目录

1.核心概念

AOP(Aspect Oriented Programming)面向切面编程：一种编程范式，指导开发者如何组织程序结构

作用：在不惊动原始设计的基础上为其进行功能增强。

连接点(JoinPoint)：程序执行过程中的任意位置

切入点(PointCut)：匹配连接点的式子

通知(Advice)：在切入点执行的操作

切面(Aspect)：描述通知与切入点的对应关系

2.小案例

目标：在接口执行前输出当前系统时间。

①在pom.xml中导入依赖spring-context、aspectjweaver

②定义dao接口与实现类

/src/main/java/com/itheima/dao/BookDao.java

package com.itheima.dao;public interface BookDao {public void save();public void update();
}

/src/main/java/com/itheima/dao/impl/BookDaoImpl.java

package com.itheima.dao.Impl;
import com.itheima.dao.BookDao;
import org.springframework.stereotype.Repository;@Repository
public class BookDaoImpl implements BookDao {public void save() {System.out.println(System.currentTimeMillis());System.out.println("book dao save ...");}public void update(){System.out.println("book dao update ...");}
}

③定义通知类

/src/main/java/com/itheima/aop/MyAdvice.java

package com.itheima.aop;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;//通知类必须配置成Spring管理的bean
@Component
//设置当前类为切面类类
@Aspect
public class MyAdvice {//设置切入点，要求配置在方法上方@Pointcut("execution(void com.itheima.dao.BookDao.update())")private void pt(){}//设置在切入点pt()的前面运行当前操作（前置通知）@Before("pt()")public void method(){System.out.println(System.currentTimeMillis());}
}

/src/main/java/com/itheima/config/SpringConfig.java

package com.itheima.config;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;@Configuration
@ComponentScan("com.itheima")
//开启注解开发AOP功能
@EnableAspectJAutoProxy
public class SpringConfig {
}

④测试

/src/main/java/com/itheima/App.java

package com.itheima;
import com.itheima.config.SpringConfig;
import com.itheima.dao.BookDao;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class App {public static void main(String[] args) {ApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig.class);BookDao bookDao = ctx.getBean(BookDao.class);bookDao.update();}
}

3.AOP工作流程

• Spring容器启动

• 读取所有切面配置中的切入点

• 初始化bean，判定bean对应类中的方法是否匹配到任意切入点

• 匹配失败，获取的bean还是原来的bean

• 匹配成功，获取的bean是原始对象的代理对象，从而不仅能运行原来的一些方法，还能运行增强的内容。

4.通知类型

前置通知

后置通知

环绕通知(重点)

返回后通知

抛出异常后通知

5.AOP通知获取数据

①获取切入点方法的参数

• JoinPoint：使用于前置、后置、返回后、抛出异常后通知

• ProceedJoinPoint：适用于环绕通知

②获取切入点方法的返回值

• 返回后通知

• 环绕通知

③获取切入点方法的运行异常信息

• 抛出异常后通知

• 环绕通知

pom.xml和/src/main/java/com/itheima/config/SpringConfig.java同上面的案例

/src/main/java/com/itheima/dao/BookDao.java

package com.itheima.dao;public interface BookDao {public String findName(int id);
}

/src/main/java/com/itheima/dao/impl/BookDaoImpl.java

package com.itheima.dao.impl;import com.itheima.dao.BookDao;
import org.springframework.stereotype.Repository;@Repository
public class BookDaoImpl implements BookDao {public String findName(int id) {System.out.println("id:"+id);return "fyx";}
}

/src/main/java/com/itheima/aop/MyAdvice.java

package com.itheima.aop;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;
import java.util.Arrays;//通知类必须配置成Spring管理的bean
@Component
//设置当前类为切面类类
@Aspect
public class MyAdvice {//设置切入点，要求配置在方法上方@Pointcut("execution(* com.itheima.dao.BookDao.findName(..))")private void pt(){}//设置在切入点pt()的前面运行当前操作（前置通知）@Before("pt()")public void before(JoinPoint jp) {Object[] args = jp.getArgs();System.out.println(Arrays.toString(args));System.out.println("before advice ...");}// @After("pt()")public void after(JoinPoint jp) {Object[] args = jp.getArgs();System.out.println(Arrays.toString(args));System.out.println("after advice ...");}//@Around("pt()")public Object around(ProceedingJoinPoint pjp) throws Throwable {Object[] args = pjp.getArgs();System.out.println(Arrays.toString(args));args[0] = 666;Object ret = pjp.proceed(args); // 获取参数处理之后再发送回去return ret;}//@AfterReturning(value="pt()",returning = "ret")public void afterReturning(String ret) {System.out.println("afterReturning advice " + ret);}//@AfterThrowing(value="pt()",throwing = "t")public void afterThrowing(Throwable t) {System.out.println("afterThrowing advice " + t);}
}

/src/main/java/com/itheima/App.java

package com.itheima;import com.itheima.config.SpringConfig;
import com.itheima.dao.BookDao;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class App {public static void main(String[] args) {ApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig.class);BookDao bookDao = ctx.getBean(BookDao.class);String name = bookDao.findName(100);System.out.println(name);}
}

6.AOP补充案例

需求：网盘分享链接输入密码时处理尾部多余空格

pom.xml和/src/main/java/com/itheima/config/SpringConfig.java同上面的案例

/src/main/java/com/itheima/dao/ResourcesDao.java

package com.itheima.dao;public interface ResourcesDao {boolean readResources(String url, String password);
}

/src/main/java/com/itheima/dao/impl/ResourcesDaoImpl.java

package com.itheima.dao.impl;import com.itheima.dao.ResourcesDao;
import org.springframework.stereotype.Repository;@Repository
public class ResourcesDaoImpl implements ResourcesDao {public boolean readResources(String url, String password) {// 模拟校验return password.equals("root");}
}

/src/main/java/com/itheima/service/ResourcesService.java

package com.itheima.service;public interface ResourcesService {public boolean openURL(String url, String password);
}

/src/main/java/com/itheima/service/impl/ResourcesServiceImpl.java

package com.itheima.service.impl;import com.itheima.dao.ResourcesDao;
import com.itheima.service.ResourcesService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;@Service
public class ResourcesServiceImpl implements ResourcesService {@Autowiredprivate ResourcesDao resourcesDao;@Overridepublic boolean openURL(String url, String password) {return resourcesDao.readResources(url, password);}
}

/src/main/java/com/itheima/aop/DateAdvice.java

package com.itheima.aop;import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;@Component
@Aspect
public class DateAdvice {//设置切入点，要求配置在方法上方@Pointcut("execution(boolean com.itheima.service.*Service.openURL(*,*))")private void servicePt(){}@Around("DateAdvice.servicePt()")public Object around(ProceedingJoinPoint pjp) throws Throwable {Object[] args = pjp.getArgs();for(int i = 0; i < args.length; i++) {// 判断参数是不是字符串if(args[i].getClass().equals(String.class)) {args[i] = args[i].toString().trim();}}Object ret = pjp.proceed(args);return ret;}
}

/src/main/java/com/itheima/App.java

package com.itheima;import com.itheima.config.SpringConfig;
import com.itheima.service.ResourcesService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class App {public static void main(String[] args) {ApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig.class);ResourcesService resourcesService = ctx.getBean(ResourcesService.class);boolean flag = resourcesService.openURL("https://pan.baidu.com/hh", "root ");System.out.println(flag);}
}