API call by HTTP POST method without using parameter name for the body

I'm using Java. How I can make a HTTP POST call API and inform in body only "JSON" value (without parameter name)?

Per example call this URL: https://api.nimble.com/api/v1/contact?access_token=12123486db0552de35ec6daa0cc836b0 (POST METHOD) and in body would only have this (without parameter name):

{'fields':{'first name': [{'value': 'Jack','modifier': '',}],'last name': [{'value': 'Daniels','modifier': '',}],'phone': [{'modifier': 'work','value': '123123123',}, {'modifier':'work','value': '2222',}],},'type': 'person','tags': 'our customers\,best'}

If this is correct, someone could give me an example please?

Using this library for the network part : http://hc.apache.org/

Using this library for the json part : http://code.google.com/p/google-gson/

Example :

public String examplePost(DataObject data) {
        HttpClient httpClient = new DefaultHttpClient();

        try {
            HttpPost httppost = new HttpPost("your url");
            // serialization of data into json
            Gson gson = new GsonBuilder().serializeNulls().create();
            String json = gson.toJson(data);
            httppost.addHeader("content-type", "application/json");

            // creating the entity to send
            ByteArrayEntity toSend = new ByteArrayEntity(json.getBytes());
            httppost.setEntity(toSend);

            HttpResponse response = httpClient.execute(httppost);
            String status = "" + response.getStatusLine();
            System.out.println(status);
            HttpEntity entity = response.getEntity();

            InputStream input = entity.getContent();
            StringWriter writer = new StringWriter();
            IOUtils.copy(input, writer, "UTF8");
            String content = writer.toString();
            // do something useful with the content
            System.out.println(content);
            writer.close();
            EntityUtils.consume(entity);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            httpClient.getConnectionManager().shutdown();
        }
    }

Hope it helps.