AOP 面向切面编程
AOP aspect oriented programming
OOP Object oriented programming
- 提供申明式服务
- 允许用户实现自定义切面
传统编程模式
自上而下，纵向的编程
Jsp -> Action -> Service -> Dao
AOP 编程：
在不改变原有的代码，增加新的功能
Jsp -> Action -> Service <- log() -> Dao
好处：
- 使得真实角色处理业务更加纯粹，不再关注公共的问题
- 公共业务由代理类完成，实现业务的分工
- 公共业务发生扩展时变得更加集中和方便
关注点：日志，安全，缓存，事务
切面 Aspect：一个关注点的模块化
实现 AOP
1、通过 Spring 接口实现
依赖
<dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjweaver</artifactId> <version>1.9.5</version> </dependency>
package com.spring.service; public interface UserService { public void add(); public void delete(); }
package com.spring.service.impl; import com.spring.service.UserService; public class UserServiceImpl implements UserService { @Override public void add() { System.out.println("add"); } @Override public void delete() { System.out.println("delete"); } }
package com.spring.aop; import org.springframework.aop.MethodBeforeAdvice; import java.lang.reflect.Method; // 前置通知 public class BeforeLog implements MethodBeforeAdvice { @Override public void before(Method method, Object[] args, Object target) throws Throwable { System.out.println(target.getClass().getName() + ": "+ method.getName()); } }
package com.spring.aop; import org.springframework.aop.AfterReturningAdvice; import java.lang.reflect.Method; // 后置通知 public class AfterLog implements AfterReturningAdvice { @Override public void afterReturning( Object result, Method method, Object[] objects, Object target) throws Throwable { System.out.println(target.getClass().getName() + ": "+ method.getName()); } }
<?xml version="1.0" encoding="utf-8" ?> <beans xmlns="http://www.springframework.org/schema/beans" 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/aop http://www.springframework.org/schema/aop/spring-aop.xsd"> <bean id="service" class="com.spring.service.impl.UserServiceImpl"/> <bean id="beforeLog" class="com.spring.aop.BeforeLog"/> <bean id="AfterLog" class="com.spring.aop.AfterLog"/> <aop:config> <aop:pointcut id="action" expression="execution(* com.spring.service.impl.UserServiceImpl.* (..))"/> <aop:advisor advice-ref="beforeLog" pointcut-ref="action"/> <aop:advisor advice-ref="AfterLog" pointcut-ref="action"/> </aop:config> </beans>
package com.spring.test; import com.spring.service.UserService; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Demo { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml"); UserService service = (UserService) context.getBean("service"); service.add(); service.delete(); } }
执行结果
com.spring.service.impl.UserServiceImpl: add add com.spring.service.impl.UserServiceImpl: add com.spring.service.impl.UserServiceImpl: delete delete com.spring.service.impl.UserServiceImpl: delete
Spring AOP 本质
就是讲公共的业务（如日期，安全等）和领域业务结合，
当执行领域业务时将会把公共业务加进来，
实现公共业务的重复利用，
领域业务更纯粹，可以专注于领域业务，
本质是动态代理
2、自定义类实现 AOP
UserService、UserServiceImpl、Demo 三个类不变
添加 Log 类和修改配置文件
package com.spring.aop; public class Log { public void before(){ System.out.println("--before--"); } public void after(){ System.out.println("--after--"); } }
<?xml version="1.0" encoding="utf-8" ?> <beans xmlns="http://www.springframework.org/schema/beans" 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/aop http://www.springframework.org/schema/aop/spring-aop.xsd"> <bean id="service" class="com.spring.service.impl.UserServiceImpl"/> <bean id="log" class="com.spring.aop.Log"/> <aop:config> <aop:aspect ref="log"> <aop:pointcut id="action" expression="execution(* com.spring.service.impl.UserServiceImpl.* (..))"/> <aop:before method="before" pointcut-ref="action"/> <aop:after method="after" pointcut-ref="action"/> </aop:aspect> </aop:config> </beans>
执行结果
--before-- add --after-- --before-- delete --after--
3、注解实现 AOP
业务类不改变
package com.spring.aop; import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.After; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before; @Aspect public class Log { @Before("execution(* com.spring.service.impl.UserServiceImpl.* (..))") public void before(){ System.out.println("--before--"); } @After("execution(* com.spring.service.impl.UserServiceImpl.* (..))") public void after(){ System.out.println("--after--"); } @Around("execution(* com.spring.service.impl.UserServiceImpl.* (..))") public Object Around(ProceedingJoinPoint pjp) throws Throwable { System.out.println("--Around before--"); Object result = pjp.proceed(); System.out.println("--Around after--"); return result; } }
<?xml version="1.0" encoding="utf-8" ?> <beans xmlns="http://www.springframework.org/schema/beans" 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/aop http://www.springframework.org/schema/aop/spring-aop.xsd"> <bean id="service" class="com.spring.service.impl.UserServiceImpl"/> <bean id="log" class="com.spring.aop.Log"/> <aop:aspectj-autoproxy /> </beans>
执行结果
--Around before-- --before-- add --Around after-- --after-- --Around before-- --before-- delete --Around after-- --after--
总结
公共业务：
日志，安全，权限，缓存，事务
分离思想
在不改变原有代码的情况下，增加额外的功能
