/******************************************************************************/
/* File: datamanager.beh                                                      */
/*                                                                            */
/* Describes the class that actually implements operations for connecting to  */
/* the intended database, executing a specified SQL statement, and finally    */
/* returning the result.  For an Insert request, it throws an exception in    */
/* case of a failure or prints an ok message.  For a Query request, it throws */
/* an exception if there is a failure, or returns a vector of vectors         */
/* representing the rows and columns.                                         */
/*                                                                            */
/******************************************************************************/

DataManager
{
    {{
    private ConnectionArgs myconnArgs;
// java.sql type needed for database processing
    private Connection connection;

    public DataManager(ConnectionArgs connArgs)
    {
	myconnArgs = connArgs;
    }


// used to extract data out of the specified database

    public Vector getData(String SQLStmt) throws Exception
    {

	Vector rows = new Vector(); // used for the returned data, a vector of vectors
	
	initializeConnection();

	// getting the data out of the database

      // java.sql types needed for database processing
      Statement statement;
      ResultSet rs;
      
      try {
         statement = connection.createStatement();
         rs = statement.executeQuery( SQLStmt );
	   rows = processResultSet( rs );
         statement.close();
      }
      catch ( SQLException sqlex ) {sqlex.printStackTrace();}

	shutdownConnection();

	return rows;
    }





// initializing the connection

    private void initializeConnection() throws SQLException
    {
      try {
         Class.forName( myconnArgs.driver );
         connection = DriverManager.getConnection(myconnArgs.url, myconnArgs.userid, myconnArgs.password );
      } 
      catch ( ClassNotFoundException cnfex ) {
         System.err.println("Failed to load JDBC driver." ); cnfex.printStackTrace();
         System.exit( 1 );  // terminate program
      }
      catch ( SQLException sqlex ) { System.err.println( "Unable to connect" );sqlex.printStackTrace();}

    }

// shutting down the connection

    private void shutdownConnection() throws SQLException
    {
      try {	connection.close(); }
      catch ( SQLException sqlex ) {System.err.println( "Unable to disconnect" );sqlex.printStackTrace();}
    }



// processing the data returned by the database

    private Vector processResultSet( ResultSet rs ) throws SQLException
    {
	Vector rows = new Vector();

	// position to first record
      boolean moreRecords = rs.next();  

	// If there are no records, return an empty Vector
      if ( ! moreRecords ) return (new Vector());

      try {

	// get column heads 
        ResultSetMetaData rsmd = rs.getMetaData();

	// get row data
         do { rows.addElement( getNextRow( rs, rsmd ) ); 
         } while ( rs.next() );
      }
      catch ( SQLException sqlex ) {sqlex.printStackTrace();}

	return rows;

     }



// get one row at a time as a Vector

   private Vector getNextRow( ResultSet rs, ResultSetMetaData rsmd ) throws SQLException
   {
      Vector currentRow = new Vector();
      
      for ( int i = 1; i <= rsmd.getColumnCount(); ++i )
         switch( rsmd.getColumnType( i ) ) {
            case Types.NULL: currentRow.addElement(null);
               break;
            case Types.VARCHAR: currentRow.addElement(rs.getString(i));
               break;
            case Types.INTEGER: currentRow.addElement(new Long(rs.getLong(i)));
               break;
            case Types.REAL: currentRow.addElement(new Float(rs.getFloat(i)));
               break;
            default: 
               System.out.println( "Type was: " + rsmd.getColumnTypeName( i ) );
         }
      
      return currentRow;
   }


// used to insert data into the specified database

    public void putData(String SQLStmt) throws Exception
    {
	initializeConnection();

	// inserting the data into the database

      try {
         Statement statement = connection.createStatement();
         int result = statement.executeUpdate( SQLStmt );
         if ( result == 1 ) System.out.println( "\nInsertion successful\n" );
           else System.out.println( "\nInsertion failed\n" );

         statement.close();
      }
      catch ( SQLException sqlex ) {
		System.out.println("\nInsert Statement caused an error: Check if entry already exists!\n\n");
		sqlex.printStackTrace();}

	shutdownConnection();
	return;
    }

    }}
}