责任链模式

责任链模式就是多个处理器一次处理同一个请求。一个请求先经过处理器A，再把请求传递给处理器B，从而形成一个链条

public abstract class AbstractHandler {
    protected AbstractHandler handler;
    public void setHandler(AbstractHandler handler) {
        this.handler = handler;
    }
    public abstract void handle();
}

public class HandlerA extends AbstractHandler{
    @Override
    public void handle() {
        System.out.println("处理器A处理");
        if (super.handler != null) {
            super.handler.handle();
        }
    }
}

public class HandlerB extends AbstractHandler{
    @Override
    public void handle() {
        System.out.println("处理器B处理");
        if (super.handler != null) {
            super.handler.handle();
        }
    }
}

public class HandlerChain {
    private AbstractHandler head;
    private AbstractHandler tail;
    public void addHandler(AbstractHandler handler) {
        handler.setHandler(null);
        if (head == null) {
            head = handler;
            tail = handler;
        }
        tail.setHandler(handler);
        tail = handler;
    }
    public void handle() {
        if (head != null) {
            head.handle();
        }
    }
}