如何在Servlet中获取HTML请求URL

Question

Am using a HTML form like this,

<form action="/myservlet?userid=12345" method="post" enctype="multipart/form-data">
<input type="file" name="file">
<input type="submit" value="Submit">
</form>

And the path of this HTML form is say for example, http://www.mywebapp.com/sample.html

In my servlet when i use the String url = req.getRequestURL().toString(); and printout the string it prints the form action URL http://www.mywebapp.com/myservlet?userid=12345 and not the HTML URL.

The expected HTML URL : http://www.mywebapp.com/sample.html (from here only i request and i need this URL)

Can anyone suggest me how to get the HTML url path in the servlet.

Answer 1

If I understand you correctly you want to get the URL of one request (the request that loaded the html) when you make a subsequent request (the form post).

HTTP is stateless and therefore there is no way to reliably do this.

Needing to do this has a bit of a whiff of a code smell about it, but if you really need the URL you're going to have to pass the URL as a hidden input in the form . There's various ways to do this, whether you use JSP/JSTL or do something client side with JavaScript, but basically you trying to get a form like this:

<form action="/myservlet?userid=12345" method="post" enctype="multipart/form-data">
   <input type="file" name="file">
   <input type="hidden" name="url" value="http://www.mywebapp.com/sample.html"/>
   <input type="submit" value="Submit">
</form>

Answer 2

It's some kind of problem, because user loaded, as you write, page http://www.mywebapp.com/sample.html and at this initial request you will get from request.getRequestURL().toString exactly this value

On next request with use a form (from client side) url is not anymore this http://www.mywebapp.com/sample.html but the one specified in form action atributte.

There are many suggestion of passing hidden value in form or something like this, but you can easly make use of simple HTTP. Everytime when you do GET request you get a new URL in your browser (or other client) window but when you do POST request URL in browser doesn't change. So now in your code if you know that this is a POST request and you want to get page from where this request is comming you can easly read it from Http Header "Referer" as:

String URLfromWherePostWasMade = request.getHeader("Referer"); 

This should work the same as all "hidden field" examples

Answer 3

Your 'HTML Page' is called the "Referrer" and you can get it in this way

HttpServletRequest.getHeader("Referer");

It will return the page where the form has been submitted, in your case

http://www.mywebapp.com/sample.html