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Apparently, RESTfull means different things to different folks.

In particular, the Rails folks seem to have decided that the correct way to handle object creation is to do a POST to the resource. On successful creation, the server should indicate that by issuing a 302 to the location of the resulting new resource.

Actually, I pretty sure that this is not the canonical RESTfull api pattern – reading examples from the wikipedia article, I can see that the canonical way to create a resource RESTfully is via a POST, returning a ’201 Created’, along with a body containing the XML result and a Location header pointing to the resource’s URL – but it was the problem I was trying to solve here.

I’m fine with that, but the folks that wrote the jersey.api.client package don’t see it that way, and their package doesn’t follow that paradigm. You can tell it to follow redirects using setFollowRedirects(true)- sure, but it’ll lose the authentication headers and thus you’ll get a 401 Unauthorized instead of display the resulting resource.

Anyway, I ended out writing a ClientFilter that detected the redirector, and followed the redirect after copying the headers. Here it is:

package com.dell.tg;

import com.sun.jersey.api.client.ClientRequest;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.filter.ClientFilter;

class RedirectFilter extends ClientFilter {

    /* (non-Javadoc)
     * Handle a redirect by doing a get to the new location, using the same headers (this avoids auth headers being dropped). This handles the common RESTful API case for creation on a POST correctly, 
     * where the POST creates the resource and then 301 redirects to the show page. 
     * @see com.sun.jersey.api.client.filter.ClientFilter#handle(com.sun.jersey.api.client.ClientRequest)
     */
    public ClientResponse handle(ClientRequest cr) {
        ClientResponse clientResponse= this.getNext().handle(cr);
        if(isRedirect(clientResponse))
        {
            cr.setMethod("GET");
            cr.setEntity(null);
            cr.setURI(clientResponse.getLocation());
            return this.getNext().handle(cr);
        }
        else
            return clientResponse;
    }
    // Some sort of 3XX response.
    private boolean isRedirect(ClientResponse clientResponse)
    {
        return clientResponse.getStatus()/100 == 3;
    }

}

and here is an example of how to use it:

package com.dell.tg;

import java.net.URISyntaxException;
import javax.ws.rs.core.MultivaluedMap;
import sun.misc.BASE64Encoder;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.filter.LoggingFilter;
import com.sun.jersey.impl.MultivaluedMapImpl;

class TGClient {
    private static final String AUTHENTICATION_HEADER = "Authorization";

    static TGClient instance;
    Client client = Client.create();
    String authentication;
    String server;

    public TGClient(String iServer, String iUser, String iPassword)
            throws URISyntaxException {
        server = iServer;
        authentication = "Basic " + encodeCredentialsBasic(iUser, iPassword);
        instance = this;
        client.setFollowRedirects(false);
        client.addFilter(new LoggingFilter()); // just for debugging happiness
        client.addFilter(new RedirectFilter());
    }

    public void createTestrun(String iName) {
        WebResource webResource = client.resource(String.format(
                "http://%s/test_runs.xml", server));

        MultivaluedMap<String, String> formData = new MultivaluedMapImpl();
        formData.add("test_run[name]", iName);
        String response = webResource.type("application/x-www-form-urlencoded")
                .header(AUTHENTICATION_HEADER, authentication).post(
                        String.class, formData);
        String fred = response.toString(); // Pretty lame - should tidy this up and get it into an XML document.

    }

    /**
     * <p>
     * Encode the specified credentials into a String as required by HTTP Basic
     * Authentication (<a href="http://www.ietf.org/rfc/rfc2617.txt">RFC
     * 2617</a>).
     * </p>
     * 
     * @param username
     *            Username to be encoded
     * @param password
     *            Password to be encoded
     */
    @SuppressWarnings("deprecation")
    private String encodeCredentialsBasic(String username, String password) {
        String auth = username + ":" + password;
        BASE64Encoder encoder = new BASE64Encoder();
        return encoder.encode(auth.getBytes());
    }
}