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如果对动态代理还未曾有一定的认识（下文会用到），请先看这篇： 

package com.imooc.ioc.demo3;public interface UserDao {    public void findAll();    public void save();    public void update();    public void delete();}package com.imooc.ioc.demo3;public class UserDaoImpl implements UserDao {    @Override    public void findAll() {        System.out.println("查询用户。。。");    }    @Override    public void save() {        System.out.println("保存用户。。。");    }    @Override    public void update() {        System.out.println("修改用户。。。");    }    @Override    public void delete() {        System.out.println("删除用户。。。");    }}

package com.imooc.ioc.demo3;import org.springframework.beans.BeansException;import org.springframework.beans.factory.config.BeanPostProcessor;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;public class MyBeanPostProcessor implements BeanPostProcessor {    @Override    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {        System.out.println("第五步：初始化前方法...");        return bean;    }    @Override    public Object postProcessAfterInitialization(final Object bean, String beanName) throws BeansException {        System.out.println("第八步：初始化后方法...");                if("userDao".equals(beanName)){            Object proxy = Proxy.newProxyInstance(bean.getClass().getClassLoader(), bean.getClass().getInterfaces(), new InvocationHandler() {                                @Override                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {                    if("save".equals(method.getName())){                        System.out.println("权限校验===================");                        return method.invoke(bean,args);                    }                    return method.invoke(bean,args);                }            });            return proxy;        }        else{            return bean;        }    }}

package com.imooc.ioc.demo3;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;/** * Bean的作用范围的测试 */public class SpringDemo3 {    @Test    public void demo3(){        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");        UserDao userDao = (UserDao)applicationContext.getBean("userDao");        userDao.findAll();        userDao.save();        userDao.update();        userDao.delete();    }}

运行结果：第五步：初始化前方法...第八步：初始化后方法...查询用户。。。权限校验===================保存用户。。。修改用户。。。删除用户。。。

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