[学习小结]Spring_通知的那些事和基于配置文件的方式来配置AOP

Spring_通知的那些事：

[b]AspectJ的了解：[/b]

代码示例：

准备一个接口：

public interface ArithmeticCalculator {

int add(int i, int j);
int sub(int i, int j);

int mul(int i, int j);
int div(int i, int j);

}

准备一个接口的实现类：

import org.springframework.stereotype.Component;

@Component("arithmeticCalculator")
public class ArithmeticCalculatorImpl implements ArithmeticCalculator {

@Override
public int add(int i, int j) {
int result = i + j;
return result;
}

@Override
public int sub(int i, int j) {
int result = i - j;
return result;
}

@Override
public int mul(int i, int j) {
int result = i * j;
return result;
}

@Override
public int div(int i, int j) {
int result = i / j;
return result;
}

}

配置文件：applicationContext.xml

<?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/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd 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-4.0.xsd"> 
<!-- 配置自动扫描的包 -->
<context:component-scan base-package="com.atguigu.spring.aop"></context:component-scan>

<!-- 配置自动为匹配 aspectJ 注解的 Java 类生成代理对象 -->
<aop:aspectj-autoproxy></aop:aspectj-autoproxy>

</beans>

首先来看一下环绕通知：

/**
* 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(public int com.atguigu.spring.aop.ArithmeticCalculator.*(..))")
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;
}

前置通知，后置通知，异常通知，返回通知

import java.util.Arrays;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

/**
* 可以使用 @Order 注解指定切面的优先级, 值越小优先级越高
*/
@Order(2)
@Aspect
@Component
public class LoggingAspect {

/**
* 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他的代码.
* 使用 @Pointcut 来声明切入点表达式.
* 后面的其他通知直接使用方法名来引用当前的切入点表达式.
*/
@Pointcut("execution(public int com.atguigu.spring.aop.ArithmeticCalculator.*(..))")
public void declareJointPointExpression(){}

/**
* 在 com.atguigu.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
*/
@Before("declareJointPointExpression()")
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));
}

/**
* 在方法执行之后执行的代码. 无论该方法是否出现异常
*/
@After("declareJointPointExpression()")
public void afterMethod(JoinPoint joinPoint){
String methodName = joinPoint.getSignature().getName();
System.out.println("The method " + methodName + " ends");
}

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

/**
* 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代码
*/
@AfterThrowing(value="declareJointPointExpression()",
throwing="e")
public void afterThrowing(JoinPoint joinPoint, Exception e){
String methodName = joinPoint.getSignature().getName();
System.out.println("The method " + methodName + " occurs excetion:" + e);
}
}

测试用例：

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

public static void main(String[] args) {

ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
ArithmeticCalculator arithmeticCalculator = (ArithmeticCalculator) ctx.getBean("arithmeticCalculator");

System.out.println(arithmeticCalculator.getClass().getName());

int result = arithmeticCalculator.add(1, 2);
System.out.println("result:" + result);

result = arithmeticCalculator.div(1000, 10);
System.out.println("result:" + result);
}

测试结果：

1.没有出现异常的情况

com.sun.proxy.$Proxy12
-->validate:[1, 2]
The method add begins with [1, 2]
The method add ends
The method add ends with 3
result:3
-->validate:[1000, 10]
The method div begins with [1000, 10]
The method div ends
The method div ends with 100
result:100

2.出现异常的情况：

com.sun.proxy.$Proxy12
-->validate:[1, 2]
The method add begins with [1, 2]
The method add ends
The method add ends with 3
result:3
-->validate:[1000, 0]
The method div begins with [1000, 0]
The method div ends
The method div occurs excetion:java.lang.ArithmeticException: / by zero

基于配置文件的方式来配置AOP

了解概述：

代码示例：

public class ArithmeticCalculatorImpl implements ArithmeticCalculator {

@Override
public int add(int i, int j) {
int result = i + j;
return result;
}

@Override
public int sub(int i, int j) {
int result = i - j;
return result;
}

@Override
public int mul(int i, int j) {
int result = i * j;
return result;
}

@Override
public int div(int i, int j) {
int result = i / j;
return result;
}

}

配置文件：applicationContext-xml.xml（关键在这里）

<?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-4.0.xsd"> 
<!-- 配置 bean -->
<bean id="arithmeticCalculator"
class="com.atguigu.spring.aop.xml.ArithmeticCalculatorImpl"></bean>

<!-- 配置切面的 bean. -->
<bean id="loggingAspect"
class="com.atguigu.spring.aop.xml.LoggingAspect"></bean>

<bean id="vlidationAspect"
class="com.atguigu.spring.aop.xml.VlidationAspect"></bean>

<!-- 配置 AOP -->
<aop:config>
<!-- 配置切点表达式 -->
<aop:pointcut expression="execution(* com.atguigu.spring.aop.xml.ArithmeticCalculator.*(int, int))"
id="pointcut"/>
<!-- 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-throwing method="afterThrowing" pointcut-ref="pointcut" throwing="e"/>
<aop:after-returning method="afterReturning" pointcut-ref="pointcut" returning="result"/>
<!--
<aop:around method="aroundMethod" pointcut-ref="pointcut"/>
-->
</aop:aspect>
<aop:aspect ref="vlidationAspect" order="1">
<aop:before method="validateArgs" pointcut-ref="pointcut"/>
</aop:aspect>
</aop:config>

</beans>