@Async 注解的用法和示例

文章目录

• • @Async 注解的用法和示例
  • • • 背景
      • 异步调用
      • @Async介绍
      • 在Spring中启用@Async
      • 示例一：基本使用方式
      • 示例二：在同一个类中调用异步方法
      • 示例三：异步方法是static方法
      • 示例四：在方法级别上修改默认的执行器

背景

异步调用

@Async介绍

在Spring中启用@Async

@Slf4j
@SpringBootApplication
@ComponentScan(basePackages = {"com.kaesar.spring"})
@EnableAsync // 开启异步调用
public class Application {
    public static void main(String[] args) {
        log.info("spring boot开始启动...");
        ApplicationContext ctx = SpringApplication.run(Application.class, args);
        String[] activeProfiles = ctx.getEnvironment().getActiveProfiles();
        for (String profile : activeProfiles) {
            log.info("当前环境为:" + profile);
        }
        log.info("spring boot启动成功...");
    }
}

示例一：基本使用方式

/**
 * 异步方法
 * 默认情况下，Spring 使用 SimpleAsyncTaskExecutor 去执行这些异步方法（此执行器没有限制线程数）。
 * 此默认值可以从两个层级进行覆盖：
 * 方法级别
 * 应用级别
 */
@Async
public void test2() {
    try {
        log.info(Thread.currentThread().getName() + " in test2, before sleep.");
        Thread.sleep(2000);
        log.info(Thread.currentThread().getName() + " in test2, after sleep.");
    } catch (InterruptedException e) {
        log.error("sleep error.");
    }
}

/**
 * 调用不同类的异步方法
 */
public void func1() {
    log.info("before call async function.");
    asyncService.test2();
    log.info("after call async function.");
    try {
        Thread.sleep(3000);
    } catch (InterruptedException e) {
        log.error("sleep error.");
    }
    log.info("func end.");
}

示例二：在同一个类中调用异步方法

示例三：异步方法是static方法

/**
 * 异步方法不能是 static 方法，不然注解失效
 */
@Async
public static void test3() {
  try {
    log.info(Thread.currentThread().getName() + " in test3, before sleep.");
    Thread.sleep(2000);
    log.info(Thread.currentThread().getName() + " in test3, after sleep.");
  } catch (InterruptedException e) {
    log.error("sleep error.");
  }

}

/**
 * 调用不同类的异步方法，异步方法是 static 方法
 */
public void func3() {
  log.info(Thread.currentThread().getName() + ": before call async function.");
  AsyncService.test3();
  log.info(Thread.currentThread().getName() + ": after call async function.");
  try {
    Thread.sleep(3000);
  } catch (InterruptedException e) {
    log.error("sleep error.");
  }
  log.info(Thread.currentThread().getName() + ": func end.");
}

示例四：在方法级别上修改默认的执行器

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.task.AsyncTaskExecutor;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

/**
 * 自定义线程池
 */
@Configuration
public class AsyncConfig {
    private static final int MAX_POOL_SIZE = 10;
    private static final int CORE_POOL_SIZE = 5;

    @Bean("asyncTaskExecutor")
    public AsyncTaskExecutor asyncTaskExecutor() {
        ThreadPoolTaskExecutor asyncTaskExecutor = new ThreadPoolTaskExecutor();
        asyncTaskExecutor.setMaxPoolSize(MAX_POOL_SIZE);
        asyncTaskExecutor.setCorePoolSize(CORE_POOL_SIZE);
        asyncTaskExecutor.setThreadNamePrefix("async-task-thread-pool-");
        asyncTaskExecutor.initialize();
        return asyncTaskExecutor;
    }
}

/**
 * 在方法级别上修改默认的执行器
 */
@Async("asyncTaskExecutor")
public void test4() {
  try {
    log.info(Thread.currentThread().getName() + ": in test4, before sleep.");
    Thread.sleep(2000);
    log.info(Thread.currentThread().getName() + ": in test4, after sleep.");
  } catch (InterruptedException e) {
    log.error("sleep error.");
  }
}

/**
 * 调用不同类的异步方法
 */
public void func4() {
  log.info(Thread.currentThread().getName() + ": before call async function.");
  asyncService.test4();
  log.info(Thread.currentThread().getName() + ": after call async function.");
  try {
    Thread.sleep(3000);
  } catch (InterruptedException e) {
    log.error("sleep error.");
  }
  log.info(Thread.currentThread().getName() + ": func end.");
}