结果集的问题!!

Question

就这里有问题,明明是多个记录,但只执行一次    
                      while(rs2.next()){                           
                             bookid = rs2.getString("bookid").trim();
  
                             m = rs2.getInt("num");    //定购数量
                             if(sales==1){
                               sql = "update bookinfo set nownum = nownum - "+ m +" where bookid ='"+bookid+"' "; 
                             }else {
                                   sql = "update bookinfo set nownum = nownum + "+ m +" where bookid ='"+bookid+"' ";
  
                            }
                            stmt.execute(sql);   //好像这里有问题,跳出while循环了
                       
                         
                        }

Answer 1

while(rs2.next()){                           
                             bookid = rs2.getString("bookid").trim();
  
                             m = rs2.getInt("num");    //定购数量
                             if(sales==1){
                               sql = "update bookinfo set nownum = nownum - "+ m +" where bookid ='"+bookid+"' ";
                             }else {
                                   sql = "update bookinfo set nownum = nownum + "+ m +" where bookid ='"+bookid+"' ";
  
                            }
                      System.out.println(sql);//把sql打印出来有好处，在数据库里直接执行这条sql
                            stmt.execute(sql);   //好像这里有问题,跳出while循环了
                       System.out.println("execute ok");//在这里打印一下
                  }
                        rs2.close();
                        return true;
                }
                catch (Exception e)
                {
                        System.out.println(e.toString());//在这里打印错误
                        return false;
                }

Answer 2

sqlStr语句没有问题,是连续使用stmt的问题
stmt.execute(sql); //是不是连续使用stmt会引起错误
我是这样定义的
        DBConnectionManager dcm = new DBConnectionManager();
        Connection conn = dcm.getConnection();
        Statement stmt=conn.createStatement();
        Statement stmt2=conn.createStatement();

Answer 3

catch (Exception e)
                {
                        System.out.println(e.toString());//在这里打印错误
                        return false;
                }错误提示:
java.sql.SQLException: [Microsoft][ODBC 驱动程序管理器] 无效的游标状态

Answer 4

上面的错误提示应该是:
java.lang.NullPointerException