I have written a web service and am now writing a tester to perform integration testing from the outside. I am writing my tester using apache httpclient 4.3. Based on the code here: http://hc.apache.org/httpcomponents-client-4.3.x/quickstart.html and here: http://hc.apache.org/httpcomponents-client-4.3.x/tutorial/html/fundamentals.html#d5e186 I have written the following code.

    Map<String, String> parms = new HashMap<>();
    parms.put(AirController.KEY_VALUE, json);
    postUrl(SERVLET, parms);
    ...

protected String postUrl(String servletName, Map<String, String> parms)
        throws AirException{
    String url = rootUrl + servletName;
    HttpPost post = new HttpPost(url);

    List<NameValuePair> nvps = new ArrayList<NameValuePair>();
    for(Map.Entry<String, String> entry:parms.entrySet()){
        BasicNameValuePair parm = new BasicNameValuePair(entry.getKey(), entry.getValue());
        nvps.add(parm);
    }

    try {
        post.setEntity(new UrlEncodedFormEntity(nvps));
    } catch (UnsupportedEncodingException use) {
        String msg = "Invalid parameters:" + parms;
        throw new AirException(msg, use);
    }

    CloseableHttpResponse response;
    try {
        response = httpclient.execute(post);
    } catch (IOException ioe) {
        throw new AirException(ioe);
    }

    String result;
    if(HttpStatus.SC_OK == response.getStatusLine().getStatusCode()){
        result = processResponse(response);
    }
    else{
        String msg = MessageFormat.format("Invalid status code {0} received from query {1}.",
                                            new Object[]{response.getStatusLine().getStatusCode(), url});
        throw new AirException(msg);
    }

    return result;
}

This code successfully reaches my servlet. In my servlet, I have (using Spring's AbstractController):

protected ModelAndView post(HttpServletRequest request, HttpServletResponse response) {
    String json = String.valueOf(request.getParameter(KEY_VALUE));
    if(json.equals("null")){
        log.info("Received null value.");
        response.setStatus(406);
        return null;
    }

And this code always falls into the null parameter code and returns a 406.

I'm sure I'm missing something simple, but can't see what it is.