Setting getColumnClass in a JTable with a ResultSet TableModel

Question

I have a problem. I create a DefaultTableModel like this -->

public static DefaultTableModel buildTableModel(ResultSet rs)
        throws SQLException {

    ResultSetMetaData metaData = rs.getMetaData();

    // names of columns
    Vector<String> columnNames = new Vector<String>(1,1);
    int columnCount = metaData.getColumnCount();

    for (int column = 1; column <= columnCount; column++) {   
        columnNames.add(metaData.getColumnName(column));
    }

    // data of the table
    Vector<Vector<Object>> data = new Vector<Vector<Object>>(10,2);

    while (rs.next()) {
        Vector<Object> vector = new Vector<Object>();

        for (int columnIndex = 1; columnIndex <= columnCount; columnIndex++) {
            vector.add(rs.getObject(columnIndex));
        }
        data.add(vector);
    }

    return new DefaultTableModel(data, columnNames);

}

The ResulSet is filled with some Data of a MySQL Database. After that I create a JTable with the DataModel and override set the tableproperties:

this.table = new JTable(buildTableModel(this.rs)){
        // Make Cells uneditable
            @Override
            public boolean isCellEditable(int row, int column) {  
                if(table.getColumnName(column).contains("key")) return false;
                if(table.getColumnName(column).contains("datum")) return false;
                if(table.getColumnName(column).contains("user")) return false;
                return true;               
            }

            @Override
            public Class<?> getColumnClass(int columnIndex) {
                Class<?> classType;
                if(columnIndex == 1)
                    classType = Boolean.class;
                else
                    classType = String.class;
                return classType;
            }
        };

If I don't use the second part (@Override getColumClass), it works fine, but if I add the getColumnClass part, I get this errormessage:

java.lang.String cannot be cast to java.lang.Boolean

The field contains "true" / "false". I'm doing something pretty wrong, but I have really no idea what exactly ;-( Can someone help me out with that?

Thanks a lot

Edit: I changed the buildTableModel to this:

public static DefaultTableModel buildTableModel(ResultSet rs)
        throws SQLException {

    ResultSetMetaData metaData = rs.getMetaData();


    // names of columns
    Vector<String> columnNames = new Vector<String>(1,1);
    int columnCount = metaData.getColumnCount();

    for (int column = 1; column <= columnCount; column++) {
        columnNames.add(metaData.getColumnName(column));
    }

    // data of the table
    Vector<Vector<Object>> data = new Vector<Vector<Object>>(10,2);

    while (rs.next()) {
        Vector<Object> vector = new Vector<Object>();

        for (int columnIndex = 1; columnIndex <= columnCount; columnIndex++) {

            if(rs.getObject(columnIndex).toString().equals("true"))
                vector.add(Boolean.TRUE);
            else        
            if(rs.getObject(columnIndex).toString().equals("false"))
                vector.add(Boolean.FALSE);
            else
                vector.add(rs.getObject(columnIndex));
        }

        data.add(vector);
    }

    return new DefaultTableModel(data, columnNames);

}

and now it works ;-)

Answer 1

metaData.getColumnType can returns (note very simple matrix and hardcoded with minimum effort)

    public Class getColumnClass(int column) {
        int type;
        try {
            type = metaData.getColumnType(column + 1);
        } catch (SQLException e) {
            return super.getColumnClass(column);
        }
        switch (type) {
            case Types.CHAR:
            case Types.VARCHAR:
            case Types.LONGVARCHAR:
                return String.class;
            case Types.BIT:
                return Boolean.class;
            case Types.TINYINT:
            case Types.SMALLINT:
            case Types.INTEGER:
                return Integer.class;
            case Types.BIGINT:
                return Long.class;
            case Types.FLOAT:
            case Types.DOUBLE:
                return Double.class;
            case Types.DATE:
                return java.sql.Date.class;
            default:
                return Object.class;
        }
    }

Answer 2

You're trying to assign a String value to a Boolean column (in your Swing table). Just make sure that the types of the data (the data model) retrieved match those of the table data model.