Exception in thread "main" java.lang.IllegalArgumentException: node to traverse cannot be null!

Exception in thread "main" java.lang.IllegalArgumentException: node to traverse cannot be null!
at org.hibernate.hql.ast.util.NodeTraverser.traverseDepthFirst(NodeTraverser.java:63)
at org.hibernate.hql.ast.QueryTranslatorImpl.parse(QueryTranslatorImpl.java:280)
at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:182)
at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
at org.hibernate.engine.query.HQLQueryPlan.(HQLQueryPlan.java:101)
at org.hibernate.engine.query.HQLQueryPlan.(HQLQueryPlan.java:80)
at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:124)
at org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:156)
at org.hibernate.impl.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:135)
at org.hibernate.impl.SessionImpl.createQuery(SessionImpl.java:1770)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:345)
at com.sun.proxy.$Proxy0.createQuery(Unknown Source)
at dao.UserDao.queryUsers(UserDao.java:20)
at biz.UserBiz.queryUsers(UserBiz.java:36)

at test.Test.main(Test.java:9)

在使用hql语句查询user列表，出现此异常

原因是hql语句错误，from写成了form，此异常一般都是hql语句错误，记录一下