I have an application which contains multiple hubs all on unique paths, so when calling the default :
routes.MapHubs("path", new HubConfiguration(...));
It blows up saying that the signalr.hubs is already defined (as mentioned here MapHubs not needed in SignalR 1.01?).
Now I can understand that it should only be called once, but then you will only get 1 path, so is there any way to handle a path per hub scenario? like how with MVC you specify the controller and action? so something like:
routes.MapHub<SomeHub>("path", new HubConfiguration(...));
== Edit for more info ==
It is mentioned often that you should never need to call this map hubs more than once, and in most scenarios I can agree, however I would not say that this is going to be the case for all applications.
In this scenario it is a website which at runtime loads any plugins which are available, each plugin is exposed the dependency injection framework to include its dependencies and the route table to include its routes. The hubs may have nothing to do with each other (other than the fact that they are both hub objects). So the hubs are not all known up front and are only known after the plugins are loaded, and yes I could wait until after this and try binding the hubs there, however then how do I have custom routes for each one then?
This seems to be a case of SignalR trying to abstract a little too much, as I dont see it being a bad idea to have custom routes rather than the default "/signalr", and as the routes all have different responsibilities it seems bad to have one entry route for them all.
So anyway I think the question still stands, as I dont see this as being a bad use case or bad design it just seems to be that I want to be able to have a route with a hub applied to it, much like in mvc you apply a controller and action to a route.
You shouldn't need more than the signalr.hubs route. If you point your browser to that route, you will see it automatically finds all public types assignable to IHub and creates a JavaScript proxy for them. You can interact with different hubs by name from JavaScript, i.e. if you have the following Hub:
public class GameHub : Hub
You can connect to that specific hub by doing:
var gameHubProxy = $.connection.gameHub;
You can also explicitly specify a name for your hub by adding the HubNameAttribute to the class:
[HubName("AwesomeHub")]
public class GameHub : Hub
You can then retrieve the specific proxy by doing
var awesomeHubProxy = $.connection.awesomeHub;
UPDATE:
I'm not sure whether SignalR will be able to run on multiple paths in the same application. It could potentially mess things up and the default assembly locator won't be able to pick up hubs loaded at runtime anyway.
However, there is a solution where you can implement your own IAssemblyLocator that will pick up hubs from your plugin assemblies:
public class PluginAssemblyLocator : DefaultAssemblyLocator
{
private readonly IEnumerable<Assembly> _pluginAssemblies;
public PluginAssemblyLocator(IEnumerable<Assembly> pluginAssemblies)
{
_pluginAssemblies = pluginAssemblies;
}
public override IList<Assembly> GetAssemblies()
{
return base.GetAssemblies().Union(_pluginAssemblies).ToList();
}
}
After you've loaded your plugins, you should call MapHubs and register an override of SignalRs IAssemblyLocator service:
protected void Application_Start(object sender, EventArgs e)
{
// Load plugins and let them specify their own routes (but not for hubs).
var pluginAssemblies = LoadPlugins(RouteTable.Routes);
RouteTable.Routes.MapHubs();
GlobalHost.DependencyResolver.Register(typeof(IAssemblyLocator), () => new PluginAssemblyLocator(pluginAssemblies));
}
NOTE: Register the IAssemblyLocator AFTER you've called MapHubs because it will also override it.
Now, there are issues with this approach. If you're using the static JavaScript proxy, it won't be re-generated every time it's accessed. This means that if your /signalr/hubs proxy is accessed before all plugins/hubs has been loaded, they won't be picked up. You can get around this by either making sure that all hubs are loaded by the time you map the route or by not using the static proxy at all.
This solution still requires you to get a reference to your plugin assemblies, I hope that's feasible...
Related
I have detected, that during loading the main page several controllers are instantiated (I think because the main page is built from several parts). The controllers instantiate the API classes to query some data through them. I was wondering how and where I could share the same API class instance between them.
I can imagine such a code:
class HomeController : Controller
{
private MyApi Api;
public HomeController()
{
this.Api = get the pervious MyApi instance form somewhere
if (this.Api == null) // 1st time
{
this.Api = new MyApi();
put this instance to somewhere to share between controllers
}
This "somewhere" is not a session, because next page load needs another MyApi instance. It must go to an object property which remains intact during the whole page load process, but is dismissed when the html result is generated. It must be really a simple thing, but I really don't know where it is :( Could somebody help me?
You can consider using Microsoft Unity Framework in your application.
Using Unity Dependency Injector you will be able to inject instances of MyApi class into the any controller and avoid writing " if (this.Api == null) " these types of checks and also managing instances of it in some Session or Application level variables, which makes code dirty.
For this specific problem "It must go to an object property which remains intact during the whole page load process, but is dismissed when the html result is generated", You can configure Unity Injected object to have a life time of "Scoped". Meaning, the object will be created once per request.
Here's is a link on configuring Unity in an asp.net core application
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/dependency-injection?view=aspnetcore-2.2
I am trying to create tools for a game to learn, as well as improve my own playing experience.
The primary .NET assembly, csass.dll, that controls the client is heavily obfuscated, and I have no control over this .dll-file at all and reading it's code is very time consuming. The game also includes a mainapi.dll which handles the communication between server and client. I have full control over this assembly and I can listen to the servers responses and send my own requests, which already gives me some pretty nice functionality, however there are some limitations I'd like to work around.
csass.dll references mainapi.dll, by default mainapi does not reference csass. In csass.dll there is a class, let's call it clickHandler, that has a public, non-static method ClickObj() of return type void. I want to call this method from within mainapi.dll, but I have no idea how to go about this, given that I have to leave csass.dll untouched.
Are there any feasible ways to 'retrieve' a clickHandler object (to then call its ClickObj() method) from within the mainapi assembly, without making any changes in csass.dll? Appreciate any and all input!
Create an interface:
public interface IClickHandler
{
void ClickObject();
}
Now create a helper class implementing that interface:
using CsAss;
public class ObjectClicker : IClickHandler
{
CsAss _csass;
public ObjectClicker(CsAss csass)
{
_csass = csass;
}
public void ClickObject()
{
_csass.clickObject();
}
}
Add a dependency on an instance of the interface into your MainAPI class:
public class MainApi
{
IClickHandler _clickHandler;
public MainApi(IClickHandler clickHandler)
{
_clickHandler = clickHandler;
// Now you have a class that can call the click handler for you
}
}
Now wire it all up:
public void StartupMethod()
{
var csass = new CsAss();
IClickHandler clickHandler = new ObjectClicker(csass);
var main = new MainApi(clickHandler);
// TODO: Start your app now that MainApi is properly configured
}
That last step is the only potentially tricky part, depending on your project layout. You need something that can create an instance of CsAss, MainApi and ObjectClicker. Normally I would solve that with the dependency injection (DI) pattern, either using a framework such as Autofac or so-called "poor man's DI" by manually instantiating from a central startup method. That gets a little more difficult with Unity since there isn't an easily accessible startup point. You could start looking into https://github.com/svermeulen/Zenject and go from there for options.
I am working with code that I have not written and am trying to understand why a particular piece of functionality is not working the way I intend. In particular, I have three projects within my solution:
API
Messages
Events
Processors
Events is a folder within Messages. API will communicate with Processors using NServiceBus via messages defined in Messages/Events. Each of the classes in Messages/Events extends IMessage.
Now within a configuration file for the bus that is shared by both Processors and API, I found these lines:
var conventionsBuilder = config.Conventions();
conventionsBuilder.DefiningEventsAs(t => t.Namespace != null && t.Namespace.StartsWith("DE.STEP.Messages") && t.Namespace.EndsWith("Events"));
return config;
This was implemented earlier, and the classes inside Messages/Events did NOT extend IMessage at an earlier time, instead the above code defined where and what a message could be qualified as. Now, since I have introduced IMessage, I figured I could remove those 3 lines of code. However, when I do, no messages ever make it to my queue from API. The code that attempts this publish is Bus.Publish<>();
How should I configure this so that I do not need to have a hard-coded string referencing the assembly where the messages are? I want my code to scan the solution for anything that extends IMessage and treat it as something that can be published and can be handled.
EDIT: As per the NServiceBus docs
By default, NServiceBus scans all assemblies in the endpoint
bin folder to find types implementing its interfaces so that
it can configure them automatically.
And Messages.dll appears in the bin of both API and Processors. So since Messages.dll contains all of my IMessages, shouldn't the default behavior suffice to make them available for publishing / subscribing? I.e. shouldn't removing the 3 lines in question have no effect?
The hierarchy of an event, if you're not using unobtrusive configuration, should be as follows:
ConcreteEvent : IEvent : IMessage
The reason for this is, after having had a look at the source code, your message endpoint mappings are processed as follows:
foreach (var mapping in messageEndpointMappings)
{
mapping.Configure((messageType, address) =>
{
var conventions = context.Settings.Get<Conventions>();
if (!(conventions.IsMessageType(messageType) || conventions.IsEventType(messageType) || conventions.IsCommandType(messageType)))
{
return;
}
if (conventions.IsEventType(messageType))
{
router.RegisterEventRoute(messageType, address);
return;
}
router.RegisterMessageRoute(messageType, address);
});
}
Conventions.IsEventType is a lookup implemented as follows:
EventsConventionCache.ApplyConvention(t, type => IsEventTypeAction(type));
I won't give you the full call stack but basically, you end up here:
t => typeof(IEvent).IsAssignableFrom(t) && typeof(IEvent) != t
This will evaluate as false for a concrete event only implementing IMessage, so RegisterEventRoute is never called for your event but rather it'll be treated as an IMessage, which follows different routing rules (only one route per IMessage).
In short, you must have IEvent interface on your event class to be able to use IBus.Publish if you are not using unobtrusive configuration.
I need to apply filtering by requesting host name on all database calls in my Web API service.
This filtering works like so:
lookup the Site to profile against based on the requesting hostname
Apply Site.Id on all subsequent data access calls made in the request
Essentially a global filter so so that data returned by the API service is always contained to the host.
One solution would be to pass the host name in as an argument on all my service methods like so:
public IEnumerable<Profiles> GetProfiles ()
{
var host = HttpContext.Current.Request.ServerVariables["SERVER_NAME"];
return profilesService.Get(host);
}
But since this is a consistent rule on all requests I would like to come up with a more elegant way to handle this so my service calls are just profileSerivce.Get();
I think I need to inject a ISiteLocator into my service layer that has either the host name or even better the Id already retrieved from the database that I can then apply. But I'm struggling with this on how and where I can reference the HttpContext to get the host name and also if it was possible to optimise this using StructureMap lifecycles.
I think I need to inject a ISiteLocator into my service layer
It seems to me you are heading into the right direction.
I'm struggling with this on how and where I can reference the
HttpContext
This is really simple actually. Define the ISiteLocator in your business layer and define an AspNetSiteLocator implementation into your ASP.NET web application, preferably close to (or inside) your Composition Root. That implementation might look like this:
public class AspNetSiteLocator : ISiteLocator
{
private readonly ISiteRepository siteRepository;
public AspNetSiteLocator(ISiteRepository siteRepository)
{
this.siteRepository = siteRepository;
}
Site ISiteLocator.GetCurrentSite()
{
return this.siteRepository.GetById(CurrentHostName);
}
private static string CurrentHostName
{
get
{
return HttpContext.Current.Request
.ServerVariables["SERVER_NAME"];
}
}
}
that has either the host name or even better the Id already retrieved
from the database
Try to let your ISiteLocator return data in a way that is most convenient to the consumers of that locator. In my example I returned a Site entity (if you have such an entity in your domain). This is probably more convenient than the host name or the Id, since consumers possibly have to query for the site again thereselves. However, perhaps Id is the most convenient, but that's up to you to find out.
how [...] to optimise this using StructureMap lifecycles
The implementation above doesn't have any state, so it can be registered with any lifetime; singleton for instance. However, every call to ISiteLocator.GetCurrentSite() will result in a new request to the ISiteRepository, which can cause too much overhead. In that case you probably want an implementation that stores the Site in a private field and always returns that instance. In that case you shoud register that implementation on a 'Per Web Request' basis (since the SERVER_NAME will not change during the request).
I'm trying to inject specific class into my WCF service but it doesn't work and I can't understand why. I'm VERY NEW to MEF and patterns, just trying to make it work. Watched series of videos to understand what it is about but bootstraping won't work in my case since it is not Silverlight
http://channel9.msdn.com/blogs/mtaulty/mef--silverlight-4-beta-part-1-introduction
Here is my Web application's Global.asax code. This is non MVC, just regular ASP.NET app:
private void Application_Start(object sender, EventArgs e)
{
RegisterRoutes();
var catalog = new WebScopedCatalog(new DirectoryCatalog(Server.MapPath("~\\bin")));
var container = new CompositionContainer(catalog);
container.ComposeParts(this);
}
FIRST, I'm not sure I even bootrstrap it properly.. SECOND, I'm using http://www.timjroberts.com/2011/02/web-scoped-mef-parts/ as a guidance for web-scoped parts. I need that because some injected objects supposed to live during request only.
Now, I have following class:
[Export(typeof(ITest))]
[WebPartCreationPolicy(WebCreationPolicy.Session)]
public class Test : ITest
{
public string TestMe()
{
return "Hello!";
}
}
And my service looks like:
[ServiceContract]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class MobileService
{
[Import]
public ITest MyTestClass { get; set; }
public MobileService()
{
int i = 10;
}
When breakpoint hits at i=10 - I have NULL inside MyTestClass. Clearly, MEF does not initialize this class for me. Am I missing something?
EDIT:
When I examine catalog - I see my class Exported but I don't see it imported anywhere...
EDIT 2:
Daniel, Thank you. It makes sense. It still feels litle like a magic for me at this point. Yes, WCF creates this service. Than I have MembershipProvider and various Utility classes that ALL need the same import. And I'm not creating neither of those classes so I can't have Mef creating them. (Service created by WCF, MembershipProvider created by who-knows-what, Utility classes have static methods..) I wanted to use Mef instead of storing my stuff in HttpContext.Current. My container object doesn't have SatisfyImports. It has SatisfyImportsOnce. What if I do it in many different constructors? Will Mef share same singleton or it will be creating new instance every time?
At this point I wonder if I should even use Mef in this particular scenario..
MEF won't satisfy imports for objects it doesn't create. What is it that creates MobileService? If it's not MEF, then the import won't be satisfied by default. Even if it is MEF, the import wouldn't be satisfied in the constructor- you can't set properties on an object you create until it is done being created (ie the constructor has finished).
You can call container.SatisfyImportsOnce(mobileService) to satisfy the imports of a part. You should try to avoid doing this everywhere you need a MEF import. If you can, you should export a part and import it from another part so that MEF handles the creation for you. However, it looks like this part may be created by WCF so you can't have MEF create it, and in that case it would be OK to use SatisfyImportsOnce.
Response to EDIT2: If you use the same container each time, MEF will by default only create one instance of the part with the export. You can set the CreationPolicy to NonShared (in either the export or import attribute) to change this.
As for whether it makes sense to use MEF the way you are trying to, I don't know enough about writing web services to give you any advice on that.
The web-scoped part creation policy that I wrote won't help with WCF services.
I've posted a new blog post that documents an approach to composeable WCF services:
http://www.timjroberts.com/2011/08/wcf-services-with-mef/
Basically, you need to implement a custom Instance Provider that is MEF-aware and can compose the WCF service object when it is created.
I wrote about how to compose your WCF in a generic way that its configuration based here:
Unit Testing, WCF and MEF
I actually built my solution on the code samples Tim Robert's provided in his post. only that I took it a bit further and instead of using code in the global asax i moved the configuration into the web.config so its easier to maintain.