springAOP通知

文章信息

• 原文链接：https://jiayq.blog.csdn.net/article/details/87730393
• 发布时间：2019-02-19 20:10:21
• 阅读量：1
• 分类：java同时被 3 个专栏收录, 订阅专栏, spring
• 标签：#springAOP通知, #AOP通知类型, #实现自定义AOP, #jdk代理与cglib代理的环绕通知, #AOP通知类型详解与练习

摘要

文章浏览阅读1.1k次。springAOP通知1.什么是AOP通知2.通知的类型3.原理4.例子4.1创建一个spring项目4.2创建Java文件4.3创建xml文件4.4运行结果5.总结1.什么是AOP通知AOP通知就是面向切面编程中冗余的代码。比如在每次对数据库进行操作之前，需要记录操作的SQL语句，或者调用方法前打印方法名，这些就是AOP的通知。用大白话说，就是在横向业务中相同的操作，比如日志，事物，异常…_aop的通知是什么意思

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springAOP通知

• 1.什么是AOP通知
• 2.通知的类型
• 3.原理
• 4.例子
• • 4.1创建一个spring项目
    • 4.2创建Java文件
    • 4.3创建xml文件
    • 4.4运行结果
• 5.总结

1.什么是AOP通知

AOP通知就是面向切面编程中冗余的代码。
比如在每次对数据库进行操作之前，需要记录操作的SQL语句，或者调用方法前打印方法名，这些就是AOP的通知。
用大白话说，就是在横向业务中相同的操作，比如日志，事物，异常等等。

2.通知的类型

1.环绕通知
1.1 jdk代理
1.2 cglib代理
2.前置通知
3.后置通知
4.异常通知
5.引介通知

3.原理

ProxyFactoryBean是FactoryBean接口的实现类，FactoryBean负责实例化一个Bean，而ProxyFactoryBean负责为其他Bean创建代理实例。在spring中，使用ProxyFactoryBean是创建AOP代理的基本方式。

4.例子

4.1创建一个spring项目

4.2创建Java文件

package aspect;

import java.lang.reflect.Method;

import org.springframework.aop.AfterReturningAdvice;

public class AfterAspect implements AfterReturningAdvice{

   @Override
   public void afterReturning(Object returnValue, Method method,
   		Object[] args, Object target) throws Throwable {
   	
   	System.out.println("AfterAspect#afterReturning");
   	
   }

}




package aspect;

import java.lang.reflect.Method;

import org.springframework.aop.MethodBeforeAdvice;

public class BeforeAspect implements MethodBeforeAdvice{

   @Override
   public void before(Method method, Object[] args, Object target)
   		throws Throwable {
   	
   	System.out.println("BeforeAspect#before");
   	
   }

}




package aspect;

import intf.PswdDao;

import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.IntroductionInterceptor;

public class IntroductionAspect implements IntroductionInterceptor , PswdDao{

   @Override
   public Object invoke(MethodInvocation invocation) throws Throwable {
   	if(implementsInterface(invocation.getMethod().getDeclaringClass())){
   		return invocation.getMethod().invoke(this, invocation);
   	} else {
   		return invocation.proceed();
   	}
   }

   @Override
   public boolean implementsInterface(Class<?> intf) {
   	return intf.isAssignableFrom(PswdDao.class);
   }

   @Override
   public void sayPswd() {
   	System.out.println("Aspect#sayPswd");
   }


}




package aspect;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

public class MyAspect implements MethodInterceptor{

   @Override
   public Object invoke(MethodInvocation arg0) throws Throwable {
   	before();
   	Object object = arg0.proceed();
   	after();
   	return object;
   }


   private void before(){
   	System.out.println("before");
   }
   
   private void after(){
   	System.out.println("after");
   }
   
}




package bean;

public class People {

   public void say(){
   	System.out.println("People#say");
   }
   
}




package client;

import intf.PswdDao;
import intf.UserDao;

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

import bean.People;

public class Main {

   public static void main(String[] args) {
   	
   	ApplicationContext applicationContext = new ClassPathXmlApplicationContext(
   			"resource/*.xml");
   	UserDao userDao = (UserDao)applicationContext.getBean("userDaoInterceptorProxy");
   	userDao.add();
   	userDao.modify();
   	System.out.println();
   	People people = (People)applicationContext.getBean("peopleInterceptorProxy");
   	people.say();
   	System.out.println();
   	userDao = (UserDao)applicationContext.getBean("userDaoBeforeProxy");
   	userDao.add();
   	userDao.modify();
   	System.out.println();
   	userDao = (UserDao)applicationContext.getBean("userDaoAfterProxy");
   	userDao.add();
   	userDao.modify();
   	System.out.println();
   	userDao = (UserDao) applicationContext.getBean("pswdDaoInterceptorProxy");
   	userDao.add();
   	userDao.modify();
   	((PswdDao) userDao).sayPswd();
   }

}




package impl;

import intf.UserDao;

public class UserDaoImpl implements UserDao{

   @Override
   public void add() {
   	System.out.println("UserDaoImpl#add");
   }

   @Override
   public void modify() {
   	System.out.println("UserDaoImpl#modify");
   }

}




package intf;

public interface PswdDao {

   void sayPswd();
   
}




package intf;

public interface UserDao {

   void add();
   
   void modify();
   
}

4.3创建xml文件

bean.xml

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
   <!-- 目标类 -->
   <bean id="userDao" class="impl.UserDaoImpl"></bean>
   <!-- 增强类 -->
   <bean id="aspect" class="aspect.MyAspect"></bean>
   <!-- 代理对象 -->
   <bean id="userDaoInterceptorProxy" class="org.springframework.aop.framework.ProxyFactoryBean">
   	<!-- 增强的接口 -->
   	<property name="proxyInterfaces">
   		<value>intf.UserDao</value>
   	</property>
   	<!-- 指定目标对象 -->
   	<property name="target" ref="userDao">
   	</property>
   	<!-- 指定增强类 -->
   	<property name="interceptorNames"> 
   		<value>aspect</value>
   	</property>
   	<property name="proxyTargetClass">
   		<value>false</value>
   	</property>
   </bean>
   <bean id="people" class="bean.People"></bean>
   <bean id="peopleInterceptorProxy" class="org.springframework.aop.framework.ProxyFactoryBean">
   	<!-- 指定目标对象 -->
   	<property name="target" ref="people">
   	</property>
   	<!-- 指定增强类 -->
   	<property name="interceptorNames"> 
   		<value>aspect</value>
   	</property>
   	<property name="proxyTargetClass">
   		<value>true</value>
   	</property>
   </bean>
   <bean id="userDaoBeforeProxy" class="org.springframework.aop.framework.ProxyFactoryBean">
   	<!-- 增强的接口 -->
   	<property name="proxyInterfaces">
   		<value>intf.UserDao</value>
   	</property>
   	<!-- 指定目标对象 -->
   	<property name="target" ref="userDao">
   	</property>
   	<!-- 指定增强类 -->
   	<property name="interceptorNames"> 
   		<value>beforeAspect</value>
   	</property>
   	<property name="proxyTargetClass">
   		<value>false</value>
   	</property>
   </bean>
   <!-- 增强类 -->
   <bean id="beforeAspect" class="aspect.BeforeAspect"></bean>
   <!-- 增强类 -->
   <bean id="afterAspect" class="aspect.AfterAspect"></bean>
   <bean id="userDaoAfterProxy" class="org.springframework.aop.framework.ProxyFactoryBean">
   	<!-- 增强的接口 -->
   	<property name="proxyInterfaces">
   		<value>intf.UserDao</value>
   	</property>
   	<!-- 指定目标对象 -->
   	<property name="target" ref="userDao">
   	</property>
   	<!-- 指定增强类 -->
   	<property name="interceptorNames"> 
   		<value>afterAspect</value>
   	</property>
   	<property name="proxyTargetClass">
   		<value>false</value>
   	</property>
   </bean>
   <bean id="intriductionAspect" class="aspect.IntroductionAspect"></bean>
   <bean id="pswdDaoInterceptorProxy" class="org.springframework.aop.framework.ProxyFactoryBean">
   	<!-- 增强的接口 -->
   	<property name="proxyInterfaces">
   		<value>intf.PswdDao</value>
   	</property>
   	<!-- 指定目标对象 -->
   	<property name="target" ref="intriductionAspect">
   	</property>
   	<!-- 指定增强类 -->
   	<property name="interceptorNames"> 
   		<value>intriductionAspect</value>
   	</property>
   	<property name="proxyTargetClass">
   		<value>false</value>
   	</property>
   </bean>
</beans>

4.4运行结果

before
UserDaoImpl#add
after
before
UserDaoImpl#modify
after

before
People#say
after

BeforeAspect#before
UserDaoImpl#add
BeforeAspect#before
UserDaoImpl#modify

UserDaoImpl#add
AfterAspect#afterReturning
UserDaoImpl#modify
AfterAspect#afterReturning

Exception in thread "main" java.lang.ClassCastException: com.sun.proxy.$Proxy5 cannot be cast to intf.UserDao
   at client.Main.main(Main.java:32)

5.总结

spring的通知类型：
1.环绕通知
1.1 jdk代理
1.2 cglib代理
2.前置通知
3.后置通知
4.异常通知
5.引介通知