(转载)Spring Bean 初始化过程

Spring 的几个接口

1.InitializingBean接口,在初始化Bean时容器会调用前者的afterPropertiesSet()方法

2.DisposableBean接口,在析构Bean时容器会调用destroy()方法,在下面的例子中好像没有体现出来(革命尚未成功,同志仍需努力)

3.BeanFactoryAware接口,当它被BeanFactory创建后,它会拥有一个指向创建它的BeanFactory的引用

4.BeanPostProcessor接口,这个接口两个方法,postProcessBeforeInitialization(Object bean, String beanName)和postProcessAfterInitialization(Object bean, String beanName) 在其他Bean构造前后执行

5.BeanFactoryPostProcessor接口,Spring IoC容器允许BeanFactoryPostProcessor在容器实际实例化任何其它的bean之前读取配置元数据,并有可能修改它

package com.test; 

public class User { 
    private String name; 
     
    public String getName() { 
        return name; 
    } 

    public void setName(String name) { 
        System.out.println("User类 setName方法"); 
        this.name = name; 
    } 
    public void init() throws Exception { 
        System.out.println("User类init 方法"); 
         
    } 
    public User(){ 
        System.out.println("User类构造方法"); 
    } 
     
} 

package com.test; 

import org.springframework.beans.BeansException; 
import org.springframework.beans.factory.BeanFactory; 
import org.springframework.beans.factory.BeanFactoryAware; 
import org.springframework.beans.factory.DisposableBean; 
import org.springframework.beans.factory.InitializingBean; 
import org.springframework.beans.factory.config.BeanFactoryPostProcessor; 
import org.springframework.beans.factory.config.BeanPostProcessor; 
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; 

public class JavaBean implements InitializingBean,DisposableBean,BeanFactoryAware,BeanPostProcessor ,BeanFactoryPostProcessor{ 
    private String name; 
    public JavaBean(){ 
        System.out.println("JavaBean类构造方法"); 
    } 
    @Override 
    public void afterPropertiesSet() throws Exception { 
        System.out.println("InitializingBean 接口 afterPropertiesSet方法"); 
         
    } 

    @Override 
    public void destroy() throws Exception { 
        System.out.println("DisposableBean 接口 destroy方法"); 
         
    } 
    public void init() throws Exception { 
        System.out.println("JavaBean类init 方法"); 
         
    } 

    @Override 
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException { 
        System.out.println("BeanFactoryAware 接口 setBeanFactory方法"); 
         
    } 

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

    @Override 
    public Object postProcessBeforeInitialization(Object bean, String beanName) 
            throws BeansException { 
        System.out.println(beanName+":BeanPostProcessor 接口 postProcessBeforeInitialization 方法"); 
        return bean; 
    } 

    public String getName() { 
        return name; 
    } 

    public void setName(String name) { 
        System.out.println("JavaBean类setName 方法"); 
        this.name = name; 
    } 
    @Override 
    public void postProcessBeanFactory( 
            ConfigurableListableBeanFactory beanFactory) throws BeansException { 
        System.out.println("BeanFactoryPostProcessor 接口 postProcessBeanFactory 方法"); 
    } 
     

} 

package com.test; 

import org.springframework.context.ApplicationContext; 
import org.springframework.context.support.ClassPathXmlApplicationContext; 

public class Test { 

    /** 
     * @param args 
     */ 
    public static void main(String[] args) { 
        System.out.println("加载Spring配置文件"); 
         ApplicationContext context =   
                new ClassPathXmlApplicationContext("spring.xml");  
         System.out.println("加载Spring配置文件结束"); 
         JavaBean bean=(JavaBean)context.getBean("javaBean"); 
         System.out.println("获取name属性:"+bean.getName()); 
         System.out.println("程序结束"); 
    } 

} 

Spring配置文件
<?xml version="1.0" encoding="UTF-8"?>  
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd"> 
<beans> 
    <bean id="javaBean" class="com.test.JavaBean" init-method="init"> 
        <property name="name" value="zhjb"></property> 
    </bean> 
    <bean id="user" class="com.test.User" init-method="init"> 
        <property name="name" value="zhjb" ></property> 
    </bean> 
</beans>


运行结果如下:

加载Spring配置文件
JavaBean类构造方法
JavaBean类setName 方法
BeanFactoryAware 接口 setBeanFactory方法
InitializingBean 接口 afterPropertiesSet方法
JavaBean类init 方法
BeanFactoryPostProcessor 接口 postProcessBeanFactory 方法
User类构造方法
User类 setName方法
user:BeanPostProcessor 接口 postProcessBeforeInitialization 方法
User类init 方法
user:BeanPostProcessor 接口 postProcessAfterInitialization方法
加载Spring配置文件结束
获取name属性:zhjb
程序结束



从结果进行分析,Bean的初始化顺序应该是

1.构造函数

2.初始化属性

3.如果实现了BeanFactoryAware 接口执行setBeanFactory方法

4..如果实现了InitializingBean 接口执行afterPropertiesSet方法

5.如果在配置文件中指定了init-method,那么执行该方法

6..如果实现了BeanFactoryPostProcessor 接口在 “new”其他类之前执行 postProcessBeanFactory 方法(通过这个方法可以改变配置文件里面的属性值的配置)

7.如果实现了BeanFactoryPostProcessor 接口,那么会在其他bean初始化方法之前执行postProcessBeforeInitialization 方法,之后执行postProcessAfterInitialization方法

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转载自mengqingyu.iteye.com/blog/1866683