（感觉这个问题虽然是个纯技术问题，但最好发到论坛里问问，因为俺在网上查了好半天也没查到解决方法。如果非要给俺整到“问答”里，俺也没脾气。）
现象描述
Struts2 + Spring，Action中注入Service，Service中注入Dao。
Service中并没有使用接口，根据网上资料，应是使用CGLIB来创建类对象。
此前，使用Set注入时，没有任何问题，一切正常。
前两天看了一下Spring in Action，对于Dao注入Service时，通过构造函数注入比较不错。
今晚改成通过构造函数注入时，发生了异常，由于对CGLIB的加载对象的过程不太了解，原因实现查不明白，各位请帮帮忙吧。
具体实现
Service类的实现
public class UserService {
private IUserDao userDao;
public UserService(IUserDao userDao) {
this.userDao = userDao;
}
}
applicationContext.xml的配置
<!---->
<bean id="sqlMapClient" class="org.springframework.orm.ibatis.SqlMapClientFactoryBean">
<property name="configLocation" value="WEB-INF/SqlMapConfig.xml">
<property name="dataSource" ref="dataSource">
</bean>
<!---->
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource">
<ref local="dataSource">
</property>
</bean>
<!---->
<aop:config proxy-target-class="true">
<aop:pointcut id="serviceOperation" expression="execution(* cn.ipcat.service.*.*(..))">
<aop:advisor pointcut-ref="serviceOperation" advice-ref="txAdvice">
</aop:config>
<!---->
<tx:advice id="txAdvice" transaction-manager="transactionManager">
<tx:attributes>
<!---->
<tx:method name="save*" rollback-for="Exception">
<!---->
<tx:method name="insert*" rollback-for="Exception">
<tx:method name="create*" rollback-for="Exception">
<!---->
<tx:method name="update*" rollback-for="Exception">
<!---->
<tx:method name="delete*" rollback-for="Exception">
<!---->
<tx:method name="*" read-only="true" rollback-for="Exception">
</tx:attributes>
</tx:advice>
<!---->
<bean id="userDao" class="cn.ipcat.entity.user.UserDao">
<property name="sqlMapClient">
<ref bean="sqlMapClient"></ref>
</property>
</bean>
<!---->
<bean id="userService" class="cn.ipcat.service.UserService">
<constructor-arg>
<ref bean="userDao">
</constructor-arg>
</bean>
struts.xml的配置
略。
我个人的测试分析
我试验了一下，只要在applicationContext.xml中不加下段记述就没事，一旦加了，就出错。
考虑，可能是“aop:pointcut”的“expression”的问题，分析可能是通过带参数的构造函数生成对象时，进行切面控制，从而导致问题，但是为什么通过Set方式注入时就没事，没想明白。
如果真的是“expression”的问题，那么对于带参数的构造函数，这里应该怎么写呢？
<!---->
<aop:config proxy-target-class="true">
<aop:pointcut id="serviceOperation" expression="execution(* cn.ipcat.service.*.*(..))">
<aop:advisor pointcut-ref="serviceOperation" advice-ref="txAdvice">
</aop:config>
具体的错误信息
在tomcat一启动时，预加载各个类对象时，就出错了。
信息: Initializing Spring root WebApplicationContext
[ERROR]_2008-11-30 22:27:27_org.springframework.web.context.ContextLoader@(ContextLoader.java:215):Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService' defined in ServletContext resource [/WEB-INF/appcontext/UserAppContext.xml]: Initialization of bean failed; nested exception is org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class cn.ipcat.service.UserService]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:480)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
at java.security.AccessController.doPrivileged(Native Method)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:221)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:729)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:381)
at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3843)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4342)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
at org.apache.catalina.core.StandardService.start(StandardService.java:516)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:578)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
Caused by: org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class cn.ipcat.service.UserService]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
at org.springframework.aop.framework.Cglib2AopProxy.getProxy(Cglib2AopProxy.java:213)
at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:110)
at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.createProxy(AbstractAutoProxyCreator.java:488)
at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:363)
at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:324)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:361)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1343)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473)
... 29 more
Caused by: java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
at net.sf.cglib.proxy.Enhancer.emitConstructors(Enhancer.java:721)
at net.sf.cglib.proxy.Enhancer.generateClass(Enhancer.java:499)
at net.sf.cglib.transform.TransformingClassGenerator.generateClass(TransformingClassGenerator.java:33)
at net.sf.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:216)
at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:377)
at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:285)
at org.springframework.aop.framework.Cglib2AopProxy.getProxy(Cglib2AopProxy.java:201)
... 36 more
2008-11-30 22:27:27 org.apache.catalina.core.StandardContext listenerStart
严重: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService' defined in ServletContext resource [/WEB-INF/appcontext/UserAppContext.xml]: Initialization of bean failed; nested exception is org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class cn.ipcat.service.UserService]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:480)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
at java.security.AccessController.doPrivileged(Native Method)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:221)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:729)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:381)
at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3843)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4342)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
at org.apache.catalina.core.StandardService.start(StandardService.java:516)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:578)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
Caused by: org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class cn.ipcat.service.UserService]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
at org.springframework.aop.framework.Cglib2AopProxy.getProxy(Cglib2AopProxy.java:213)
at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:110)
at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.createProxy(AbstractAutoProxyCreator.java:488)
at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:363)
at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:324)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:361)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1343)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473)
... 29 more
Caused by: java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
at net.sf.cglib.proxy.Enhancer.emitConstructors(Enhancer.java:721)
at net.sf.cglib.proxy.Enhancer.generateClass(Enhancer.java:499)
at net.sf.cglib.transform.TransformingClassGenerator.generateClass(TransformingClassGenerator.java:33)
at net.sf.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:216)
at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:377)
at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:285)
at org.springframework.aop.framework.Cglib2AopProxy.getProxy(Cglib2AopProxy.java:201)
... 36 more
2008-11-30 22:27:27 org.apache.catalina.core.StandardContext start
严重: Error listenerStart
2008-11-30 22:27:27 org.apache.catalina.core.StandardContext start
严重: Context [] startup failed due to previous errors
2008-11-30 22:27:27 org.apache.catalina.core.ApplicationContext log
信息: Closing Spring root WebApplicationContext
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