java - 运行Java代码时无法从mysql数据库检索行

我有一个将从公司表中获取行并将其插入JComboBox的代码。

当APP在调试模式下运行时，结果集中将填充数据。但是在正常执行时，结果集为空！

我正在使用Netbeans IDE 7.0.1进行开发，并使用phpmyadmin mysql数据库版本5.1.37。

下面是我的代码：

       boolean isvalue = false; // variable to identify if the company name found or not.
        ResultSet rs = null;
        try {
            st = con.createStatement();
            if(con == null) {
                logger.error("Database Connection Not available.");
                throw new NullPointerException();
            }
            //Set the company name to combo box
            rs = st.executeQuery("Select comp_name from company");
            while (rs.next()) {
                comboCompanyName.addItem(rs.getString("comp_name"));
                isvalue = true; //Set true if found
            }
        } catch (SQLException ex) {
            System.out.println("SQLError found while updating information." + ex.getMessage());
        } catch (Exception ex) {
           System.out.println("Error found while updating information." + ex.getMessage());
        }
        if (!isvalue) //Check company information available
        {
            JOptionPane.showMessageDialog(null, "System could not found any company information.", "Error", JOptionPane.WARNING_MESSAGE);
        }

帮助我。
提前致谢。

最佳答案

除了使用value变量，还可以尝试：

PreparedStatement statement = con.prepareStatement("SELECT comp_name FROM company");
  ResultSet result = statement.executeQuery();
    int i=0;
    while (result.next()) {
      jComboBox1.addItem(result.getString(1));
        i++;
       }
     if(i==0){
    JOptionPane.showMessageDialog(null, "System could not found any company information.", "Error",JOptionPane.WARNING_MESSAGE);
   }