职责链模式：推卸责任-526互联

职责链模式是一种行为设计模式，它允许你将请求沿着处理者链进行传递，直到其中一个处理者能够处理该请求为止。

// 抽象处理者
public abstract class Handler {
    protected Handler successor;

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

    public abstract void handleRequest(Request request);
}

// 具体处理者1
public class ConcreteHandler1 extends Handler {
    public void handleRequest(Request request) {
        if (request.getType() == RequestType.TYPE1) {
            System.out.println("ConcreteHandler1 handles the request.");
        } else if (successor != null) {
            successor.handleRequest(request);
        }
    }
}

// 具体处理者2
public class ConcreteHandler2 extends Handler {
    public void handleRequest(Request request) {
        if (request.getType() == RequestType.TYPE2) {
            System.out.println("ConcreteHandler2 handles the request.");
        } else if (successor != null) {
            successor.handleRequest(request);
        }
    }
}

// 请求类
public class Request {
    private final RequestType type;

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

    public RequestType getType() {
        return type;
    }
}

// 请求类型枚举
public enum RequestType {
    TYPE1, TYPE2
}

public class Client {
    public static void main(String[] args) {
        // Setup the chain of handlers
        Handler handler1 = new ConcreteHandler1();
        Handler handler2 = new ConcreteHandler2();
        Handler handler3 = new ConcreteHandler3();
        handler1.setSuccessor(handler2);
        handler2.setSuccessor(handler3);

        // Send requests to the first handler
        handler1.handleRequest(new Request("Type1"));
        handler1.handleRequest(new Request("Type2"));
        handler1.handleRequest(new Request("Type3"));
    }
}

涉及到的角色

角色	作用
Handler	定义处理请求的接口和知道“下一个处理者”
ConcreteHandler	具体的处理者
Client	请求者