大话设计模式-职责链模式学习总结

一、概念

职责链模式:使多个对象都有机会处理请求,从而避免请求的发送者和接受者之间的耦合关系。将这个对象连成一条链,并沿着这条链传递该请求,直到有一个对象接受它为止。

二、类图及基本代码

//处理请示的接口
public abstract class Handler {
    protected Handler successor;
    //设置后继者
    public void SetSuccessor(Handler successor){
        this.successor=successor;
    }
    //处理请求
    public abstract void HandleRequest(int request);


}

//具体处理者,处理它所负责的请求,可访问它的后继者,
//如果可处理该请求,就处理之,否则将该请求转发给它的后继者


//有权处理0~10
public class ConcreteHandler1 extends Handler{

    @Override
    public void HandleRequest(int request) {
        if(request>=0&&request<10){
            System.out.println(this.getClass().getName()+"处理请求"+request);
        }else if(successor!=null){
            successor.HandleRequest(request);
        }
    }

}

//有权处理10~20
public class ConcreteHandler2 extends Handler{

    @Override
    public void HandleRequest(int request) {
        if(request>=10&&request<20){
            System.out.println(this.getClass().getName()+"处理请求"+request);
        }else if(successor!=null){
            successor.HandleRequest(request);
        }
    }

}

//有权处理20~30以内
public class ConcreteHandler3 extends Handler{

    @Override
    public void HandleRequest(int request) {
        if(request>=20&&request<30){
            System.out.println(this.getClass().getName()+"处理"+request);
        }else if (successor!=null) {
            successor.HandleRequest(request);
        }
    }

}

//客户端
public class Client {
    public static void main(String[] args) {
        Handler handler1=new ConcreteHandler1();
        Handler handler2=new ConcreteHandler2();
        Handler handler3=new ConcreteHandler3();

        handler1.SetSuccessor(handler2);
        handler2.SetSuccessor(handler3);


        int requests[]=new int[]{
                2,5,14,22,18,3,27,20
        };
        for (int i : requests) {
            handler1.HandleRequest(i);
        }
    }

}

三、实例之请假及涨工资

//管理者(抽象)
public abstract class Manager {
    protected String name;
    protected Manager superior;
    public Manager(String name){
        this.name=name;
    }

    //设置管理者的上级
    public void SetSuperior(Manager superior){
        this.superior=superior;
    }

    //处理请求
    public abstract void RequestApplications(Request request);
}

//经理
public class CommonManager extends Manager{

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

    @Override
    public void RequestApplications(Request request) {
        if(request.getRequestType()=="请假"&&request.getNumber()<=2){
            System.out.println(name+"批准"+request.getRequestType()+"  数量:"+request.getNumber());
        }else if(superior!=null){
            superior.RequestApplications(request);
        }
    }

}

//总经理
public class GeneralManager extends Manager{

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

    @Override
    public void RequestApplications(Request request) {
        if(request.getRequestType()=="请假"){
            System.out.println(name+"批准"+request.getRequestType()+"  数量:"+request.getNumber());
        }else if(request.getRequestType()=="加薪"&&request.getNumber()<=500){
            System.out.println(name+"批准"+request.getRequestType()+"  数量:"+request.getNumber());
        }else if(request.getRequestType()=="加薪"&&request.getNumber()>500){
            System.out.println(name+"不批准"+request.getRequestType()+" 数量:"+request.getNumber());
        }
    }

}

//总监
public class Majordomo extends Manager{

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

    @Override
    public void RequestApplications(Request request) {
        if(request.getRequestType()=="请假"&&request.getNumber()<=5){
            System.out.println(name+"批准"+request.getRequestType()+"  数量:"+request.getNumber());
        }else if(superior!=null){
            superior.RequestApplications(request);
        }
    }

}

//申请
public class Request {
    //申请类型
    private String requestType;
    //申请内容
    private String requestContent;
    //数量
    private int number;
    public String getRequestType() {
        return requestType;
    }
    public void setRequestType(String requestType) {
        this.requestType = requestType;
    }
    public String getRequestContent() {
        return requestContent;
    }
    public void setRequestContent(String requestContent) {
        this.requestContent = requestContent;
    }
    public int getNumber() {
        return number;
    }
    public void setNumber(int number) {
        this.number = number;
    }




}

/*
 * 客户端的申请都是由经理a开始,具体由谁处理,客户端并不知道
 */
public class Client {
    public static void main(String[] args) {
        CommonManager a=new CommonManager("a");
        CommonManager b=new CommonManager("b");
        CommonManager c=new CommonManager("c");

        a.SetSuperior(b);
        b.SetSuperior(c);


        Request request=new Request();
        request.setRequestType("请假");
        request.setRequestContent("小菜请假");
        request.setNumber(1);

        a.RequestApplications(request);

        Request request2=new Request();
        request2.setNumber(4);
        request2.setRequestType("请假");
        request2.setRequestContent("小菜请假");

        a.RequestApplications(request2);


        Request request3=new Request();
        request3.setNumber(500);
        request3.setRequestType("加薪");
        request3.setRequestContent("小菜请求加薪");

        a.RequestApplications(request3);


        Request request4=new Request();
        request4.setNumber(1000);
        request4.setRequestType("加薪");
        request4.setRequestContent("小菜请求加薪");

        a.RequestApplications(request4);
    }

}

四、总结

1、好处。降低系统耦合度,可以简化对象之间的相互连接,只需要保存一个指向其后继者的引用,并不需要保存它对所有的候选接受者的引用。增强了给对象指派职责的灵活性,可以通过对职责链的增加或修改来增加或改变处理一个请求的职责。
2、使用时机。当有多个对象可以处理同一个请求,但具体哪一个对象处理该请求由运行时刻自动确定,即不明确该请求的具体接受者。

The path and dream is up to you to weave.

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