My web api looks like:
[Route("api/[controller]")]
public class ValuesController : Controller
{
private readonly ApplicationDbContext _context;
public ValuesController(ApplicationDbContext context)
{
_context = context;
}
[HttpGet]
public string Get()
{
// get random user
var user = _context.Users.SingleOrDefault();
return user?.Email ?? "";
}
}
Trying to call it via jquery:
$.get('/api/values', function (email) {
console.log(email)
})
I've 2 questions:
1/. Why didn't console.log(email) work although I was getting the response successful?
There was nothing in the Console tab.
2/. When I made a request to server (/api/values), the breakpoint had been caught:
My question: where had ValuesController been called within context? I'd sent a request from client, then the constructor was hit (I'm sure that I didn't send something like ApplicationDbContext from client to server :v)
UPDATE: By changing $.get('/api/values', {}, function (email) {} to $.get('/api/values', function (email) {}. I've fixed the first problem. It's my bad. Sorry about that.
Shorter Answer
My question: where had ValuesController been called within context? I'd sent a request from client, then the constructor was hit.
The HTTP Request arrived. ASP.NET MVC Routing told the application to use the ValuesController to handle the request. The application constructed the ValuesController, supplying an instance of ApplicationDbContext via dependency injection.
Longer Answer
The Startup.Configure method is used to specify how the ASP.NET application will respond to individual HTTP requests. Since you are using Web API, you have configured app.UseMvc(). Result: when an HTTP Request arrives, MVC Routing tells the application to use the appropriate controller.
The Startup.ConfigureServices method is used to specify services that are available via dependency injection. Since you are injecting an ApplicationDbContext into your constructor, you have configured services.AddDbContext<ApplicationDbContext>(). Result: when the application constructs a ValuesController, ASP.NET Dependency Injection will provide an instance of the ApplicationDbContext.
Related
I want to send messages from the server (from a class, not a controller) via the SignalR Hub.
The hub works for messages originating from the client but not for messages from the server.
I've tried multiple methods of which non seem to work. For example, I tried retrieving the hub context using:
GlobalHost.ConnectionManager.GetHubContext<MyHub>()
with no success.
What is the best and up-to-date method of doing this in .NET Core?
Temporary Solution:
Having a websocket client inside the host api. Then making it connect to itself. This is not an ideal solution but works as a temporary fix.
You can inject the context in your class as service. Your class must be initialized via DI and added as a service. There is no difference between class or controller.
public class SomeClass
{
public IHubContext<ChatHub, IChatClient> _strongChatHubContext { get; }
public SomeClass(IHubContext<ChatHub, IChatClient> chatHubContext)
{
_strongChatHubContext = chatHubContext;
}
public async Task SendMessage(string message)
{
await _strongChatHubContext.Clients.All.ReceiveMessage(message);
}
}
You can also get service like following by injecting IHttpContextAccessor
var _strongChatHubContext = httpContextAccessor.HttpContext.RequestServices.GetRequiredService<IHubContext<ChatHub, IChatClient>>()
reference:
https://learn.microsoft.com/en-us/aspnet/core/signalr/hubcontext?view=aspnetcore-2.1
First you need to somewhere instantiate your hub (normally when your app is bootstrapping).
MyHub myHub = new MyHub();
Then on your class inject the context:
private readonly IHubContext<NotifyHub, ITypedHubClient> hubContext;
And in your class method just call the hub:
hubContext.Clients.All.yourHubMethod(yourPayload);
It is possible to have host address in app services?
For example we want send email to customer with specific link point to site address. How is this possible?
This came up via Google & the existing answer didn't really help. I don't necessarily agree that app services are the wrong domain for this; in ABP for example, a service is closely connected to a controller and services usually only exist in order to service web requests there. They often execute code in an authorised state that requires a signed-in user, so the whole thing is happening in the implicit domain context of an HTTP request/response cycle.
Accordingly - https://learn.microsoft.com/en-us/aspnet/core/fundamentals/http-context?view=aspnetcore-2.2#use-httpcontext-from-custom-components
Add services.AddHttpContextAccessor(); to something like your Startup.cs - just after wherever you already call services.AddMvc().
Use dependency injection to get hold of an IHttpContextAccessor in your service - see below.
Using constructor-based dependency injection, we add a private instance variable to store the injected reference to the context accessor and a constructor parameter where the reference is provided. The example below has a constructor with just that one parameter, but in your code you probably already have a few in there - just add another parameter and set _httpContextAccessor inside the constructor along with whatever else you're already doing.
using HttpContext = Microsoft.AspNetCore.Http.HttpContext;
using IHttpContextAccessor = Microsoft.AspNetCore.Http.IHttpContextAccessor;
// ...
public class SomeService : ApplicationService
{
private readonly IHttpContextAccessor _httpContextAccessor;
public SomeService(IHttpContextAccessor httpContextAccessor)
{
_httpContextAccessor = httpContextAccessor;
}
}
Now service code can read the HTTP context and from there things like the HTTP request's host and port.
public async Task<string> SomeServiceMethod()
{
HttpContext context = _httpContextAccessor.HttpContext;
string domain = context.Request.Host.Host.ToLowerInvariant();
int? port = context.Request.Host.Port;
// ...
}
HttpContext.Current.Request.Url
can get you all the info on the URL. And can break down the url into its fragments.
I want to make API(s) using ASP.NET WEB API which should be private or protected.
Using the API(s) I am planning to make Xamarin application and a MVC Website.
Only the Apps can use the API(s), otherwise if anyone get the API(s) then he/she can retrieve data using the API(s). I don't want so!
How can I do it? I need some suggestion.
You can secure you api with API Key Authentication mechanism. Here is a good tutorial
Starting go inside your global.asax.cs file and add
GlobalConfiguration.Configuration.MessageHandlers.Add(new AuthHandler())
Create a class AuthHandler in your project and make that class interface with DelegatingHandler:
public class AuthHandler: DelegatingHandler
Create two methods within your AuthHandler class called ValidateCredentials and SendAsync. The SendAsync method is overridded.
private bool ValidateCredentials(AuthenticationHeaderValue authVal){}
protected override async Task<HttpResponseMessage> SendAsync(HttpResponseMessage request, CancellationToken cancelTok){}
When a class or method has the Authorize filter applied, the MessageHandler in your global.asax is called which calls the Auth handler you created, for example:
[Authorize]
public class SomeController : ApiControler{}
So whats left is the actual authentication of the user. You need to get the header value (placed by the client application), decode it and check it against your database or whatever you use.
private bool ValidateCredentials(AuthenticationHeaderValue authVal)
{
try{
string decodedHeader = new Classes.Strings().decode(authVal);
this.user = // some query to check against database goes here
return true;
}
catch{
// some type of error control here
return false
}
}
protected override async Task<HttpResponseMessage> SendAsync(HttpResponseMessage request, CancellationToken cancelTok)
{
if(ValidateCredentials(request.Headers.Authorization))
{
// store user here to use around the api on this request
}
}
So in short HTTP needs to store your authentication header value. Use that value on each request to filter any class or function you require authentication on. Next, I would read up on http headers, specifically the Authentication header value.
I am building a Spring Cloud project (Brixton.M4 with Spring Boot 1.3.1) with Eureka, Zuul and FeignClient where I am trying to add multi tenancy support (Tenants are identified by subdomain : tenant1.myservice.com). To do so, I would like to somehow pass the original subdomain along requests that are forwarded from a service to the other via Feign but I can't seem to be able to find the right way to do it.
What I have is a client that exposes a #RestController which calls a #FeignClient to communicate with my backend which exposes server operations to the client through its own #RestController.
The #FeignClient using same interface as my #RestController on the server :
#FeignClient(name = "product")
public interface ProductService extends IProductService {
}
What I am currently trying to do is set a header in a RequestInterceptor :
#Component
public class MultiTenancyRequestInterceptor implements RequestInterceptor {
private CurrentTenantProvider currentTenantProvider;
#Autowired
public MultiTenancyRequestInterceptor(CurrentTenantProvider currentTenantProvider) {
this.currentTenantProvider = currentTenantProvider;
}
#Override
public void apply(RequestTemplate template) {
try {
template.header("TENANT", currentTenantProvider.getTenant());
} catch (Exception e) {
// "oops"
}
}
}
My provider class is a simple component where I'm trying to inject a request / session scope bean :
#Component
public class CurrentTenantProvider {
#Autowired
private CurrentTenant currentTenant;
//...
}
The bean (I tried both session and request scope) :
#Bean
#Scope(value = WebApplicationContext.SCOPE_SESSION, proxyMode = ScopedProxyMode.TARGET_CLASS)
public CurrentTenant currentTenant() {
return new CurrentTenant();
}
On the server, I use Hibernate multitenant provider that is supposed to catch the header value and use it to define which DB to connect to :
#Autowired
private HttpServletRequest httpRequest;
#Override
public String resolveCurrentTenantIdentifier() {
return httpRequest.getHeader("TENANT");
}
It seems the Feign call to the server is done in another thread and out of the incoming request scope, so i'm not sure how to pass that value along.
It all works fine when I hardcode the tenant value in the RequestInterceptor so I know the rest is working properly.
I have also looked at many other posts about Zuul "X-Forwaded-For" header and cannot find it in the request received on the server. I have also tried adding a ZuulFilter to pass host name to next request but what I see is that original request to the Client is picked up by the ZuulFilter and I can add but not when the Feign request is sent to the backend service even if I map it in zuul (i guess that is intended ?).
I am not really sure what's the next step and would appreciate some suggestions.
Hope that it's of any use for you but we're doing sth similar in Spring-Cloud-Sleuth but we're using a ThreadLocal to pass span between different libraries and approaches (including Feign + Hystrix).
Here is an example with the highlighted line where we retrieve the Span from the thread local: https://github.com/spring-cloud/spring-cloud-sleuth/blob/master/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/client/TraceFeignClientAutoConfiguration.java#L123
I have set up Ninject to work with SignalR (hosted on IIS) as described in the answer to this question: SignalR 2 Dependency Injection with Ninject.
This works in most cases, except when the client is disconnecting from the hub the HttpContext.Current variable is null and thus Ninject can't inject the value and throws an exception.
I've read up on the issue and found out that most people recommend that the current HttpContext should be retrieved from IRequest.GetHttpContext() (which is accessible from the hubs context). Sadly this doesn't help when trying to inject the value (I could pass on the context from the hub, but that would defeat the purpose of having dependency injection).
Code example (some parts removed for brevity):
public class TestHub : Hub
{
public TestHub(ITestService testService)
{
TestService = testService;
}
// When the disconnection request is issued, a ArgumentNullException
// for the HttpContext construction is thrown
public override Task OnDisconnected(bool stopCalled)
{
TestService.DoSomething();
}
}
public class TestService : ITestService
{
public TestService(HttpContextBase httpContext)
{
HttpContext = httpContext;
}
public void DoSomething()
{
// Service uses some data from the httpContext
TestLogger.Log(HttpContext.User.Identity.Name);
}
}
Is there any way to inject HttpContextBase into services that are in turn injected into SignalR hubs without accessing HttpContext.Current?
In case the HttpContext is actually available at construction time, you could use the following binding:
kernel.Bind<HttpContextBase>()
.ToMethod(ctx => Context.Request.GetHttpContext())
.WhenAnyAncestorMatches(ctx => typeof(Hub).IsAssignableFrom(ctx.Plan.Type));
The When condition checks whether the HttpContextBase is injected into a Hub (or derived class) or into any dependency of a Hub.
In case the HttpContextBase is only ever injected when contstructing Hubs, you could also just leave out the When condition.
I have worked around the issue now, and thus this is not a solution to the problem, but an unclean way to mitigate it.
Since the missing HttpContext only happens on client disconnects, I have first of marked all my injected services as Lazy<T>, so they don't get resolved immediately, but only when they are accessed. After applying this change, the exceptions are thrown only when code in the SignalR OnDisconnected event of the hub is triggered. So I had to modify the code in that is executed in the OnDisconnected method to use (or pass in as parameter) the context retrieved directly from the hub. In my case not much code gets executed in there, but it could become a problem if more is required in the future.
The patch applied to the sample code from my question:
public class TestHub : Hub
{
public TestHub(Lazy<ITestService> testService)
{
TestService = testService;
}
public override Task OnDisconnected(bool stopCalled)
{
DoSomethingThatInvolvesHttpContext(Context.Request.GetHttpContext());
}
}