springboot 启动类加上 @EnableAsync 注解
@Async才会生效

@Async注解 标注在方法上 或 类上
调用异步方法时会立即返回结果，方法的实际执行将提交给Spring TaskExecutor 线程池执行。

在启动类上添加@EnableAsync注解

不指定线程池的名称，使用默认的线程池 SimpleAsyncTaskExecutor

@Async注解的方法的返回值只能是void或者Future类型


默认线程池的默认配置
核心线程数 8
最大线程数 Integet.MAX_VALUE
队列  LinkedBlockingQueue
容量 Integet.MAX_VALUE
空闲线程保留时间 60s
拒绝策略 AbortPolicy


spring:
  task:
    execution:
      pool:
        max-size: 10
        core-size: 5
        keep-alive: 2s
        queue-capacity: 1000
        thread-name-prefix: my-executor



指定线程池
@Async("my-executor")

    @Bean("async-executor")
    public Executor asyncExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(10);
        taskExecutor.setMaxPoolSize(100);
        taskExecutor.setQueueCapacity(50);
        taskExecutor.setKeepAliveSeconds(200);
        taskExecutor.setThreadNamePrefix("async-executor-");
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        taskExecutor.initialize();
        return taskExecutor;
    }