Spring AOP--返回通知，异常通知和环绕通知

在上篇文章中学习了Spring AOP，并学习了前置通知和后置通知。地址为：http://www.VEVb.com/dreamfree/p/4095858.html

在本文中，将继续上篇的学习，继续了解返回通知、异常通知和环绕通知。具体的含义详见代码注释

 1 package com.yl.spring.aop; 2  3 import java.util.Arrays; 4  5 import org.aspectj.lang.JoinPoint; 6 import org.aspectj.lang.ProceedingJoinPoint; 7 import org.aspectj.lang.annotation.After; 8 import org.aspectj.lang.annotation.AfterReturning; 9 import org.aspectj.lang.annotation.AfterThrowing;10 import org.aspectj.lang.annotation.Around;11 import org.aspectj.lang.annotation.Aspect;12 import org.aspectj.lang.annotation.Before;13 import org.springframework.stereotype.Component;14 15 @Component16 @Aspect17 public class LoggingAspect {18     19     /**20      * 在com.yl.spring.aop.ArithmeticCalculator接口的每一个实现类的每一个方法开始之前执行一段代码21      */22     @Before("execution(public int com.yl.spring.aop.ArithmeticCalculator.*(..))")23     public void beforeMethod(JoinPoint joinPoint) {24         String methodName = joinPoint.getSignature().getName();25         Object[] args = joinPoint.getArgs();26         System.out.println("The method " + methodName + " begins with " + Arrays.asList(args));27     }28     29     /**30      * 在com.yl.spring.aop.ArithmeticCalculator接口的每一个实现类的每一个方法执行之后执行一段代码31      * 无论该方法是否出现异常32      */33     @After("execution(public int com.yl.spring.aop.ArithmeticCalculator.*(..))")34     public void afterMethod(JoinPoint joinPoint) {35         String methodName = joinPoint.getSignature().getName();36         Object[] args = joinPoint.getArgs();37         System.out.println("The method " + methodName + " ends with " + Arrays.asList(args));38     }39     40     /**41      * 方法正常结束后执行的代码42      * 返回通知是可以访问到方法的返回值的43      */44     @AfterReturning(value="execution(public int com.yl.spring.aop.ArithmeticCalculator.*(..))", returning="result")45     public void afterReturning(JoinPoint joinPoint, Object result) {46         String methodName = joinPoint.getSignature().getName();47         System.out.println("The method " + methodName + " return with " + result);48     }49     50     /**51      * 在方法出现异常时会执行的代码52      * 可以访问到异常对象，可以指定在出现特定异常时在执行通知代码53      */54     @AfterThrowing(value="execution(public int com.yl.spring.aop.ArithmeticCalculator.*(..))", throwing="ex")55     public void afterThrowing(JoinPoint joinPoint, Exception ex) {56         String methodName = joinPoint.getSignature().getName();57         System.out.println("The method " + methodName + " occurs exception: " + ex);58     }59     60     /**61      * 环绕通知需要携带ProceedingJoinPoint类型的参数62      * 环绕通知类似于动态代理的全过程：ProceedingJoinPoint类型的参数可以决定是否执行目标方法。63      * 而且环绕通知必须有返回值，返回值即为目标方法的返回值64      */65     @Around("execution(public int com.yl.spring.aop.ArithmeticCalculator.*(..))")66     public Object aroundMethod(ProceedingJoinPoint pjd) {67         Object result = null;68         String methodName = pjd.getSignature().getName();69         //执行目标方法70         try {71             //前置通知72             System.out.println("The method " + methodName + " begins with " + Arrays.asList(pjd.getArgs()));73             result = pjd.proceed();74             //返回通知75             System.out.println("The method " + methodName + " ends with " + Arrays.asList(pjd.getArgs()));76         } catch (Throwable e) {77             //异常通知78             System.out.println("The method " + methodName + " occurs expection : " + e);79             throw new RuntimeException(e);80         }81         //后置通知82         System.out.println("The method " + methodName + " ends");83         return result;84     }85     86 }

切面的优先级　　

　　为项目增加一个新的切面类，负责验证功能，则需要指定切面执行的顺序。即切面的优先级。具体方法是给切面类增加@Order注解，并指定具体的数字，值越小优先级越高

 1 package com.yl.spring.aop; 2  3 import java.util.Arrays; 4  5 import org.aspectj.lang.JoinPoint; 6 import org.aspectj.lang.annotation.Aspect; 7 import org.aspectj.lang.annotation.Before; 8 import org.springframework.core.annotation.Order; 9 import org.springframework.stereotype.Component;10 11 /**12  * 可以使用@Order注解指定切面的优先级，值越小优先级越高13  * @author yul14  *15  */16 @Order(2)17 @Component18 @Aspect19 public class ValidationAspect {20     21     @Before("execution(public int com.yl.spring.aop.ArithmeticCalculator.*(..))")22     public void vlidateArgs(JoinPoint joinPoint) {23         System.out.println("validate: " + Arrays.asList(joinPoint.getArgs()));24     }25 }

切点表达式的重用：

　　在LoggingAspect类中，切点的表达式可以先定义，在使用。

 1 package com.yl.spring.aop; 2  3 import java.util.Arrays; 4  5 import org.aspectj.lang.JoinPoint; 6 import org.aspectj.lang.ProceedingJoinPoint; 7 import org.aspectj.lang.annotation.After; 8 import org.aspectj.lang.annotation.AfterReturning; 9 import org.aspectj.lang.annotation.AfterThrowing;10 import org.aspectj.lang.annotation.Around;11 import org.aspectj.lang.annotation.Aspect;12 import org.aspectj.lang.annotation.Before;13 import org.aspectj.lang.annotation.Pointcut;14 import org.springframework.core.annotation.Order;15 import org.springframework.stereotype.Component;16 @Order(1)17 @Component18 @Aspect19 public class LoggingAspect {20     21     /**22      * 定义一个方法，用于声明切入点表达式。一般的，该方法中再不需要添加其他的代码23      * 使用@Pointcut 来声明切入点表达式24      * 后面的其他通知直接使用方法名直接引用方法名即可25      */26     @Pointcut("execution(public int com.yl.spring.aop.ArithmeticCalculator.*(..))")27     public void declareJoinPointExpression() {28         29     }30     31     /**32      * 在com.yl.spring.aop.ArithmeticCalculator接口的每一个实现类的每一个方法开始之前执行一段代码33      */34     @Before("declareJoinPointExpression()")35     public void beforeMethod(JoinPoint joinPoint) {36         String methodName = joinPoint.getSignature().getName();37         Object[] args = joinPoint.getArgs();38         System.out.println("The method " + methodName + " begins with " + Arrays.asList(args));39     }40     41     /**42      * 在com.yl.spring.aop.ArithmeticCalculator接口的每一个实现类的每一个方法执行之后执行一段代码43      * 无论该方法是否出现异常44      */45     @After("declareJoinPointExpression()")46     public void afterMethod(JoinPoint joinPoint) {47         String methodName = joinPoint.getSignature().getName();48         Object[] args = joinPoint.getArgs();49         System.out.println("The method " + methodName + " ends with " + Arrays.asList(args));50     }51     52     /**53      * 方法正常结束后执行的代码54      * 返回通知是可以访问到方法的返回值的55      */56     @AfterReturning(value="declareJoinPointExpression()", returning="result")57     public void afterReturning(JoinPoint joinPoint, Object result) {58         String methodName = joinPoint.getSignature().getName();59         System.out.println("The method " + methodName + " return with " + result);60     }61     62     /**63      * 在方法出现异常时会执行的代码64      * 可以访问到异常对象，可以指定在出现特定异常时在执行通知代码65      */66     @AfterThrowing(value="declareJoinPointExpression()", throwing="ex")67     public void afterThrowing(JoinPoint joinPoint, Exception ex) {68         String methodName = joinPoint.getSignature().getName();69         System.out.println("The method " + methodName + " occurs exception: " + ex);70     }71     72     /**73      * 环绕通知需要携带ProceedingJoinPoint类型的参数74      * 环绕通知类似于动态代理的全过程：ProceedingJoinPoint类型的参数可以决定是否执行目标方法。75      * 而且环绕通知必须有返回值，返回值即为目标方法的返回值76      */77     @Around("declareJoinPointExpression()")78     public Object aroundMethod(ProceedingJoinPoint pjd) {79         Object result = null;80         String methodName = pjd.getSignature().getName();81         //执行目标方法82         try {83             //前置通知84             System.out.println("The method " + methodName + " begins with " + Arrays.asList(pjd.getArgs()));85             result = pjd.proceed();86             //返回通知87             System.out.println("The method " + methodName + " ends with " + Arrays.asList(pjd.getArgs()));88         } catch (Throwable e) {89             //异常通知90             System.out.println("The method " + methodName + " occurs expection : " + e);91             throw new RuntimeException(e);92         }93         //后置通知94         System.out.println("The method " + methodName + " ends");95         return result;96     }97     98 }

当处于不同的类，甚至不同的包时，可以使用包名.类名.方法名

具体代码如下：

 1 package com.yl.spring.aop; 2  3 import java.util.Arrays; 4  5 import org.aspectj.lang.JoinPoint; 6 import org.aspectj.lang.annotation.Aspect; 7 import org.aspectj.lang.annotation.Before; 8 import org.springframework.core.annotation.Order; 9 import org.springframework.stereotype.Component;10 11 /**12  * 可以使用@Order注解指定切面的优先级，值越小优先级越高13  * @author yul14  *15  */16 @Order(2)17 @Component18 @Aspect19 public class ValidationAspect {20     21     @Before("com.yl.spring.aop.LoggingAspect.declareJoinPointExpression()")22     public void vlidateArgs(JoinPoint joinPoint) {23         System.out.println("validate: " + Arrays.asList(joinPoint.getArgs()));24     }25 }