首页 > 编程语言 > 详细

Spring的BeanFactoryPostProcessor和BeanPostProcessor

时间:2017-11-21 00:31:49      阅读:312      评论:0      收藏:0      [点我收藏+]

PostProcessor:后处理器; 
BeanPostProcessor:Bean的后置处理器(处理的对象是Bean); 
BeanFactoryPostProcessor:BeanFactory的后置处理器(处理的对象是BeanFactory)

(1)看一下BeanFactoryPostProcessor接口的源码:

@FunctionalInterface
public interface BeanFactoryPostProcessor {

    /**
     * Modify the application context‘s internal bean factory after its standard
     * initialization. All bean definitions will have been loaded, but no beans
     * will have been instantiated yet. This allows for overriding or adding
     * properties even to eager-initializing beans.
     * @param beanFactory the bean factory used by the application context
     * @throws org.springframework.beans.BeansException in case of errors
     */
    void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;
}

 

①方法postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)的作用是什么? 
源码中是这样说明的:

//Modify the application context‘s internal bean factory after its standard initialization.

bean factory已经经历了standard initialization; 
方法的入参ConfigurableListableBeanFactory beanFactory即是standard initialization后的bean factory; 
把standard initialization后的bean factory交给我们处理,我们可以对其进行修改。 
②什么时候调用postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)? 
源码中是这样说明的:

// All bean definitions will have been loaded, but no beans will have been instantiated yet.

 

bean factory已经经历了standard initialization,所有的bean definitions也已经被加载到bean factory之中,但是还没有创建(实例化)任何的Bean。 
③方法的入参beanFactory 
方法的入参ConfigurableListableBeanFactory beanFactory即是我们需要处理的对象;beanFactory已经经历了standard initialization,所有的bean definitions也已经被加载到beanFactory之中。 
④如何操作(处理)beanFactory呢? 
操作beanFactory的常见方式: 
对加载到beanFactory中的bean definitions进行修改。

通过参数beanFactory,可以获取相关Bean的bean definition,并修改bean definition。

(2)代码示例: 
User类:

public class User {
    private String username;
    private int age;

    public void setUsername(String username) {
        System.out.println("setUsername()");
        this.username = username;
    }

    public void setAge(int age) {
        System.out.println("setAge()");
        this.age = age;
    }

    public User(){
        System.out.println("Constructor()");
    }

    @Override
    public String toString() {
        return "User [username=" + username + ", age=" + age + "]";
    }

}

BeanFactoryPostProcessor处理器:

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    public MyBeanFactoryPostProcessor(){
        System.out.println("BeanFactoryPostProcessor实现类的构造器");
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.println("BeanFactoryPostProcessor.postProcessBeanFactory()");

        //获取指定的BeanDefinition
        BeanDefinition bd = beanFactory.getBeanDefinition("user1");
        //根据BeanDefinition获取MutablePropertyValues
        MutablePropertyValues pvs = bd.getPropertyValues();

        //增加
        pvs.add("age", 20);
        //覆盖
        pvs.add("username", "Richard");
    }
}

 

Bean配置文件:

    <bean id="user1" class="com.User">
        <!-- 这里只为属性username赋值,属性age没有赋值 -->
        <property name="username" value="Jack"></property>
    </bean>

    <bean class="com.MyBeanFactoryPostProcessor"></bean>

 

测试类:

    public static void main(String[] args) {
        ApplicationContext context=new ClassPathXmlApplicationContext("applicationContext.xml");

        User user1=(User)context.getBean("user1");
        System.out.println(user1);
    }

运行结果: 

BeanFactoryPostProcessor实现类的构造器 
BeanFactoryPostProcessor.postProcessBeanFactory() 
Constructor() 
setUsername() 
setAge() 
User [username=Richard, age=20]

(3)注意点: 
BeanFactoryPostProcessor接口和BeanPostProcessor接口非常相似,都是spring初始化bean时对外暴露的扩展点。

①BeanFactory的后置处理器:Spring提供的一种特殊的Bean 
②BeanFactory的后置处理器,需要实现BeanFactoryPostProcessor接口 
③需要在Bean的配置文件中,注册BeanFactory的后置处理器,但不需要设置id属性。IOC容器会自动识别这是个BeanFactory的后置处理器,自动的使用它。

<bean class="com.MyBeanFactoryPostProcessor"></bean>

 

④实例化BeanFactoryPostProcessor实现类,并调用BeanFactoryPostProcessor的postProcessBeanFactory()方法; 
这2步会很早进行,在Bean实例被创建之前进行。 
⑤Bean的后置处理器,操作的对象是Bean,会对容器中的所有Bean进行处理,每个Bean都要经过2个处理方法postProcessBeforeInitialization()和postProcessAfterInitialization(); 
BeanFactory的后置处理器,操作的对象是BeanFactory,因此只会有一次处理过程(很早进行,在Bean实例被创建之前进行),即只调用处理方法postProcessBeanFactory()一次。

Spring的BeanFactoryPostProcessor和BeanPostProcessor

原文:http://www.cnblogs.com/taiwan/p/7868725.html

(0)
(0)
   
举报
评论 一句话评论(0
关于我们 - 联系我们 - 留言反馈 - 联系我们:wmxa8@hotmail.com
© 2014 bubuko.com 版权所有
打开技术之扣,分享程序人生!