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SpringBoot下使用自定義監(jiān)聽事件的流程分析

更新時間：2023年08月07日 09:32:18 作者：楓葉梨花

事件機制是Spring的一個功能,目前我們使用了SpringBoot框架,所以記錄下事件機制在SpringBoot框架下的使用,同時實現(xiàn)異步處理,這篇文章主要介紹了SpringBoot下使用自定義監(jiān)聽事件,需要的朋友可以參考下

SpringBoot的實例程序

實現(xiàn)一個保存用戶的時候，向用戶提供的郵箱發(fā)送一封郵件的功能，同時采用異步處理。

自定義事件

import org.springframework.context.ApplicationEvent;
public class EmailEvent extends ApplicationEvent {
	private static final long serialVersionUID = 3733891603598996786L;
	private String emailAddress;
	public EmailEvent(String emailAddress) {
		super(emailAddress);
		this.emailAddress = emailAddress;
	}
	public String getEmailAddress() {
		return emailAddress;
	}
	public void setEmailAddress(String emailAddress) {
		this.emailAddress = emailAddress;
	}
}

定義事件監(jiān)聽器

import java.util.concurrent.TimeUnit;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ApplicationListener;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;
@Component
public class EmailEventListener implements ApplicationListener<EmailEvent> {
	private static Logger log = LoggerFactory.getLogger(EmailEventListener.class);
	// 異步處理
	@Async
	@Override
	public void onApplicationEvent(EmailEvent event) {
		log.info("監(jiān)聽到事件--郵箱地址:" + event.getEmailAddress());
		//模擬處理的耗時3s
		try {
			TimeUnit.SECONDS.sleep(3);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		log.info("事件處理完成");
	}
}

發(fā)布事件

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;
@Component
public class EmailEventPublish {
	@Autowired
	private ApplicationContext applicationContext;
	public void publishEvent(String emailAddress) {
		EmailEvent event = new EmailEvent(emailAddress);
		applicationContext.publishEvent(event);
	}
}

調(diào)用事件

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import com.example.demo.event.EmailEventPublish;
@RestController
public class EventController {
	private static Logger log = LoggerFactory.getLogger(EventController.class);
	@Autowired
	private EmailEventPublish emailEventPublish;
	@RequestMapping("/event")
	public void publishEvent(@RequestParam String emailAddress) {
		// 發(fā)布事件 -- 采用異步處理
		emailEventPublish.publishEvent(emailAddress);
		// 正常該語句先執(zhí)行
		log.info("Controller業(yè)務(wù)處理");
	}
}

結(jié)果

訪問如下地址

http://localhost:8080/event?emailAddress=plf@163.com

結(jié)果為

2023-08-04 21:21:14.338 INFO 6400 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring FrameworkServlet 'dispatcherServlet'
2023-08-04 21:21:14.338 INFO 6400 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization started
2023-08-04 21:21:14.370 INFO 6400 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization completed in 32 ms
2023-08-04 21:21:14.429 INFO 6400 --- [nio-8080-exec-1] .s.a.AnnotationAsyncExecutionInterceptor : No task executor bean found for async processing: no bean of type TaskExecutor and no bean named 'taskExecutor' either
2023-08-04 21:21:14.534 INFO 6400 --- [nio-8080-exec-1] c.e.demo.controller.EventController : Controller業(yè)務(wù)處理
2023-08-04 21:21:14.535 INFO 6400 --- [cTaskExecutor-1] c.example.demo.event.EmailEventListener : 監(jiān)聽到事件--郵箱地址:plf@163.com
2023-08-04 21:21:17.536 INFO 6400 --- [cTaskExecutor-1] c.example.demo.event.EmailEventListener : 事件處理完成

上述結(jié)果可知是實現(xiàn)了異步處理，先打印了事件之后的程序，等時間到再執(zhí)行監(jiān)聽程序的代碼。

實現(xiàn)異步處理就是在監(jiān)聽事件執(zhí)行業(yè)務(wù)代碼的方法上添加 @Async 注解，同時在啟動類上添加 @EnableAsync 即可。

上面的日志還提到了 TaskExecutor ,這是如果有自定義的線程池就會去調(diào)用，如果沒有就用默認的。我們也可以自己定義一個 TaskExecutor 。

import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;
@EnableAsync
@Configuration
public class ThreadPool implements AsyncConfigurer {
	@Nullable
	@Override
	@Bean("taskExecutor")
	public Executor getAsyncExecutor() {
		ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
		// 線程池創(chuàng)建時候初始化的線程數(shù)
		executor.setCorePoolSize(10);
		// 線程池最大的線程數(shù)，只有在緩沖隊列滿了之后才會申請超過核心線程數(shù)的線程
		executor.setMaxPoolSize(20);
		// 用來緩沖執(zhí)行任務(wù)的隊列
		executor.setQueueCapacity(200);
		// 允許線程的空閑時間60秒
		executor.setKeepAliveSeconds(60);
		// 線程池名的前綴
		executor.setThreadNamePrefix("taskExecutor-");
		// 線程池對拒絕任務(wù)的處理策略
		executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
		executor.initialize();
		return executor;
	}
	@Nullable
	@Override
	public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
		return null;
	}
}

結(jié)果

2023-08-04 21:27:36.507 INFO 7848 --- [nio-8080-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring FrameworkServlet 'dispatcherServlet'
2023-08-04 21:27:36.507 INFO 7848 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization started
2023-08-04 21:27:36.537 INFO 7848 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization completed in 30 ms
2023-08-04 21:27:36.757 INFO 7848 --- [nio-8080-exec-2] c.e.demo.controller.EventController : Controller業(yè)務(wù)處理
2023-08-04 21:27:36.757 INFO 7848 --- [ taskExecutor-1] c.example.demo.event.EmailEventListener : 監(jiān)聽到事件--郵箱地址:plf@163.com
2023-08-04 21:27:39.757 INFO 7848 --- [ taskExecutor-1] c.example.demo.event.EmailEventListener : 事件處理完成

可知是使用我們定義的線程池[ taskExecutor-1] 。