How to Logout of an Application Where I Used OAuth2 To Login With Google?

You can log out and redirect to your site:

var logout = function() {
    document.location.href = "https://www.google.com/accounts/Logout?continue=https://appengine.google.com/_ah/logout?continue=http://www.example.com";
}

For me, it works (java - android)

void RevokeAcess()
{
    try{
    HttpClient client = new DefaultHttpClient();
    HttpPost post = new HttpPost("https://accounts.google.com/o/oauth2/revoke?token="+ACCESS_TOKEN);
    org.apache.http.HttpResponse response = client.execute(post);
    }
    catch(IOException e)
    {
    }
    CookieManager.getInstance().removeAllCookie(); // this is clear the cookies which tends to same user in android web view
}

You have to call this function in AsyncTask in android

To logout from the app only but not the Gmail:

window.gapi.load('auth2', () => {
      window.gapi.auth2
        .init({
          client_id:
            '<Your client id configired on google console>'
        })
        .then(() => {
          window.gapi.auth2
            .getAuthInstance()
            .signOut()
            .then(function() {
              console.log('User signed out.');
            });
        });
    });

I'm using above in my ReactJs code.

You can simply Create a logout button and add this link to it and it will utimately log you out from the app and will redirect to your desired site:

https://appengine.google.com/_ah/logout?continue=http://www.YOURSITE.com

just toggle YOURSITE with your website

This works to sign the user out of the application, but not Google.

var auth2 = gapi.auth2.getAuthInstance();
auth2.signOut().then(function () {
  console.log('User signed out.');
});

Source: https://developers.google.com/identity/sign-in/web/sign-in

Ouath just makes the Google instance null, hence it you out of Google. Now that's how the architecture is made. Logging out of Google, if you Logout of your app is a dirty work, but can't help if the requirement stipulates the same. Hence add the following to your signOut() function. My project was an Angular 6 app:

document.location.href = "https://www.google.com/accounts/Logout?continue=https://appengine.google.com/_ah/logout?continue=http://localhost:4200";

Here localhost:4200 is the URL of my app. If your login page is xyz.com then input that.

this code will work to sign out

    <script>
      function signOut() 
      {
        var auth2 = gapi.auth2.getAuthInstance();
        auth2.signOut().then(function () {   
        console.log('User signed out.');   
        auth2.disconnect();   
      }); 
        auth2.disconnect();
      } 
    </script>

I hope we can achieve this by storing the token in session while logging in and access the token when he clicked on logout.

    String _accessToken=(String)session.getAttribute("ACCESS_TOKEN");
    if(_accessToken!=null)
    {
        StringBuffer path=httpRequest.getRequestURL();
        reDirectPage="https://www.google.com/accounts/Logout?
        continue=https://appengine.google.com/_ah/logout?
        continue="+path;
    }
    response.sendRedirect(reDirectPage);

It looks like Google recently broke something with their revoke stuff (it's started returning 400 errors for us). You now have to call

auth2.disconnect();

In our case we then have to wait a couple of seconds for the disconnect call to complete otherwise the sign-in code will re-authorise before it's done. It'd be good if google returned a promise from the disconnect method.

If any one want it in Java, Here is my Answer, For this you have to call Another Thread.

1. Try this code, if you are using onSignIn() function
2.
        <script src="https://apis.google.com/js/platform.js?onload=onLoad" async defer></script>
       <script>
       function signOut() {
       onLoad();
       var auth2 = gapi.auth2.getAuthInstance();
       auth2.signOut().then(function () {
       console.log('User signed out.');
       if(auth2.isSignedIn)
       {
          auth2.isSignedIn.set(false);
       }
       });
       }
       function onLoad() {
          gapi.load('auth2', function() {
            gapi.auth2.init();
          });
        }
        </script>