Solved : Why does PreparedStatement getMetaData returns null

[Darren Wilkinson]

Hello,

I'm puzzled by why the line in my code where I try to get the meta data of a prepared statement returns null, as the API says,

Consequently, it is possible to invoke the method getMetaData on a PreparedStatement object rather than waiting to execute it

public Boolean insertMappedData() {
        System.out.println("AbstractMapping.insertMappedData() start");
        Boolean isMapped = new Boolean(false);
        
        try {
 
            ResultSetMetaData prepMetaData = this.preparedStatement.getMetaData();
            Statement s = this.connectionManager.getConnection().createStatement();
            ResultSet rs2 = s.executeQuery("SELECT TOP 1 * FROM tbl_common_table");
            ResultSetMetaData commMetaData = rs2.getMetaData();
 
            int prepCount = prepMetaData.getColumnCount(); // This line throws the null pointer exception
            int commCount = commMetaData.getColumnCount();
            
            if(prepCount != commCount) {
                System.out.println("Column counts don't match.");
            } else {
                System.out.println("Column counts do match.");
                int index = 1;
                while(index <= prepMetaData.getColumnCount()) {
                    System.out.println("Prep Column "+prepMetaData.getColumnName(index)+" Size "+prepMetaData.getColumnDisplaySize(index));
                    System.out.println("Comm Column "+commMetaData.getColumnName(index)+" Size "+commMetaData.getColumnDisplaySize(index));
                    index++;
                }
            }
            s.close();
 
            isMapped = !this.preparedStatement.execute();
 
        } catch (DataTruncation dt) {
        
            Logger.getLogger(AbstractMapping.class.getName()).log(Level.SEVERE, null, dt);
            
        } catch (SQLFeatureNotSupportedException sfns) {
        
            Logger.getLogger(AbstractMapping.class.getName()).log(Level.SEVERE, null, sfns);
            
        } catch (SQLException ex) {
        
            Logger.getLogger(AbstractMapping.class.getName()).log(Level.SEVERE, null, ex);
        
        } catch (Exception e) {
        
            Logger.getLogger(AbstractMapping.class.getName()).log(Level.SEVERE, null, e);
            
        }
           
        System.out.println(isMapped);
        
        System.out.println("AbstractMapping.insertMappedData() end");
        return isMapped;
    }

Thanks for looking at this for me.
[ July 08, 2008: Message edited by: Darren Wilkinson ]

[Darren Wilkinson]

It's ok, I re-read the API with fresh eyes and noticed its says getMetaData() returns null if the underlying driver cannot return a ResultSetMetaData object.

I'm connecting to a MSSQL database using the jtds driver.

So the null return must be because this driver does cannot return a ResultSetMetaData object.

Thanks for taking a look and sorry for wasting anyones time.