spring注解 @EnableAsync @Async实现异步调用(实例)

对于一些简单的场景而言，其实spring的异步注解就非常好用.
本篇以SpringBoot项目为讲解：

@EnableAsync
public class Application extends WebMvcConfigurationSupport {

@Service
@Async
public class AsyncService {

	public void asyncSleep2()  {
		System.out.println("次线程2 " + Thread.currentThread().getName());
		System.out.println("次线程2 开始异步休眠3秒");
		try {
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("次线程2 异步休眠休眠结束");
	}


	public void asyncSleep1() {
		System.out.println("次线程1 " + Thread.currentThread().getName());
		System.out.println("次线程1 开始异步休眠3秒");
		try {
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("次线程1 异步休眠休眠结束");
	}
}

@Async
public void asyncSleep2()  {
		System.out.println("次线程2 " + Thread.currentThread().getName());
		System.out.println("次线程2 开始异步休眠3秒");
		try {
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("次线程2 异步休眠休眠结束");
	}

用this肯定是不可行的，那我本类里注入一个本Service，可以实现吗？答案也是不可以的，项目都没办法启动，错误如下：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'async1Controller': Unsatisfied dependency expressed through field 'asyncService'; nested exception is 
org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'asyncSayService1': Bean with name 'asyncSayService1' has been injected into other beans [asyncSayService1] 
in its raw version as part of a circular reference, but has eventually been wrapped. This means that said other beans do not use the final version of the bean. 
This is often the result of over-eager type matching - consider using 'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.

有实现类继承接口的形式，可以实现异步吗？
答案也是不可行的，可自行测试。

public Integer getAsyncHello1() {
		System.out.println("getAsyncHello1-Start 主线程1："+Thread.currentThread().getName());
		asyncService.asyncSleep1();
		System.out.println("getAsyncHello1-End");

		return 1;
	}

asyncSleep1是一个异步方法，我将注解配置到了类上，就代表着我这个类里的所有方法都是需要异步实现的。

public void asyncSleep1() {
		System.out.println("次线程1 " + Thread.currentThread().getName());
		System.out.println("次线程1 开始异步休眠3秒");
		try {
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("次线程1 异步休眠休眠结束");
	}

如果asyncSleep1异步的话，那么如上我们应该打印出getAsyncHello1主线程的两个输出，然后再打印次线程的输出，并且我们通过输出可以看到线程名也不一样，就证明是开启了两个线程

简简单单的两个注解，就实现了异步操作。下篇讲述原理，从根源来了解实现。