相关疑难解决方法(0)

为什么JPA需要域对象的无参数构造函数？我正在使用eclipselink并在部署期间遇到此异常.

Exception [EclipseLink-63] (Eclipse Persistence Services-1.1.0.r3639-SNAPSHOT): 
org.eclipse.persistence.exceptions.DescriptorException

Exception Description: The instance creation method   
[com.me.model.UserVO.<Default Constructor>], with no parameters, 
  does not exist, or is not accessible.
Internal Exception: java.lang.NoSuchMethodException: 
  com.me.model.UserVO.<init>()
Descriptor: RelationalDescriptor(com.me.model.UserVO --> 
  [DatabaseTable(user)])