httpclient发送Json请求，结果返回Json.
public static JSONObject post(String url,JSONObject json){HttpClient client = new DefaultHttpClient();HttpPost post = new HttpPost(url);JSONObject response = null;try {StringEntity s = new StringEntity(json.toString());s.setContentEncoding("UTF-8");s.setContentType("application/json");post.setEntity(s);HttpResponse res = client.execute(post);if(res.getStatusLine().getStatusCode() == HttpStatus.OK.value()){HttpEntity entity = res.getEntity();String charset = EntityUtils.getContentCharSet(entity);response = new JSONObject(new JSONTokener(new InputStreamReader(entity.getContent(),charset)));}} catch (Exception e) {throw new RuntimeException(e);}return response;}