I have created a REST service using Node.js and MongoDB for using in one of my Android app.
The get methods is working as expected when called from Android App.
I am trying to build a JSON object from Android App with necessary details and post to the service.I am unable to post to my collections. Below is the code snippet I have used in my Node.js
app.post('/accounts/put/:uObject', function(req, res, next) {
var username=uObject.name;
db.collection('test').insert({"username":username},function(err,docs){if(err){
res.send("There was some problem during insertions of linkes");
}
else{
res.send("Fail");
} });
});
What Am I doing wrong in this? I am getting the object as parameter and getting the values inside the function and passing to the insert.
To get the parameter from the route you need to use req.params, in your case req.params.uObject. Also common practice in JavaScript is to return early upon a condition being met.
app.post('/accounts/put/:uObject', function(req, res, next) {
var username = req.params.uObject;
db.collection('test').insert({
"username": username
}, function(err, docs) {
if (err) {
return res.send("There was some problem during insertions of linkes");
}
res.send("Fail");
});
});
Related
I'm trying to set up a Websocket client that communicates with a websever via JSON. I don't find any good examples online.
I only found this code online :
var ws = new WebSocket('ws://host.com/path');
ws.onopen = () => {
// connection opened
ws.send('something'); // send a message
};
ws.onmessage = (e) => {
// a message was received
console.log(e.data);
};
ws.onerror = (e) => {
// an error occurred
console.log(e.message);
};
ws.onclose = (e) => {
// connection closed
console.log(e.code, e.reason);
};
I don't know how to integrate this code into my app-code to function.
Do I need to install some packages for it?
I'm doing a project for my studies, and at the end I should have a Quiz-App which connects to a server to get the questions and answers for the game.
Thanks for anny help!
You do not need anything else to work with a WebSocket in react-native (or any relatively new JS environment for that matter). The example that you found covers pretty much anything that you need to get started. The next step is to bind that to your React logic. For instance, you can create a WebSocketController component that would look (details omitted) like this
class WebSocketController extends React.Component {
componentDidMount(){
this.ws = new WebSocket('ws://host.com/path');
this.ws.onmessage = this.handleMessage.bind(this);
this.ws.onerror = //...
}
handleMessage(e){
// dispatch event (รก la redux, flux), or do something else
}
componentWillUnmount(){
// close WS
}
}
Render this within your React hierarchy and it will be started along the rest of your components. If you need something more specific, let us know.
I am attempting to create a real-time communication capability for a Phonegap/Cordova app. I am using SignalR 2 to handle the communication.
The thing I am struggling with is getting a message to a particular user. Every single example out there shows saving Context.User.Identity.Name, which is useless to me because the remote site's User.Identity context is not shared by my phonegap app.
In essence, I am not authenticating a user in the traditional sense, so I need another way of linking the SignalR connectionID with the username I pass along.
Taken from the official ASP.NET signalr Examples, I have the following code which overrides the OnConnected event. Unfortunately it takes no parameters and expects User.Identity to be not null:
public override Task OnConnected()
{
using (var db = new UserContext())
{
// Retrieve user.
var user = db.Users
.Include(u => u.Rooms)
.SingleOrDefault(u => u.UserName == Context.User.Identity.Name);
// If user does not exist in database, must add.
if (user == null)
{
user = new User()
{
UserName = Context.User.Identity.Name
};
db.Users.Add(user);
db.SaveChanges();
}
else
{
// Add to each assigned group.
foreach (var item in user.Rooms)
{
Groups.Add(Context.ConnectionId, item.RoomName);
}
}
}
return base.OnConnected();
}
Now, maybe what I'd need is to have a version of this method that takes a string as a parameter and then I'd use that as my user identifier.
But how to go about that?
You need to create a new IUserIdProvider for the user and use dependency injection to register your provider and use it.
public interface IUserIdProvider
{
string GetUserId(IRequest request);
}
Register your provider with Global Host
GlobalHost.DependencyResolver.Register(typeof(IUserIdProvider), () => new MyIdProvider());
Usage:
public class MyHub : Hub
{
public void Send(string userId, string message)
{
Clients.User(userId).send(message);
}
}
Taken from: http://www.asp.net/signalr/overview/guide-to-the-api/mapping-users-to-connections#IUserIdProvider
I'm using Firebase Android SDK and became interested in sending synchronous request instead of asynchronous. According to the documentation, in any request callbacks are presented. But what about the synchronicity?
Thanks!
There is no way to synchronously load data from the Firebase Database.
While it is common for developers new to Firebase to wish for a synchronous method, it simply doesn't fit with Firebase's data synchronization model. Also see my answer here: Setting Singleton property value in Firebase Listener
It is not possible to load data synchronously with the official SDK. However, you can access all the data in firebase using the REST API. This would allow you to make synchronous calls. As mentioned about, Firebase is a realtime database and you will be missing the feature of updates when your data changes.
I made a simple class to call tasks synchronously in Android.
Note that this is similar to Javascript's async await function.
Check my gist.
TasksManager.class
public class TasksManager {
...
public ExecutorService getExecutor() {
if (mDefaultExecutor == null || mDefaultExecutor.isShutdown() || mDefaultExecutor.isTerminated()) {
// Create a new ThreadPoolExecutor with 2 threads for each processor on the
// device and a 60 second keep-alive time.
int numCores = Runtime.getRuntime().availableProcessors();
ThreadPoolExecutor executor = new ThreadPoolExecutor(
numCores * 2,
numCores * 2,
60L,
TimeUnit.SECONDS,
new LinkedBlockingQueue<>()
);
mDefaultExecutor = executor;
}
return mDefaultExecutor;
}
public static <TResult> Task<TResult> call(#NonNull Callable<TResult> callable) {
return Tasks.call(getInstance().getExecutor(), callable);
}
}
Here's a sample code to use it.
TasksManager.call(() -> {
Tasks.await(AuthManager.signInAnonymously());
// You can use multiple Tasks.await method here.
// Tasks.await(getUserTask());
// Tasks.await(getProfileTask());
// Tasks.await(moreAwesomeTask());
// ...
startMainActivity();
return null;
}).addOnFailureListener(e -> {
Log.w(TAG, "signInAnonymously:ERROR", e);
});
While it is not possible to load data from the FirebaseDatabase in a synchronous way, it is possible to wait for the load to finish synchronously.
You can wrap your value listener in a CountDownLatch and count down,
once the onDataChange or onCancelled implementation is called.
This is actually what the Tasks api is doing internally if you call Tasks.await(someTask).
You should use the value listener for single event listening, because in this case I assume you don't want continued updates. And use a proper timeout for the CountDownLatch, since Firebase won't timeout, ever.
reference.addListenerForSingleValueEvent(...);
You also have to take into account, that if you have the FirebaseDatabase
cache enabled, the first result might not be the actual value on the
server.
I have to add: While this might work, it is against the idea how firebase is designed and supposed to be used, as Frank already said.
If you are using Kotlin, add an extension function:
private suspend fun <TResult> Task<TResult>.await(): TResult? {
return try {
Tasks.await(this)
} catch (e: Exception) {
null
}
}
Now you can do
val snapshot = fireStore.collection(USER_ROOT_PATH).document(documentPath)?.get()?.await()
I have an issue with my network client design. I have a use case, when the client tries to request an item from a REST API, but in case the API returns a 404 HTTP status code I need to send a request to create the item on the server and then request the item again.
I would like to use RxJava to avoid the callback hell. Is this a valid use case RxJava? Is it possible to create such a conditional sub-request?
Thank you for your time and answers.
Based on your question, I assume you have something that look like
public Observable<Item> getItem();
that will either return the item, or fire an error and
public Observable<?> createItem();
That will create one.
You can use those two together like so:
public Observable<Item> getOrCreateItem() {
return getItem().onErrorResumeNext(error -> {
// Depending on your framework, figure out which is the result code
if (error.getResultCode() == 404) {
return createItem().flatMap(ignored -> getItem());
} else {
return Observable.error(error);
}
});
}
With Retrofit, you'd have to simply make sure the exception is a RetrofitError, cast it, and get the response and the status code. (((RetrofitError) error).getResponse().getStatus())
Where is the documentation/sample for all overloads of invokeApi function for Azure Mobile Service client SDK for Android?
I found this article and tried following code, which does not work. There are no compile time or run time errors, invokeApi gets called, but it does not come back to onSuccess or onFailure. If I call invokeApi without order object, everything works as expected
PizzaOrder order = new PizzaOrder();
order.Size = "Large";
order.Flavor = "Four cheeses";
order.UserPhone = "555-555-1234";
ListenableFuture<PizzaOrderResponse> testresult = mClient.invokeApi("bookservice", order, PizzaOrderResponse.class);
Futures.addCallback(testresult, new FutureCallback<PizzaOrderResponse>() {
#Override
public void onFailure(Throwable exc) {
// failure handling code here
}
#Override
public void onSuccess(PizzaOrderResponse testresult) {
// success handling code here
}
});
One of the properties in the data object being returned by the custom API had incorrect data type. I am still not sure where the good documentation is and why custom API call did not fail but at least it is working now.