Unable to locate Spring NamespaceHandler for XML schema namespace [http://www.springframework.org/s

错误：
org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Unable to locate Spring NamespaceHandler for XML schema namespace [http://www.springframework.org/schema/aop]
Offending resource: class path resource [beans.xml]

原因：找不到http://www.springframework.org/schema/aop

解决办法：还未找到。谷歌了的方法试过了，不行。估计是版本的问题。怎么回事呢？

今天又多了个错误：java.lang.NullPointerException
at com.bjsxt.service.UserService.add(UserService.java:19)
at com.bjsxt.service.testUserService.testAdd(testUserService.java:16)
今天添加了javassist.jar等包，成功运行了。泪奔啊。足足改了四个小时的bug才成功的。

错误3：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'user': Injection of resource dependencies failed; nested exception is java.lang.NoClassDefFoundError: Ljavax/transaction/TransactionManager;

解决方法：添加jta.jar。
错误4：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'u': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in class path resource [beans.xml]: Error setting property values; nested exception is org.springframework.beans.NotWritablePropertyException: Invalid property 'annotatedClasses' of bean class [org.springframework.orm.hibernate3.LocalSessionFactoryBean]: Bean property 'annotatedClasses' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?

Caused by: org.springframework.beans.NotWritablePropertyException: Invalid property 'annotatedClasses' of bean class [org.springframework.orm.hibernate3.LocalSessionFactoryBean]: Bean property 'annotatedClasses' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?