Displaying data in a table

[Donald King]

I am writing a simple application that retrieves data from an Access database and displays it in a table (JTable). I need to be able to repopulate the table with new rows from the database, based on user filtering requests.
I'm using the DefaultTableModel.setDataVector methods to do this, although I'm not sure this is the right thing to do. The Java documentation says:
"Because the JTable is now much easier to set up with custom models the DefaultTableModel is less useful than it was in previous releases. Instead of copying the data in an application into the DefaultTableModel, we recommend wrapping it in the methods of the TableModel interface and passing the real data to the JTable as above."
Unfortunately, there is no description on how to do this using the TableModel interface. In particular, there are no methods defined in TableModel for loading in vectors of data, just column at a time, which seems tedious. If I follow the documentations recommendation, how do I get data into the table?
- Don

[Cindy Glass]

This is a nice tutorial on tables:
http://www.utt.ro/upt/ac/tutorial/uiswing/components/table.html
This is the code for a simple table using a TableModel:
http://www.utt.ro/upt/ac/tutorial/uiswing/components/example-swing/SimpleTableDemo.java

[Donald King]

Thanks. The sample code you attached was almost identical to what I started with. But I ran into problems with the update. My application is retrieving rows using a default query from a database table and displaying them in the JTable. If the user chooses to change the query, I am going back to the db and populating the table with a new set of rows.
In order to have the new rows displayed, I need to update the JTable's TableModel. Using DefaultTableModel, I can reset the data through the setDataVector method. This operation causes the DefaultTableModel object to fire a message to the JTable to repaint itself. In the sample code you attached, if I change the data array, it won't repaint in the table automatically. How do I get this new data reflected in the table?
- Don

[Paul Bull]

Hey Donald,
I was working on a similar program recently and the following is what I did to get the data from the ResultSet into the JTable and
get it to repaint itself. I got this information from Ivor Horton's "Beginning Java2" (Wrox publishing) Ch.18.
A great book for beginning Java programmers.
The following code was put into a seperate class as an extension of AbstractTableModel. The purpose of this class is to implement a method (setResultSet) which takes a row from the ResultSet places it into a String array. The array is then placed into a vector. This is done in a while loop using the .next() method of
ResultSet until all the rows of the ResultSet are placed into the vector. Details are as follows:

 String[] columnNames = new String[0];  //empty array of names
 Vector dataRows = new Vector();        //empty vector of rows
 public void setResultSet(ResultSet results){
 //Make the data in the resultset available through the table    model interface  
  try{
    ResultSetMetaData metadata = results.getMetaData();
    //Get the number of columns
    int columns = metadata.getColumnCount();  
    //An array to hold the names
    columnNames = new String[columns];        
    //Get the column names
    for(int i = 0; i < columns; i++)
      columnNames[i] = metadata.getColumnLabel(i + 1);
    //Get all rows.
    dataRows = new Vector();
    String[] rowData;
    while(results.next()){
    //Create array to hold the data
      rowData = new String[columns];    
    //For each column  
      for(int i = 0; i < columns; i++) 
      //Retrieve the data item
        rowData[i] = results.getString(i + 1);  
      //Store the row in the vector
        dataRows.addElement(rowData);
   }
   //Signal the table there is new model data
   fireTableChanged(null);             }
   catch(SQLException sqle){
     System.err.println(sqle);
    }
  }
  public int getColumnCount(){
    //Return number of columns...
 return columnNames.length;
  }
  public int getRowCount(){
    //Return number of rows...
 if(dataRows == null)
   return 0;
 else
   return dataRows.size();
  }
  public Object getValueAt(int row, int column){
    //Return the value at position row, column...
 return ((String[])(dataRows.elementAt(row)))[column];
  }
  public String getColumnName(int column){
    //Return the name for the column...
    return columnNames[column] == null ? "No Name" 
    : columnNames[column];
  }
}

After this class is created another class is created to implement
the GUI to hold the JTable. The above mentioned class (being an extension of AbstractTableModel) is put into the JTable, thus the vector of query rows is loaded into the JTable.

  GetResults model; //instantiation of class that extends AbstractTableModel
  Statement statement; //Statement used to query database
  JScrollPane resultsPane; //Scrollpane used to hold JTable
//instantiation of the class that retrieves the ResultSet and puts it in the vector
  model = new GetResults(); //Name of class that extends   AbstractModelClass 
  JTable table = new JTable(model);
  table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
  resultsPane = new JScrollPane(table);
  model.setResultSet(statement.executeQuery("Whatever your query is�));

(edited by Cindy to format code)

[This message has been edited by Cindy Glass (edited February 22, 2001).]