private static ResultSet rs=null;
    private static Statement aStatement=null;
    private static Connection aConnection=null;
private static void getDBConnection()
    {
        try
        {
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            aConnection=DriverManager.getConnection("jdbc:odbc:mydata","sa","sa");
        }catch(ClassNotFoundException e1)
        {
            JOptionPane.showMessageDialog(null, "驱动没找到，连接失败","Error",JOptionPane.ERROR_MESSAGE);
            
        }catch(SQLException e2)
        {
            JOptionPane.showMessageDialog(null, "用户名密码错误,连接失败","Error",JOptionPane.ERROR_MESSAGE);
            
        }
    }
public static Vector getAll()
    {
        Vector <Category> Categories=new Vector();
        String strSQL;
        strSQL="SELECT * FROM Categories";
        try
        {
            getDBConnection();
            aStatement=aConnection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_UPDATABLE);
            rs=aStatement.executeQuery(strSQL);
            while (rs.next())
            {
                Category aCategory=new Category();
                aCategory.setCategoryID(rs.getInt("CategoryID"));
                aCategory.setCategoryName(rs.getString("CategoryName"));
                aCategory.setDescription(rs.getString("Description"));
                byte [] buf1=rs.getBytes("Picture");
                aCategory.setPicture(buf1);
                
                Categories.add(aCategory);
            }
            rs.first();
        }
        catch(SQLException e)
        {
            JOptionPane.showMessageDialog(null, e.getMessage(),"Error",JOptionPane.ERROR_MESSAGE);
            
        }
        return Categories;
    }
public static Category GetNextCategory()
    {
        Category aCategory=new Category();
        try
        {
            if (rs.isLast())
            {
                JOptionPane.showMessageDialog(null, "已经是最后一条记录了","提示",JOptionPane.INFORMATION_MESSAGE);
            }
            else
            {
                rs.next();
                
            }
            aCategory=getCategory(rs);
        }catch(SQLException e)
        {
            JOptionPane.showMessageDialog(null, e.getMessage(),"Error",JOptionPane.ERROR_MESSAGE);
            
        }
        return aCategory;
    }

 catch(SQLException e)
        {
           e.printStackTrace();//加这个就可以看到控制台里详细信息了
            JOptionPane.showMessageDialog(null, e.getMessage(),"Error",JOptionPane.ERROR_MESSAGE);
            
        }