JMenuItem displays an empty Jframe when clicked

Question

I am writing a java swing application that collects data from textfields and stores it in a database. I have a JmenuItem that i want to use to display the data in the database. I have a class that collects the data from the database and inserts the data in the jtable. The class extends jframe. Now the problem i have is executing that class from the jmenuitem. When i click the jmenuitem it displays an empty jframe without the table.

here is the code for the class with the jtable. The class is Reports2

 public class Reports2 extends JFrame {
Connection con = null;
Statement st;
ResultSet rs;
public static void main(String[]args) throws Exception {


    try {

        Connection con= null ;
        Statement st;
        ResultSet rs;
        String url = "jdbc:mysql://localhost:3306/first";
    String user = "root";
    String password = "Admin123";
    try{
    con = DriverManager.getConnection(url,user,password);

        st = con.createStatement();
        String qry = "SELECT * FROM request";
        rs = st.executeQuery(qry);
        JTable table = new JTable(buildTableModel(rs));
        JFrame frame = new JFrame("Reports");
        frame.setSize(800, 700);
        frame.add(table);
        frame.setVisible(true);



    } catch (SQLException ex) {
        Logger.getLogger(Reports2.class.getName()).log(Level.SEVERE, null, ex);
    }
}catch(Exception e){


}}


public static DefaultTableModel buildTableModel(ResultSet rs) throws Exception{
ResultSetMetaData  metaData =  rs.getMetaData();
    Vector<String> columnNames = new Vector <String>();
    int columnCount = metaData.getColumnCount();
    for(int column = 1; column<=columnCount;column++){
    columnNames.add(metaData.getColumnName(column));
    }
    Vector<Vector<Object>> data = new Vector<Vector<Object>>();
    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);
}

}

Here is the code of the jmenuitem. The Jmenuitem variable name is get_reports.

private void get_reportActionPerformed(java.awt.event.ActionEvent evt) {                                           
Reports2 report = new Reports2();
report.setSize(800, 700);
report.setVisible(true);

Answer 1

• You don't need a main method in your Reports2 class. You main frame class already has a main to launch from. Take out the main method and wrap everything from that main in a Report2 constructor

• Your Reports2 class is already a JFrame yet you are creating another JFrame. Don't do that. instead just add to the class JFrame

  JTable table = new JTable(buildTableModel(rs));
  //JFrame frame = new JFrame("Reports");         <--- take this out
  //frame.setSize(800, 700);                      <--- don't set size, just pack
  setTitle("Reports");                            <--- set title
  add(new JScrollPane(table));                    <--- add to scrollpane
  pack();                                         <--- pack
  setVisible(true);                               <--- set visible
  

  Notice how I took out the JFrame, since the class is already a JFrame

• As seen above, I use .pack() which is preferred rather than setting the size

• And lastly, all you need to do in the actionPerformed is instantiate the Reports2, that's it

  private void jMenuItem1ActionPerformed(java.awt.event.ActionEvent evt) 
  {                                           
      Report2 report = new Report2();
  } 
  

I ran it, and it works fine with the above mentioned fixes. Given your SQL is correct, it should run for you also.

---

Side Note: NEVER, EVER swallow your exceptions

} catch (Exception ex) {

}

Put something meaningful that will allow you to see what exceptions are being thrown if any.

} catch (Exception ex) {
    ex.printStackTrace();
}

---

Also I would consider using a JDialog (instead of a second JFrame) as you can control its modality. It's just as easy to create a JDialog as it is to create a JFrame. It's almost the exact same process