Java: How to make a thread wait on IO from user and then proceed

Question

In a DbInterface class a function openDB() opens connection to a Oracle DB on a server. For security reasons the user has to enter their password in a JFrame textarea before the program can proceed with the connection. Now this Jframe has an action listener which waits for the user to enter the password and calls the OpenDBContinue() method.

Now the issue is: openDB() does not wait on Jframe IO to finish and assuming DB has been opened returns back control to the calling class (whoever called openDB()) and they go ahead and start quering the DB which obviously fails!

Now how do I make openDB() wait on Jframe IO to finish? Here is the code to give you an idea.

public void openDB(int inFileInx,String inRemoteDBURLFull) throws FileNotFoundException
{   
    if(this.password!=null)
        try
        {   openDBcontinue(inFileInx,inRemoteDBURLFull);
        }
        catch(Exception exp)
            {   DpmLogger.dtlException("SPDBInterfaceException:OpenDB", exp);
            }
    else {
            passwd  =       new JFrame();
            passwd.setLocation(SpdMain.bTabbedPanel.getWidth()/2,SpdMain.bTabbedPanel.getHeight()/2);
            passwd.setTitle("Enter Passwd for user "+username);
            JPasswordField p =new JPasswordField(10);
            p.addActionListener(this);
            p.setActionCommand(inFileInx+","+inRemoteDBURLFull);
            passwd.add(p);
            passwd.setPreferredSize(new Dimension(300,50));
            passwd.pack();
            passwd.setVisible(true);
            pass=new Thread(new Runnable()  
            {   
                public void run() {
                    DpmLogger.dtlTraceOut("The password thread has completed and has got password from the user",DpmLogger.TRACE_RARE,myId);
                }

            });

            try {
                    pass.join();
                } catch (InterruptedException e) 
                    {
                        DpmLogger.dtlTraceOut("Password thread unable to join",DpmLogger.TRACE_RARE,myId);
                    }

                DpmLogger.dtlTraceOut("Password thread now joined",DpmLogger.TRACE_RARE,myId);
        }

}


public void actionPerformed(ActionEvent e) 
{   JTextField p=(JTextField)e.getSource();
    if(password==null)
    password=p.getText();
    passwd.setVisible(false);

    String[] inVars=e.getActionCommand().split(",");
    try
    {   openDBcontinue(Integer.parseInt(inVars[0]),inVars[1]);
             pass.start();
    }
    catch(Exception exp)
    {   DpmLogger.dtlException("SPDBInterfaceException:OpenDB", exp);
    }
}

As you can see I am trying to make the method wait on a 'pass' thread with join(). The action listener starts the pass thread when IO finishes. But it does not work. OpenDB() returns without waiting on 'pass' to run. Is this because the method is not inside a thread? Do I have to make this DBInterface class extend Thread class? I am confused!

Answer 1

For security reasons the user has to enter their password in a JFrame textarea

For:

1. Convenience (and a possible solution) swap the JFrame for a modal dialog or JOptionPane. E.G. as seen in this answer.
   
2. Security use a JPassWordField instead of the 'textarea' as seen in the tutorial.
   

Answer 2

You could use a JDialog, but that would require you to manage the close operations (add buttons and mess about with states), or you could simply use a JOptionPane

Either (when set to modal) will cause the Event Dispatching Thread to pause execution at that point until they are closed.

public class TestDialog01 {

    public static void main(String[] args) {
        new TestDialog01();
    }

    public TestDialog01() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                PasswordPane pane = new PasswordPane();
                int result = JOptionPane.showConfirmDialog(null, pane, "Password", JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE);
                if (result == JOptionPane.OK_OPTION) {
                    // get the result...
                }

            }
        });
    }

    public class PasswordPane extends JPanel {

        private JTextField userName;
        private JPasswordField password;

        public PasswordPane() {
            userName = new JTextField(12);
            password = new JPasswordField(12);

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.insets = new Insets(2, 2, 2, 2);
            gbc.gridx = 0;
            gbc.gridy = 0;
            add(new JLabel("User Name:"), gbc);
            gbc.gridx++;
            add(userName, gbc);

            gbc.gridy++;
            gbc.gridx = 0;
            add(new JLabel("Password:"), gbc);
            gbc.gridx++;
            add(password, gbc);
        }

        public String getUserName() {

            return userName.getText();

        }

        public char[] getPassword() {

            return password.getPassword();

        }
    }
}

Check out How to Make Dialogs for more info