简介

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，直到有一个对象处理它为止。

类图

代码

抽象职责链

public abstract class Handler {
   protected Handler successor;
   protected final String requestInfo = "处理类：%s，处理请求：%s";
   public void setSuccessor(Handler handler) {
       this.successor = handler;
   }

   public abstract void handlerRequest(int request) ;
}

具体职责链实现

public class ConcreteHandler1 extends Handler{
    @Override
    public void handlerRequest(int request) {
        if (request >= 0 && request < 10) {
            System.out.println(String.format(requestInfo, this.getClass().getSimpleName(), request));
        } else if(successor != null) {
            successor.handlerRequest(request);
        }
    }
}

public class ConcreteHandler2 extends Handler {

    @Override
    public void handlerRequest(int request) {
        if (request >= 10 && request < 20) {
            System.out.println(String.format(requestInfo, this.getClass().getSimpleName(), request));
        } else if (successor != null) {
            successor.handlerRequest(request);
        }
    }
}

public class ConcreteHandler3 extends Handler {
    @Override
    public void handlerRequest(int request) {
        if (request >= 20 || request < 30) {
            System.out.println(String.format(requestInfo, this.getClass().getSimpleName(), request));
        } else if (successor != null) {
            successor.handlerRequest(request);
        }
    }
}

客户端代码

public class Client {
    public static void main(String[] args) {
        final ConcreteHandler1 concreteHandler1 = new ConcreteHandler1();
        final ConcreteHandler2 concreteHandler2 = new ConcreteHandler2();
        final ConcreteHandler3 concreteHandler3 = new ConcreteHandler3();

        concreteHandler1.setSuccessor(concreteHandler2);
        concreteHandler2.setSuccessor(concreteHandler3);

        int[] requests = new int[]{5, 20, 10, 13, 18, 29};
        for (int request : requests) {
            concreteHandler1.handlerRequest(request);
        }
    }
}