springboot 中事件监听模式的一种实现

mysgk 2018-10-15 原文

前言: 事件监听模式是一种常用的设计模式，在springboot 中我们如何实现呢？
首先我们要理解事件监听中需要的几个角色

事件发布者（即事件源）
事件监听者
事件本身
废话不多说直接上代码

定义事件本身

事件本身需要继承ApplicationEvent

package com.yxd;

import java.util.List;
import java.util.Map;
import org.springframework.context.ApplicationEvent;

public class DemoEvent extends ApplicationEvent{

    private String type;
    private List<Map> msg;
    
    public DemoEvent(Object object, String type ,List<Map> msg) {
        super(object);
        this.msg = msg;
        this.type = type;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public List<Map> getMsg() {
        return msg;
    }

    public void setMsg(List<Map> msg) {
        this.msg = msg;
    }

}

如图：

定义事件源

事件源需要注入 ApplicationContext

package com.yxd;

import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;

@Component
public class DemoPublisher {

    @Autowired
    ApplicationContext applicationContext;
    
    public void publish(String type , List<Map> msg) {
        applicationContext.publishEvent(new DemoEvent(this,type, msg ));
    }
}

如图：

定义监听者

监听者需要实现 ApplicationListener

package com.yxd;

import java.util.List;
import java.util.Map;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;

@Component
public class DemoListener1 implements ApplicationListener<DemoEvent> {

    @Override
    public void onApplicationEvent(DemoEvent event) {
        List<Map> msg = event.getMsg();
        String type = event.getType();
        System.out.println("listener1 接收到了 publisher 发送的消息类型 :" + type +", 消息内容: " + msg);
    }
}

如图：

测试

package com.yxd;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Autowired
    DemoPublisher demoPublisher;

    @RequestMapping("testListener")
    public String testListener() {
        ArrayList<Map> list = new ArrayList<>();        
        HashMap<String, String> m1 =  new HashMap<>();
        m1.put("1", "2");
        HashMap<String, String> m2 =  new HashMap<>();
        m2.put("3", "4");
        HashMap<String, String> m3 =  new HashMap<>();
        m3.put("5", "6");       
        list.add(m1);
        list.add(m2);
        list.add(m3);
        demoPublisher.publish("测试消息",list);
        return "消息发布成功";
    }
}

如图：