Spring Boot Async异步执行任务过程详解

Z时代
2024-01-10
分类：综合

异步调用就是不用等待结果的返回就执行后面的逻辑，同步调用则需要等带结果再执行后面的逻辑。

通常我们使用异步操作都会去创建一个线程执行一段逻辑，然后把这个线程丢到线程池中去执行，代码如下：


ExecutorService executorService = Executors.newFixedThreadPool(10);
executorService.execute(() -> {
  try {
    // 业务逻辑
  } catch (Exception e) {
    e.printStackTrace();
  } finally {
  }
 });

这样的方式看起来没那么优雅，尽管用了java的lambda。在Spring Boot" title="Spring Boot">Spring Boot中有一种更简单的方式来执行异步操作，只需要一个@Async注解即可。


@Async
public void saveLog() {
  System.err.println(Thread.currentThread().getName());
}

我们可以直接在Controller中调用这个业务方法，它就是异步执行的，会在默认的线程池中去执行。需要注意的是一定要在外部的类中去调用这个方法，如果在本类调用是不起作用的，比如this.saveLog()。最后在启动类上开启异步任务的执行，添加@EnableAsync即可。

另外关于执行异步任务的线程池我们也可以自定义，首先我们定义一个线程池的配置类，用来配置一些参数，具体代码如下：


import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration; 
/**
 * 异步任务线程池配置
 * 
 * @author yinjihuan
 */
@Configuration
@ConfigurationProperties(prefix = "spring.task.pool")
public class TaskThreadPoolConfig { 
  //核心线程数
  private int corePoolSize = 5; 
  //最大线程数
  private int maxPoolSize = 50; 
  //线程池维护线程所允许的空闲时间
  private int keepAliveSeconds = 60; 
  //队列长度
  private int queueCapacity = 10000;
  //线程名称前缀
  private String threadNamePrefix = "FSH-AsyncTask-";
  public String getThreadNamePrefix() {
    return threadNamePrefix;
  }
  public void setThreadNamePrefix(String threadNamePrefix) {
    this.threadNamePrefix = threadNamePrefix;
  }
  public int getCorePoolSize() {
    return corePoolSize;
  }
  public void setCorePoolSize(int corePoolSize) {
    this.corePoolSize = corePoolSize;
  }
  public int getMaxPoolSize() {
    return maxPoolSize;
  }
  public void setMaxPoolSize(int maxPoolSize) {
    this.maxPoolSize = maxPoolSize;
  }
  public int getKeepAliveSeconds() {
    return keepAliveSeconds;
  }
  public void setKeepAliveSeconds(int keepAliveSeconds) {
    this.keepAliveSeconds = keepAliveSeconds;
  }
  public int getQueueCapacity() {
    return queueCapacity;
  }
  public void setQueueCapacity(int queueCapacity) {
    this.queueCapacity = queueCapacity;
  }
}

然后我们重新定义线程池的配置：


import java.lang.reflect.Method;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
@Configuration 
public class AsyncTaskExecutePool implements AsyncConfigurer {  
  private Logger logger = LoggerFactory.getLogger(AsyncTaskExecutePool.class);
  @Autowired  
  private TaskThreadPoolConfig config;
  @Override 
  public Executor getAsyncExecutor() { 
    ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); 
    executor.setCorePoolSize(config.getCorePoolSize());  
    executor.setMaxPoolSize(config.getMaxPoolSize());  
    executor.setQueueCapacity(config.getQueueCapacity());  
    executor.setKeepAliveSeconds(config.getKeepAliveSeconds());  
    executor.setThreadNamePrefix(config.getThreadNamePrefix());
    //线程池对拒绝任务（无线程可用）的处理策略，目前只支持AbortPolicy、CallerRunsPolicy
    //AbortPolicy:直接抛出java.util.concurrent.RejectedExecutionException异常 -->
    //CallerRunsPolicy:主线程直接执行该任务，执行完之后尝试添加下一个任务到线程池中，可以有效降低向线程池内添加任务的速度 -->
    //DiscardOldestPolicy:抛弃旧的任务、暂不支持；会导致被丢弃的任务无法再次被执行 -->
    //DiscardPolicy:抛弃当前任务、暂不支持；会导致被丢弃的任务无法再次被执行 -->
    executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy()); 
    executor.initialize();  
    return executor;  
  } 
  @Override 
  public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {// 异步任务中异常处理 
    return new AsyncUncaughtExceptionHandler() { 
      @Override 
      public void handleUncaughtException(Throwable arg0, Method arg1, Object... arg2) { 
        logger.error("=========================="+arg0.getMessage()+"=======================", arg0); 
        logger.error("exception method:" + arg1.getName()); 
      } 
    }; 
  }  
}