java 实现责任链设计模式

责任链设计模式是一种行为设计模式，它通过一系列对象来处理请求，并将请求沿着对象链传递，直到有一个对象能够处理请求为止。以下是 Java 实现责任链设计模式的示例：

首先，需要定义一个处理请求的接口，例如：

public interface Handler {
    void setNextHandler(Handler nextHandler);
    void handleRequest(Request request);
}

然后，实现具体的处理者类，例如：

public class ConcreteHandler1 implements Handler {
    private Handler nextHandler;
    
    @Override
    public void setNextHandler(Handler nextHandler) {
        this.nextHandler = nextHandler;
    }
    
    @Override
    public void handleRequest(Request request) {
        if (request.getType() == RequestType.TYPE1) {
            System.out.println("ConcreteHandler1 handles request " + request);
        } else if (nextHandler != null) {
            nextHandler.handleRequest(request);
        }
    }
}

public class ConcreteHandler2 implements Handler {
    private Handler nextHandler;
    
    @Override
    public void setNextHandler(Handler nextHandler) {
        this.nextHandler = nextHandler;
    }
    
    @Override
    public void handleRequest(Request request) {
        if (request.getType() == RequestType.TYPE2) {
            System.out.println("ConcreteHandler2 handles request " + request);
        } else if (nextHandler != null) {
            nextHandler.handleRequest(request);
        }
    }
}

//...其他具体的处理者类

最后，定义一个请求类：

public class Request {
    private RequestType type;
    private String content;
    
    public Request(RequestType type, String content) {
        this.type = type;
        this.content = content;
    }
    
    public RequestType getType() {
        return type;
    }
    
    public String getContent() {
        return content;
    }
    
    @Override
    public String toString() {
        return "[" + type + ", " + content + "]";
    }
}

在客户端中，可以创建一个处理者链，并将请求传递给处理者链的第一个处理者：

public class Client {
    public static void main(String[] args) {
        Handler handler1 = new ConcreteHandler1();
        Handler handler2 = new ConcreteHandler2();
        //...其他具体的处理者
        
        //设置处理者链
        handler1.setNextHandler(handler2);
        //...设置其他处理者的下一个处理者
        
        //创建请求
        Request request1 = new Request(RequestType.TYPE1, "Request 1");
        Request request2 = new Request(RequestType.TYPE2, "Request 2");
        //...其他请求
        
        //传递请求
        handler1.handleRequest(request1);
        handler1.handleRequest(request2);
        //...处理其他请求
    }
}

输出结果：

ConcreteHandler1 handles request [TYPE1, Request 1]
ConcreteHandler2 handles request [TYPE2, Request 2]