Question

I have a Filter Servlet that filters request from a Servlet. I do not want to do something on a request for a Image, so I have for example this code:

if (baseURL.endsWith("png")) 
{
 chain.doFilter(servletrequest, servletresponse);
}

Which on the doFilter method of of the filter, I don’t do anything and just call chain.doFilter, I expected that the response image will be sent properly in the client however the Content-Type that comes back is "application/octet-stream" instead of "image/png"

Any idea why this happens?

Answer 1

I have a Filter Servlet that filters request from a Servlet. I do not want to do something on a request for a Image

The FilterChain#doFilter() does not prevent that the request ends up in your servlet if its URL pattern also matches the request URL. You seem to be thinking that this is the case. This is thus not correct.

If you do not want that image requests end up in your servlet, then you have to map the servlet on a more specific URL pattern. For example, /app/* instead of /*. Then you can filter the requests as follows:

if (httpServletRequest.getRequestURI().endsWith(".png")) {
    chain.doFilter(request, response);
}
else {
    request.getRequestDispatcher("/app" + httpServletRequest.getRequestURI()).forward(request, response);
}

The URL pattern of /* should not be used on servlets, but on filters only.

Further, the content type is by default already automatically determined based on the file extension. I assume that you really have a some.png resource, not a somepng resource as your initial endsWith() argument value would also match.

See also:

• How to access static resources when mapping a global front controller servlet on /*