Question

public class Life implements BeanNameAware, BeanFactoryAware,  
    ApplicationContextAware, BeanPostProcessor, InitializingBean,  
    DisposableBean {  
private int counter; // counter  

public int getCounter() {  
    return counter;  
}  

public void setCounter(int counter) {  
    this.counter = counter;  
    System.out.println("1. Spring setter DI：" + this.counter);  
}  

public Life() {  
    System.out.println("0. Spring calls constructor");  
}  

@Override  
public void destroy() throws Exception {  
    System.out.println("8. DisposableBean#destroy：" + ++counter);  
}  

public void _destroy() throws Exception {  
    System.out.println("8'. bean#_destroy：" + ++counter);  
}  

@Override  
public void afterPropertiesSet() throws Exception {  
    System.out.println(new Date().getTime());  
    System.out.println("6. InitializingBean#afterPropertiesSet："  
            + ++counter);  
}  

public void init() throws Exception {  
    System.out.println("6'. bean#init：" + ++counter);  
}  

@Override  
public Object postProcessBeforeInitialization(Object bean, String beanName)  
        throws BeansException {  
    System.out.println(new Date().getTime());  
    System.out  
            .println("5. BeanPostProcessor#postProcessBeforeInitialization："  
                    + ++counter);  
    return bean;  
}  

@Override  
public Object postProcessAfterInitialization(Object bean, String beanName)  
        throws BeansException {  
    System.out  
            .println("7. BeanPostProcessor#postProcessAfterInitialization："  
                    + ++counter);  
    return bean;  
}  

@Override  
public void setApplicationContext(ApplicationContext applicationContext)  
        throws BeansException {  
    System.out.println("4. ApplicationContextAware#setApplicationContext："  
            + ++counter);  
}  

@Override  
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {  
    System.out.println("3. BeanFactoryAware#setBeanFactory：" + ++counter);  
}  

@Override  
public void setBeanName(String name) {  
    System.out.println("2. BeanNameAware#setBeanName：" + ++counter);  
}  
}

代码：

public class Test {  
    public static void main(String[] args) {  
        ApplicationContext context = new ClassPathXmlApplicationContext("life.xml");  
        context.getBean("holder");  
    }  
}

代码：

<beans xmlns="http://www.springframework.org/schema/beans"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xsi:schemaLocation="http://www.springframework.org/schema/beans  
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">  
    <bean id="life" class="test.Life" init-method="init"  
        destroy-method="_destroy">  
        <property name="counter" value="1" />  
    </bean>  
    <bean id="holder" class="java.lang.String" />

为什么输出是：

0. Spring calls constructor
1. Spring setter DI：1
2. BeanNameAware#setBeanName：2
3. BeanFactoryAware#setBeanFactory：3
4. ApplicationContextAware#setApplicationContext：4
**1320491454906
6. InitializingBean#afterPropertiesSet：5
6'. bean#init：6**
1320491454921
5. BeanPostProcessor#postProcessBeforeInitialization： 7
7. BeanPostProcessor#postProcessAfterInitialization：8

根据Spring in Action 3rd and Spring-Reference：

6如果任何bean实现了BeanPostProcessor接口，则Spring调用     他们的postProcessBeforeInitialization（）方法。

7如果任何bean实现InitializingBean接口，则Spring调用它们     afterPropertiesSet（）方法。同样，如果bean声明了     init-method，然后将调用指定的初始化方法。

订单似乎有问题？！

Answer 1

BeanPostProcessor（postProcess...Initialization）的方法在其他bean的初始化期间被调用，而不是在后处理器本身。类似地，在你的Spring in Action引用中postProcessBeforeInitialization()在第6点调用的方法是在上下文中声明的其他BeanPostProcessor的方法，而不是被初始化的bean的方法。

在您的情况下，在holder初始化期间会调用这些方法。

因此，BeanPostProcessor是一种允许特殊目的bean（后处理器）拦截其他bean初始化的机制。

困惑！！ Bean的生命周期方法链

1 个答案: