打印spring加载的bean信息 .

在启动应用程序的时或是调试时如果能够打印出spring管理的bean的信息，那么对于调试来说有很大的帮助，以下配置可以在spring创建一个bean之后打印出bean的消息，方便调试

public class InstantiationTracingBeanPostProcessor implements BeanPostProcessor {

    // simply return the instantiated bean as-is
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        return bean; // we could potentially return any object reference here…
    }
    //在创建bean后输出bean的信息
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
       // System.out.println(“Bean ‘” + beanName + “‘ created : ” + bean.toString());
        if (bean instanceof ServletDispatcherResult){
         ServletDispatcherResult result = (ServletDispatcherResult) bean;
        }
        return bean;
    }
}

在配置文件中

<?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:lang=”http://www.springframework.org/schema/lang“
       xsi:schemaLocation=”
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-2.0.xsd“>

    <!–
        when the above bean (‘messenger’) is instantiated, this custom
        BeanPostProcessor implementation will output the fact to the system console
     –>
    <bean class=”test.InstantiationTracingBeanPostProcessor”/>
</beans>

每次创建bean实例结束之后都会执行继承了BeanPostProcessor 类的postProcessAfterInitialization方法，就可以打印出bean的消息