Question

Im made a sort of autentication on my web application using GWT. So i make these functions in the GWTServiceImpl Class :

public class PageMenuLogin extends FlowPanel {
    public PageMenuLogin() {
        PageMenuLogin.getService().isSetSession(new AsyncCallback<String>() {
            @Override
            public void onFailure(Throwable caught) {
                InlineLabel err=new InlineLabel();
                err.setText("Errore Di Connessione");
                PageMenuLogin.this.add(err);
            }

            @Override
            public void onSuccess(String result) {
                if(result.compareTo("")==0) {
                    designLogin();
                } else {
                    designLogout(result);
                }
            }
        });
    }

    public final void designLogin() {
        final InlineLabel menu_err=new InlineLabel("");
        menu_err.setStyleName("menu_err");
        this.add(menu_err);        

        Button menu_login_button=new Button("Login");
        this.add(menu_login_button);

        menu_login_button.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
                getService().checkLogin("nickname", "password", new AsyncCallback<Boolean>() {
                    @Override
                    public void onFailure(Throwable caught) {
                        menu_err.setText("Comunicazione Fallita");
                    }

                    @Override
                    public void onSuccess(Boolean result) {
                        if (result) {
                            // I LOAD THE PROFILE PAGE
                        } else {
                            menu_err.setText("Username e password non validi");
                        }
                    }
                });
            }
        });
    }
}

********************************************************************************

public class GWTServiceImpl extends RemoteServiceServlet implements GWTService {
    HttpServletRequest request;
    HttpSession session;
    public String isSetSession() {
        this.request = this.getThreadLocalRequest();
        this.session=this.request.getSession();

        if(this.session.getAttribute("nickname")==null) {
            return "";
        } else {
            return (String)this.session.getAttribute("nickname");
        }
    }

    public boolean checkLogin(String username, String password) {
        if("i check on the database if the user exist") {
            this.session.setAttribute("nickname", value);
            return true;
        } 

        return false;
    }
}

On client side, i call the GWTServiceImpl functions (server side), i check the return values and i do some operations.

Is this the right way to work with session on GWT? Any suggestion/tips/helps would be appreciated 🙂

Thanks for your time!!!

EDIT

New GWTServiceImpl :

public class GWTServiceImpl extends RemoteServiceServlet implements GWTService {

    HttpSession session;

    public String isSetSession() {
        HttpSession session=getThreadLocalRequest().getSession();
        if(session.getAttribute("nickname")==null) {
            return "";
        } else {
            return (String)session.getAttribute("nickname");
        }
    }

    public boolean checkLogin(String nickname, String password) {
        HttpSession session=getThreadLocalRequest().getSession();
        Database mydb=Configuration.getDatabase();
        mydb.connetti();

        // faccio md5 ed escape
        String log_check_user=nickname;
        String log_check_pass=password;

        // controllo che l'utente esista
        ArrayList<String[]> db_result=null;
        db_result=mydb.selectQuery("SELECT nickname FROM users WHERE  nickname='"+log_check_user+"' AND password='"+log_check_pass+"'");
        mydb.disconnetti();
        if(!db_result.isEmpty()) {
            session.setAttribute("nickname", nickname);
            return true;
        }

        return false;
    }

    public boolean checkLogout() {
        HttpSession session=getThreadLocalRequest().getSession();
        session.invalidate();
        return true;
    }
}

Answer 1

Looks like it should work. I do a lot of work with GWT, although I often forego the use of the RemoteServiceServlet in favour of passing data back and forth via JSON.

A few suggestions, though. When you’re calling a method or field within the same class, you don’t need to include the this keyword. It doesn’t hurt, but tends to make your code longer than it needs to be. Feel free to keep it though, if you find it makes things clearer for you.

Also, unless you’ve got methods that actually use the request, you don’t need to create the request object; you can just do

session = getThreadLocalRequest().getSession();

A final suggestion: Since you’re using the session in more than one method, it might be a good idea to initialize it right away; So, instead of initializing it in isSetSession(), you could just write HttpSession session = getThreadLocalRequest().getSession();, or initialize it in the class’s constructor. As it stands now, if you happen to call checkLogin() before isSetSession(), you’ll get a NullPointerException since session hasn’t yet been initialized.