Spring AOP四种创建通知(拦截器)类型
1、Spring只支持方法拦截，也就是说，只能在方法的前后进行拦截，而不能在属性前后进行拦截。
2、Spring支持四种拦截类型：目标方法调用前（before），目标方法调用后（after），目标方法调用前后（around），以及目标方法抛出异常（throw）。
3、前置拦截的类必须实现MethodBeforeAdvice接口，实现其中的before方法。
4、后置拦截的类必须实现AfterReturningAdvice接口，实现其中的afterReturning方法。
5、前后拦截的类必须实现MethodInterceptor接口，实现其中的invoke方法。前后拦截是唯一可以控制目标方法是否被真正调用的拦截类型，也可以控制返回对象。而前置拦截或后置拦截不能控制，它们不能印象目标方法的调用和返回。
但是以上的拦截的问题在于，不能对于特定方法进行拦截，而只能对某个类的全部方法作拦截。所以下面引入了两个新概念：“切入点”和“引入通知”。
6、”切入点“的定义相当于更加细化地规定了哪些方法被哪些拦截器所拦截，而并非所有的方法都被所有的拦截器所拦截。在ProxyFactoryBean的属性中，interceptorNames属性的对象也由拦截（Advice）变成了引入通知（Advisor），正是在Advisor中详细定义了切入点（PointCut）和拦截（Advice）的对应关系，比如常见的基于名字的切入点匹配（NameMatchMethodPointcutAdvisor类）和基于正则表达式的切入点匹配（RegExpPointcutAdvisor类）。这些切入点都属于”静态切入点“，因为他们只在代理创建的时候被创建一次，而不是每次运行都创建。
下面我们进行实例的开发
首先创建业务接口：
package AdvisorTest;
public interface Shopping ...{
public String buySomething(String type);
public String buyAnything(String type);
public void testException();
}下面是业务实现类，我们的通知就是以这些实现类作为切面，在业务方法前后加入我们的通知代码
package AdvisorTest;
public class ShoppingImpl implements Shopping ...{
private Customer customer;
public Customer getCustomer() ...{
return customer;
}
public void setCustomer(Customer customer) ...{
this.customer = customer;
}
public String buySomething(String type) ...{
System.out.println(this.getCustomer().getName()+" bye "+type+" success");
return null;
}
public String buyAnything(String type) ...{
System.out.println(this.getCustomer().getName()+" bye "+type+" success");
return null;
}
public void testException()...{
throw new ClassCastException();
}
}（1）前置通知
配置了前置通知的bean,在执行业务方法前，均会执行前置拦截器的before方法
package AdvisorTest;
import java.lang.reflect.Method;
import org.springframework.aop.MethodBeforeAdvice;
//前置通知
public class WelcomeAdvice implements MethodBeforeAdvice ...{
public void before(Method method, Object[] args, Object obj)
throws Throwable ...{
String type=(String)args[0];
System.out.println("Hello welcome to bye "+type);
}
}（2）后置通知
配置了前置通知的bean,在执行业务方法前，均会执行前置拦截器的afterReturnning方法packageAdvisorTest;
import java.lang.reflect.Method;
import org.springframework.aop.AfterReturningAdvice;
import org.springframework.aop.MethodBeforeAdvice;
//后置通知
public class ThankYouAdvice implements AfterReturningAdvice ...{
public void afterReturning(Object obj, Method method, Object[] arg1,
Object arg2) throws Throwable ...{
String type=(String)arg1[0];
System.out.println("Hello Thankyou to bye "+type);
}
}（3）环绕通知
配置了前置通知的bean,在执行业务方法前后，均会执行前置拦截器的invoke方法
需要注意的是必须调用目标方法，如不调用，目标方法将不被执行
package AdvisorTest;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
public class MethodAdvisor implements MethodInterceptor ...{
public Object invoke(MethodInvocation invocation) throws Throwable ...{
String str=(String)invocation.getArguments()[0];
System.out.println("this is before"+str+" in MethodInterceptor");
Object obj=invocation.proceed(); //调用目标方法，如不调用，目标方法将不被执行
System.out.println("this is after"+str+" in MethodInterceptor");
return null;
}
}（4）异常通知
ThrowsAdvice是一个标示接口，我们可以在类中定义一个或多个，来捕获定义异常通知的bean抛出的异常，并在抛出异常前执行相应的方法
public void afterThrowing(Throwable throwa){}或者
public void afterThrowing(Method method,Object[] args,Object target,Throwable throwable){
package AdvisorTest;
import org.springframework.aop.ThrowsAdvice;
public class ExceptionAdvisor implements ThrowsAdvice ...{
public void afterThrowing(ClassCastException e)...{
System.out.println("this is from exceptionAdvisor");
}
}配置文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd" >
<beans>
<bean id="customer" class="AdvisorTest.Customer">
<constructor-arg index="0">
<value>gaoxiang</value>
</constructor-arg>
<constructor-arg index="1">
<value>26</value>
</constructor-arg>
</bean>
<bean id="shoppingImpl" class="AdvisorTest.ShoppingImpl">
<property name="customer">
<ref local="customer"/>
</property>
</bean>
<!-- 前置通知 -->
<bean id="welcomeAdvice" class="AdvisorTest.WelcomeAdvice"/>
<bean id="welcomeAdviceShop" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="proxyInterfaces">
<value>AdvisorTest.Shopping</value>
</property>
<property name="target">
<ref local="shoppingImpl"/>
</property>
<property name="interceptorNames">
<list>
<value>welcomeAdvice</value>
</list>
</property>
</bean>
<!-- 后置通知 -->
<bean id="thankyouAdvice" class="AdvisorTest.ThankYouAdvice"/>
<bean id="thankyouAdviceShop" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="proxyInterfaces">
<value>AdvisorTest.Shopping</value>
</property>
<property name="target">
<ref local="shoppingImpl"/>
</property>
<property name="interceptorNames">
<list>
<value>thankyouAdvice</value>
</list>
</property>
</bean>
<!-- 环绕通知 -->
<bean id="methodAdvice" class="AdvisorTest.MethodAdvisor"/>
<bean id="methodAdviceShop" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="proxyInterfaces">
<value>AdvisorTest.Shopping</value>
</property>
<property name="target">
<ref local="shoppingImpl"/>
</property>
<property name="interceptorNames">
<list>
<value>methodAdvice</value>
</list>
</property>
</bean>
<!-- 异常通知 -->
<bean id="exceptionAdvice" class="AdvisorTest.ExceptionAdvisor"/>
<bean id="exceptionAdviceShop" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="proxyInterfaces">
<value>AdvisorTest.Shopping</value>
</property>
<property name="target">
<ref local="shoppingImpl"/>
</property>
<property name="interceptorNames">
<list>
<value>exceptionAdvice</value>
</list>
</property>
</bean>
</beans>测试代码：
package AdvisorTest;
import java.io.File;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.FileSystemResource;
public class TestAdvisor ...{
public static void main(String[] args) ...{
String filePath=System.getProperty("user.dir")+File.separator+"AdvisorTest"+File.separator+"hello.xml";
BeanFactory factory=new XmlBeanFactory(new FileSystemResource(filePath));
Shopping shopping=null;
System.out.println("不使用任何通知");
shopping=(Shopping)factory.getBean("shoppingImpl");
shopping.buySomething("something");
shopping.buyAnything("anything");
System.out.println("使用前置通知");
shopping=(Shopping)factory.getBean("welcomeAdviceShop");
shopping.buySomething("something");
shopping.buyAnything("anything");
System.out.println("使用后置通知");
shopping=(Shopping)factory.getBean("thankyouAdviceShop");
shopping.buySomething("something");
shopping.buyAnything("anything");
System.out.println("使用环绕通知");
shopping=(Shopping)factory.getBean("methodAdviceShop");
shopping.buySomething("something");
shopping.buyAnything("anything");
System.out.println("使用异常通知");
shopping=(Shopping)factory.getBean("exceptionAdviceShop");
shopping.testException();
}
}运行结果一目了然：不使用任何通知
gaoxiangbyesomethingsuccess
gaoxiangbyeanythingsuccess
使用前置通知
Hellowelcometobyesomething
gaoxiangbyesomethingsuccess
Hellowelcometobyeanything
gaoxiangbyeanythingsuccess
使用后置通知
gaoxiangbyesomethingsuccess
HelloThankyoutobyesomething
gaoxiangbyeanythingsuccess
HelloThankyoutobyeanything
使用环绕通知
thisisbeforesomethinginMethodInterceptor
gaoxiangbyesomethingsuccess
thisisaftersomethinginMethodInterceptor
thisisbeforeanythinginMethodInterceptor
gaoxiangbyeanythingsuccess
thisisafteranythinginMethodInterceptor
使用异常通知
thisisfromexceptionAdvisor