spring、springMVC、SpringBoot这一系列对AOP都有很好的支持（其实都是Spring管理的）
一。概念
（1）面向切面编程，实际上就是给某个方法（或者某些），做一个代理，，很抽象？代理模式详解
代理可以抽象出来，为类似方法进行代理，，从而降低代码量，（相同的功能，如关闭流什么的，只写一次，不仅方便维护，大大减少了工作量）
（2）切点，
指的是，对那个方法进行代理，或者某些方法。
切点方法需要 @Pointcut
@Pointcut("execution(public * xatu.zsl.contoller.*.*(..))")public void poincut(){}
（3）通知
即对 被代理方法，加上的操作。
前置通知@Before(“poincut()”)后置通知@After(“poincut()”)返回时通知@AfterReturning(pointcut = “poincut()”,returning = “object”) returning指定返回对象。抛出异常时通知@AfterThrowing(“poincut()”)环绕通知@Around(“poincut()”)
二。使用
前置通知@Before(“poincut()”)
@Before("poincut()")public void before(JoinPoint joinPoint){logger.info("before");ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();HttpServletRequest request = attributes.getRequest();//获取URLlogger.info("url={}",request.getRequestURL());//请求方法logger.info("mathod={}",request.getMethod());//iplogger.info("ip={}",request.getRemoteAddr());//类方法logger.info("class_method{}",joinPoint.getSignature().getDeclaringTypeName()+"."+joinPoint.getSignature().getName());//参数logger.info("args={}",joinPoint.getArgs());}
后置通知@After(“poincut()”)
@After("poincut()")public void after(){logger.info("after");}
返回时通知@AfterReturning(pointcut = “poincut()”,returning = “object”) returning指定返回对象。
@AfterReturning(pointcut = "poincut()",returning = "object")public void afterReturning(Object object){logger.info("return = {}",object.toString());// logger.info("return = ");}
抛出异常时通知@AfterThrowing(“poincut()”)
@AfterThrowing("poincut()")public void afterThrowing(){logger.info("抛出异常了。");}
环绕通知@Around(“poincut()”)
@Around("poincut()")public void around(ProceedingJoinPoint joinPoint) throws Throwable {logger.info("环绕通知。");joinPoint.proceed();}
三。细节
（1）
@AfterReturning和 @Around(“poincut()”)，，，会有特殊冲突，，搞了半天
SpringBoot中会出现空指针异常
Spring中启动时会出现错误无法启动，错误代码如下：解决方法（注释掉，@Around(“poincut()”)）
警告: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService' defined in file [G:\work_space\study_spring\spring_demo\target\classes\xatu\zsl\service\UserServiceImpl.class]: Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: error at ::0 can't find referenced pointcut poincutException in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService' defined in file [G:\work_space\study_spring\spring_demo\target\classes\xatu\zsl\service\UserServiceImpl.class]: Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: error at ::0 can't find referenced pointcut poincutat org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:776)at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:861)at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541)at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)at xatu.zsl.MainTest.main(MainTest.java:16)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:483)at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)Caused by: java.lang.IllegalArgumentException: error at ::0 can't find referenced pointcut poincutat org.aspectj.weaver.tools.PointcutParser.parsePointcutExpression(PointcutParser.java:301)at org.springframework.aop.aspectj.AspectJExpressionPointcut.buildPointcutExpression(AspectJExpressionPointcut.java:207)at org.springframework.aop.aspectj.AspectJExpressionPointcut.checkReadyToMatch(AspectJExpressionPointcut.java:193)at org.springframework.aop.aspectj.AspectJExpressionPointcut.getClassFilter(AspectJExpressionPointcut.java:170)at org.springframework.aop.support.AopUtils.canApply(AopUtils.java:220)at org.springframework.aop.support.AopUtils.canApply(AopUtils.java:279)at org.springframework.aop.support.AopUtils.findAdvisorsThatCanApply(AopUtils.java:311)at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.findAdvisorsThatCanApply(AbstractAdvisorAutoProxyCreator.java:118)at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.findEligibleAdvisors(AbstractAdvisorAutoProxyCreator.java:88)at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.getAdvicesAndAdvisorsForBean(AbstractAdvisorAutoProxyCreator.java:69)at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:347)at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:299)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:422)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1583)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545)... 16 more
（2）JoinPoint joinPoint，参数不能出现在afterReturning()，，中，，不知道为什么，，容易出错，，
