Question

我正在尝试使用BeanPostProcessor运行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;
    }

}

这里是弹簧配置文件

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

这是我的bean类

public class Car {

    private String wheel; 

    public String getWheel() {
        return wheel;
    } 
    public void setWheel(String wheel) {
        this.wheel = wheel;
    } 


    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        System.out.println("application context loaded");
        Car car = context.getBean("car", Car.class);
    }
}

在运行上面的主要方法时，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)

有人可以让我知道我做错了什么以及如何解决这个异常。另外，它的根本原因是什么？

Answer 1

您声明的任何BeanPostProcessor bean将被ApplicationContext bean工厂选中并使用。你的实现做到了这个

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

    return this;
}

而不是对目标bean做任何事情，它只是返回自己。因此它覆盖了它使用DisplayNamePostProcessor bean处理的所有bean。

使用BeanPostProcessor在Spring中获取BeanNotOfRequiredTypeException

1 个答案: