Question

当我尝试以下列方式访问bean时

ConfigurableApplicationContext context = new ClassPathXmlApplicationContext("factoryMethodDemo.xml");
    System.out.println(context.getBean("bean2",BeanLifeCycle.class));
    System.out.println(context.getBean("bean",FactoryMethodDemo.class));
    context.close();

这里BeanLifeCycle.class实现所有生命周期接口，如BeanNameAware ... DisposableBean等。 FactoryMethodDemo.class是一个简单的bean

FactoryMethodDemo.java

        package com.demo;

    import org.springframework.context.ConfigurableApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;

    public class FactoryMethodDemo {
        private String message;

        public FactoryMethodDemo() {
        }

        public void setMessage(String message) {
            System.out.println("setMessage Called");
            this.message = message;
        }

        public void defaultInit() {
            System.out.println("defaultInit");

        }

        public static void main(String[] args) {
            ConfigurableApplicationContext context = new ClassPathXmlApplicationContext("factoryMethodDemo.xml");
            System.out.println(context.getBean("bean2",BeanLifeCycle.class));
            System.out.println(context.getBean("&bean",FactoryMethodDemo.class));
            context.close();
        }
    }

BeanLifeCycle.java

        package com.demo;

    import org.springframework.beans.BeansException;
    import org.springframework.beans.factory.BeanFactory;
    import org.springframework.beans.factory.BeanFactoryAware;
    import org.springframework.beans.factory.BeanNameAware;
    import org.springframework.beans.factory.DisposableBean;
    import org.springframework.beans.factory.InitializingBean;
    import org.springframework.beans.factory.config.BeanPostProcessor;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;

    public class BeanLifeCycle implements BeanNameAware, BeanFactoryAware, ApplicationContextAware, BeanPostProcessor, InitializingBean, DisposableBean {

        private String property;

        public void setProperty(String property) {
            System.out.println("setProperty");
        }

        @Override
        public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
            System.out.println("setBeanFactory");
        }

        @Override
        public void setBeanName(String beanName) {
            System.out.println("setBeanName");
        }

        @Override
        public void setApplicationContext(ApplicationContext arg0) throws BeansException {
            System.out.println("setApplicationContext");

        }

        @Override
        public Object postProcessAfterInitialization(Object arg0, String arg1) throws BeansException {
            System.out.println("postProcessAfterInitialization");
            return new Object();
        }

        @Override
        public Object postProcessBeforeInitialization(Object arg0, String arg1) throws BeansException {
            System.out.println("postProcessBeforeInitialization");
            return new Object();
        }

        @Override
        public void afterPropertiesSet() throws Exception {
            // THis is treated as init method
            System.out.println("afterPropertiesSet");
        }

        @Override
        public void destroy() throws Exception {
            System.out.println("destroy");
        }


    }

factoryMethodDemo.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <beans  xmlns="http://www.springframework.org/schema/beans" x        mlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
    <bean id="bean" class="com.demo.FactoryMethodDemo">
    <property name="message" value="message"></property>
    </bean>
    <bean id="bean2" class="com.demo.BeanLifeCycle">
    <property name="property" value="property"></property></bean>
    </beans>

抛出异常

线程“main”中的异常org.springframework.beans.factory.BeanNotOfRequiredTypeException：名为'bean'的bean必须是[com.demo.FactoryMethodDemo]类型，但实际上是[java.lang.Object]类型

显然返回了Object类型而不是FactoryMethodDemo，有人请解释在场景背后发生的事情导致此类异常。谢谢你的时间和提前帮助

Answer 1

我怀疑com.demo.FactoryMethodDemo将实现FactoryBean接口：

这意味着bean在应用程序上下文中不可用于查找，因为FactoryMethodDemo bean负责创建另一个bean（标识为bean）。

如果你看一下FactoryMethodDemo的实现，你很可能会发现有一个getObject的实现，它将返回一个id为{{1}的bean实例。 }。

因为“工厂bean”与普通bean不同，所以您将无法使用bean方法查找它，因为它不会被注册。但是，您应该能够执行以下操作：

getBean(String beanId, Class beanType)

这将返回创建bean“bean”的“工厂”。

另见Spring Reference Docs

需要说明：线程“main”中的异常org.springframework.beans.factory.BeanNotOfRequiredTypeException：

1 个答案: