15、责任链模式

6.4.3 案例实现
现需要开发一个请假流程控制系统。请假一天以下的假只需要小组长同意即可；请假1天到3天的假还需要部门经理同意；请求3天到7天还需要总经理同意才行。
类图如下

//请假条类
public class LeaveRequest {
    private String name;
    //请假天数
    private int num;
    //原因
    private String content;

    public LeaveRequest(String name, int num, String content) {
        this.name = name;
        this.num = num;
        this.content = content;
    }

    public String getName() {
        return name;
    }

    public int getNum() {
        return num;
    }

    public String getContent() {
        return content;
    }
}

//抽象处理者类
public abstract class Handler {
    protected final static int NUM_ONE=1;
    protected final static int NUM_THREE=3;
    protected final static int NUM_SEVEN=7;
    //该领导处理的请求天数区间
    private int numStart;
    private int numEnd;
    //声明后续者（声明上级领导）
    private Handler nextHandler;

    public Handler(int numStart) {
        this.numStart = numStart;
    }

    public Handler(int numStart, int numEnd) {
        this.numStart = numStart;
        this.numEnd = numEnd;
    }
    //设置上级领导对象

    public void setNextHandler(Handler nextHandler) {
        this.nextHandler = nextHandler;
    }
    //各级领导处理请求条的方法
    protected abstract void handleLeave(LeaveRequest leaveRequest);
    //提交请求条
    public final void submit(LeaveRequest leaveRequest){
        //该领导进行审批
        this.handleLeave(leaveRequest);
        if (this.nextHandler !=null && leaveRequest.getNum() >this.numEnd){
            //提交给上级领导进行审批
            this.nextHandler.submit(leaveRequest);
        }else {
            System.out.println("流程结束...");
        }
    }
}

//小组长类（具体的处理者）
public class GroupLeader extends Handler {
    public GroupLeader(){
        super(0,Handler.NUM_ONE);
    }

    @Override
    protected void handleLeave(LeaveRequest leaveRequest) {
        System.out.println(leaveRequest.getName()+"申请请假:"+
        leaveRequest.getNum()+",原因："+leaveRequest.getContent());
        System.out.println("小组长审批：同意");
    }
}

//部门经理类（具体的处理者）
public class Manager extends Handler {
    public Manager(){
        super(Handler.NUM_ONE,Handler.NUM_THREE);
    }

    @Override
    protected void handleLeave(LeaveRequest leaveRequest) {
        System.out.println(leaveRequest.getName()+"申请请假:"+
        leaveRequest.getNum()+",原因："+leaveRequest.getContent());
        System.out.println("部门经理审批：同意");
    }
}

//总经理类（具体的处理者）
public class GeneralManager extends Handler {
    public GeneralManager(){
        super(Handler.NUM_THREE,Handler.NUM_SEVEN);
    }

    @Override
    protected void handleLeave(LeaveRequest leaveRequest) {
        System.out.println(leaveRequest.getName()+"申请请假:"+
        leaveRequest.getNum()+"天,原因："+leaveRequest.getContent());
        System.out.println("总经理审批：同意");
    }
}

public class Client {
    public static void main(String[] args) {
        //创建一个请假条对象
        LeaveRequest leaveRequest=new LeaveRequest("小何",1,"感冒");
        //创建各级领导对象
        GroupLeader groupLeader=new GroupLeader();
        Manager manager=new Manager();
        GeneralManager generalManager=new GeneralManager();
        //设置处理者链
        groupLeader.setNextHandler(manager);
        manager.setNextHandler(generalManager);
        //小何提交请假申请
        groupLeader.submit(leaveRequest);
    }
}