spring boot TaskExecutor线程池大小

Question

我使用的是spring boot 2.0.2，并使用Async来执行任务。

我注册一个TaskExecutor来控制线程池大小，如下所示：

public class ThreadConfig {
@Bean
public TaskExecutor threadPoolTaskExecutor() {

    ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();

    executor.setCorePoolSize(2);
    executor.setMaxPoolSize(3);
    executor.setQueueCapacity(3);
    executor.setThreadNamePrefix("anniversary");

    executor.initialize();
    System.out.println("******* name "  + executor.getThreadNamePrefix());
    System.out.println("********** core pool size " + executor.getCorePoolSize());

    return executor;
}

}

但是在运行期间，创建了超过20个线程，

*********Thread[SimpleAsyncTaskExecutor-1,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-2,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-3,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-4,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-5,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-6,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-7,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-8,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-9,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-10,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-11,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-12,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-13,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********
**********Thread[SimpleAsyncTaskExecutor-14,5,com.abc.team1.project1.anniversary.AnniversaryApplication]*********