如何知道在Java应用程序中登录的用户是谁？

Question

I created a java application where login credentials are required to have access. How can I know which is the user who is logged in? Is there any way to know?

I do not know if they realized the doubt, if not I try to explain better.

----------------CODE-----------------

private void jBLoginActionPerformed(java.awt.event.ActionEvent evt) {                                        

String sql="select * from logins where username=? and password=? and idTipoLogin=?";
try{
    pst=(PreparedStatement) conexao.prepareStatement(sql);
    pst.setString(1, jTUser.getText());
    pst.setString(2, jPass.getText());
    pst.setString(3, jComboBoxTipoLogin.getSelectedItem().toString());

    rs=pst.executeQuery();
    if(rs.next()){

        String idTipoLogin = rs.getString("idTipoLogin"); 

        if (idTipoLogin.equals("Administrador")) {

            jTTarefasAdmin ah = new jTTarefasAdmin();
            ah.setVisible(true);

        }
         else {
            jTTarefasTecnico eh = new jTTarefasTecnico();
            eh.setVisible(true);

        }
        this.setVisible(false);
        }
    else{
        JOptionPane.showMessageDialog(null, "User Invalid");
          }
        }catch(Exception e){
    JOptionPane.showMessageDialog(null, e);
        }

}

The idea is to know what is the user who is logged into the system. As there are several users, I want to know specifically what is being accessed to login.

Answer 1

You can maintain a Collection of the logged in user, I think a HashMap would be good enough for your purpose.

 // This should be a class member
 Map<String, String> loggedInUsers = new HashMap<String, String>();

 // Now when user logs in add it to the HashMap
 loggedInUser.put(jTUser.getText(), jTUser.getText());

 // When a user logs out remove the user from the Map
 loggedInUser.remove(jTUser.getText());

If you just want a plain list of Users then you can store them in an ArrayList.

 List<String> loggedInUsers = new ArrayList<String>();
 loggedInUser.add(jTUser.getText());

Answer 2

From what I understood, you have one system that does the authentication of the user and the same user has access to other systems. On these other systems you want to know who the user is.

You could do this: Once the user is authenticated, create a unique id and put that in the session. Then access the session every time you need to know if the user is logged in. For other systems, pass that unique id to the system and allow them to query for the user.

Flow: 1. User logs in 2. System creates a unique id 3. Move that id with every request the user makes to other systems 4. On the other systems, allow them to access the authentication server and query based on the id.

This is a lot to do manually and there are plenty of systems out there that handle it all for you.

Links to get you started

http://en.wikipedia.org/wiki/Single_sign-on

http://en.wikipedia.org/wiki/Federated_identity