Should I put connection.close() on all finaly in java

Question

Should I put connection.close() inside finally on try catch block? I tried to put connection.close() but i got and error "java.lang.NullPointerException"

here is the code on logging in is it Good to put rs.close() and pst.close() in every statement likeso below i insert it becuz if it is not there something pop up like database is locked..

Login

if(evt.getKeyCode()==KeyEvent.VK_ENTER){
        String sql = "select * from User_Table\n" +
                 "inner join Role_Table on User_Table.Role_ID=Role_Table.Role_ID\n" +
                 "where Username = ? and Password = ? and Role_Name = ?";
    try {
        pst = conn.prepareStatement(sql);
        pst.setString(1, jTextField1.getText());
        pst.setString(2, jPasswordField1.getText());
        pst.setString(3, (String) RoleComboBox.getSelectedItem());

        rs=pst.executeQuery();
    if(rs.next()){
        String A = rs.getString("First_Name");
        String B = rs.getString("Role_Name");
    if(RoleComboBox.getSelectedItem().toString().equals("Admin")){
        JOptionPane.showMessageDialog(null, "Hello "+B+" "+A,"Successfully Login",JOptionPane.INFORMATION_MESSAGE);
        rs.close();
        pst.close();
        AdminPortal AP = new AdminPortal();
        AP.setVisible(true);
        this.dispose();
    .... //and so on

    }else if(RoleComboBox.getSelectedItem().toString().equals("Laboratorist,EO")){
        JOptionPane.showMessageDialog(null, "Successfully Login");
        rs.close();
        pst.close();
    }}
    else{
        JOptionPane.showMessageDialog(null, "Incorrect Input","Error",JOptionPane.ERROR_MESSAGE);
    }
    }catch(Exception e){
        JOptionPane.showMessageDialog(null, e);
    }finally {
       try {
           rs.close();
           pst.close();
           conn.close();
       }catch(Exception e){

       }
    }
    }

here is the code on logout when I didn't put the con.close() there my system works fine but when i logout and login again it starts to got some error like database is locked but when I put the con.close()" i got some error "java.lang.NullPointerException"

Logout

int YesOrNo = JOptionPane.showConfirmDialog(null, "Do you want to logout?", "Logout",JOptionPane.YES_NO_OPTION);
    if(YesOrNo == 0){
        try {
            dispose();
            LoginForm LF = new LoginForm ();
            LF.setVisible(true);
            AddPatient.getObj().dispose();
            AddAppointments.getObj().dispose();
        } catch (Exception ex) {

        }finally{
            try{
                rs.close();
                pst.close();
                conn.close();
            }catch(Exception e){

            }
        }
    }else{

    }

i hope someone can help

Use try-with-resources. – Martin Heralecký Jan 03 '19 at 13:14 — Martin Heralecký, Jan 03 '19 at 13:14

score 0 · Answer 1 · answered Jan 03 '19 at 13:12

0

If you have no further use of the connection you can close it on finally block.

answered Jan 03 '19 at 13:12

Abdul Rahman Shamair

580
1
11
22

i got an error sayin java.lang.NullPointerException i already put the conn.close() in every finally on try catch block – Sieccc Jan 03 '19 at 13:50
kindly share the code for your error as there can be many cases in which NullPointerException can occur. – Abdul Rahman Shamair Jan 04 '19 at 06:41
Null pointer generally occur when you are accessing the variable before the initialization. – Abdul Rahman Shamair Jan 04 '19 at 06:43
or in your case it can be due to the fact that you close connection with your database, using con.close() in finally block and than after that you are again accessing the "con" variable elsewhere in your code. – Abdul Rahman Shamair Jan 04 '19 at 06:45
again sharing your code will help a lot :-) – Abdul Rahman Shamair Jan 04 '19 at 06:46
I added the codes now thank you – Sieccc Jan 04 '19 at 09:38
kindly upload your whole project on github and pass the link. – Abdul Rahman Shamair Jan 07 '19 at 17:06

score 0 · Answer 2 · answered Jan 03 '19 at 13:12

0

Yes, all types of connections should be closed in finally block.

answered Jan 03 '19 at 13:12

TheSprinter

1,523
17
30

i got an error sayin java.lang.NullPointerException i already put the conn.close() in every finally on try catch block – Sieccc Jan 03 '19 at 13:50
1

close connection if there is no further use of that connection. i think in your case you closed before its final use. – TheSprinter Jan 03 '19 at 16:59

Should I put connection.close() on all finaly in java

2 Answers2