How to check that a ResultSet contains a specifica

问题:

Having rs, an instance of java.sql.ResultSet, how to check that it contains a column named "theColumn"?

回答1:

You can use ResultSetMetaData to iterate through the ResultSet columns and see if the column name matches your specified column name.

Example:

ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();

// get the column names; column indexes start from 1
for (int i = 1; i < numberOfColumns + 1; i++) {
    String columnName = rsMetaData.getColumnName(i);
    // Get the name of the column's table name
    if ("theColumn".equals(columnName)) {
        System.out.println("Bingo!");
    }
}

回答2:

Try using the method ResultSet#findColumn(String)

private boolean isThere(ResultSet rs, String column)
{
  try
  {
    rs.findColumn(column);
    return true;
  } catch (SQLException sqlex)
  {
    logger.debug("column doesn't exist {}", column);
  }
  return false;
}

回答3:

You can do:

rs.findColumn("theColum")

and check for SQLException

回答4:

Use the ResultSetMetaData class.

public static boolean hasColumn(ResultSet rs, String columnName) throws SQLException {
    ResultSetMetaData rsmd = rs.getMetaData();
    int columns = rsmd.getColumnCount();
    for (int x = 1; x <= columns; x++) {
        if (columnName.equals(rsmd.getColumnName(x))) {
            return true;
        }
    }
    return false;
}

回答5:

Use the ResultSetMetaData object provided by the ResultSet object via rs.getMetaData()