spring中bean的生命周期

1. Spring启动，查找并加载需要被Spring管理的bean，进行Bean的实例化

2. Bean实例化后对将Bean的引入和值注入到Bean的属性中

3. 如果Bean实现了BeanNameAware接口的话，Spring将Bean的Id传递给setBeanName()方法

4. 如果Bean实现了BeanFactoryAware接口的话，Spring将调用setBeanFactory()方法，将BeanFactory容器实例传入

5. 如果Bean实现了ApplicationContextAware接口的话，Spring将调用Bean的setApplicationContext()方法，将bean所在应用上下文引用传入进来。

6. 如果Bean实现了BeanPostProcessor接口，Spring就将调用他们的postProcessBeforeInitialization()方法。

7. 如果Bean 实现了InitializingBean接口，Spring将调用他们的afterPropertiesSet()方法。类似的，如果bean使用init-method声明了初始化方法，该方法也会被调用

8. 如果Bean 实现了BeanPostProcessor接口，Spring就将调用他们的postProcessAfterInitialization()方法。

9. 此时，Bean已经准备就绪，可以被应用程序使用了。他们将一直驻留在应用上下文中，直到应用上下文被销毁。

10. 如果bean实现了DisposableBean接口，Spring将调用它的destory()接口方法，同样，如果bean使用了destory-method 声明销毁方法，该方法也会被调用

代码实现：

public class Book implements BeanNameAware,BeanFactoryAware,
ApplicationContextAware,InitializingBean,DisposableBean {

private String bookName;
public Book(){
System.out.println("Book Initializing ");
}

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

public void setBeanName(String name) {
System.out.println("Book.setBeanName invoke");
}

public void destroy() throws Exception {
System.out.println("Book.destory invoke");
}

public void afterPropertiesSet() throws Exception {
System.out.println("Book.afterPropertiesSet invoke");
}

public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
System.out.println("Book.setApplicationContext invoke");
}

public String getBookName() {
return bookName;
}

public void setBookName(String bookName) {
this.bookName = bookName;
System.out.println("setBookName: Book name has set.");
}

public void myPostConstruct(){
System.out.println("Book.myPostConstruct invoke");
}

// 自定义初始化方法
@PostConstruct
public void springPostConstruct(){
System.out.println("@PostConstruct");
}

public void myPreDestory(){
System.out.println("Book.myPreDestory invoke");
System.out.println("---------------destroy-----------------");
}

// 自定义销毁方法
@PreDestroy
public void springPreDestory(){
System.out.println("@PreDestory");
}

@Override
protected void finalize() throws Throwable {
System.out.println("------inside finalize-----");
}
}

自定义实现BeanPostProcessor 的MyBeanPostProcessor：

public class MyBeanPostProcessor implements BeanPostProcessor {

// 容器加载的时候会加载一些其他的bean，会调用初始化前和初始化后方法
// 这次只关注book(bean)的生命周期
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if(bean instanceof Book){
System.out.println("MyBeanPostProcessor.postProcessBeforeInitialization");
}
return bean;
}

public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if(bean instanceof Book){
System.out.println("MyBeanPostProcessor.postProcessAfterInitialization");
}
return bean;
}
}

在resources 目录下新建Bean-Lifecycle.xml：

<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-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

<!-- 扫描bean -->
<context:component-scan base-package="com.bean.lifecycle"/>

<!-- 实现了用户自定义初始化和销毁方法 -->
<bean id="book" class="com.bean.lifecycle.Book" init-method="myPostConstruct" destroy-method="myPreDestory">
<!-- 注入bean 属性名称 -->
<property name="bookName" value="thingking in java" />
</bean>

<!--引入自定义的BeanPostProcessor-->
<bean class="com.bean.lifecycle.MyBeanPostProcessor"/>

</beans>

测试类：

public class SpringBeanLifecycleApplication {

public static void main(String[] args) throws InterruptedException {
// 为面试而准备的Bean生命周期加载过程
ApplicationContext context = new ClassPathXmlApplicationContext("Bean-Lifecycle.xml");
Book book = (Book)context.getBean("book");
System.out.println("Book name = " + book.getBookName());
((ClassPathXmlApplicationContext) context).destroy();

}

}

结果：

Book Initializing
setBookName: Book name has set.
Book.setBeanName invoke
Book.setBeanFactory invoke
Book.setApplicationContext invoke
MyBeanPostProcessor.postProcessBeforeInitialization
@PostConstruct
Book.afterPropertiesSet invoke
Book.myPostConstruct invoke
MyBeanPostProcessor.postProcessAfterInitialization
Book name = thingking in java

@PreDestory
Book.destory invoke
Book.myPreDestory invoke
---------------destroy-----------------