动态代理是基于接口的，spring配置是基于类的！！！！！！！！！！
注意：JDK的动态代理，只能对实现接口的类实现代理，生成代理对象，如果这个类没有实现接口，是生成不了代理对象的。如本例UserManagerImpl实现了UserManager，如果去掉了UserManager接口，会出现异常（找不到cglib库）。
要解决这个问题，要添加cglib库，即：/spring_home/cglib/cglib-nodep-2.1_3.jar
如果目标对象实现了接口，默认情况下会使用JDK的动态代理实现AOP；如果有些目标对象没有实现接口，而有些又实现了，那么框架会在jdk动态代理和cglib直接灵活切换，实现了接口的使用动态代理，没有实现接口的采用cglib，因此较为保险的做法是总是引入cglib库。
如下面的代码， Spring注入的是接口，关联的是实现类。 这里注入了实现类，所以报异常了。 （出现在事务处理过程中）
<bean id="aa" class="com.jdbcdemo.util.HibernateUtil"></bean>
<bean id="ld" class="com.jdbcdemo.dao.impl.LogDaoImpl">
<property name="sessionFactory" ref="sessionFactory"></property>
</bean>
<bean id="userDao" class="com.jdbcdemo.dao.impl.UserDaoImpl">
<property name="sessionFactory" ref="sessionFactory"></property>
<property name="logDaoImpl" ref="ld"></property>
</bean>
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘userDao‘ defined in file [E:\JavaProj\Hibernate_Spring_Study\WebRoot\WEB-INF\classes\applicationContext_beans.xml]: Initialization of bean failed; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert property value of type [$Proxy0 implementing com.jdbcdemo.dao.LogDao,org.springframework.beans.factory.InitializingBean,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised] to required type [com.jdbcdemo.dao.impl.LogDaoImpl] for property ‘logDaoImpl‘; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type [$Proxy0 implementing com.jdbcdemo.dao.LogDao,org.springframework.beans.factory.InitializingBean,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised] to required type [com.jdbcdemo.dao.impl.LogDaoImpl] for property ‘logDaoImpl‘: no matching editors or conversion strategy found
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解决办法1， <aop:config proxy-target-class="true"> ，表示可以用类注入：
<?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"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd">
<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory">
<ref bean="sessionFactory"/>
</property>
</bean>
<tx:annotation-driven transaction-manager="transactionManager" />
<tx:advice id="txAdvice" >
<tx:attributes>
<tx:method name="add"/>
</tx:attributes>
</tx:advice>
<aop:config proxy-target-class="true">
<aop:pointcut expression="execution(* com.jdbcdemo.dao.impl.*.*(..))" id="allManagerMethod"/>
<aop:advisor advice-ref="txAdvice" pointcut-ref="allManagerMethod"/>
</aop:config>
</beans>
解决办法2，在tx:annotation-driven中表示可以用类注入：
<?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"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd">
<bean id="transactionManager"class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory">
<ref bean="sessionFactory"/>
</property>
</bean>
<tx:annotation-driven transaction-manager="transactionManager"proxy-target-class="true"/>
<tx:advice id="txAdvice" >
<tx:attributes>
<tx:method name="add"/>
</tx:attributes>
</tx:advice>
<aop:config >
<aop:pointcut expression="execution(* com.jdbcdemo.dao.impl.*.*(..))"id="allManagerMethod"/>
<aop:advisor advice-ref="txAdvice" pointcut-ref="allManagerMethod"/>
</aop:config>
</beans>