Java 责任链模式 (Chain-Of-Responsibility)

责任链模式是一种行为设计模式，它允许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。这些对象被连成一条链，并沿着这条链传递请求，直到有一个对象处理它为止。

定义处理器抽象类

java

        public abstract class Handler {
    protected Handler nextHandler;

    public void setNextHandler(Handler nextHandler) {
        this.nextHandler = nextHandler;
    }

    public void handleRequest(String request) {
        if (nextHandler != null) {
            nextHandler.handleRequest(request);
        }
    }
}

实现具体处理器

java

        public class ConcreteHandlerA extends Handler {
    @Override
    public void handleRequest(String request) {
        if (request.equals("A")) {
            System.out.println("ConcreteHandlerA handled request: " + request);
        } else {
            super.handleRequest(request);
        }
    }
}

public class ConcreteHandlerB extends Handler {
    @Override
    public void handleRequest(String request) {
        if (request.equals("B")) {
            System.out.println("ConcreteHandlerB handled request: " + request);
        } else {
            super.handleRequest(request);
        }
    }
}

public class ConcreteHandlerC extends Handler {
    @Override
    public void handleRequest(String request) {
        if (request.equals("C")) {
            System.out.println("ConcreteHandlerC handled request: " + request);
        } else {
            super.handleRequest(request);
        }
    }
}

使用责任链模式

java

        public class ChainOfResponsibilityPatternDemo {
    public static void main(String[] args) {
        // 创建处理器
        Handler handlerA = new ConcreteHandlerA();
        Handler handlerB = new ConcreteHandlerB();
        Handler handlerC = new ConcreteHandlerC();

        // 设置责任链
        handlerA.setNextHandler(handlerB);
        handlerB.setNextHandler(handlerC);

        // 处理请求
        handlerA.handleRequest("A");
        handlerA.handleRequest("B");
        handlerA.handleRequest("C");
        handlerA.handleRequest("D");
    }
}