首先確定將要Proxy的目標，在Spring中默認采用JDK中的dynamic proxy，它只能夠?qū)崿F(xiàn)接口的代理，如果想對類進行代理的話，需要采用CGLIB的proxy。顯然，選擇“編程到接口”是更明智的做法，下面是將要代理的接口：

  public interface FooInterface {
    public void printFoo();
    public void dummyFoo();
  }
 
  以及其一個簡單的實現(xiàn)：
 
  public class FooImpl implements FooInterface {
    public void printFoo() {
      System.out.println("In FooImpl.printFoo");
    }
    public void dummyFoo() {
      System.out.println("In FooImpl.dummyFoo");
    }
  }
 
  接下來創(chuàng)建一個Advice，在Spring中支持Around,Before,After returning和Throws四種Advice，這里就以簡單的Before Advice舉例：
 
  public class PrintBeforeAdvice implements MethodBeforeAdvice {
    public void before(Method arg0, Object[] arg1, Object arg2) throws Throwable {
      System.out.println("In PrintBeforeAdvice");
    }
  }
 
  有了自己的business interface和advice，剩下的就是如何去裝配它們了，首先利用ProxyFactory以編程方式實現(xiàn)，如下：
 
  public class AopTestMain {
    public static void main(String[] args) {
      FooImpl fooImpl = new FooImpl();
      PrintBeforeAdvice myAdvice = new PrintBeforeAdvice();
     
      ProxyFactory factory = new ProxyFactory(fooImpl);
      factory.addBeforeAdvice(myAdvice);
      FooInterface myInterface = (FooInterface)factory.getProxy();

      myInterface.printFoo();
      myInterface.dummyFoo();
    }
  }
 
  現(xiàn)在執(zhí)行程序，神奇的結果就出現(xiàn)了：
 
  In PrintBeforeAdvice
  In FooImpl.printFoo
  In PrintBeforeAdvice
  In FooImpl.dummyFoo
 
  雖然這樣能體會到Spring中AOP的用法，但這決不是值得推薦的方法，既然使用了Spring，在ApplicationContext中裝配所需要 的bean才是最佳策略，實現(xiàn)上面的功能只需要寫個簡單的applicationContext就可以了，如下：
 
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"
    "http://www.springframework.org/dtd/spring-beans.dtd">

  <beans>
    <description>The aop application context</description>
    <bean id="fooTarget" class="FooImpl"/>
    <bean id="myAdvice" class="PrintBeforeAdvice"/>
    <bean id="foo" class="org.springframework.aop.framework.ProxyFactoryBean">
     <property name="proxyInterfaces">
       <value>FooInterface</value>
     </property>
     <property name="target">
       <ref local="fooTarget"/>
     </property>
     <property name="interceptorNames">
       <list>
         <value>myAdvice</value>
       </list>
     </property>
    </bean>
  </beans>

  當然，main中的代碼也要進行相應的修改：
    
  public static void main(String[] args) {
    ClassPathXmlApplicationContext context = new 
             ClassPathXmlApplicationContext("applicationContext.xml");
    FooInterface foo = (FooInterface)context.getBean("foo");
    foo.printFoo();
    foo.dummyFoo();
  }
 
  現(xiàn)在運行一下，結果將和上面的運行結果完全一樣，這樣是不是更優(yōu)雅？當需要更改實現(xiàn)時，只需要修改配置文件就可以了，程序中的代碼不需任何改動。
 
  但是，這時候會發(fā)現(xiàn)被proxy的object中的所有方法調(diào)用時都將運行advice中的before，這顯然不能滿足絕大多數(shù)情況下的需要，此時，只 需借用Advisor就可以了，當然要在Advisor中利用pattern設置好哪些方法需要advice，更改applicationContext 如下：
 
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"
    "http://www.springframework.org/dtd/spring-beans.dtd">

  <beans>
    <description>The springeva application context</description>
    <bean id="fooTarget" class="FooImpl"/>
    <bean id="printBeforeAdvice" class="PrintBeforeAdvice"/>
    <bean id="myAdvisor"
          class="org.springframework.aop.support.RegexpMethodPointcutAdvisor">
      <property name="advice">
        <ref local="printBeforeAdvice"/>
      </property>
      <property name="pattern">
        <value>.*print.*</value>
      </property>
    </bean>
    <bean id="foo" class="org.springframework.aop.framework.ProxyFactoryBean">
      <property name="proxyInterfaces">
        <value>FooInterface</value>
      </property>
      <property name="target">
        <ref local="fooTarget"/>
      </property>
      <property name="interceptorNames">
        <list>
          <value>myAdvisor</value>
        </list>
      </property>
    </bean>
  </beans>

  主程序不需進行任何修改，運行結果已經(jīng)變樣了：

  In PrintBeforeAdvice
  In FooImpl.printFoo
  In FooImpl.dummyFoo
 
  至此，應該已經(jīng)理解了Spring中AOP的使用方法，當然Spring中AOP最重要的應用是Transaction Manager，舉個這方面的applicationContext例子看看：
 
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "spring-beans.dtd">

  <beans>
    <bean id="propertyConfigurer"   
         class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
      <property name="location">
        <value>/WEB-INF/jdbc.properties</value>
      </property>
    </bean>
    <bean id="dataSource"
          class="org.springframework.jdbc.datasource.DriverManagerDataSource">
      <property name="driverClassName">
        <value>${jdbc.driverClassName}</value>
      </property>
      <property name="url">
        <value>${jdbc.url}</value>
      </property>
      <property name="username">
        <value>${jdbc.username}</value>
      </property>
      <property name="password">
        <value>${jdbc.password}</value>
      </property>
    </bean>
    <bean id="sessionFactory"
          class="org.springframework.orm.hibernate.LocalSessionFactoryBean">
      <property name="dataSource">
        <ref local="dataSource"/>
      </property>
      <property name="mappingResources">
        <value>smartmenu.hbm.xml</value>
      </property>
      <property name="hibernateProperties">
        <props>
          <prop key="hibernate.dialect">${hibernate.dialect}</prop>
        </props>
      </property>
    </bean>
 
    <bean id="transactionManager"       
          class="org.springframework.orm.hibernate.HibernateTransactionManager">
      <property name="sessionFactory">
        <ref local="sessionFactory"/>
      </property>
    </bean>
    <bean id="smartmenuTarget" class="SmartMenuHibernate">
      <property name="sessionFactory">
        <ref local="sessionFactory"/>
      </property>
    </bean>
    <bean id="smartMenu"
        class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
      <property name="transactionManager">
        <ref local="transactionManager"/>
      </property>
      <property name="target">
        <ref local="smartmenuTarget"/>
      </property>
      <property name="transactionAttributes">
        <props>
          <prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
          <prop key="find*">PROPAGATION_REQUIRED,readOnly</prop>
        </props>
      </property>
    </bean>
  </beans>
 
  嗯，要想徹底理解Spring的AOP，最好還是多看看源碼，開源就是好啊！