Spring Boot中使用SpringEvent组件

Spring的事件机制是基于观察者模式的实现，主要由以下三个部分组成：

事件（Event）：事件是应用中发生的重要事情，通常是一个继承自ApplicationEvent的类。

事件发布器（Publisher）：发布事件的对象，通常是Spring的应用上下文（ApplicationContext）。

事件监听器（Listener）：监听并处理事件的对象，通常是实现了ApplicationListener接口的类。

• 同步方法

1. 创建自定义事件，自定义事件需要继承ApplicationEvent类，并添加相应的属性和构造方法

package com.ssdl.baize.pub;

import org.springframework.context.ApplicationEvent;

public class CustomEvent extends ApplicationEvent {
    private String message;

    public CustomEvent(Object source, String message) {
        super(source);
        this.message = message;
    }

    public String getMessage() {
        return message;
    }
}

2. 创建事件监听器，用于监听和处理自定义事件。事件监听器需要实现ApplicationListener接口，并覆盖onApplicationEvent方法。

package com.ssdl.baize.pub;

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;

@Component
@Slf4j
public class CustomEventListener implements ApplicationListener<CustomEvent> {

    @Override
    public void onApplicationEvent(CustomEvent event) {
        try {
            Thread.sleep(5000L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        log.info("休眠5秒");
        log.info("Received custom event - {}" , event.getMessage());
    }
}

3.发布事件，要在某个组件中注入ApplicationEventPublisher，并调用其publishEvent方法。

package com.ssdl.baize.pub;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.stereotype.Component;

@Component
public class CustomEventPublisher {

    @Autowired
    private ApplicationEventPublisher applicationEventPublisher;

    public void publishEvent(String message) {
        CustomEvent customEvent = new CustomEvent(this, message);
        applicationEventPublisher.publishEvent(customEvent);
    }
}

4.测试

	@Autowired
    private CustomEventPublisher customEventPublisher;

    @GetMapping(path = "/pub")
    @ApiOperation(value = "发布订阅")
    public String pub(@RequestParam("message") String message) {
        log.info("start");
         customEventPublisher.publishEvent(message);
         log.info("发送完成!!!");
         return "OK";
    }

5.结果

• 异步方法
  说明：创建自定义事件、发布事件、测试这三个如同步方法一样，只需要更改创建事件监听器即可

package com.ssdl.baize.pub;

import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;

@Configuration
@EnableAsync
public class AsyncConfig {
}

package com.ssdl.baize.pub;

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.event.EventListener;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;

@Component
@Slf4j
public class AsyncCustomEventListener {

    @Async
    @EventListener(condition = "#event.message.startsWith('filter')")
    public void handleCustomEvent(CustomEvent event) {
        try {
            Thread.sleep(5000L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        log.info("休眠5秒");
        log.info("Async received custom event - {}" , event.getMessage());
    }
}

注：condition 限制只接收filter开头的消息

结果：