log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: insert into tbl_user (uname, upass) values (?, ?)
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: could not insert: [entity.User]
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:94)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2176)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2656)
    at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:279)
    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)
    at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
    at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
    at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:563)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:551)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:547)
    at dao.UserDaoTest.testSave(UserDaoTest.java:49)
    at dao.UserDaoTest.main(UserDaoTest.java:24)
Caused by: com.microsoft.sqlserver.jdbc.SQLServerException: 不能将值 NULL 插入列 'uid'，表 'neusoftbookdb.dbo.tbl_user'；列不允许有空值。INSERT 失败。
    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDatabaseError(Unknown Source)
    at com.microsoft.sqlserver.jdbc.IOBuffer.processPackets(Unknown Source)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.sendExecute(Unknown Source)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.doExecuteUpdate(Unknown Source)
    at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.executeUpdate(Unknown Source)
    at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)
    at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)
    ... 17 more