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：



我们访问接口






三个监听者都得到了消息。。

项目结构