如何在jdbc中使用ResultSet.getBinaryStream（）从所有列中获取值？

Question

如何使用jdbc将整个表写入平面文件（文本文件）？到目前为止，我已经尝试了以下方法：

Statement statement = connection.createStatement();
   ResultSet result = statement.executeQuery("SELECT * FROM tablename");
   BufferedInputStream buffer;
   FileOutputStream out = new FileOutputStream("flatfile.txt");
   while(result.next() )
   {
      buffer =  new BufferedInputStream(result.getBinaryStream("????") );
      byte[] buf = new byte[4 * 1024]; //4K buffer
      int len;
      while( (len = buffer.read(buf, 0, buf.length) ) != -1 )
      {
          out.write(buf, 0, len );
      }
   }
   out.close();

“ ？？？” 只是我的占位符。我被困在传递什么作为争论。

Answer 1

您可以使用以下代码从表中获取所有列名和整个数据。writeToFile方法将包含写入文件的逻辑（如果还不够明显的话:)）

    ResultSetMetaData metadata = rs.getMetaData();
    int columnCount = metadata.getColumnCount();    
    for (int i = 1; i <= columnCount; i++) {
        writeToFile(metadata.getColumnName(i) + ", ");      
    }
    System.out.println();
    while (rs.next()) {
        String row = "";
        for (int i = 1; i <= columnCount; i++) {
            row += rs.getString(i) + ", ";          
        }
        System.out.println();
        writeToFile(row);

    }