AOP 面向切面編程
AOP aspect oriented programming
OOP Object oriented programming
- 提供申明式服務
- 允許用戶實現自定義切面
傳統編程模式
自上而下,縱向的編程
Jsp
->
Action
->
Service
->
Dao
AOP 編程:
在不改變原有的代碼,增加新的功能
Jsp
->
Action
->
Service <- log()
->
Dao
好處:
- 使得真實角色處理業務更加純粹,不再關注公共的問題
- 公共業務由代理類完成,實現業務的分工
- 公共業務發生擴展時變得更加集中和方便
關注點:日誌,安全,緩存,事務
切面 Aspect:一個關注點的模塊化
實現 AOP
1、通過 Spring 接口實現
依賴
<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;
// 後置通知
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();
}
}
執行結果
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 本質
就是講公共的業務(如日期,安全等)和領域業務結合,
當執行領域業務時將會把公共業務加進來,
實現公共業務的重複利用,
領域業務更純粹,可以專注於領域業務,
本質是動態代理
2、自定義類實現 AOP
UserService、UserServiceImpl、Demo 三個類不變
添加 Log 類和修改配置文件
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>
執行結果
--before--
add
--after--
--before--
delete
--after--
3、註解實現 AOP
業務類不改變
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>
執行結果
--Around before--
--before--
add
--Around after--
--after--
--Around before--
--before--
delete
--Around after--
--after--
總結
公共業務:
日誌,安全,權限,緩存,事務
分離思想
在不改變原有代碼的情況下,增加額外的功能