mini-spring基础篇：IoC（十一）：Aware接口

一、Aware接口

代码分支：aware-interface
之前都是基于main分支来追踪源码，从现在开始，我们基于每章开始的代码分支追踪源码。

mini-spring源码作者建议如此，这样阅读难度会更小。

Aware是感知、意识的意思，Aware接口是标记性接口，其实现子类能感知容器相关的对象。常用的Aware接口有BeanFactoryAware和ApplicationContextAware，分别能让其实现者感知所属的BeanFactory和ApplicationContext。

让实现BeanFactoryAware接口的类能感知所属的BeanFactory，实现比较简单，查看AbstractAutowireCapableBeanFactory#initializeBean前三行。

实现ApplicationContextAware的接口感知ApplicationContext，是通过BeanPostProcessor。由bean的生命周期可知，bean实例化后会经过BeanPostProcessor的前置处理和后置处理。定义一个BeanPostProcessor的实现类ApplicationContextAwareProcessor，在AbstractApplicationContext#refresh方法中加入到BeanFactory中，在前置处理中为bean设置所属的ApplicationContext。

改用dom4j解析xml文件。

至止，bean的生命周期如下：

测试：

spring.xml

xml 复制代码

<?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:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
	         http://www.springframework.org/schema/beans/spring-beans.xsd
		 http://www.springframework.org/schema/context
		 http://www.springframework.org/schema/context/spring-context-4.0.xsd">

    <bean id="helloService" class="org.springframework.test.service.HelloService"/>

</beans>

java 复制代码

public class HelloService implements ApplicationContextAware, BeanFactoryAware {

	private ApplicationContext applicationContext;

	private BeanFactory beanFactory;

	@Override
	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
		this.beanFactory = beanFactory;
	}

	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		this.applicationContext = applicationContext;
	}

	public ApplicationContext getApplicationContext() {
		return applicationContext;
	}

	public BeanFactory getBeanFactory() {
		return beanFactory;
	}
}

java 复制代码

public class AwareInterfaceTest {

	@Test
	public void test() throws Exception {
		ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:spring.xml");
		HelloService helloService = applicationContext.getBean("helloService", HelloService.class);
		assertThat(helloService.getApplicationContext()).isNotNull();
		assertThat(helloService.getBeanFactory()).isNotNull();
	}
}