Java获取数据库空值

JAVA里面的List值获取不到，运行看不到字段下的数据
//action
public String execute()throws Exception{
List list=yhService.findAll(pageNow,pageSize);
Map request=(Map)ActionContext.getContext().get("request");
Pager page=new Pager(getPageNow(),yhService.findYhsize());
request.put("list", list);
request.put("page", page);
return SUCCESS;
}
//dao.imp
public class yhDAO extends BaseDAO implements IyhDAO{
public List findAll(int pageNow,int pageSize) {
// TODO Auto-generated method stub
try{
Session session=this.getSession();
Transaction ts=session.beginTransaction();
Query query=session.createQuery("from Users order by userid");
int firstResult=(pageNow-1)*pageSize;
query.setFirstResult(firstResult);
query.setMaxResults(pageSize);
List list=query.list();
ts.commit();
session.close();
// session=null;
return list;
}catch(Exception e){
e.printStackTrace();
return null;
}
}
//问题
[07:21:47] DEBUG ast.AST "--- HQL AST ---
 \-[QUERY] 'query'
    \-[SELECT_FROM] 'SELECT_FROM'
       \-[FROM] 'from'
          \-[RANGE] 'RANGE'
             \-[IDENT] 'Users'
"
[07:21:47] DEBUG ast.ErrorCounter "throwQueryException() : no errors"
[07:21:47] DEBUG antlr.HqlSqlBaseWalker "select << begin [level=1, statement=select]"
org.hibernate.hql.ast.QuerySyntaxException: Users is not mapped [from Users]
at org.hibernate.hql.ast.util.SessionFactoryHelper.requireClassPersister(SessionFactoryHelper.java:158)
at org.hibernate.hql.ast.tree.FromElementFactory.addFromElement(FromElementFactory.java:87)
at org.hibernate.hql.ast.tree.FromClause.addFromElement(FromClause.java:70)
at org.hibernate.hql.ast.HqlSqlWalker.createFromElement(HqlSqlWalker.java:255)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:305