I've been trying to pass native headers to disconnect event using StompJS but I don't know how to declare them (I guess it must be a similar approach like for connect event described here: http://www.sergialmar.com/2014/03/detect-websocket-connects-and-disconnects-in-spring-4/)
The event listener looks following:
#Component
public class DocumentStompDisconnectEvent implements ApplicationListener<SessionDisconnectEvent> {
#Override
#EventListener
public void onApplicationEvent(SessionDisconnectEvent event) {
StompHeaderAccessor sha = StompHeaderAccessor.wrap(event.getMessage());
String documentId = sha.getNativeHeader("documentId").get(0);
System.out.println("Disconnect event [documentId: " + documentId + "]");
}
}
When I try to pass those headers to connect event, then it works fine:
function connect() {
stompClient = Stomp.over(socket);
stompClient.connect({userId: "${userId}", documentId: "${documentId}"}, function (frame) {
but at the moment I don't have any idea how to pass them to disconnect event.
Related
I have a (serverside) blazor app and I want to let users fill in a small form and press a button to create SignalR groups that they can then send messages to.
I have a Hub class that looks like this:
public class RoomHub : Hub
{
public async Task JoinRoomAsync(string groupName)
{
await Groups.AddToGroupAsync(Context.ConnectionId, groupName);
}
public async Task LeaveRoomAsync(string groupName)
{
await Groups.RemoveFromGroupAsync(Context.ConnectionId, groupName);
}
public async Task BroadcastToRoomAsync(string groupName, string message)
{
await Clients.Group(groupName).SendAsync("OnMessage", message);
}
}
and a Service class that gets called from my blazor component, which looks like this:
public class RoomService : IRoomService
{
private ICosmosDbService _dbService;
private RoomHub _roomHub;
public RoomService(ICosmosDbService dbService, RoomHub roomHub)
{
this._dbService = dbService;
this._roomHub = roomHub;
}
public async Task<Room> CreateRoom(string name)
{
Room r = new Room();
r.Id = Guid.NewGuid().ToString();
r.Name = name;
await _dbService.AddItemAsync(r);
await _roomHub.JoinRoomAsync(r.Name);
return r;
}
public async Task SendToRoom(Room r, string message)
{
await _roomHub.BroadcastToRoomAsync(r.Name, message);
return;
}
}
When I add the RoomHub class to my services in Startup.cs and run my application, when I press the button to create a Group it tells me the Hub's Context variable is null and fails.
I've tried looking around for other ways to do this, and arrived at the conclusion that it has something to do with injecting an IHubContext<RoomHub> object instead, but the object this provides does not seem related at all to my Hub class and I can't use it to create groups directly because I don't have access to the ConnectionId I need to do so.
I feel like there's a gap between the Hub and HubContext that I do not understand. What is the correct way to create a SignalR Group, starting from a button press on a Blazor component?
Before you can access your Hub, you need to build and start your Hub connection using HubConnection and HubConnectionBuilder. This needs to include the url for your Hub and the handler methods for the data received from the Hub.
Start by adding a HubConnection field in your Service class.
private HubConnection _hubConnection;
Depending on your Service lifetime and other considerations, you can build your connection in the Service class constructor or it's own method. For an example, we'll add a StartConnectionAsync task.
public async Task StartConnectionAsync()
{
// Create the connection
_hubConnection = new HubConnectionBuilder()
.WithUrl(_hubUrl) // _hubUrl is your base Url + Hub Url
.Build();
// Add Handler for when a client receives a broadcast message
_hubConnection.On<string>("OnMessage", this.SomeEventHandler);
// Then you start the connection
await _hubConnection.StartAsync();
}
Without using a typed Hub, you'll call your Hub methods using magic strings. e.g.
await _hubConnection.SendAsync("JoinRoomAsync", groupName);
This should get you started. Based on what you posted above, I think this github repo is similar to what you're intending to do.
I have a scenario where one of the clients is sending a request to Hub Class method AddMessage, which in turn should broadcast that message to all clients including the one who initiated it.
The problem is that I am able to call the Hub method AddMessage from the client as shown in the following code, but I couldn't find a way to handle the broadcast message on the client side which is initiated in the Hub class using the following line.
Clients.All.NotifyMessageToClients(name, message);
SignalR Hub Class
using System;
using Microsoft.AspNet.SignalR;
using System.Threading.Tasks;
public class SignalRChatHub : Hub
{
public void AddMessage(string name, string message)
{
// Following call is supposed to notify all clients with passed parameters.
// They could have a method called NotifyMessageToClients to fetch the broadcasted message
Clients.All.NotifyMessageToClients(name, message);
}
}
SignalR Client
using System;
using Microsoft.AspNet.SignalR.Client;
public partial class Default : System.Web.UI.Page
{
HubConnection hubConnection;
IHubProxy stockTickerHubProxy;
public Default()
{
hubConnection = new HubConnection("http://localhost:6898/");
stockTickerHubProxy = hubConnection.CreateHubProxy("SignalRChatHub");
}
async public void SendAddNotification(string msgFrom, string msg)
{
// Following line calls Addmessage method in SignalRChatHub class
await stockTickerHubProxy.Invoke("Addmessage", "Ajendra", "Hello StackOverflow");
}
// I might need the method NotifyMessageToClients here... to receive broadcasted message
}
I have some idea about how to achieve the same in jQuery but not in C# by creating a client as I did above. How would I achieve this?
If the above approach doesn't make sense in any way, please suggest me the right one.
You need to listen to events from the server like this:
public partial class Default : System.Web.UI.Page
{
HubConnection hubConnection;
IHubProxy stockTickerHubProxy;
public Default()
{
hubConnection = new HubConnection("http://localhost:6898/");
stockTickerHubProxy = hubConnection.CreateHubProxy("SignalRChatHub");
// listen to server events...
// n is "name" and m is "message", but you can change to "a" and "b" or anything else...
stockTickerHubProxy.On<string, string>("NotifyMessageToClients", (n, m) =>
{
Console.WriteLine("Message received from server. Name: {0} | Message: {1}", n, m);
});
}
// "async" methods should return Task instead of void....
// unless they are event handlers for UI applications...
public async Task SendAddNotification(string msgFrom, string msg)
{
// first, start the connection...
await stockTickerHubProxy.Start();
// Following line calls Addmessage method in SignalRChatHub class
await stockTickerHubProxy.Invoke("Addmessage", "Ajendra", "Hello StackOverflow");
// you don't stop the connection, otherwise you won't be able to receive calls from the server
}
}
...if you need to update UI in WPF, for example, you should implement your event like this:
stockTickerHubProxy.On<string, string>("NotifyMessageToClients", (a,b) =>
Dispatcher.InvokeAsync(() =>
{
// update UI...
textBox.Text += string.Format("Name: {0} | Message: {1}", a, b);
})
);
I suggest reading this guide for deeper details.
I'm trying to use a Toast message in a handler fragment class but I can't access the main class' context. The handler is in the same class as the main activity, PlayFrets(which is also the UI thread).I've read through the plethora of questions on this topic on stackoverflow, but almost every solution involves passing getActivity() or getActivity().getApplicationContext() into the context field of Toast. When I try this I get errors
Here is the relevant code:
public class PlayFrets extends Activity {
.
.
.
static Handler mHandler = new Handler(Looper.getMainLooper()){
public void handleMessage(final Message msg){
if(msg.obj != null){
runOnUiThread(new Runnable() {
public void run() {
//error happens here on Toast message
Toast.makeText(getActivity(), "Background Thread sent "+ msg.what + " bytes: " + msg.obj,Toast.LENGTH_SHORT).show();
}
});
}
else{
}
}
};
}
These are my attempts at passing the context and the errors each variation generates.
Toast.makeText(PlayFrets.this.getActivity()...)
^^^The method getActivity() is undefined for the type PlayFrets
Toast.makeText(PlayFrets.this...)
^^^No enclosing instance of the type PlayFrets is accessible in scope
Toast.makeText(getActivity().getApplicationContext()...)
^^^The method getActivity() is undefined for the type new Runnable(){}
What is the proper way to pass the main activity's context into the handler fragement for use in a Toast message?
Activity is a context itself. Instead of all things you try you should
not create static handler - that's why your attempt to pass PlayFrets.this fails
pass PlayFrets.this as context
no need to call runOnUiThread() because handler handles messages on UI thread in presented case
Your handler code should look like this:
Handler mHandler = new Handler() {
public void handleMessage(final Message msg){
if(msg.obj != null){
Toast.makeText(PlayFrets.this, "Background Thread sent "+ msg.what + " bytes: " + msg.obj,Toast.LENGTH_SHORT).show();
}
else{
}
}
};
I've just started learning signalR and I'm trying to implement a search feature.
How would i go about periodically updating a user's search result. My initial idea is to run a timed job via IRegisteredObject to trigger a check from client with search params like so:
public class BackgroundTimer : IRegisteredObject
{
private Timer taskTimer;
private IHubContext hub;
public BackgroundTimer()
{
HostingEnvironment.RegisterObject(this);
hub = GlobalHost.ConnectionManager.GetHubContext<SearchHub>();
taskTimer = new Timer(OnTimerElapsed, null, TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(5));
}
private void OnTimerElapsed(object sender)
{
hub.Clients.All.checkForUpdates();
}
}
public class SearchHub : Hub
{
public void Search(string searchText)
{
string jsonResult = string.Empty;
//TODO save result to jsonResult
Clients.Caller.broadcastMessage(jsonResult);
}
}
However i can't help but think there are much more efficient ways to accomplish this. Any advice pls
With this code you are just doing what the clients could instead, poll the server each second. Either publish a message on all actions that alter the search result and act on that. Or use SqlDependency.
I'm making a small game in LibGDX. I'm saving the player's username locally as well as on a server. The problem is that the application is not waiting for the result of the call so the online database's ID is not saved locally. Here's the overall flow of the code:
//Create a new user object
User user = new User(name);
//Store the user in the online database
NetworkService networkService = new NetworkService();
String id = networkService.saveUser(user);
//Set the newly generated dbase ID on the local object
user.setId(id);
//Store the user locally
game.getUserService().persist(user);
in this code, the id variable is not getting set because the saveUser function is returning immediately. How can I make the application wait for the result of the network request so I can work with results from the server communication?
This is the code for saveUser:
public String saveUser(User user) {
Map<String, String> parameters = new HashMap<String, String>();
parameters.put("action", "save_user");
parameters.put("json", user.toJSON());
HttpRequest httpGet = new HttpRequest(HttpMethods.POST);
httpGet.setUrl("http://localhost:8080/provisioner");
httpGet.setContent(HttpParametersUtils.convertHttpParameters(parameters));
WerewolfsResponseListener responseListener = new WerewolfsResponseListener();
Gdx.net.sendHttpRequest (httpGet, responseListener);
return responseListener.getLastResponse();
}
This is the WerewolfsResponseListener class:
class WerewolfsResponseListener implements HttpResponseListener {
private String lastResponse = "";
public void handleHttpResponse(HttpResponse httpResponse) {
System.out.println(httpResponse.getResultAsString());
this.lastResponse = httpResponse.getResultAsString();
}
public void failed(Throwable t) {
System.out.println("Saving user failed: "+t.getMessage());
this.lastResponse = null;
}
public String getLastResponse() {
return lastResponse;
}
}
The asynchrony you are seeing is from Gdx.net.sendHttpRequest. The methods on the second parameter (your WerewolfsResponseListener) will be invoked whenever the request comes back. The success/failure methods will not be invoked "inline".
There are two basic approaches for dealing with callbacks structured like this: "polling" or "events".
With polling, your main game loop could "check" the responseListener to see if its succeeded or failed. (You would need to modify your current listener a bit to disambiguate the success case and the empty string.) Once you see a valid response, you can then do the user.setId() and such.
With "events" then you can just put the user.setId() call inside the responseListener callback, so it will be executed whenever the network responds. This is a bit more of a natural fit to the Libgdx net API. (It does mean your response listener will need a reference to the user object.)
It is not possible to "wait" inline for the network call to return. The Libgdx network API (correctly) assumes you do not want to block indefinitely in your render thread, so its not structured for that (the listener will be queued up as a Runnable, so the earliest it can run is on the next render call).
I would not recommend this to any human being, but if you need to test something in a quick and dirty fashion and absolutely must block, this will work. There's no timeout, so again, be prepared for absolute filth:
long wait = 10;
while(!listener.isDone())
{
Gdx.app.log("Net", "Waiting for response");
try
{
Thread.sleep(wait *= 2);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
public static class BlockingResponseListener implements HttpResponseListener
{
private String data;
private boolean done = false;
private boolean succeeded = false;
#Override
public void handleHttpResponse(HttpResponse httpResponse)
{
Gdx.app.log("Net", "response code was "+httpResponse.getStatus().getStatusCode());
data = httpResponse.getResultAsString();
succeeded = true;
done = true;
}
#Override
public void failed(Throwable t)
{
done = true;
succeeded = false;
Gdx.app.log("Net", "Failed due to exception ["+t.getMessage()+"]");
}
public boolean succeeded()
{
return succeeded;
}
public boolean isDone()
{
return done;
}
public String getData()
{
return data;
}
}