Migrate wiki articles to Vaadin documentation (#9912)

* Vaadin Tutorial For Swing Developers
* Setting And Reading Session Attributes
* Enabling Server Push
* Cleaning Up Resources In A UI
* Sending Email From Java Applications
* Using Parameters With Views
* Optimizing Sluggish UI
* Configuring Push For Your Enviroment
* Setting And Reading Cookies
* Using Polling
* Creating An Application That Preserves State On Refresh
* Finding The Current UI And Page And Vaadin Session
* Sending Events From The Client To The Server Using RPC
* Handling Logout
* Remember To Set The Locale
* Scalable Web Applications
* MVC Basics In ITMill Toolkit
* Access Control For Views
* Customizing The Startup Page In An Application

1 files changed, 29 insertions, 0 deletions

diff --git a/documentation/articles/HandlingLogout.asciidoc b/documentation/articles/HandlingLogout.asciidoc
new file mode 100644
index 0000000000..e83ef7705b
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+++ b/documentation/articles/HandlingLogout.asciidoc
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+[[handling-logout]]
+Handling logout
+---------------
+What should happen the user wants to log out from a Vaadin application
+depends on how the user is stored when the user logged in.
+
+If the user information is stored in the `VaadinSession`, that session
+should be closed using its `close()` method. If the information on the
+other hand is stored in the `HttpSession` or `PortletSession`, then that
+session should be invalidated using the `invalidate()` method in Vaadin's
+`WrappedSession` that represents either underlying session type.
+
+Aside from removing the user's information, the user should also be
+redirected to a logout page to avoid keeping the UI open in the browser
+after all server-side information about is has been removed.
+
+[source,java]
+....
+private void logout() {
+    // Close the VaadinServiceSession
+    getUI().getSession().close();
+
+    // Invalidate underlying session instead if login info is stored there
+    // VaadinService.getCurrentRequest().getWrappedSession().invalidate();
+
+    // Redirect to avoid keeping the removed UI open in the browser
+    getUI().getPage().setLocation(getLogoutPageLocation());
+}
+....