设计模式之责任链模式

责任链模式(Chain of responsibility pattern): 通过责任链模式, 我们可以为某个请求创建一个对象链. 每个对象依序检查此请求并对其进行处理或者将它传给链中的下一个对象。很适合做审批流开发。

类图

handler：定义处理请求的接口并且实现后继链

实现

/** 
 * 请求处理者抽象类
 */
public abstract class Handler {

	//节点之后的其他处理者
    protected Handler successor;

    public Handler(Handler successor) {
        this.successor = successor;
    }
	
	//处理方式
    protected abstract void handleRequest(Request request);
}

/** 
 * 第一位处理者
 */
public class ConcreteHandler1 extends Handler {
    public ConcreteHandler1(Handler successor) {
        super(successor);
    }

    @Override
    protected void handleRequest(Request request) {
        if (request.getType() == RequestType.type1) {
            System.out.println(request.getName() + " is handle by ConcreteHandler1");
            return;
        }
        if (successor != null) {
            successor.handleRequest(request);
        }
    }
}

/** 
 * 第二位处理者
 */
public class ConcreteHandler2 extends Handler{
    public ConcreteHandler2(Handler successor) {
        super(successor);
    }

    @Override
    protected void handleRequest(Request request) {
        if (request.getType() == RequestType.type2) {
            System.out.println(request.getName() + " is handle by ConcreteHandler2");
            return;
        }
        if (successor != null) {
            successor.handleRequest(request);
        }
    }
}

/** 
 * 请求
 */ 
public class Request {
    private RequestType type;
    private String name;

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

    public RequestType getType() {
        return type;
    }

    public String getName() {
        return name;
    }
}
  

public enum RequestType {
    type1, type2
}

public class Client {
    public static void main(String[] args) {
        Handler handler1 = new ConcreteHandler1(null);
        Handler handler2 = new ConcreteHandler2(handler1);
        Request request1 = new Request(RequestType.type1, "request1");
        handler2.handleRequest(request1);
        Request request2 = new Request(RequestType.type2, "request2");
        handler2.handleRequest(request2);
    }
}