请教异常org.hibernate.exception.SQLGrammarException: could not execute query


请教高手下面异常是什么问题，搞了半天还是解决不了
org.hibernate.exception.SQLGrammarException: could not execute query
org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:67)
org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
org.hibernate.loader.Loader.doList(Loader.java:2148)
org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2029)
org.hibernate.loader.Loader.list(Loader.java:2024)
org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:375)
org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:308)
org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:153)
org.hibernate.impl.SessionImpl.list(SessionImpl.java:1106)
hql语句，映射文件都反复检查了，还是找不出原因
Toperator operator=null;
String str = "from Toperator t where t.operatorName='"+operatorName+"' and t.operatorPwd='"+operatorPwd+"'";
                System.out.println(str);
Session session=factory.openSession(); Transaction ts=session.beginTransaction();
Query query=session.createQuery(str);
List list=query.list();  在调用list方法就出错了
Iterator it=list.iterator();
if(it.hasNext()){
operator=(Toperator)it.next();
}
ts.commit();
session.close();