定义：将能够处理同一类请求的对象连成一条链，所提交的请求将沿着链传递，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：
1. 大学中，奖学金的审批
2. 公司中，公文的审批。

举例：员工请求，小于3天，主任审批；大于3天小于10天，经理审理；大于10天，小于30天，总经理审批；否则直接让他辞职回家

封装请假的基本信息

/**
 * 封装请假的基本信息
 */
public class LeaveRequest {
    private String empName;
    private int leaveDays;
    private String reason;

    public LeaveRequest(String empName, int leaveDays, String reason) {
        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;
    }
}

将主任，经理，总经理等抽成一个抽象类

public abstract class Leader {
    protected String name;
    protected Leader nextLeader;//责任链上的后继对象(即上司)

    public Leader(String name) {
        this.name = name;
    }

    /**
     * 设置下一个对象
     */
    public void setNextLeader(Leader nextLeader) {
        this.nextLeader = nextLeader;
    }

    /**
     * 领导处理请求
     */
    public abstract void handleRequest(LeaveRequest request);
}

定义主任

public class DirectorLeader extends Leader{

    public DirectorLeader(String name) {
        super(name);
    }

    @Override
    public void handleRequest(LeaveRequest request) {
        if(request.getLeaveDays()<3){
            System.out.println("员工："+request.getEmpName()+"请假，天数："+request.getLeaveDays()+",理由："+request.getReason());
            System.out.println("主任："+this.name+",审批通过！");
        }else{
          if(nextLeader!=null){
              this.nextLeader.handleRequest(request);
          }
        }
    }
}

定义经理

public class ManagerLeader extends Leader {
    public ManagerLeader(String name) {
        super(name);
    }

    @Override
    public void handleRequest(LeaveRequest request) {
        if (request.getLeaveDays() < 10) {
            System.out.println("员工：" + request.getEmpName() + "请假，天数：" + request.getLeaveDays() + ",理由：" + request.getReason());
            System.out.println("经理：" + this.name + ",审批通过！");
        } else {
            if (nextLeader != null) {
                nextLeader.handleRequest(request);
            }
        }
    }
}

定义总经理

public class GeneralManager extends Leader {
    public GeneralManager(String name) {
        super(name);
    }

    @Override
    public void handleRequest(LeaveRequest request) {
        if (request.getLeaveDays() < 30) {
            System.out.println("员工：" + request.getEmpName() + "请假，天数：" + request.getLeaveDays() + ",理由：" + request.getReason());
            System.out.println("总经理：" + this.name + ",审批通过！");
        } else {
            System.out.println(request.getEmpName() + "居然请假" + request.getLeaveDays() + "天！" + request.getEmpName() + "明天不用上班了");
        }
    }
}

测试

 DirectorLeader director = new DirectorLeader("张主任");
        ManagerLeader manager = new ManagerLeader("王经理");
        GeneralManager generalManager = new GeneralManager("周总");
        director.setNextLeader(manager);
        manager.setNextLeader(generalManager);

        LeaveRequest request = new LeaveRequest("杨过", 30, "救姑姑小龙女");
        director.handleRequest(request);

责任链相当于代替了多个if …else if()语句