Java Spring查找方法与抽象类

我想了解Spring是如何从抽象类创建bean的，就好像它正在实例化一个抽象类一样，因为众所周知这是不可能的。想知道“abstractLookupBean”bean实例化了什么

多谢各位

public abstract class AbstractLookupDemoBean implements DemoBean {

    public abstract MyHelper getMyHelper();

    public void someOperation() {
        getMyHelper().doSomethingHelpful();
    }
}

DemoBean类

public interface DemoBean {
    public MyHelper getMyHelper();

    public void someOperation();
}

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans"    
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    
       xsi:schemaLocation="http://www.springframework.org/schema/beans       
         http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">

    <bean id="helper" class="com.rami.methodlookup.helper.MyHelper" scope="prototype"/>     

    <bean id="abstractLookupBean" class="com.rami.methodlookup.helper.AbstractLookupDemoBean">         
        <lookup-method name="getMyHelper" bean="helper"/>     
    </bean>   

    <bean id="standardLookupBean" class="com.rami.methodlookup.helper.StandardLookupDemoBean">         
        <property name="myHelper">             
            <ref local="helper"/>         
        </property>     
    </bean> 
</beans>

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请参阅spring文档

…如果方法是抽象的，则动态生成的子类将实现该方法。否则，动态生成的子类将重写在原始类中定义的具体方法

    public static void main(String[] args) {
    GenericXmlApplicationContext ctx = null; 
    try{
        ctx = new GenericXmlApplicationContext();
        ctx.load("applicationContext.xml");
        ctx.refresh();
        DemoBean abstractBean = (DemoBean) ctx.getBean("abstractLookupBean"); //What is getting instantiated?
    }finally{
        ctx.close();
    }