) {
    9.         if(request.getDay() <= min){
    10.             System.out.println("审核完成");
    11.             return;
    12.         }
    14.         System.out.println("一级领导审核通过");
    16.         if(null != this.nextHandler){
    17.             this.nextHandler.handLeave(request);
    18.         }
    19.     }
    21.     @Override
    22.     public void setNextHandler(AbstractLeave nextHandler) {
    23.         super.setNextHandler(nextHandler);
    24.     }
    25. }

    二级审核人

    1. /**
    2.  * @author meikb
    3.  * @desc
    4.  * @date 2020-05-23 16:57
    5.  */
    6. public class SecondLeader extends AbstractLeave{
    7.     @Override
    8.     public void handLeave(LeaveRequest request) {
    9.         if(request.getDay() <= middle){
    10.             System.out.println("二级审核完成");
    11.             return;
    12.         }
    14.         System.out.println("二级审核通过");
    16.         if(null != this.nextHandler){
    17.             this.nextHandler.handLeave(request);
    18.         }
    19.     }
    21.     @Override
    22.     public void setNextHandler(AbstractLeave nextHandler) {
    23.         super.setNextHandler(nextHandler);
    24.     }
    25. }

    三级审核人

    1. /**
    2.  * @author meikb
    3.  * @desc
    4.  * @date 2020-05-23 16:57
    5.  */
    6. public class ThridLeader extends AbstractLeave{
    7.     @Override
    8.     public void handLeave(LeaveRequest request) {
    9.         System.out.println("三级领导审核完成");
    11.         if(null != this.nextHandler){
    12.             this.nextHandler.handLeave(request);
    13.         }
    14.     }
    16.     @Override
    17.     public void setNextHandler(AbstractLeave nextHandler) {
    18.         super.setNextHandler(nextHandler);
    19.     }
    20. }

    主函数

    1. /**
    2.  * @author meikb
    3.  * @desc 主函数
    4.  * @date 2020-05-23 17:06
    5.  */
    6. public class ChainMain {
    7.     public static void main(String[] args) {
    8.         LeaveRequest request = new LeaveRequest(4);
    10.         FirstLeader firstLeader = new FirstLeader();
    11.         SecondLeader secondLeader = new SecondLeader();
    12.         ThridLeader thridLeader = new ThridLeader();
    14.         firstLeader.setNextHandler(secondLeader);
    15.         secondLeader.setNextHandler(thridLeader);
    16.         firstLeader.handLeave(request);
    17.     }
    18. }