Vaadin Spring - Prevent to navigate back

Vaadin 6 / 7 / 8
1

Hello everyone,

Im currently working on Spring Application and found it quite good stuff, but i faced a problem and can’t solve it.
I have Navigator with SpringViewProvider binded and UI class is also @PreserveOnRefresh. Currently viewProvider contains 3 views (“”, “login”, “viewA”).
After successful navigation on “login” view, i’m able to press back button and return to “login” view again(which is not good). I tried so far on “viewA” enter use Page.getCurrent().setUriFragment(uri, false);
And this didn’t worked out.
How to solve this problem?

2

You can control access to views by using a ViewChangeListener:

https://vaadin.com/wiki/-/wiki/Main/Access+control+for+views

3

Note that instead of showing an error, you can also just use navigator.navigateTo to navigate to some other view than your login view.

-Olli

4

Hello,
@Tobias Demuth, i forgot to mention that i already use ViewChangeListener. My Bad.

VIEW_TOKENS:

String HOME = ""; String SIGNIN = "login"; String VIEWA = "viewA"; List<String> AVAILABLE_TOKENS = Arrays.asList( HOME, SIGNIN, VIEWA ); ViewListener:

public class MyViewListener implements ViewChangeListener {
    @Override
    public boolean beforeViewChange(ViewChangeEvent event) {
        if(ViewTokens.AVAILABLE_TOKENS.contains(
                UI.getCurrent().getNavigator().getState())) {
            return true;
        }
        return false;
    }
    @Override
    public void afterViewChange(ViewChangeEvent event) {
    }
}
5

@Olli your suggestion i’ve tried in a first place, but for a some reason it won’t work at all. As i said i tried also like this idea:

if(getUI().getNavigator().getState() == ViewToken.ViewA) {
     Page.getCurrent().setUriFragment(ViewToken.SIGNIN, false);
}

But it failed.

6

Can you debug it a little: Are you hitting the beforeViewChange/afterViewChange methods when you navigate using the back button at all?

-Olli

7

@Olli Yes, I am. If i hit the view that doesnt specified in a VIEW_TOKENS, then it wont navigate to that view and uriFragment is changed to prvious state. For example:

case 1:
Initially is given: http://localhost:8090/#!signin
what trying to do: change ‘signin’ on ‘viewthatdoesntspecified’
Result: View change doesn’t happen, uri remains as it was ( see ‘Initially’)

case 2:
Initially is given: http://localhost:8090/#!signin
what trying to do: change ‘signin’ on ‘viewA’
Result: View changes accordingly,but on back button press, it returns to previous state (at this point: ‘signin’)

To sum up, my point is to make case 1 work everytime, also include case 2 working properly

I assume, i got your question correctly

8

As for case 1:

public boolean beforeViewChange(ViewChangeEvent event) { if(ViewTokens.AVAILABLE_TOKENS.contains( UI.getCurrent().getNavigator().getState())) { return true; } return false; } If I’m understanding your case correctly, you’re trying to navigate somewhere that doesn’t exist in AVAILABLE_TOKENS, so you end up returning false from the beforeViewChange method on line 6, which means that you’re
blocking the view change completely
. Instead, you could just set up an Error View with navigator.setErrorView(new ErrorView()) , where the ErrorView can show you either an error page (“view doesn’t exist”) or redirect you to, for example, the login view. For the latter possibility, see below:

case 2:
In your LoginView’s
enter
 method, check that if you’re already logged in. How you do this depends on how your authentication is set up - a simple way would be to use a cookie. If you’re logged in, just tell navigator to take you to whereever you want to with navigator.navigateTo(…).

-Olli

9

@Olli Thank you so much for assist, i finally resolve the problem. i found pretty easy solution besides cookies ( found only partial solution of that) . And yes, about case 2 - I was thinking exactly the same as you did. After few hours i made thing get working! :wink:

Sorry for soo ‘fast’ response[quote=Olli Tietäväinen]
As for case 1:

public boolean beforeViewChange(ViewChangeEvent event) { if(ViewTokens.AVAILABLE_TOKENS.contains( UI.getCurrent().getNavigator().getState())) { return true; } return false; } If I’m understanding your case correctly, you’re trying to navigate somewhere that doesn’t exist in AVAILABLE_TOKENS, so you end up returning false from the beforeViewChange method on line 6, which means that you’re
blocking the view change completely
. Instead, you could just set up an Error View with navigator.setErrorView(new ErrorView()) , where the ErrorView can show you either an error page (“view doesn’t exist”) or redirect you to, for example, the login view. For the latter possibility, see below:

case 2:
In your LoginView’s
enter
 method, check that if you’re already logged in. How you do this depends on how your authentication is set up - a simple way would be to use a cookie. If you’re logged in, just tell navigator to take you to whereever you want to with navigator.navigateTo(…).

-Olli
[/quote]

10

Nice to hear that you got it working!

-Olli