设计模式-责任链（Chain Of Responsibility）

基本来源于 [CyC2018-设计模式]([https://github.com/CyC2018/CS-Notes/blob/master/notes/设计模式 - 目录.md](https://github.com/CyC2018/CS-Notes/blob/master/notes/设计模式 - 目录.md))

目录

意图（Intent）

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收者之间的耦合关系。将这些对象连成一条链，并沿着这条链发送该请求，直到有一个对象处理它为止。

类图（Class Diagram）

  • Handler：定义处理请求的接口，并且实现后继链（successor）

实现（Implementation）

public abstract class Handler {

    protected Handler successor;


    public Handler(Handler successor) {
        this.successor = successor;
    }


    protected abstract void handleRequest(Request request);
}

public class ConcreteHandler1 extends Handler {

    public ConcreteHandler1(Handler successor) {
        super(successor);
    }


    @Override
    protected void handleRequest(Request request) {
        if (request.getType() == RequestType.TYPE1) {
            System.out.println(request.getName() + " is handle by ConcreteHandler1");
            return;
        }
        if (successor != null) {
            successor.handleRequest(request);
        }
    }
}

public class ConcreteHandler2 extends Handler {

    public ConcreteHandler2(Handler successor) {
        super(successor);
    }


    @Override
    protected void handleRequest(Request request) {
        if (request.getType() == RequestType.TYPE2) {
            System.out.println(request.getName() + " is handle by ConcreteHandler2");
            return;
        }
        if (successor != null) {
            successor.handleRequest(request);
        }
    }
}

public class Request {

    private RequestType type;
    private String name;


    public Request(RequestType type, String name) {
        this.type = type;
        this.name = name;
    }


    public RequestType getType() {
        return type;
    }


    public String getName() {
        return name;
    }
}

public enum RequestType {
    TYPE1, TYPE2
}

/*
这里定义了两个 Handler 分别为：handler1 与 handler2，其中 handler2 的 successor（继任者）是 handler1；定义了两个 Request 分别为：request1 与 request2，其中 request1 的类型是 TYPE1，request2 的类型是 TYPE2。
当将 request1 交给 handler2 处理时，由于 handler2 只能处理 TYPE2 的请求且 handler2 存在 successor( 即 handler1 )，所以将 request1 交给 handler2 的 successor( 即 handler1 ) 处理。
这也对应了最后输出：
request1 is handle by ConcreteHandler1
request2 is handle by ConcreteHandler2
*/
public class Client {

    public static void main(String[] args) {

        Handler handler1 = new ConcreteHandler1(null);
        Handler handler2 = new ConcreteHandler2(handler1);

        Request request1 = new Request(RequestType.TYPE1, "request1");
        handler2.handleRequest(request1);

        Request request2 = new Request(RequestType.TYPE2, "request2");
        handler2.handleRequest(request2);
    }
}

request1 is handle by ConcreteHandler1
request2 is handle by ConcreteHandler2

JDK

posted @ 2020-08-20 08:46  WuMinda  阅读(133)  评论(0)    收藏  举报