What's the proper way to set the Location header for an HTTP 201 response in a Java Servlet application

Question

Consider the following code sending an HTTP 201 \"Created\" response to the client:

    String url = \"/app/things?id=42\"; // example
    response.setStatus(Htt         


        

Answer 1

Unfortunately, the servlet API does not provide a method which directly returns the absolute URL up to with the context root. For that I have several times had to use a combination of getRequestURL(), getRequestURI() and getContextPath().

String absoluteContextRootURL = request.getRequestURL().toString().replace(request.getRequestURI().substring(1), request.getContextPath());

Answer 2

Just send the absolute path. The restriction to an absolute URI is a known defect in RFC 2616 and will be fixed in HTTPbis (see http://trac.tools.ietf.org/wg/httpbis/trac/ticket/185).

Please note that RFC 7231 now includes relative URIs in the spec. See other answers for how to handle relative URIs.

Answer 3

Decided to go with Julian Reschke's advice and violate the spec! At least I added the following comment:

        /* Note: strictly speaking (per section 14.30 of RFC 2616), the Location header 
         * requires an *absolute URI*. However, in practice, many web 
         * applications send an *absolute path* instead. This is interoperable, 
         * that is, works in popular web browsers  (according to 
         * http://en.wikipedia.org/wiki/HTTP_location).
         * 
         * As the information required to set the Location header to an absolute URI
         * is not generally available to a Servlet, we go with the flow and send
         * an absolute path instead (in violation of RFC 2616).
         * 
         * There is an issue filed with Hypertext Transfer Protocol Bis (httpbis) 
         * working group to resolve this problem here:
         * http://trac.tools.ietf.org/wg/httpbis/trac/ticket/185
         */
        response.setHeader("Location", url);

The reason I don't want to send the absolute URI myself is because I have seen problems with this when behind load-balancers and other production infrastructure. Although in dev mode "http://localhost:8080/foo" tends to work fine :))

Will accept Julian's answer now ...

Answer 4

You might try

new URL(new URL(request.getRequestURL().toString()), url).toString();

That will at least be smart about canonicalizing away any .. or other oddities. Other than that, I don't think it's much better than string manipulation.

Answer 5

In case you are using JAX RS, there is a method in javax.ws.rs.core.Response which automatically converts relative URLs:

public static Response.ResponseBuilder created(java.net.URI location)

Create a new ResponseBuilder for a created resource, set the location header using the supplied value.

Parameters:

• location - the URI of the new resource. If a relative URI is supplied it will be converted into an absolute URI by resolving it relative to the request URI.

Note however that there is a bug in the JAX RS implementation CXF which leads to incorrect absolute URLs.