一个简单示例轻松理解Spring中的AOP

SpringAOP基本概念

AOP：（Aspect Oriented Programming）面向切面编程，一种在已存在代码段中动态嵌入其他代码段的技术，用来在不改变原有代码的情况下添加一些新的通用功能，如记录日志、参数预处理等。

**通知Advice：**需要在原有程序中新增的功能；

**连接点JoinPoint：**程序中可以接入通知的点，包括类、方法等；

**切入点PointCut：**程序运行过程中实际接入通知的点，是一种特殊的连接点；

**切面Aspect：**是一个类，在这个类中定义切入点和通知；

AOP简单实例

原程序如下

@Service public class AopTestService { @CutPointAnno public void test(){ System.out.println("测试方法执行"); } @CutPointAnno public void testThrowable(){ throw new RuntimeException(); } } //此注解标注的方法被标记为切面 public @interface CutPointAnno { }

切面，包括以注解形式定义的切入点和通知，这里定义了SpringAOP提供的四种通知类型（前置通知，后置通知，环绕通知，异常通知）其中，异常通知在程序抛出异常时执行

@Aspect @Component public class SimpleAspect { @Pointcut("@annotation(cn.sunyog.aop.CutPointAnno)") public void pointCut(){} @Before("pointCut()") public void doBefore(JoinPoint joinPoint) { System.out.println("前置通知"); } @After("pointCut()") public void doAfter(JoinPoint joinPoint){ System.out.println("后置通知"); } @Around("pointCut()") public void doAround(ProceedingJoinPoint joinPoint) throws Throwable { System.out.println("环绕通知，前段"); joinPoint.proceed();//程序执行 System.out.println("环绕通知，后段"); } @AfterThrowing("pointCut()") public void doThrowing(JoinPoint joinPoint){ System.out.println("异常通知"); } }

启动Aop代理配置

@Configuration @ComponentScan("cn.sunyog.aop")//包扫描，扫描此包中所有的Bean，注册到容器中 @EnableAspectJAutoProxy//启用SpringAOP代理，包括jdk动态代理和cglib代理两种形式 public class AopConfig { }

启动容器，测试Aop是否成功

public class AOPTest { private ApplicationContext ctx; @Before public void doBefore(){ ctx=new AnnotationConfigApplicationContext(AopConfig.class); } @After public void doAfter(){ } @Test public void test(){ AopTestService service = ctx.getBean(AopTestService.class); service.test(); System.out.println(); service.testThrowable(); } }

打印结果

环绕通知，前段 前置通知 测试方法执行 后置通知 环绕通知，后段 环绕通知，前段 前置通知 异常通知 后置通知

可见，通知的执行顺序为：

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