Java Exception: Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionfactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is org.hibernate.HibernateException: Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]

簡而言之，就是缺少 javassist.jar
http://jboss.org/javassist/downloads/