jdbc 连接mysql 首次成功，之后连接就报错

在系统中使用jdbc 连接mysql， 首次成功，之后连接就报错，驱动用的是mysql-connector-java-5.1.15-bin.jar
连接代码

 Connection conn = null;
        Statement stat = null;
        ResultSet rs = null;
        String url = "jdbc:mysql://*********:3306/*******?useUnicode=true&characterEncoding=GBK";
        String sql = null;
        String tableName = "***";
        List<ClockBO> clock = new ArrayList<ClockBO>();

            sql = "select * from "
                    + tableName
                    + " where timevalue between '"
                    + startTime
                    + "' and '" + endTime + "' and doorName='" + doorName.substring(2) + "'";
            System.out.println(sql);
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(url, "root", "****");
            stat = conn.createStatement();

            rs = stat.executeQuery(sql);

            while (rs.next()) {

                ClockBO bo = new ClockBO();
                ClockPKBO pkbo = new ClockPKBO();
                pkbo.setCardNo1(rs.getString(1));
                pkbo.setCardNo2(rs.getString(2));
                pkbo.setTimeValue(ft.format(rs.getTimestamp(6)));
                bo.setPersonNo(rs.getString(3));
                bo.setPersonName(rs.getString(4));
                bo.setDepartment(rs.getString(5));
                bo.setCtlIp(rs.getString(7));
                bo.setDoorNo(rs.getString(8));
                bo.setDoorName(rs.getString(9));
                bo.setStateId(rs.getString(10));
                bo.setRptState(rs.getString(11));
                bo.setStateStr(rs.getString(12));
                bo.setClockPK(pkbo);
                clock.add(bo);
                System.out.println(rs.getString(4));
                System.out.println(bo.toString());
            }

        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            try{
            if(null!=rs){
                rs.close();
            }
            if(null!=stat){
                stat.close();
            }
            if(null!=conn){
                conn.commit();
            conn.close();
            }
            }catch(SQLException e){
                e.printStackTrace();
            }
        }

首次连接可以查出数据，再次调用就在连接的时候就抛出异常了，异常信息如下

java.sql.SQLException: ResultSet is from UPDATE. No Data.
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1078)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:975)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:920)
at com.mysql.jdbc.ResultSetImpl.next(ResultSetImpl.java:6999)
at com.mysql.jdbc.ConnectionImpl.loadServerVariables(ConnectionImpl.java:4184)
at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3585)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2534)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2304)
at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:834)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:346)

为什么会出现这种情况呢？

终于解决这个问题了，反编译了jdbc连接包，发现在连接数据的语句执行时需要在目标数据库执行sql语句，并根据结果进行某些处理，
而出现这个问题的原因就在这儿，由于数据库的版本过低，是3.X的版本，而在连接包中的内置SQL语句在该版本的数据库上执行不成功，
没有返回结果，导致出现了resultset为空的异常，我不知道这算不算是一个bug，反正我就换了一个低版本的jdbc连接包，问题就不再出现了。

http://bbs.csdn.net/topics/390038904

把conn.commit();去掉试试，这里又没有事务，提交事务干嘛

http://blog.csdn.net/gotohbu/article/details/4501811