springboot async 异步多线程

配置线程池

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@Configuration @EnableAsync public class AsyncConfiguration {     @Bean("doSomethingExecutor")  public Executor doSomethingExecutor() {   ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();   // 核心线程数：线程池创建时候初始化的线程数   executor.setCorePoolSize(10);   // 最大线程数：线程池最大的线程数，只有在缓冲队列满了之后才会申请超过核心线程数的线程   executor.setMaxPoolSize(20);   // 缓冲队列：用来缓冲执行任务的队列   executor.setQueueCapacity(500);   // 允许线程的空闲时间60秒：当超过了核心线程之外的线程在空闲时间到达之后会被销毁   executor.setKeepAliveSeconds(60);   // 线程池名的前缀：设置好了之后可以方便我们定位处理任务所在的线程池   executor.setThreadNamePrefix("do-something-");   // 缓冲队列满了之后的拒绝策略：由调用线程处理（一般是主线程）   executor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());   executor.initialize();   return executor;  } }

 

@Async注解

@RestController
public class AsyncController {
 
 @Autowired
 private AsyncService asyncService;
 
 @GetMapping("/open/something")
 public String something() {
  int count = 10;
  for (int i = 0; i < count; i++) {
   asyncService.doSomething("index = " + i);
  }
  return "success";
 }
}
 
 
@Slf4j
@Service
public class AsyncService {
 
 // 指定使用beanname为doSomethingExecutor的线程池
 @Async("doSomethingExecutor")
 public String doSomething(String message) {
  log.info("do something, message={}", message);
  try {
   Thread.sleep(1000);
  } catch (InterruptedException e) {
   log.error("do something error: ", e);
  }
  return message;
 }
}

异步多结果聚合返回 CompletableFuture

@RestController
public class AsyncController {
 
 @Autowired
 private AsyncService asyncService;
 
 @SneakyThrows
 @ApiOperation("异步 有返回值")
 @GetMapping("/open/somethings")
 public String somethings() {
  CompletableFuture<String> createOrder = asyncService.doSomething1("create order");
  CompletableFuture<String> reduceAccount = asyncService.doSomething2("reduce account");
  CompletableFuture<String> saveLog = asyncService.doSomething3("save log");
   
  // 等待所有任务都执行完
  CompletableFuture.allOf(createOrder, reduceAccount, saveLog).join();
  // 获取每个任务的返回结果
  String result = createOrder.get() + reduceAccount.get() + saveLog.get();
  return result;
 }
}
 
 
@Slf4j
@Service
public class AsyncService {
 
 @Async("doSomethingExecutor")
 public CompletableFuture<String> doSomething1(String message) throws InterruptedException {
  log.info("do something1: {}", message);
  Thread.sleep(1000);
  return CompletableFuture.completedFuture("do something1: " + message);
 }
 
 @Async("doSomethingExecutor")
 public CompletableFuture<String> doSomething2(String message) throws InterruptedException {
  log.info("do something2: {}", message);
  Thread.sleep(1000);
  return CompletableFuture.completedFuture("; do something2: " + message);
 }
 
 @Async("doSomethingExecutor")
 public CompletableFuture<String> doSomething3(String message) throws InterruptedException {
  log.info("do something3: {}", message);
  Thread.sleep(1000);
  return CompletableFuture.completedFuture("; do something3: " + message);
 }
}

 

注意事项

@Async注解会在以下几个场景失效，也就是说明明使用了@Async注解，但就没有走多线程。

• 异步方法使用static关键词修饰；
• 异步类不是一个Spring容器的bean（一般使用注解@Component和@Service，并且能被Spring扫描到）；
• SpringBoot应用中没有添加@EnableAsync注解；
• 在同一个类中，一个方法调用另外一个有@Async注解的方法，注解不会生效。原因是@Async注解的方法，是在代理类中执行的。

需要注意的是：

异步方法使用注解@Async的返回值只能为void或者Future及其子类，当返回结果为其他类型时，方法还是会异步执行，但是返回值都是null