java - 如何动态确定 ResultSet 列类型

Question

我需要在运行时动态为数据库中的所有表生成 INSERT stmt。我正在逐一获取表内容(数据)并在运行时确定列类型，同时循环遍历 ResultSet 和 ResultSetMetaData，以便为字符串类型添加双引号(“)，而不为非字符串类型的列添加相同的双引号(”) 。但是，根据当前逻辑的实现，它会忽略第一条记录，并且对于表中的所有剩余记录都可以正常工作。我知道它为什么可以工作，就像在获取 rs.getColumnType(int columnIndex) 时一样。我们需要给出从 1 个索引开始的列名称..但无法构建逻辑，以便它也检查第一行而不是此刻忽略它..

请参阅下面的代码片段

if (rs != null) {
    while (rs.next()) {
        sqlString = new StringBuffer();

        for (int i = 1; i <= columnCount; i++) {
            Object obj = rs.getObject(i);

            if (obj == null) {
                sqlString.append("null");
                sqlString.append(",");
            }
            else
            {
                int sqlTypes = rsmd.getColumnType(i);

                switch (sqlTypes) {
                    case Types.VARCHAR:
                        sqlString.append("\"");
                        if (obj != null)
                            sqlString.append(rs.getString(i));

                        sqlString.append("\"");
                        sqlString.append(",");
                        break;
                    case Types.NULL:
                        sqlString.append("null");
                        sqlString.append(",");
                        break;
                    case Types.CHAR:
                        sqlString.append("\"");
                        if (obj != null)
                            sqlString.append(rs.getString(i));

                        sqlString.append("\"");
                        sqlString.append(",");
                        break;
                    case Types.TIMESTAMP:
                        sqlString.append("\"");
                        if (obj != null)
                            sqlString.append(rs.getTimestamp(i));

                        sqlString.append("\"");
                        sqlString.append(",");
                        break;
                    case Types.DOUBLE:
                        if (obj != null)
                            sqlString.append(rs.getDouble(i));

                        sqlString.append(",");
                        break;
                    case Types.INTEGER:
                        if (obj != null)
                            sqlString.append(rs.getInt(i));

                        sqlString.append(",");
                        break;
                    case Types.SMALLINT:
                        if (obj != null)
                            sqlString.append(rs.getInt(i));

                        sqlString.append(",");
                        break;
                    case Types.DECIMAL:
                        if (obj != null)
                            sqlString.append(rs.getBigDecimal(i));

                        sqlString.append(",");
                        break;

                    /*default:
                        if (obj != null)
                            sqlString.append(obj.toString());

                        sqlString.append(",");
                        break;*/
                }
            }
        }

Answer 1

您是否尝试过使用这样的 do while 循环:

if (rs != null) {
  do{
    sqlString = new StringBuffer();

    for (int i = 1; i <= columnCount; i++) {
        Object obj = rs.getObject(i);

        if (obj == null) {
            sqlString.append("null");
            sqlString.append(",");
        }
        else
        {
            int sqlTypes = rsmd.getColumnType(i);

            switch (sqlTypes) {
                case Types.VARCHAR:
                    sqlString.append("\"");
                    if (obj != null)
                        sqlString.append(rs.getString(i));

                    sqlString.append("\"");
                    sqlString.append(",");
                    break;
                case Types.NULL:
                    sqlString.append("null");
                    sqlString.append(",");
                    break;
                case Types.CHAR:
                    sqlString.append("\"");
                    if (obj != null)
                        sqlString.append(rs.getString(i));

                    sqlString.append("\"");
                    sqlString.append(",");
                    break;
                case Types.TIMESTAMP:
                    sqlString.append("\"");
                    if (obj != null)
                        sqlString.append(rs.getTimestamp(i));

                    sqlString.append("\"");
                    sqlString.append(",");
                    break;
                case Types.DOUBLE:
                    if (obj != null)
                        sqlString.append(rs.getDouble(i));

                    sqlString.append(",");
                    break;
                case Types.INTEGER:
                    if (obj != null)
                        sqlString.append(rs.getInt(i));

                    sqlString.append(",");
                    break;
                case Types.SMALLINT:
                    if (obj != null)
                        sqlString.append(rs.getInt(i));

                    sqlString.append(",");
                    break;
                case Types.DECIMAL:
                    if (obj != null)
                        sqlString.append(rs.getBigDecimal(i));

                    sqlString.append(",");
                    break;

                /*default:
                    if (obj != null)
                        sqlString.append(obj.toString());

                    sqlString.append(",");
                    break;*/
            }
        }while (rs.next());
    }