javaa技术--SpringBoot异步任务调用(12)

1.定义异步任务

（1）代码示例如下：
@Component
@Async
public class AsyncTask {
    public void task1() throws InterruptedException {
        long start = System.currentTimeMillis();
        Thread.sleep(3000);
        long end = System.currentTimeMillis();
        System.out.println("当前线程：" + Thread.currentThread().getName() + "，" + "任务一耗时：" + (end - start) + "ms");}
    public void task2() throws InterruptedException {
        long start = System.currentTimeMillis();
        Thread.sleep(3000);
        long end = System.currentTimeMillis();
        System.out.println("当前线程：" + Thread.currentThread().getName()  + "，" + "任务二耗时：" + (end - start) + "ms");}
    public void task3() throws InterruptedException {
        long start = System.currentTimeMillis();
        Thread.sleep(3000);
        long end = System.currentTimeMillis();
        System.out.println("当前线程：" + Thread.currentThread().getName() + "，" + "任务三耗时：" + (end - start) + "ms");}
（2）@Async表明是一个异步任务，可以加在方法和类上

2.调用异步任务

@RestController
public class TaskService {
    @Autowired
    private AsyncTask asyncTask;
    @RequestMapping("/taskService")
    public String doTask() throws InterruptedException {
        long start = System.currentTimeMillis();
        asyncTask.task1();
        asyncTask.task2();
        asyncTask.task3();
        long end = System.currentTimeMillis();
        System.out.println("任务总耗时：" + (end - start) + "ms");
        return "任务总耗时：" + (end - start) + "ms";}}

3.开启异步任务

（1）代码示例如下：
@EnableAsync
@SpringBootApplication
public class ScheduleTaskApplication {
    public static void main(String[] args) {
        SpringApplication.run(ScheduleTaskApplication.class, args);}
（2）SpringBoot异步任务默认使用的线程池为SimpleAsyncTaskExecutor,特点如下:
   <1>默认定义多少异步任务，创建多少线程
      1.1.创建线程数量太多，占用内存过大，会造成OutOfMemoryError 
   <2>SimpleAsyncTaskExecutor不提供拒绝策略机制
   <3>SimpleAsyncTaskExecutor可通过设置参数concurrencyLimit
      3.1.指定启用的线程数目
      3.2.默认concurrencyLimit取值为-1，即不启用资源节流

4.如果不使用默认的线程池可以自定义异步任务线程池

（1）自定义异步任务线程池有两种方式
（2）第一种：启动类继承AsyncConfigurerSupport
  <1>代码示例如下：
@SpringBootApplication
@EnableAsync
public class Application extends AsyncConfigurerSupport {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);}
    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(2);
        executor.setMaxPoolSize(2);
        executor.setQueueCapacity(500);
        executor.setThreadNamePrefix("GithubLookup-");
        executor.initialize();
        return executor;}
（3）第二种：自定义配置类实现AsyncConfigurer    
   <1>代码示例如下：
@Configuration
public class AsyncThreadPoolConfig implements AsyncConfigurer {
	/**
     * 自定义线程池
     * @return 线程池对象
     */
    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();
        threadPoolTaskExecutor.setCorePoolSize(5);
        threadPoolTaskExecutor.setMaxPoolSize(8);
        threadPoolTaskExecutor.setQueueCapacity(10);
        threadPoolTaskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
        threadPoolTaskExecutor.initialize();
        return threadPoolTaskExecutor;}
	/**
     * 自定义异常处理器
     * @return 异常处理器对象
     */
    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        AsyncUncaughtExceptionHandler syncUncaughtExceptionHandler = (ex, method, params) -> ex.printStackTrace();
        return syncUncaughtExceptionHandler;}}}

5.获取异步任务对应的线程名称

（1）线程池从默认的SimpleAsyncTaskExecutor转换成自定义的ThreadPoolTaskExecutor