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();
   

    }
}

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