JDBC通用的查询方法。

JDBC通用的查询方法。

formId查询的条件字段，tableName是表名，fieldName要查询的字段  


private static String getValue(String formId,String tableName,String fieldName)throws WfException{
       Connection con = DbConnectionManager.getInstance().getConnection(
                                  poolName);
                  Statement st = null;
                  String value = null;
                  try {
                          st = con.createStatement();
                          String iSql = "select "+fieldName+" from "+tableName+" where applyid='"+formId+"'";
                          ResultSet rs = st.executeQuery(iSql);
                          if (rs.next()) {
                             value = rs.getString(1);
                          }
                  } catch (Exception e) {
                      throw new WfException(ErrorInfo.EXT_PROC_MANAGER_ERROR,"获取值失败!",
                                    ErrorInfo.getTrace(e, e.getStackTrace()));
                  } finally {
                      DbConnectionManager.getInstance().freeConnection(poolName, con);
                  }
                  return value;

   }