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How to handle no request on servlet

I have a .jsp page where I've coded a form that submits some input to a servlet. The servlet manipulates the input and then sends a message to the same page. This is working fine, however, when I get back to the .jsp page, or in other words, when I get the answer from the servlet, the url that is visible in the browser contains the path to the servlet (e.g http:/index.jsp/servlet_name ), so, when I refresh the page, the browser redirects to the servlet and it get stuck because there was no get/post submission, so doGet() or doPost() are never active.. Is it possible to handle no get/post request in the servlet ? If not, how should I handle this problem ?
Ps: I'm using jquery mobile to build the pages (in the event of a possible solution with this framework)

I think you got it wrong. Even when you refresh, normally either doGet() / doPost() is activated. Your browser often asks you first if you're refreshing post requests.
What could be happening is your servlet is serving another request without form data, hence you get the impression it's not doing anything

Dynamically update JSP page via Servlet

I am new to web programming with Java. I have a Client/Server written (in Java) and I want updates from the Client to be sent from the Server to a web interface for a user to view. The timing of the updates will be random, but I want to be able to dynamically update a web page with new data without the browser having to refresh.
Hope this makes sense:
I've tried creating a Servlet that Observes (implements Observer) my Server (which extends Observable) for updates (Strings), however I don't know how to dynamically add these to a browser window. I have tried printing directly from the Servlet using PrintWriter out = response.getWriter(); in the doGet() method, but response.getWriter() is unavailable in the Servlet's update() method.
My initial thoughts were to use a JSP page (I need to eventually incorporate HTML/CSS) that receives the Observer updates from the Server but I'm not sure.
I've done some research into Comet/PUSH, but I'm not sure if this is what I need - perhaps a bit overkill? Any advice on how to achieve what I'm after would be greatly appreciated.

The most common way to do this is for the client to poll the server for changes. Use an AJAX request on the client side to poll an endpoint on your server.
You will then need to use JQuery / Javascript to update your web page with the new data retrieved from the AJAX request.
I would suggest using JQuery in theb rowser and using the AJAX function: http://api.jquery.com/jQuery.ajax/
It allows you to do a callback after the request and in that call back you can update the content of your web page with the data retrieved from the request.

You cannot update a web page from server, not without recurring to polling or push.
If you want a true push, then comet is not overkill, otherwise you can use a polling script on the web page.

Spring mvc result page and back browser button

On my MVC spring application I send a form to a page using post method to perform a search with some parameters. The results of the search is a list and, for every entry is possible to navigate to a details page. It works fine but, when an user try to come back to result page with back browser button (or a Javascript), I get an "Expire page" error. Refreshing the page, it rexecutes the post submit and it works fine.
To prevent this error I added
response.setHeader("Cache-Control", "no-cache");
to the search controller and everything works fine with Safari and Firefox but I get the same "Expire page" error when I try to execute the web application with IE (8 and 9).
What's the right way to go to a detail page and come back without getting any error?
thanks for your time!Andrea

The right way is to use GET instead of POST: searching is an idempotent operation which doesn't cause any change on the server, and such operations should be done with a GET.

Not expiring a POST request seems to undermine the very idea of a POST:
Per RFC 2616, the POST method should be used for any context in which a request is non-idempotent: that is, it causes a change in server state each time it is performed, such as submitting a comment to a blog post or voting in an online poll.
Instead, I would restructure how you view the detail records, maybe with an overlay DIV that doesn't refresh the underlying page that shows the results. With many modern web apps, using the BACK button can cause issues with page flow.

Run Servlet Without POST or GET

I am new to servlets, and would like to follow the Model2 paradigm by keeping all my "code" in servlets, and html/beans in jsp pages. But, is there a way to run a servlet when I access a jsp page without using a form submission. For example, I have a login page. If the user logs in and then somehow goes back to the login page I want to check for the existance of their session and automatically move them on to their welcome page. This is one real world example, but it seems it would come in handy to run code without having to submit a form for a multitude of reasons.

you dont have to submit a form to invoke a servlet. All you have to do is have the browser hit the url that is mapped to the servlet. That could happen when submitting a form, clicking a link, invoking an xhr, using curl or wget from the command line, etc.
Also, keeping all code in servlets is not good design. Your servlets should handle incoming requests, invoke business logic implemented in separate classes (for good modularity and testing purposes), and return the appropriate response.

If I recall correctly, in Model2, the user never navigates to (JSP) pages - only controllers (servlets). Trying to access a lower layer of code (a servlet) direcltly from a view (the page) is a violation of MVC/Model2.

How to handle authentication through AJAX with a java web app that uses form based login

I have a java web application running on WebSphere 7. The application uses form authentication method and part of the application accesses some protected resources using ajax requests. However, when the user's session expires, I am getting the login page in place of the content that is supposed to be refreshed by the ajax request.
Is there a good way to handle this problem? WebSphere returns a response status 200 with the login page so I cannot rely on that.
Maybe there is a way to tell the server that basic authentication should be used in certain circumstances but I don't know how.
I also thought of checking first if the session is new by making a request to unprotected resources first then return a certain status but it looks like a code smell solution...

This is how I handled it in a similar situation. In our case, the AJAX response is always JSON. When the login expires, the authentication filter always sends a login form in HTML. So I check the content-type like this,
if ((this.getHeader('Content-type') || '').include('application/json'))
If it's not JSON, I simply redirect to another protected page, which will trigger a full screen login and then that page will direct user back to the AJAX page.

You can send back some unique response or some error code(make sure you wont get this error code as valid response in any case) when the user session is not there to the Ajax call from WebSphere. And in the Ajax call method, on process response, check whether its error code.If its error code, redirect him to login page or do what ever and other case will be the valid data.