为什么@Async注释spring会创建两次bean？

Question

我正在尝试使用Spring的@Async。但是我注意到定义了@Async的bean的构造函数被调用了两次。

public class TestAsyncAnnotation {

    public TestAsyncAnnotation() {
        System.out.println("-----------con----------");
    }
    @Async
    public void show() {
        System.out.println("From show method");
    }
}

构造

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.0.xsd
    http://www.springframework.org/schema/task
    http://www.springframework.org/schema/task/spring-task-3.0.xsd">

    <context:annotation-config/>
    <task:annotation-driven/>
    <bean name="testAsync" class="com.deva.mvc.testassync.TestAsyncAnnotation" />
</bean>