Question

在我的 servlet 中，我有以下方法：

private void showUserReservations(HttpServletRequest request, HttpServletResponse response) throws IOException, SQLException, ServletException {
    String username = null;

    HttpSession session = request.getSession();

    if (session.getAttribute("loggedUser") != null) {
        username = (String) session.getAttribute("loggedUser");
    }

    // get data from DB
    List<Operation> userReservations = operationsDbUtil.getUserReservations(username);
    if (userReservations != null) {
        request.setAttribute("AVAILABLE_DATA", userReservations);
        response.getWriter().write(gson.toJson(userReservations));
    }
}

我必须在我的 android应用中获取这些数据，以填充片段中的ListView。如果我在不需要会话属性的方法上运行我的android代码，则会正确获取数据。当我运行此showUserReservations（）方法时，就会出现问题，因为该servlet无法检索loggingUser属性。

通过遵循本指南Shared Preferences to keep the user logged in，我使我的用户使用共享的首选项进行登录，但是，如何让servlet知道哪个用户正在发出请求？有没有办法发送保存在共享首选项中的用户名，所以这部分代码

 if (session.getAttribute("loggedUser") != null) {
        username = (String) session.getAttribute("loggedUser");
    }

可以正常运行吗？

与servlet通信的Android代码

private String strUrl = null;
private String jsonString = null;
View view;
ListView listView;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    view = inflater.inflate(R.layout.fragment_my_reservations, container, false);
    Button btn = view.findViewById(R.id.jsonBtn);


    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            showJson(view);
        }
    });

    return view;
}

public void showJson(View view) {
    new FillListTask().execute();
}

public class FillListTask extends AsyncTask<Void, Void, String> {
    @Override
    protected void onPreExecute() {
        strUrl = "http://xxx.xxx.x.x./xxxxxxxxxxx;
    }

    @Override
    protected void onPostExecute(String result) {
        TextView textView = view.findViewById(R.id.tvJson);
        textView.setText(result);
    }

    @Override
    protected String doInBackground(Void... voids) {
        try {

            URL url = new URL(strUrl);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("GET");
            httpURLConnection.connect();

            InputStream inputStream = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
            StringBuilder stringBuilder = new StringBuilder();

            while ((jsonString = bufferedReader.readLine()) != null) {
                stringBuilder.append(jsonString + "\n");
            }

            bufferedReader.close();
            inputStream.close();
            httpURLConnection.disconnect();

            return stringBuilder.toString().trim();


        } catch (IOException exception) {
            System.out.println(exception.getMessage());
        }
        return null;
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }
  }
}

像这样，我可以从不需要session属性的方法中从servlet中获取数据。

从Android应用向Servlet发送GET请求时检索会话属性

0 个答案: