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
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