Spring4深入理解AOP02----AOP简介，AspectJ基于注解（5种通知，切面优先级）

参考代码下载github:https://github.com/changwensir/java-ee/tree/master/spring4

一、AOP简介

AOP 术语

二、AspectJ

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <context:component-scan base-package="Spring4_AOP.aopAnnotation"/>

    <!--使AspectJ注解起作用：自动为匹配的类生成代理对象-->
    <aop:aspectj-autoproxy/>
</beans>

日志切面

* 4. 编写切面类（把横切关注点的代码抽象到切面的类中）:
 * 4.1 一个一般的 Java 类
 * 4.2 在其中添加要额外实现的功能.
 *
 * 5. 配置切面
 * 5.1 切面必须是 IOC 中的 bean: 实际添加了 @Component 注解
 * 5.2 声明是一个切面: 添加 @Aspect
 * 5.3 声明通知: 即额外加入功能对应的方法！！.

@Aspect
@Component
public class LoggingAspect {
    /**
     * 重用切入点定义
     * 定义一个方法，用于声明切入点表达式，一般地，该方法中再不需要添入其它的代码
     */
    @Pointcut("execution(* Spring4_AOP.aopAnnotation.*.*(..))")
    public void declareJoinPointerExpression() {}

    //1、前置通知： 在目标方法开始之前执行（就是要告诉该方法要在哪个类哪个方法前执行）
    //@Before("execution(public int Spring4_AOP.aopAnnotation.*.*(int ,int))")
    @Before("declareJoinPointerExpression()")
    public void beforeMethod(JoinPoint joinPoint) {
        String methodName = joinPoint.getSignature().getName();
        Object [] args = joinPoint.getArgs();

        System.out.println("The method " + methodName + " begins with " + Arrays.asList(args));
    }

    //2、后置通知：在目标方法执行后（无论是否发生异常），执行的通知
    //注意，在后置通知中还不能访问目标执行的结果!!!，执行结果需要到返回通知里访问
    //@After("execution(* Spring4_AOP.aopAnnotation.*.*(..))")
    @After("declareJoinPointerExpression()")
    public void afterMethod(JoinPoint joinPoint){
        String methodName = joinPoint.getSignature().getName();
        System.out.println("The method " + methodName + " ends");
    }

    //无论连接点是正常返回还是抛出异常, 后置通知都会执行. 如果只想在连接点返回的时候记录日志, 应使用返回通知代替后置通知.

    //3、返回通知:在方法正常结束后执行的代码，返回通知是可以访问到方法的返回值的！！！
    //@AfterReturning(pointcut = "execution(* Spring4_AOP.aopAnnotation.*.*(..))", returning = "result")
    @AfterReturning(value = "declareJoinPointerExpression()", returning = "result")
    public void afterReturning(JoinPoint joinPoint, Object result){
        String methodName = joinPoint.getSignature().getName();
        System.out.println("The method " + methodName + " AfterReturning ends with " + result);
    }

    //4、异常通知：在目标方法出现异常 时会执行的代码，可以访问到异常对象：且可以!!指定在出现特定异常时在执行通知!!,如果是修改为nullPointerException里，只有空指针异常才会执行
//    @AfterThrowing(pointcut = "execution(* Spring4_AOP.aopAnnotation.*.*(..))", throwing = "except")
    @AfterThrowing(value = "declareJoinPointerExpression())", throwing = "except")
    public void afterThrowing(JoinPoint joinPoint, Exception except){
        String methodName = joinPoint.getSignature().getName();
        System.out.println("The method " + methodName + "  occurs exception " + except);
    }

    /**
     * 5、环绕通知 需要携带 ProceedingJoinPoint 类型的参数.
     * 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.
     * 且环绕通知必须有返回值, 返回值即为目标方法的返回值
     */
    //   @Around("execution(* Spring4_AOP.aopAnnotation.*.*(..))")
    @Around("declareJoinPointerExpression()")
    public Object aroundMethod(ProceedingJoinPoint pjd){

        Object result = null;
        String methodName = pjd.getSignature().getName();

        try {
            //前置通知
            System.out.println("The method " + methodName + " begins with " + Arrays.asList(pjd.getArgs()));
            //执行目标方法
            result = pjd.proceed();
            //返回通知
            System.out.println("The method " + methodName + " ends with " + result);
        } catch (Throwable e) {
            //异常通知
            System.out.println("The method " + methodName + " occurs exception:" + e);
            throw new RuntimeException(e);
        }
        //后置通知
        System.out.println("The method " + methodName + " ends");

        return result;
    }

}

@Pointcut("execution(* Spring4_AOP.aopAnnotation.*.add(..)) ||execution(* Spring4_AOP.aopAnnotation.*.sub(..))")
    public void declareJoinPointerExpression() {}

3).环绕通知

    @Test
    public void testAOPAnnotation() {
        //1、创建Spring的IOC的容器
        ApplicationContext ctx = new ClassPathXmlApplicationContext("Spring4_AOP/applicationContext-aop.xml");

        //2、从IOC容器中获取bean的实例
        ArithmeticCalculator arithmeticCalculator = (ArithmeticCalculator) ctx.getBean("arithmeticCalculator");

        //3、使用bean
        int result = arithmeticCalculator.div(3, 1);
        System.out.println("result:" + result);
    }

2-1.指定切面的优先级

@Order(1)
@Aspect
@Component
public class ValidationAspect {
    @Before("execution(public int Spring4_AOP.aopAnnotation.*.*(int ,int))")
    public void validateArgs(JoinPoint joinPoint){
        System.out.println("-->validate:" + Arrays.asList(joinPoint.getArgs()));
    }
}

@Order(2)
@Aspect
@Component
public class LoggingAspect {
   ......
}

2-3.重用切入点定义

三 、用基于 XML 的配置声明切面

ArithmeticCalulator2与上面ArithmeticCalulator接口内容 一样

public class ArithmeticCalculatorImplXML implements ArithmeticCalculator2 {
    public int add(int i, int j) {
        return i + j;
    }

    public int sub(int i, int j) {
        return i - j;
    }

    public int mul(int i, int j) {
        return i * j;
    }

    public int div(int i, int j) {
        return i / j;
    }
}

public class LoggingAspectXML {
    public void beforeMethod(JoinPoint joinPoint){
        String methodName = joinPoint.getSignature().getName();
        Object [] args = joinPoint.getArgs();

        System.out.println("The method " + methodName + " begins with " + Arrays.asList(args));
    }

    public void afterMethod(JoinPoint joinPoint){
        String methodName = joinPoint.getSignature().getName();
        System.out.println("The method " + methodName + " ends");
    }

    public void afterReturning(JoinPoint joinPoint, Object result){
        String methodName = joinPoint.getSignature().getName();
        System.out.println("The method " + methodName + " ends with " + result);
    }

    public void afterThrowing(JoinPoint joinPoint, Exception e){
        String methodName = joinPoint.getSignature().getName();
        System.out.println("The method " + methodName + " occurs excetion:" + e);
    }
}

public class ValidationAspectXML {

    public void validateArgs(JoinPoint joinPoint){
        System.out.println("-->validate:" + Arrays.asList(joinPoint.getArgs()));
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

       <!-- 配置 bean -->
       <bean id="arithmeticCalculatorXML" class="Spring4_AOP.aopXML.ArithmeticCalculatorImplXML">
       </bean>

       <!-- 配置切面的 bean. -->
       <bean id="loggingAspect" class="Spring4_AOP.aopXML.LoggingAspectXML">
       </bean>
       <bean id="validationAspect" class="Spring4_AOP.aopXML.ValidationAspectXML">
       </bean>

       <!-- 配置 AOP -->
       <aop:config>
              <!-- 配置切点表达式 -->
              <aop:pointcut id="pointcut"
                            expression="execution(* Spring4_AOP.aopXML.ArithmeticCalculatorImplXML.*(int ,int))"/>
              <!-- 配置切面及通知 -->
              <aop:aspect ref="loggingAspect" order="2">
                     <aop:before method="beforeMethod" pointcut-ref="pointcut"/>
                     <aop:after method="afterMethod" pointcut-ref="pointcut"/>
                     <aop:after-returning method="afterReturning" returning="result" pointcut-ref="pointcut"/>
                     <aop:after-throwing method="afterThrowing" throwing="e" pointcut-ref="pointcut"/>
              </aop:aspect>

              <aop:aspect ref="validationAspect" order="1">
                     <aop:before method="validateArgs" pointcut-ref="pointcut"/>
              </aop:aspect>
       </aop:config>
</beans>

    @Test
    public void testXML() {
        //1、创建Spring的IOC的容器
        ApplicationContext ctx = new ClassPathXmlApplicationContext("Spring4_AOP/applicationContext-xml.xml");

        //2、从IOC容器中获取bean的实例
        ArithmeticCalculatorImplXML arithmeticCalculator = (ArithmeticCalculatorImplXML) ctx.getBean("arithmeticCalculatorXML");

        //3、使用bean
        int result = arithmeticCalculator.add(3, 3);
        System.out.println("result:" + result);

        arithmeticCalculator.div(10, 0);
    }

Spring4深入理解AOP02----AOP简介，AspectJ基于注解（5种通知，切面优先级）

原文：http://blog.csdn.net/ochangwen/article/details/52557724