AOP 面向切面编程
AOP学习
AOP概述
AOP(Aspect Oriented Programming)是面向切面编程，是OOP的扩展，可以解决OOP代码开发过程中遇到的问题。利用AOP可以对业务逻辑的各个部分进行隔离，从而使得业务逻辑各部分之间的耦合度降低，提高程序的可重用性，同时提高了开发的效率。
AOP的应用场景
应用场景有很多，这里只列举一小部分
- 打印操作日志,防止小伙伴删库跑路
- 测试系统性能
- 事务控制
AOP和Spring AOP、AspectJ
- AOP最早是AOP联盟提出的，并且制定规范
- Spring AOP 遵循AOP规范，Spring AOP只能在Spring中使用
- AspectJ是一个面向切面的框架，它扩展了Java语言，AspectJ定义了AOP语法。Aspect可以在Spring框架以及其他框架内使用
AOP实现原理
AOP实现是通过动态代理实现的
- jdk动态代理: 对实现接口的类产生代理
- cglib动态代理：对没有实现接口的类产生代理
Spring底层如果类实现了接口用jdk动态代理，没有实现接口默认用CGLIB动态代理。当然这是默认的，如果需要也可以强制使用。当然这是后话了
/** * JDK动态代理，利用反射完成 */ public class JdkProxy implements InvocationHandler { private Object target; public JdkProxy(Class target) { this.target = target; } @Override public Object invoke(Object target, Method method, Object[] args) throws Throwable { System.out.println("===before==="); Object obj = method.invoke(target, args); System.out.println("===after==="); return obj; } public Object getProxy() { return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this); } }
/** * Cglib动态代理，通过继承生成目标类的代理类 */ public class CglibProxy implements MethodInterceptor { private Object target; public CglibProxy(Object target) { this.target = target; } @Override public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable { //方法前增强 System.out.println("***before***"); Object obj = methodProxy.invoke(proxy, args); //方法后增强 System.out.println("***after****"); return obj; } public Object getInstance() { //创建增强器 Enhancer enhancer = new Enhancer(); //设置父类 enhancer.setSuperclass(this.target.getClass()); //设置回调 enhancer.setCallback(this); //返回对象 Object obj = enhancer.create(); return obj; } }
Cglib动态代理，要记得引包
<!-- https://mvnrepository.com/artifact/cglib/cglib -->
<dependency>
<groupId>cglib</groupId>
<artifactId>cglib</artifactId>
<version>3.2.8</version>
</dependency>
AOP相关术语
- Joincut :连接点，可以理解为被拦截的点
- Pointcut: 切入点，实际上被拦截的点。因为项目中有许多能够被拦截的方法，我们只需根据需求拦截方法
- Advice: 通知，也叫做增强，可以理解为对方法的增强。比如要在方法的前面增加业务逻辑
- Introduction：引介，对类的增强，很少用。除非需要更改被代理类的内部属性
- Weaving: 织入，把通知应用到目标对象的过程
- Aspect: 切面，是多个通知和切入点的组合
- Target: 目标对象
- Proxy: 代理对象
Spring中五种通知类型
- ＠Before: 前置通知，在方法之前增强
- ＠After: 后置通知，在方法之后增强
- @AfterReturing: 后置返回通知，可以接收方法的返回值
- @AfterThrowing: 异常抛出通知,方法有异常的时候执行
- @Around: 环绕通知，可以在方法执行前和执行后进行增强。事务就是用@Around实现的
Spring整合AOP
github项目源码地址： https://github.com/AmberBar/Learning/tree/master/SpringAOP
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>groupId</groupId> <artifactId>SpringAOP</artifactId> <version>1.0-SNAPSHOT</version> <dependencies> <!-- https://mvnrepository.com/artifact/org.springframework/spring-core --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>4.3.10.RELEASE</version> </dependency> <!-- https://mvnrepository.com/artifact/org.springframework/spring-beans --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>4.0.8.RELEASE</version> </dependency> <!-- https://mvnrepository.com/artifact/org.springframework/spring-context --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>4.0.8.RELEASE</version> </dependency> <!-- https://mvnrepository.com/artifact/junit/junit --> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.8.2</version> <!--<scope>test</scope>--> </dependency> <!-- https://mvnrepository.com/artifact/org.springframework/spring-test --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>4.0.8.RELEASE</version> <scope>test</scope> </dependency> <!-- https://mvnrepository.com/artifact/cglib/cglib --> <dependency> <groupId>cglib</groupId> <artifactId>cglib</artifactId> <version>3.2.8</version> </dependency> <!-- https://mvnrepository.com/artifact/org.aspectj/aspectjweaver --> <dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjweaver</artifactId> <version>1.9.1</version> </dependency> </dependencies> </project>
package com.amber.dao; public interface ProductDao { void create(); void delete(); String update(); void addBatch(); void delBatch(); }
package com.amber.dao; public class ProduceDaoImpl implements ProductDao { @Override public void create() { System.out.println("=========this is create method =============="); } @Override public void delete() { System.out.println("=========this is delete method =============="); } @Override public String update() { System.out.println("=========this is update method =============="); return "amber"; } @Override public void addBatch() { System.out.println("=========this is addBatch method =============="); } @Override public void delBatch() { System.out.println("=========this is delBatch method =============="); int i = 1/0; } }
基于Xml的形式
<?xml version="1.0" encoding="utf-8" ?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd"> <!--配置扫描--> <context:component-scan base-package="com.amber"> </context:component-scan> <bean id="userDao" class="com.amber.dao.ProduceDaoImpl"></bean> <bean id="aspectOption" class="com.amber.aspect.AspectOption"></bean> <!--xml aop配置--> <aop:config> <!--设置切入点--> <aop:pointcut id="create" expression="execution(* com.amber.dao.ProductDao.create(..))" ></aop:pointcut> <aop:pointcut id="delete" expression="execution(* com.amber.dao.ProductDao.delete(..))" ></aop:pointcut> <aop:pointcut id="delBatch" expression="execution(* com.amber.dao.ProductDao.delBatch(..))" ></aop:pointcut> <aop:pointcut id="addBatch" expression="execution(* com.amber.dao.ProductDao.addBatch(..))" ></aop:pointcut> <aop:pointcut id="update" expression="execution(* com.amber.dao.ProductDao.update(..))" ></aop:pointcut> <!--设置切面类--> <aop:aspect ref="aspectOption"> <!--设置前置通知--> <aop:before method="before" pointcut-ref="create"></aop:before> <!--设置后置通知--> <aop:after method="after" pointcut-ref="delete"></aop:after> <!--环绕通知--> <aop:around method="around" pointcut-ref="addBatch"></aop:around> <!--设置后置返回通知--> <aop:after-returning method="afterReturning" pointcut-ref="update" returning="result"></aop:after-returning> <!--设置后置异常通知--> <aop:after-throwing method="afterThrowing" pointcut-ref="delBatch" throwing="e"></aop:after-throwing> </aop:aspect> </aop:config> </beans>
package com.amber.xml; import com.amber.dao.ProductDao; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration("classpath:applicationContext_xml.xml") public class ProductDaoTest { @Autowired ProductDao productDao; @Test public void beforeTest() { productDao.create(); } @Test public void afterTest() { productDao.delete(); } @Test public void afterReturingTest() { productDao.update(); } @Test public void aroundTest() { productDao.addBatch(); } @Test public void delBatchTest() { productDao.delBatch(); } }
基于注解形式
package com.amber.xml; import com.amber.dao.ProductDao; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration("classpath:applicationContext_xml.xml") public class ProductDaoTest { @Autowired ProductDao productDao; @Test public void beforeTest() { productDao.create(); } @Test public void afterTest() { productDao.delete(); } @Test public void afterReturingTest() { productDao.update(); } @Test public void aroundTest() { productDao.addBatch(); } @Test public void delBatchTest() { productDao.delBatch(); } }
<?xml version="1.0" encoding="utf-8" ?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd"> <!--配置扫描--> <context:component-scan base-package="com.amber"> </context:component-scan> <bean id="userDao" class="com.amber.dao.ProduceDaoImpl"></bean> <bean id="aspectOption" class="com.amber.aspect.AspectOption"></bean> <!--配置注解代理--> <aop:aspectj-autoproxy ></aop:aspectj-autoproxy> </beans>
package com.amber.xml.aspect; import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.*; /** * 基于注解 */ @Aspect public class AspectOption { /** * 前置增强，在方法之前执行 */ public void before() { System.out.println("AspectOption before"); } /** * 后置增强，在方法执行之后执行 */ public void after() { System.out.println("AspectOption after"); } /** * 后置通知增强，可以获取到方法的返回值 * @param result */ public void afterReturning(String result) { System.out.println("AspectOption afterReturning " + result); } /** * 环绕通知，在方法执行之前和执行之后运行 * @param joinPoint */ public void around(ProceedingJoinPoint joinPoint) { System.out.println("AspectOption around before"); try { Object obj = joinPoint.proceed(); } catch (Throwable throwable) { throwable.printStackTrace(); } System.out.println("AspectOption around after"); } /** * 异常抛出通知,方法抛出异常的时候执行 * @param e */ public void afterReturing(Throwable e) { System.out.println("AspectOption afterReturing"); System.out.println(e); } }
