request.getServletPath() returned null from Spring MVC - spring

Question

I made a filter to capture HttpServletRequest sevlet path from all requests
#Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest)req;
HttpServletResponse response = (HttpServletResponse)res;
// debug to see the output
String path = request.getServletPath();
filterChain.doFilter(request, response);
}
There is a URL in jsp that has no controller or view mapped to it
<div>
<spring:url value="/app" var="app_url" htmlEscape="true"/>
<spring:message code="label_3rd_app" />
</div>
However, when click on the url while debugging on the filter, I see request.getServletPath() value from two request:
/null
/null/app
My question is why request.getServletPath() never returns /app instead?

Answer 1

You're getting null because
request.getServletPath();
is for Servlets, and you're doing it inside a Filter. To get it in a Filter you have to manually build it like this:
HttpServletRequest request = (HttpServletRequest) req;
String path = request.getRequestURI().substring(request.getContextPath().length());
more info why:
How to get request URI without context path?

Answer 2

Mr. Lalibertes solution is not working correctly as the result of getRequestURI is uri-encoded and getServletPath is not.
Better use Springs UrlPathHelper for getting the servlet path in such situations.
new org.springframework.web.util.UrlPathHelper().getPathWithinApplication(servletRequest);
This method delivers the uri-decoded servlet path as getServletPath would have - if it would'nt be null.

Answer 3

For people coming to this question just because your context path was null (like me): I was calling request.getContextPath() in a background thread.
The request then became 'out of scope', if I understand this bug report discussion correctly: https://bugs.eclipse.org/bugs/show_bug.cgi?id=401768
Also, I know I'm not supposed to use normal threads in servlet environments, but use Executor instead. But the problem would probably remain: https://developer.jboss.org/thread/232135.
Solution was to extract all needed info from the request before handing off to background thread.