String code = request.getParameter("code")

/** * 常量類 * @author rory.wu * */public class Constants { // 第三方用戶唯一憑證 public static String appid = ""; // 第三方用戶唯一憑證密鑰 public static String appsecret = ""; //商戶ID public static String mch_id=""; //獲取openId public static String oauth_url = "https://api.weixin.qq.com/sns/oauth/access_token?appid=APPID&secret=SECRET&code=CODE&grant_type=authorization_code";}

/** * 通用工具類 * @author rory.wu * @version . * @since 年月日 */ public class CommonUtil { private static Logger log = Logger.getLogger(CommonUtil.class); public static JSONObject httpsRequestToJsonObject(String requestUrl, String requestMethod, String outputStr) {  JSONObject jsonObject = null;  try {  StringBuffer buffer = httpsRequest(requestUrl, requestMethod, outputStr);  jsonObject = JSONObject.fromObject(buffer.toString());  } catch (ConnectException ce) {  log.error("連接超時："+ce.getMessage());  } catch (Exception e) {  log.error("https請求異常："+e.getMessage());  }  return jsonObject; }  private static StringBuffer httpsRequest(String requestUrl, String requestMethod, String output)  throws NoSuchAlgorithmException, NoSuchProviderException, KeyManagementException, MalformedURLException,  IOException, ProtocolException, UnsupportedEncodingException {  URL url = new URL(requestUrl);  HttpsURLConnection connection = (HttpsURLConnection) url.openConnection();  connection.setDoOutput(true);  connection.setDoInput(true);  connection.setUseCaches(false);  connection.setRequestMethod(requestMethod);  if (null != output) {  OutputStream outputStream = connection.getOutputStream();  outputStream.write(output.getBytes("UTF-"));  outputStream.close();  }  // 從輸入流讀取返回內容  InputStream inputStream = connection.getInputStream();  InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "utf-");  BufferedReader bufferedReader = new BufferedReader(inputStreamReader);  String str = null;  StringBuffer buffer = new StringBuffer();  while ((str = bufferedReader.readLine()) != null) {  buffer.append(str);  }  bufferedReader.close();  inputStreamReader.close();  inputStream.close();  inputStream = null;  connection.disconnect();  return buffer; } } 　　/** * 獲取用戶的openId，并放入session * @param code 微信返回的code */ private void setOpenId(String code) {  session.put("code", code);  String oauth_url = Constants.oauth_url.replace("APPID", Constants.appid).replace("SECRET", Constants.appsecret).replace("CODE", String.valueOf(session.get("code")));  log.info("oauth_url:"+oauth_url);  JSONObject jsonObject = CommonUtil.httpsRequestToJsonObject(oauth_url, "POST", null);  log.info("jsonObject:"+jsonObject);  Object errorCode = jsonObject.get("errcode");  if(errorCode != null) {  log.info("code不合法");  }else{  String openId = jsonObject.getString("openid");  log.info("openId:"+openId);  session.put("openId", openId);  } }oauth_url返回的格式是：　　{ 　　　"access_token":"ACCESS_TOKEN", 　　　"expires_in":,  "refresh_token":"REFRESH_TOKEN",  "openid":"OPENID", "scope":"SCOPE",  "unionid": "o_bmasdasdsad_sgVthMZOPfL"  }Code無效時：　　{　　 "errcode":　　　,"errmsg":"invalid code" }