JDBC实现分页查询，同时使用动态数据源

方法是通过jdbc来实现分页的，这样做的目的是可以实现多数据库的情况下，都能使用的方法。
但是这个方法貌似会存在性能问题，因为结果集会全部数据查询出来...

public JSONObject query(JSONObject object, int pageIndex, int pageSize) {
    JSONObject result = new JSONObject();
    if(object == null || object.getBoolean("success") == false) {
        result.put("success", false);
        if(object == null) {
            result.put("msg", "没有成功获取到基本对象");
        } else if(object.getString("msg") != null) {
            result.put("msg", object.getString("msg"));
        }
    } else {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        //Statement statement = null;
        ResultSet rs = null;
        try {
            connection = createConnection(object.getString("className"), object.getString("url"), object.getString("user"), object.getString("pwd"));
            String sql = object.getString("sql");
            System.out.println(sql);
            preparedStatement = connection.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
            if(pageIndex == 1 && pageSize == 1) {
                rs = preparedStatement.executeQuery();
            } else {
                preparedStatement.setMaxRows(((pageIndex - 1) * pageSize) + pageSize);//查询的最大行数
                //preparedStatement.setMaxRows(pageSize);
                rs = preparedStatement.executeQuery();
                //rs.first();
                rs.absolute((pageIndex - 1) * pageSize + 1);//利用绝对定位定位到结果集的每页第二条数据
                rs.relative(-1);//利用结果集的相对定位定位到每页的第一条数据
            }
            JSONArray datas = new JSONArray();
            JSONArray data = null;
            ResultSetMetaData metaData = null;
            int colnumCount = 0;
            String colnumName = null;
            Object tmp = null;
            SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Reader reader = null;
            BufferedReader bufferedReader = null;
            char[] chbTmp = null;
            StringBuffer sb = new StringBuffer();
            while(rs.next()) {
                //获取数据
                data = new JSONArray();
                metaData = rs.getMetaData();
                colnumCount = metaData.getColumnCount() + 1;
                for (int i = 1; i < colnumCount; i++) {
                    colnumName = metaData.getColumnName(i);
                    tmp = rs.getObject(colnumName);
                    if(tmp == null) {
                        data.add("");
                    } else {
                        if(tmp.getClass() == Timestamp.class) {
                            data.add(dateFormat.format(tmp));
                        } else if(tmp.getClass() == CLOB.class) {
                            chbTmp = new char[20];
                            reader = rs.getClob(colnumName).getCharacterStream();
                            bufferedReader = new BufferedReader(reader);
                            bufferedReader.read(chbTmp);
                            sb.delete(0, chbTmp.length);
                            sb.append(chbTmp);
                            data.add(sb.toString() + "...");
                        } else {
                            data.add(tmp);
                        }
                    }
                }
                datas.add(data);;
            }
            JSONArray colnums = new JSONArray();
            if(datas.size() > 0) {
                //获取列名
                metaData = rs.getMetaData();
                colnumCount = metaData.getColumnCount() + 1;
                for (int i = 1; i < colnumCount; i++) {
                    colnumName = metaData.getColumnName(i);
                    colnums.add(colnumName);
                }
            } else {
                colnums.add("没有成功获取列的信息");
            }
            result.put("colnum", colnums);
            result.put("datas", datas);
            result.put("success", true);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            result.put("success", false);
            result.put("msg", e.getMessage());
        } catch (SQLException e) {
            e.printStackTrace();
            result.put("success", false);
            result.put("msg", e.getMessage());
        } catch (IOException e) {
            e.printStackTrace();
            result.put("success", false);
            result.put("msg", e.getMessage());
        } finally {
            close(connection, preparedStatement, rs);
        }
    }
    return result;
}