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Недавно я попытался разработать сервлет, а затем подключить его к своему приложению для Android, но не могу заставить его работать должным образом. Это мой сервлет входа в систему

  @WebServlet(name = "login", value = "/auth/login") public class AuthUser extends HttpServlet {  private Gson gson = new Gson();   public void init() {  Dao.registerDriver();  }   public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {  response.setContentType("application/json");  response.setCharacterEncoding("UTF-8");  String id = request.getParameter("id");  String psw = request.getParameter("psw");   HttpSession s = request.getSession();  PrintWriter out = response.getWriter();   HashMaplt;String, Objectgt; responseJson = new HashMaplt;gt;();  Student student;   if(id != null amp;amp; psw != null) {  student = FetchFromDB.fetchStudentData(id);   if (student != null amp;amp; student.getPassword().equals(psw)) {  s.setAttribute("username", student.getNumber());  s.setAttribute("surname", student.getSurname());  s.setAttribute("role", student.getRole());   responseJson.put("id", request.getSession().getId());  responseJson.put("user", student);  responseJson.put("message", "Logged succesfully");  out.print(new Gson().toJson(responseJson));  } else {  responseJson.put("message", "The mail or the username is not correct, please try again");  out.println(new Gson().toJson(responseJson));  }  } else {  responseJson.put("message", "The mail or username value is null, check that out");  }  out.flush();  }   public void destroy() {  } }   

Я вызываю этот сервлет со своей страницы входа в мое приложение для Android следующим образом:

 private void login() throws MalformedURLException {  RequestQueue queue = Volley.newRequestQueue(this);  String username = usernameText.getText().toString();  String psw = passwordText.getText().toString();  String url = Costants.URL   "auth/login?id=" username "amp;psw=" psw "";   JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,  url,  null,  response -gt; {   Log.d("In onResponse", "" response);  try {  Log.d("In callServer", "Object returned: "  response.toString());  intent.putExtra("key-username", usernameText.getText().toString());  intent.putExtra("key-role", response.getJSONObject("user").getString("role"));  intent.putExtra("key-surname", response.getJSONObject("user").getString("surname"));  intent.putExtra("key-session-id", response.getString("id"));  startActivity(intent);  } catch (JSONException e) {  e.printStackTrace();  }  }, error -gt; {  VolleyLog.d("In onErrorResponse", "Error: "   error.getMessage());  Toast.makeText(getApplicationContext(),  error.getMessage(), Toast.LENGTH_SHORT).show();  });  // Access the RequestQueue through your singleton class.   MySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsonObjReq);   }  

When I click in the login button it works, so it communicates with the servlet and the main activity starts as it should do. BUT when I try to make another call from my MainActivity the session in the servlet won’t be recognised and so the user appears as unkown, here’s the code of the mainActivity.

 public class MainActivity extends AppCompatActivity {   private ActivityMainBinding binding;  String usernameOfLoggedUser;  String surnameOfLoggedUser;  String roleOfLoggedUser;  String sessionId;  Bundle extras;  private UserViewModel viewModel;  private BookedLessonsViewModel bookedLessonsViewModel;   @Override  protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);   extras = getIntent().getExtras();  usernameOfLoggedUser = extras.getString("key-username", "NoValue");  surnameOfLoggedUser = extras.getString("key-surname", "NoValue");  roleOfLoggedUser = extras.getString("key-role", "NoValue");  sessionId = extras.getString("key-session-id", "NoValue");  showWelcomeToast(usernameOfLoggedUser);  setViewModelUser(usernameOfLoggedUser, roleOfLoggedUser, surnameOfLoggedUser);  fetchBookedLessons(usernameOfLoggedUser);  setupUIElements();  }   /**  * Fetch lessons from db and set the model view for the lessons booked  * @param username  */  private void fetchBookedLessons(String username) {  String url = Costants.URL   "book/bookedLessonsForUser";  ArrayListlt;BookedLessongt; bookedLessons = new ArrayListlt;gt;();  CustomRequest jsonCustomReq = new CustomRequest(  Request.Method.GET,  url,  null,  sessionId,  new Response.Listenerlt;JSONObjectgt;() {  @Override  public void onResponse(JSONObject response) {  Log.d("in onResponse", response.toString()); // int i = 0; // try { // JSONArray reservations = response.getJSONArray("reservations"); // while(i lt; reservations.length()) { // JSONObject reservation = reservations.getJSONObject(i); // String idUser = reservation.getString("idUser"); // String idTeacher = reservation.getString("idTeacher"); // String subject = reservation.getString("nameSubject"); // String day = reservation.getString("day"); // String slot = reservation.getString("slot"); // String status =reservation.getString("status"); // // BookedLesson bookedLesson = new BookedLesson(idUser, idTeacher, slot, subject, day, status); // bookedLessons.add(bookedLesson); // i  ; // } // } catch (JSONException e) { // e.printStackTrace(); // } finally { // setViewModelLessons(bookedLessons); // }  }  },  new Response.ErrorListener() {  @Override  public void onErrorResponse(VolleyError error) {   }  }  );  MySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsonCustomReq);  }   private void showWelcomeToast(String username) {  Toast toast = Toast.makeText(getApplicationContext(), "You are logged as: "   username, Toast.LENGTH_SHORT*2);  toast.show();  }    @Override  protected void onResume() {  super.onResume();  fetchBookedLessons(usernameOfLoggedUser);  }   private void setupUIElements() {  binding = ActivityMainBinding.inflate(getLayoutInflater());  setContentView(binding.getRoot());   BottomNavigationView navView = findViewById(R.id.nav_view);  // Passing each menu ID as a set of Ids because each  // menu should be considered as top level destinations.  AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(  R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications)  .build();  NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_activity_main);  NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);  NavigationUI.setupWithNavController(binding.navView, navController);  }   /**  * Set the model view for the user so that every fragment has the data for the logged user  * @param usernameOfLoggedUser  * @param roleOfLoggedUser  * @param surnameOfLoggedUser  */  private void setViewModelUser(String usernameOfLoggedUser, String roleOfLoggedUser, String surnameOfLoggedUser) {  viewModel = new ViewModelProvider(this).get(UserViewModel.class);   viewModel.setUser(usernameOfLoggedUser);  viewModel.setRole(roleOfLoggedUser);  viewModel.setSurname(surnameOfLoggedUser);  viewModel.getUser().observe(this, username -gt; {  Log.d("In onCreate", "Share data: "   username);  });  }   /**  * Pass the array fetched and set the model view for the lessons  * @param lessons  */  private void setViewModelLessons(ArrayListlt;BookedLessongt; lessons) {  bookedLessonsViewModel = new ViewModelProvider(this).get(BookedLessonsViewModel.class);   bookedLessonsViewModel.setBookedLessons(lessons);   bookedLessonsViewModel.getBookedLessons().observe(this, bookedLessons -gt; {  Log.d("In getBookedLessons", "Lessons: "   bookedLessons.size());  });  } }  

Но я получаю взамен это значение:

 -26 13:48:47.053 12225-12225/com.example.bookinglessons D/in onResponse: {"message":"you're not logged"}  

Если вы знаете, что происходит, это было бы действительно полезно, заранее спасибо.

Я нашел решение для такого рода проблем. Вам просто нужно добавить эти строки в onCreate вашего первого действия (основная активность в моем случае).

 CookieManager cookieManager = new CookieManager(); CookieHandler.setDefault(cookieManager);  

Это решило мои проблемы и руководило сеансом.