public static String httpPostWithJSON(String url) throws Exception {

    HttpPost httpPost = new HttpPost(url);
    CloseableHttpClient client = HttpClients.createDefault();
    String respContent = null;
    
//    json方式
    JSONObject jsonParam = new JSONObject(); 
    jsonParam.put("name", "admin");
    jsonParam.put("pass", "123456");
    StringEntity entity = new StringEntity(jsonParam.toString(),"utf-8");//解決中文亂碼問題  
    entity.setContentEncoding("UTF-8");  
    entity.setContentType("application/json");  
    httpPost.setEntity(entity);
    System.out.println();
    
  
//    表單方式
//    List<BasicNameValuePair> pairList = new ArrayList<BasicNameValuePair>(); 
//    pairList.add(new BasicNameValuePair("name", "admin"));
//    pairList.add(new BasicNameValuePair("pass", "123456"));
//    httpPost.setEntity(new UrlEncodedFormEntity(pairList, "utf-8"));  
    
    
    HttpResponse resp = client.execute(httpPost);
    if(resp.getStatusLine().getStatusCode() == 200) {
      HttpEntity he = resp.getEntity();
      respContent = EntityUtils.toString(he,"UTF-8");
    }
    return respContent;
  }

  
  public static void main(String[] args) throws Exception {
    String result = httpPostWithJSON("http://localhost:8080/hcTest2/Hc");
    System.out.println(result);
  }

public class HcServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;
    
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doPost(request, response);
  }

  
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    request.setCharacterEncoding("UTF-8"); 
    response.setContentType("text/html;charset=UTF-8"); 
    String acceptjson = ""; 
    User user = new User();
    BufferedReader br = new BufferedReader(new InputStreamReader( 
        (ServletInputStream) request.getInputStream(), "utf-8")); 
    StringBuffer sb = new StringBuffer(""); 
    String temp; 
    while ((temp = br.readLine()) != null) { 
      sb.append(temp); 
    } 
    br.close(); 
    acceptjson = sb.toString(); 
    if (acceptjson != "") { 
      JSONObject jo = JSONObject.parseObject(acceptjson);
      user.setUsername(jo.getString("name"));
      user.setPassword(jo.getString("pass"));
    } 
    
    request.setAttribute("user", user);
    request.getRequestDispatcher("/message.jsp").forward(request, response);
  }
}