Java职责链简单范式设计

1.抽象处理器（Handler）

package com.vz.chain;

import java.util.Objects;

/**
 * @author visy.wang
 * @description: 抽象处理器 
 * @date 2023/6/6 16:39
 */
public abstract class Handler<Q,R> {
    private Handler<Q,R> next;
    private Handler<Q,R> last = this;

    public final Handler<Q,R> add(Handler<Q,R> handler){
        this.last.setNext(handler);
        this.last = handler;
        return this;
    }

    public final void setNext(Handler<Q,R> handler){
        this.next = handler;
    }

    protected abstract R doHandle(Q request, R response);

    public final R handle(Q request, R response){
        //先执行自己的处理
        response = this.doHandle(request, response);
        if(Objects.nonNull(this.next)){
            //再执行下一个处理器的处理，上一个响应会作为下一个处理器的参数
            response = next.handle(request, response);
        }
        return response;
    }
}

2.处理器实现类

package com.vz.chain;

/**
 * @author visy.wang
 * @description: 处理器A
 * @date 2023/6/6 16:56
 */
public class AHandler extends Handler<XRequest, XResponse>{
    @Override
    protected XResponse doHandle(XRequest request, XResponse response) {
        System.out.println("Handler A");
        Long id = request.getId();
        response.append(id);
        response.addToTotal(id);
        return response;
    }
}

package com.vz.chain;

/**
 * @author visy.wang
 * @description: B处理器
 * @date 2023/6/6 16:59
 */
public class BHandler extends Handler<XRequest, XResponse>{
    @Override
    protected XResponse doHandle(XRequest request, XResponse response) {
        System.out.println("Handler B");
        Long id = request.getId() + 1;
        response.append(id);
        response.addToTotal(id);
        return response;
    }
}

package com.vz.chain;

/**
 * @author visy.wang
 * @description: C处理器
 * @date 2023/6/6 16:59
 */
public class CHandler extends Handler<XRequest, XResponse>{
    @Override
    protected XResponse doHandle(XRequest request, XResponse response) {
        System.out.println("Handler C");
        Long id = request.getId() + 2;
        response.append(id);
        response.addToTotal(id);
        return response;
    }
}

3.自定义参数和返回

package com.vz.chain;

import lombok.Data;

/**
 * @author visy.wang
 * @description: 入参
 * @date 2023/6/6 16:41
 */
@Data
public class XRequest {
    private Long id;
    private String name;
}

package com.vz.chain;

import lombok.Data;

import java.util.ArrayList;
import java.util.List;

/**
 * @author visy.wang
 * @description: 返回数据
 * @date 2023/6/6 16:41
 */
@Data
public class XResponse {
    private Long total;

    private List<Long> idList;
    public void append(Long id){
        if(idList == null){
            idList = new ArrayList<>();
        }
        idList.add(id);
    }

    public void addToTotal(Long count){
        if (total == null){
            total = 0L;
        }
        total = total + count;
    }
}

4.使用

package com.vz.chain;

import com.alibaba.fastjson.JSON;

/**
 * @author visy.wang
 * @description: 测试类
 * @date 2023/6/6 16:39
 */
public class Test {

    public static void main(String[] args) {
        XRequest request = new XRequest();
        request.setId(1L);
        request.setName("Hahaha");
        XResponse response = new XResponse();


        Handler<XRequest, XResponse> aHandler = new AHandler(), bHandler = new BHandler(), cHandler = new CHandler();

        response = aHandler.add(bHandler).add(cHandler).handle(request, response);

        System.out.println(JSON.toJSONString(response));
    }
}

5.打印结果

Handler A
Handler B
Handler C
{"idList":[1,2,3],"total":6}