Java – how to obtain the column name of the primary key through JDBC

I have the following code:

DatabaseMetaData dmd = connection.getMetaData();
ResultSet rs = dmd.getPrimaryKeys(null,null,tableName);

while(rs.next()){
    primaryKey = rs.getString("COLUMN_NAME");
}

RS is not empty, and rs.next() always returns false. Does anyone have an idea? thank you.

Solution

>The metadata interface is implemented by the driver vendor Some drivers and some DB may not support it

DatabaseMetaData dm = conn.getMetaData( );
ResultSet rs = dm.getExportedKeys( "","","table1" );
while( rs.next( ) ) 
{    
  String pkey = rs.getString("PKCOLUMN_NAME");
  System.out.println("primary key = " + pkey);
}

You can also use getcrossreference or getimportedkeys to retrieve the primary key