【Spring】spring事件监听异步处理

在Spring框架中，ApplicationEventMulticaster接口是用于发布事件的核心组件。要支持异步处理事件，可以通过配置一个能够执行异步任务的TaskExecutor与SimpleApplicationEventMulticaster配合使用。以下是一个配置示例：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.task.TaskExecutor;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.event.SimpleApplicationEventMulticaster;
import org.springframework.context.event.EventListener;

@Configuration
public class AsyncEventConfig {

    @Bean(name = "applicationEventMulticaster")
    public SimpleApplicationEventMulticaster simpleApplicationEventMulticaster(TaskExecutor taskExecutor) {
        SimpleApplicationEventMulticaster multicaster = new SimpleApplicationEventMulticaster();
        multicaster.setTaskExecutor(taskExecutor);
        return multicaster;
    }

    @Bean
    public TaskExecutor taskExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        // 配置线程池参数，比如核心线程数、最大线程数、队列容量等
        executor.setCorePoolSize(5);
        executor.setMaxPoolSize(10);
        executor.setQueueCapacity(20);
        executor.initialize();
        return executor;
    }

    // 示例监听器，处理CustomEvent类型的事件
    @Component
    public static class CustomEventListener {

        @Async // 这个注解让方法异步执行，需要在类上启用@EnableAsync
        @EventListener
        public void handleCustomEvent(CustomEvent event) {
            System.out.println("Received custom event asynchronously: " + event.getMessage() + " thread name:" + Thread.currentThread());
            
            // 在此处执行具体的异步事件处理逻辑
        }
    }
}

// 启用异步方法支持
@Configuration
@EnableAsync
public class AsyncConfig { }

注意：

• 上述代码中的@EnableAsync注解会开启对异步方法调用的支持，并通过代理方式实现。
• handleCustomEvent方法上添加了@Async注解，这表示该方法应该被异步调用。
• 将自定义的SimpleApplicationEventMulticaster设置为应用上下文的默认事件多播器，这样发布的事件将由配置好的线程池异步执行。

发布事件时仍然按照常规方式进行，例如在某个服务类中：

@Autowired
private ApplicationEventPublisher publisher;

public void publishCustomEvent(String message) {
    System.out.println("publishEvent thread name:" + Thread.currentThread());
    CustomEvent event = new CustomEvent(this, message);
    publisher.publishEvent(event);
}

publishEvent thread name:Thread[http-nio-8081-exec-2,5,main]
Received custom event asynchronously: A custom message thread name:Thread[taskExecutor-6,5,main]

当调用publishCustomEvent方法发布事件时，由于已经设置了异步的ApplicationEventMulticaster，所以监听该事件的CustomEventListener类的handleCustomEvent方法将在单独的线程中执行，从而实现了事件的异步处理。