失败：HTTP错误代码：406 - Spring REST响应错误

Question

当我尝试使用REST API时出现此错误：

         **java.lang.RuntimeException: Failed : HTTP error code : 406**

以下是映射请求的Controller代码：

 @RequestMapping(method = RequestMethod.POST, value = "/addUser", headers = "Accept=application/json")
    public @ResponseBody 
    Response addUser(@RequestBody String request) {

}

这是发送req -

的代码

private static Response sendRequest(Request request, String restClientURL) {
    Gson gs = new Gson();
    //RaaSServiceLocator raasServiceLocator = RaaSServiceLocator.getInstance();
    Response resp = new Response();
    ObjectMapper objectMap = new ObjectMapper();
    try {
        String json = gs.toJson(request);
        String jsonResponse = getRestRsponseJson(
                getClient("POST", restClientURL), json);
        resp = objectMap.readValue(jsonResponse, Response.class);
    } catch (JsonParseException e) {
        e.getMessage();
    } catch (JsonMappingException e) {
        e.getMessage();
    } catch (IOException e) {
        e.getMessage();
    }
    return resp;
}

public static String getRestRsponseJson(Object client, String jsonType) {
    DefaultHttpClient defaultclient = new DefaultHttpClient();

    //defaultclient.setCredentialsProvider(credentialsProvider);

    StringBuffer resp = new StringBuffer();
    // Changes Done
    String jsonResponse = "";
    BufferedReader br = null;
    try {
        if (client instanceof HttpPost) {
            HttpPost postRequest = (HttpPost) client;
            postRequest.addHeader("accept", "application/json");
            StringEntity input = new StringEntity(jsonType);
            postRequest.setEntity(input);
            HttpResponse response = defaultclient.execute(postRequest);
            String output = null;

            if (response.getStatusLine().getStatusCode() != 201
                    && response.getStatusLine().getStatusCode() != 200) {
                throw new RuntimeException("Failed : HTTP error code : "
                        + response.getStatusLine().getStatusCode());
            }


            br = new BufferedReader(new InputStreamReader(
                    (response.getEntity().getContent()),"UTF-8")); //findbugfix
            while ((output = br.readLine()) != null) {
                resp.append(output);
                jsonResponse = resp.toString();
            }
        }
    } catch (IllegalStateException e) {
        e.getMessage();
    } catch (IOException e) {
        e.getMessage();
    } finally{
        if(br != null){
            try {
                br.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    return jsonResponse;
}

public static Object getClient(String clientType, String method) {

    Object obj = null;
    String engineContext = "http://localhost:8080/addUser";
    String url = engineContext.concat(method);
    System.out.println("RaaS engine URL: " + engineContext);

    if ("POST".equalsIgnoreCase(clientType)) {
        obj = new HttpPost(url);
    } else if ("GET"
            .equalsIgnoreCase(clientType)) {
        obj = new HttpGet(url);
    } else if ("DELETE"
            .equalsIgnoreCase(clientType)) {
        obj = new HttpDelete(url);
    } else if ("PUT"
            .equalsIgnoreCase(clientType)) {
        obj = new HttpPut(url);
    }
    return obj;
}

为什么这个错误（406-Not Acceptable）会发生，尽管映射器应该处理映射到正确的类型？