spring扩展点之一：BeanFactoryPostProcessor和BeanPostProcessor - duanxz

public interface BeanPostProcessor {  
  
    /** 
     * Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean 
     * initialization callbacks (like InitializingBean's {@code afterPropertiesSet} 
     * or a custom init-method). The bean will already be populated with property values.    
     */  
　　//实例化、依赖注入完毕，在调用显示的初始化之前完成一些定制的初始化任务  
    Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;  
  
      
    /** 
     * Apply this BeanPostProcessor to the given new bean instance <i>after</i> any bean 
     * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}   
     * or a custom init-method). The bean will already be populated with property values.       
     */  
　　//实例化、依赖注入、初始化完毕时执行  
    Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;  
  
}

package com.meituan.hyt.test1;  
  
import org.springframework.beans.factory.annotation.Value;  
import org.springframework.stereotype.Component;  
  
@Component  
public class User {  
    @Value("老名字")  
    private String name;  
    @Value("50")  
    private Integer id;  
  
    public Integer getId() {  
        return id;  
    }  
  
    public void setId(Integer id) {  
        this.id = id;  
    }  
  
    public String getName() {  
        return name;  
    }  
  
    public void setName(String name) {  
        this.name = name;  
    }  
  
    @Override  
    public String toString() {  
        return "User{" +  
                "name='" + name + '\'' +  
                ", id=" + id +  
                '}';  
    }  
} 

package com.meituan.hyt.test1;  
  
import org.springframework.beans.BeansException;  
import org.springframework.beans.factory.config.BeanPostProcessor;  
  
public class UserPostProcessor implements BeanPostProcessor {  
    @Override  
    public Object postProcessBeforeInitialization(Object o, String s) throws BeansException {  
        if(o instanceof User){  
            User user = (User)o;  
            user.setName("新名字");  
            user.setId(100);  
            return user;  
        }  
        return o;  
    }  
  
    @Override  
    public Object postProcessAfterInitialization(Object o, String s) throws BeansException {  
        return o;  
    }  
}  

package com.meituan.hyt.test1;  
  
import org.springframework.context.ApplicationContext;  
import org.springframework.context.support.ClassPathXmlApplicationContext;  
  
  
public class Main2 {  
    public static void main(String[] args) {  
        ApplicationContext cxt = new ClassPathXmlApplicationContext("applicationContext.xml");  
        User user = (User) cxt.getBean("user");  
        System.out.println(user.toString());  
    }  
}  

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;

}

package com.meituan.hyt.test1;  
  
import org.springframework.beans.BeansException;  
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;  
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;  
  
public class UserBeanFactoryPostProcessor implements BeanFactoryPostProcessor {  
    @Override  
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {  
        System.out.println("BeanFactoryPostProcessor doing");  
    }  
}  

<bean id="userBeanFactoryPostProcessor" class="com.meituan.hyt.test1.UserBeanFactoryPostProcessor"/>