У меня есть простая HTML-страница, распечатанная внутри сервлета. Здесь я настроил firebase admin sdk и установил прослушиватель событий значения для пути.
Когда события срабатывают, я хочу изменить элемент Div и отобразить там результаты.
РЕДАКТИРОВАТЬ: слушатель работает над дальнейшим тестированием с помощью журналов.
Но я до сих пор не знаю, как отразить изменения внутри элемента div, поскольку слушатели являются асинхронными. Скорее всего поэтому скрипт не работает.
Может кто-нибудь, пожалуйста, направьте меня относительно того, что я должен делать. Код выглядит следующим образом:
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.google.firebase.FirebaseApp;
import com.google.firebase.FirebaseOptions;
import com.google.firebase.auth.FirebaseCredentials;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
@WebServlet("/WebWaitlistViewServelet")
public class WebWaitlistViewServelet extends HttpServlet {
private static final long serialVersionUID = 1L;
public WebWaitlistViewServelet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter pw = response.getWriter();
try {
String cityName=request.getParameter("city");
String restId = request.getParameter("restid");
String userId = request.getParameter("userid");
if(cityName == null || restId == null || userId == null){
System.out.println("Error getting values");
return;
}else{
System.out.println(cityName+" "+restId+" "+userId);
}
pw.println("<HTML>");
pw.println("<HEAD>");
pw.println("<script>");
pw.println("function changePosition(position){ document.getElementById(\"positionInList\").innerHTML = position };");
pw.println("function changeTimeTillTurn(timetillturn){ document.getElementById(\"timeTillTurn\").innerHTML = timetillturn };");
pw.println("function showTimeTillTurn(){ document.getElementById(\"timeDiv\").style.display = \"visible\" };");
pw.println("function hideTimeTillTurn(){ document.getElementById(\"timeDiv\").style.display = \"hidden\" };");
pw.println("</script>");
pw.println("</HEAD>");
pw.println("<BODY>");
pw.println("<DIV align=\"center\">");
pw.println("<B>Your position in the waitlist is:</B>");
pw.println("</DIV><br/>");
pw.println("<DIV id=\"positionInList\" align=\"center\" style=\"color:blue\">");
pw.println("Loading...");
pw.println("</DIV><br/>");
pw.println("<DIV id=\"timeDiv\" align=\"center\">");
pw.println("<B>Approximate time till your turn is: </B><span id=\"timeTillTurn\" style=\"color:blue\">Loading...</span>");
pw.println("</DIV>");
pw.println("<BODY>");
pw.println("</HTML>");
pw.flush();
InputStream is = getServletContext().getResourceAsStream("/WEB-INF/firebaseauth/firebase_admin_sdk_key.json");
// Initialize the app with a service account, granting admin privileges
FirebaseOptions options = new FirebaseOptions.Builder()
.setCredential(FirebaseCredentials.fromCertificate(is))
.setDatabaseUrl("https://restaurantrepo.firebaseio.com")
.build();
try {
FirebaseApp.initializeApp(options);
} catch (Exception e) {
//
}
// As an admin, the app has access to read and write all data, regardless of Security Rules
DatabaseReference waitlistRef = FirebaseDatabase.getInstance().getReference().child(cityName).child(restId).child("waitlist");
Comparator<WaitlistedPerson> sortComparator = new Comparator<WaitlistedPerson>() {
@Override
public int compare(WaitlistedPerson lhs, WaitlistedPerson rhs) {
//sort ascending... the bigger the time entered, the later the person has joined... thus the higher the time entered the lower the position
//on waitlist
if(lhs.getTimeentered()<rhs.getTimeentered()){
//if time entered is lower, keep the person higher in the list
return -1;
}else if(lhs.getTimeentered()==rhs.getTimeentered()){
//if the time entered is the same, there are two cases possible
//1.. one person is remotely entered and one has entered at the resto POS... in this case, give priority to POS entered user
//2.. both people have remotely entered ... in this case, give preference to the person with lowest userid (he/she started using our app earlier)
//
//cases that will never happen are
//1.. two people with same userid entered remotely at same time .. can't happen as a second entry simply overwrites the old entry
//2.. two people with same time entered at POS ... can't happen as the resto host can only enter one party at a time..
if(!lhs.isRemotelyEntered() && rhs.isRemotelyEntered()){
//Log.d("FragmentCreate","lhs userid "+lhs.getUserid()+" lhs remotelyentered "+lhs.isRemotelyEntered());
//Log.d("FragmentCreate","rhs userid "+rhs.getUserid()+" rhs remotelyentered "+rhs.isRemotelyEntered());
return -1;
}else if(lhs.isRemotelyEntered() && rhs.isRemotelyEntered()){
//return the lowest user id
//userid is of format Uxx ... so get the xx part begining from index 1 of the string and get the number
int lhsuserid = Integer.parseInt(lhs.getUserid().substring(1));
int rhsuserid = Integer.parseInt(rhs.getUserid().substring(1));
//Log.d("FragmentCreate"," The userids are lhsuserid "+lhsuserid+" rhsuserid"+rhsuserid);
//Do not get tempted to use String compareto function as this will give wrong results
// U11 will get priority over U4 in string compareto due to 1 being lexicographically smaller
//Thus never use lexicographical sorting ever.
//The user ids can never be equal as two remotely entered users will never have two entries (can't... it's impossible due to firebase)
if(lhsuserid<rhsuserid){
return -1;
}else if(lhsuserid==rhsuserid){
//can never happen in real life... two remotely entered users can never have same id ever... just made for safeguard
return 0;
}else{
return 1;
}
}else if(!lhs.isRemotelyEntered() && !rhs.isRemotelyEntered()){
//both entered at POS and have same time
//can never happen in real life...
//made this just for testing scenarios in case i screw up and give wrong inputs
return 0;
}else{
//Log.d("FragmentCreate","lhs userid "+lhs.getUserid()+" lhs remotelyentered "+lhs.isRemotelyEntered());
//Log.d("FragmentCreate","rhs userid "+rhs.getUserid()+" rhs remotelyentered "+rhs.isRemotelyEntered());
return 1;
}
}else{
return 1;
}
}
};
ArrayList<WaitlistedPerson> listOfPeople = new ArrayList<>();
ValueEventListener eventListener = new ValueEventListener(){
@Override
public void onCancelled(DatabaseError error) {
pw.println("<script>hideTimeTillTurn();</script>");
pw.println("<script>changePosition('Sorry, some error occured');</script>");
System.out.println("Sorry. some error occured");
}
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
int positionCounter=0;
if(dataSnapshot.getChildrenCount()==1 || dataSnapshot.getChildrenCount() == 0 ){
//Log.d("FragmentCreate","This indicates that the restaurant probably closed down and removed all customers from the list");
pw.println("<script>hideTimeTillTurn();</script>");
pw.println("<script>changePosition('You are no longer in the waitlist');</script>");
System.out.println("You are no longer in the waitlist");
}else{
if(dataSnapshot.hasChild(userId)){
double averageWaitTime=0.0d;
long timeEnteredInMillis=0;
listOfPeople.clear();
Iterable<DataSnapshot> peopleInList = dataSnapshot.getChildren();
for(DataSnapshot currentPerson : peopleInList){
if(currentPerson.getKey().equals("dummy")){
continue;
}
if(currentPerson.getKey().equals(userId)){
//This is our node.... break the loop and enjoy using the counter
averageWaitTime = currentPerson.child("averagewaittimeperparty").getValue(Double.class);
timeEnteredInMillis = currentPerson.child("timeentered").getValue(Long.class);
listOfPeople.add(new WaitlistedPerson(currentPerson));
}else{
listOfPeople.add(new WaitlistedPerson(currentPerson));
}
}
//sort the list using our custom comparator and the get the index
Collections.sort(listOfPeople,sortComparator);
//find the position of the user now
for(WaitlistedPerson person : listOfPeople){
++positionCounter;
if(person.getUserid().equals(userId)){
break;
}
}
double timetillturn = Math.round(averageWaitTime * ((double)positionCounter));
long timeShouldComeAt = timeEnteredInMillis + (long)(timetillturn*60000);
Date timeWhenTurnArrives = new Date(timeShouldComeAt);
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm");
pw.println("<script>showTimeTillTurn();</script>");
pw.println("<script>changePosition('"+positionCounter+"');</script>");
pw.println("<script>changeTimeTillTurn('"+sdf.format(timeWhenTurnArrives)+"');</script>");
System.out.println(positionCounter+" "+sdf.format(timeWhenTurnArrives));
}else{
pw.println("<script>hideTimeTillTurn();</script>");
pw.println("<script>changePosition('You are no longer in the waitlist');</script>");
System.out.println("You are no longer in the waitlist");
}
}
}
};
waitlistRef.addValueEventListener(eventListener);
} catch (Exception e) {
e.printStackTrace();
}finally{
try {
pw.close();
} catch (Exception e) {
//do nothing here
}
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
