Java 使用BeanPostProcessor时在Spring中获取BeanNotOfRequiredTypeException

我正在尝试使用

BeanPostProcessor

运行一个Spring示例

下面是bean后处理器

public class DisplayNamePostProcessor implements BeanPostProcessor{

    DisplayNamePostProcessor(){
        System.out.println("DisplayNamePostProcessor instantiated");
    }

    public Object postProcessBeforeInitialization(Object bean, String beanName)
            throws BeansException {
        System.out.println("postProcessBeforeInitialization for bean "+beanName);

        return this;
    }

    public Object postProcessAfterInitialization(Object bean, String beanName)
            throws BeansException {
        System.out.println("postProcessAfterInitialization for bean "+beanName);
        return this;
    }

}

这里是spring配置文件

    <bean id="car" class="com.core.Car" >
            <property name="wheel" value="four" />
        </bean>
<bean class="com.core.DisplayNamePostProcessor"></bean>

在运行上述主方法时，我得到以下异常

Exception in thread "main" org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'car' must be of type [com.core.Car], but was actually of type [com.core.DisplayNamePostProcessor]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:361)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:198)
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1121)

有人能告诉我我做错了什么以及如何解决这个异常吗。另外，它的根本原因是什么？

您声明的任何bean都将被

ApplicationContext

bean工厂提取并使用。您的实现可以做到这一点

public Object postProcessBeforeInitialization(Object bean, String beanName)
        throws BeansException {
    System.out.println("postProcessBeforeInitialization for bean "+beanName);

    return this;
}

---

它没有对目标

bean

执行任何操作，而是简单地返回自身。因此，它使用

DisplayNamePostProcessor

bean覆盖它处理的所有bean。

ohh..我的错..谢谢你让我知道。我怎么会错过呢：(

public Object postProcessBeforeInitialization(Object bean, String beanName)
        throws BeansException {
    System.out.println("postProcessBeforeInitialization for bean "+beanName);

    return this;
}