Spring Bean的一生
Spring Bean的一生
When you work directly in Java, you can do anything you like with your objects and do not always need to rely on the container lifecycle.
前言:
在Ioc容器启动后相应的Bean并没有立即实例化,此时Ioc容器仅仅拥有所有对象的BeanDefinition(Bean对象在Spring中的描述,包含该Bean在容器中实例化所需的信息,通过解析xml/javaconfig后所得)
Spring Bean生命周期的管理
Spring bean factory
能管理Beans
的生命周期,通过实现InitializingBean和DisposableBean
这两个接口都只声明一个方法让我们可以初始化/关闭
bean中的资源
当然在整个生命周期中也提供了一些Call Back Methods,这些方法类似于Servlet
中的监听器的实现
- 当
Bean
处于post-initialization
阶段时,我们可以通过实现InitializingBean
接口来实现afterPropertiesSet()
- 当
Bean
处于pre-destruction
阶段时,我们可以实现DisposableBean
接口来实现destroy()
方法
Spring Bean的生命周期图
Code Time
以Rick
类交给Spring容器管理,方法顺序为其在Spring容器中的执行顺序
Rick.java
public class Rick implements InitializingBean, DisposableBean {
public Rick(){
System.out.println("Rick is in [Rick] - Rick()");
}
public void customInit(){
System.out.println("Rick is in [Rick] - customInit()");
}
@PostConstruct
public void postConstruct(){
System.out.println("Rick is in [@PostConstruct] - postConstruct()");
}
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("Rick is in [InitializingBean] - afterPropertiesSet()");
}
@PreDestroy
public void preDestroy(){
System.out.println("Rick is in [@PreDestroy] - preDestroy()");
}
@Override
public void destroy() throws Exception {
System.out.println("Rick is in [DisposableBean] - destroy()");
}
public void customDestroy(){
System.out.println("Rick is in [Rick] - customDestroy()");
}
}
加入BeanPostProcess
RickBeanPostProcess.java
public class RickBeanPostProcess implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (bean instanceof Rick) {
System.out.println("Rick is in [BeanPostProcessor] - postProcessBeforeInitialization()");
}
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (bean instanceof Rick) {
System.out.println("Rick is in [BeanPostProcessor] - postProcessAfterInitialization()");
}
return bean;
}
}
配置类
RickConfig.java
@Configuration
public class RickConfig {
/**
* 指定自定义初始化方法和自定义销毁方法
* @return Rick
*/
@Bean(initMethod = "customInit",destroyMethod = "customDestroy")
public Rick rick(){
return new Rick();
}
@Bean
public RickBeanPostProcess rickBeanPostProcess(){
return new RickBeanPostProcess();
}
}
测试类
Client.java
public class Client {
public static void main(String[] args) {
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(RickConfig.class);
((AnnotationConfigApplicationContext) applicationContext).close();
}
}
最终结果如下
Rick is in [Rick] - Rick()
Rick is in [BeanPostProcessor] - postProcessBeforeInitialization()
Rick is in [@PostConstruct] - postConstruct()
Rick is in [InitializingBean] - afterPropertiesSet()
Rick is in [Rick] - customInit()
Rick is in [BeanPostProcessor] - postProcessAfterInitializa
Rick is in [@PreDestroy] - preDestroy()
Rick is in [DisposableBean] - destroy()
Rick is in [Rick] - customDestroy()
参考
Spring Framework Documentation