Java /休眠查询问题

Question

我在尝试使用WHERE子句执行SQL / HQL语句时遇到问题。

调用时，应用程序将连接并执行此方法，而不会出现错误：

public void listPlayers( ){
      Session session = sessionFactory.openSession();
      Transaction tx = null;
      try{
         tx = session.beginTransaction();
         List players = session.createQuery("FROM Player").list(); 
         for (Iterator iterator = 
                           players.iterator(); iterator.hasNext();){
            Player player = (Player) iterator.next(); 


           String tmpMessage = player.getFirstName().toString();
           System.out.println(tmpMessage);
              writer.write("First Name: "+player.getPlayerName()+", Wealth: "+player.getWealth()+"\r\n");
             writer.flush();

         }
         tx.commit();
      }catch (HibernateException e) {
         if (tx!=null) tx.rollback();
         e.printStackTrace(); 
      }finally {
         session.close(); 
      }
   }

但是，当我尝试这样做时； 我收到一个错误：找不到player_name字段：

      public void loadPlayer(String usr){
      Session session = sessionFactory.openSession();


      Transaction tx = null;
      try{
         tx = session.beginTransaction();
         String hql = "SELECT * FROM Player P WHERE P.player_name = "+usr;
         Query query = session.createQuery(hql); 
         List players = query.list();
         for (Iterator iterator = 
                           players.iterator(); iterator.hasNext();){
            Player player = (Player) iterator.next(); 

            System.out.print("  Location: " + player.getLocation()); 
            System.out.println("  Wealth: " + player.getWealth()); 
         }
         tx.commit();
      }catch (HibernateException e) {
         if (tx!=null) tx.rollback();
         e.printStackTrace(); 
      }finally {
         session.close(); 
      }
   }

我的mySQL数据库有一个名为Player的表，其中pID，player_name，位置，财富作为列值

我试图将播放器名称传递给loadPlayer（String username）方法，以便它可以查找与播放器关联的所有信息并写回套接字。 我在这里做错了什么？

Answer 1

我认为您的查询不正确。 尝试这样的事情

String hql = "SELECT * FROM Player P WHERE P.playerName = :playerName";         
Query query = session.createQuery(hql); 
query.setParameter("playerName", usr);