AspectJ开发

aspectJ 是基于java语言的aop框架,提供了强大的aop功能。

aspectJ的实现主要有两种,一种是基于xml的声明式aspectJ，另一种是基于注解的aspectJ。

1.基于xml的声明式aspectJ

接口userDao 

public interface userDao {
 ???public void addUser();
 ???public void deleteUser();
}
接口实现类UserDaoImp 

public class UserDaoImp implements userDao {

 ???@Override
 ???public void addUser() {
 ???????System.out.println("添加用户");
 ???}
 ???@Override
 ???public void deleteUser() {
 ???????System.out.println("删除用户");
 ???}
}

//切面类MyAspect

public class MyAspect {
 ???//前置通知
 ???//JoinPoint连接点
 ???public void myBefore(JoinPoint joinPoint) {
 ???????System.out.println("前置通知的目标类：" + joinPoint.getTarget());
 ???????System.out.println("被植入增强的方法是：" + joinPoint.getSignature().getName());
 ???}

 ???//后置通知
 ???public void myAfterReturning(JoinPoint joinPoint) {
 ???????System.out.println("后置通知，被植入增强的目标方法是:" + joinPoint.getSignature().getName());
 ???}

 ???/*环绕通知
 ????* ProceedingJoinPoint 是JoinPoint子接口，表示可执行目标方法
 ????* 类型必须是Object类型的返回值
 ????* 必须接收一个参数，类型为ProceedingJoinPoint
 ????* 必须抛出异常throws Throwable
 ????* */
 ???public Object myAround(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
 ???????System.out.println("环绕开始");
 ???????//执行当前目标方法
 ???????Object obj = proceedingJoinPoint.proceed();
 ???????System.out.println("环绕结束");
 ???????return obj;
 ???}

 ???//异常通知
 ???public void myAfterThrowing(JoinPoint joinPoint, Throwable e) {
 ???????System.out.println("异常通知开始,出错了" + e.getMessage());
 ???}

 ???//最终通知
 ???public void myAfter() {
 ???????System.out.println("最终通知，始终要执行");
 ???}
}

在xml中的配置

<!-- 1 目标类 -->
 ???<bean id="userDao" class="com.itheima.ioc.aspectJ.UserDaoImp"/>
 ???<!-- 2 切面 -->
 ???<bean id="myAspect" class="com.itheima.ioc.aspectJ.MyAspect"/>
 ???<!-- 3 aop编程 -->
 ???<aop:config>
 ???????<!-- 配置切面 -->
 ???????<aop:aspect id="myaspect" ref="myAspect">
 ???????????<!-- 3.1 配置切入点，通知最后增强哪些方法 -->
 ???????????<aop:pointcut expression="execution(* com.itheima.ioc.aspectJ.*.*(..))"
 ?????????????????????????id="myPointCut"/>
 ???????????<!-- 3.2 关联通知Advice和切入点pointCut -->
 ???????????<!-- 3.2.1 前置通知 -->
 ???????????<aop:before method="myBefore" pointcut-ref="myPointCut"/>
 ???????????<!-- 3.2.2 后置通知,在方法返回之后执行，就可以获得返回值
 ????????????returning属性：用于设置后置通知的第二个参数的名称,类型是Object -->
 ???????????<aop:after-returning method="myAfterReturning"
 ????????????????????????????????pointcut-ref="myPointCut" returning="joinPoint"/>
 ???????????<!-- 3.2.3 环绕通知 -->
 ???????????<aop:around method="myAround" pointcut-ref="myPointCut"/>
 ???????????<!-- 3.2.4 抛出通知：用于处理程序发生异常-->
 ???????????<!-- * 注意：如果程序没有异常，将不会执行增强 -->
 ???????????<!-- * throwing属性：用于设置通知第二个参数的名称，类型Throwable -->
 ???????????<aop:after-throwing method="myAfterThrowing"
 ???????????????????????????????pointcut-ref="myPointCut" throwing="e"/>
 ???????????<!-- 3.2.5 最终通知：无论程序发生任何事情，都将执行 -->
 ???????????<aop:after method="myAfter" pointcut-ref="myPointCut"/>
 ???????</aop:aspect>
 ???</aop:config>
</beans>
测试代码

public class xmlAspectJTest {
 ???public static void main(String[] args) {
 ???????ApplicationContext applicationContext =
 ???????????????new ClassPathXmlApplicationContext("applicationContext.xml");
 ???????userDao userdao = (userDao) applicationContext.getBean(userDao.class);
 ???????userdao.deleteUser();
// ???????userdao.addUser();
 ???}
}
测试结果

前置通知的目标类：com.itheima.ioc.aspectJ.UserDaoImp@291f18
被植入增强的方法是：deleteUser
环绕开始
删除用户
最终通知，始终要执行
环绕结束
后置通知，被植入增强的目标方法是:deleteUser

2.基于注解的aspectJ

@Aspect//注册声明切面
@Component//将这个切面标示为spring中的bean

public class MyAspect {

 ???//前置通知
 ???@Pointcut("execution(* com.itheima.ioc.aspectJ.*.*(..))")
 ???//使用一个返回值为空，方法体为空的方法来命名切入点
 ???public void myPointCut(){}

 ???@Before("myPointCut()")
 ???public void myBefore(JoinPoint joinPoint) {
 ???????System.out.println("前置通知的目标类：" + joinPoint.getTarget());
 ???????System.out.println("被植入增强的方法是：" + joinPoint.getSignature().getName());
 ???}

 ???//后置通知
 ???@AfterReturning("myPointCut()")
 ???public void myAfterReturning(JoinPoint joinPoint) {
 ???????System.out.println("后置通知，被植入增强的目标方法是:" + joinPoint.getSignature().getName());
 ???}

 ???/*环绕通知
 ????* ProceedingJoinPoint 是JoinPoint子接口，表示可执行目标方法
 ????* 类型必须是Object类型的返回值
 ????* 必须接收一个参数，类型为ProceedingJoinPoint
 ????* 必须抛出异常throws Throwable
 ????* */
 ???@Around("myPointCut()")
 ???public Object myAround(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
 ???????System.out.println("环绕开始");
 ???????//执行当前目标方法
 ???????Object obj = proceedingJoinPoint.proceed();
 ???????System.out.println("环绕结束");
 ???????return obj;
 ???}

 ???//异常通知
 ???@AfterThrowing(value = "myPointCut()",throwing = "e")
 ???public void myAfterThrowing(JoinPoint joinPoint, Throwable e) {
 ???????System.out.println("异常通知开始,出错了" + e.getMessage());
 ???}

 ???//最终通知
 ???@After("myPointCut()")
 ???public void myAfter() {
 ???????System.out.println("最终通知，始终要执行");
 ???}
}
接口Dao

public interface Dao {
 ???public void addUser();
 ???public void deleteUser();
}
实现接口UserDaoImp 类

@Repository("Dao")//spring注解，标示为spring中的bean，相当于在spring中的配置<bean id="Dao" class="类的全限定路径.UserDaoImp"/>

public class UserDaoImp implements Dao {
 ???@Override
 ???public void addUser() {
 ???????System.out.println("添加用户");
 ???}

 ???@Override
 ???public void deleteUser() {
 ???????System.out.println("删除用户");
 ???}
}

 在xml中的配置

指定需要扫描的包

<contxt:component-scan base-package="com.itheima.ioc"/>
使注解生效
<aop:aspectj-autoproxy/>

 最后测试和基于xml声明的测试是一样的，结果也一样。

AspectJ开发

原文地址：https://www.cnblogs.com/jasonboren/p/10593398.html