spring 框架说明文档学习记录(3.6)

容器扩展

一般的，应用开发者不需要继承实现ApplicationContext。与之相对的，Spring IOC容器能够通过引入特别集成接口来扩展。

使用BeanPostProcessor定制bean

我们可以通过实现BeanPostProcessor接口定义的回调函数来实现自己的实例化逻辑、依赖解决逻辑等等。如果你想在Spring容器完成实例化、配置或初始化bean后实现一些逻辑，你可以引入一个或多个BeanPostProcessor实现。

你可以配置多个BeanPostProcessor实例，并通过设置order属性来控制BeanPostProcessor的执行顺序。仅在BeanPostProcessor实现Ordered接口时才可设置该属性，如果你编写自己的BeanPostProcessor，你也应该考虑继承Ordered接口。

简单示例

package scripting;import org.springframework.beans.factory.config.BeanPostProcessor;import org.springframework.beans.BeansException;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...  }  public Object postProcessAfterInitialization(Object bean,      String beanName) throws BeansException {    System.out.println("Bean '" + beanName + "' created : " + bean.toString());    return bean;  }}

<?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.xsd        http://www.springframework.org/schema/lang        http://www.springframework.org/schema/lang/spring-lang.xsd">  <lang:groovy id="messenger"        script-source="classpath:org/springframework/scripting/groovy/Messenger.groovy">    <lang:property name="message" value="Fiona Apple Is Just So Dreamy."/>  </lang:groovy>  <!--  when the above bean (messenger) is instantiated, this custom  BeanPostProcessor implementation will output the fact to the system console  -->  <bean class="scripting.InstantiationTracingBeanPostProcessor"/></beans>

BeanFactoryPostProcessor
PropertyPlaceholderConfigurer

PropertyOverrideConfigurer

FactoryBean