I have a question to make sure what I want to do. I know that I should Dispose if I want to RollBack Transaction in a request. But my question is that is it necessary to use Dispose for DbContext after SaveChangeAsync() or it would be done automatically after request is done?
UPDATE:
I use Unit of Work in Repository pattern so I have a UnitOfWork class that has an interface and it has all the Repository of my entities and a private readonly instance of DbContext :
public class UnitOfWork : IUnitOfWork
{
private readonly ApplicationDbContext _db;
public UnitOfWork(ApplicationDbContext db)
{
_db = db;
}
}
Then I add an instance of IUnitOfWork per request and define it in the constructor.
In my JSF application i have a process that takes to long to complete and i don't want that the user keeps waiting till its finish. I'm trying to implement some kind of 'fire and forget task' to run in background.
I'm doing it using an #Asynchronous method. This is the right approach?
My controller:
#ViewScoped
#Named
public class Controller implements Serializable {
private static final long serialVersionUID = -6252722069169270081L;
#Inject
private Record record;
#Inject
private Service service;
public void save() {
this.record.generateHash();
boolean alreadyExists = this.service.existsBy(this.record.getHash());
if (alreadyExists)
Messages.add(null, new FacesMessage(FacesMessage.SEVERITY_ERROR, "Error", "This record already exists"));
else {
this.service.save(this.record);
this.clearFields();
}
}
}
My service:
#Stateless
public class Service extends AbstractService<Record> {
private static final long serialVersionUID = -6327726420832825798L;
#Inject
private BeanManager beanManager;
#Override
public void save(Record record) {
super.save(record);
this.preProcess(record);
}
#Asynchronous
private void preProcess(Cd cd) {
// Long task running here ...
this.beanManager.fireEvent(cd);
}
}
But even with this approach the user keeps stuck at the page till the preProcess method finishes.
The problem here is that annotations that modify the behavior of EJBs (and CDI beans) are only applied when called by the "proxy" object that gets injected to appropriate injection points, like fields annotated with #EJB or #Inject.
This is because of how the containers implement the functionality that modifies the behavior. The object that the container injects to clients of EJBs (and normal-scoped CDI beans) is actually a proxy that knows how to call the correct instance of the target bean (e.g. the correct instance of e #RequestScoped bean). The proxy also implements the extra behaviors, like #Transactional or #Asynchronous. Calling the method through this bypasses the proxy functionalities! For this reason placing these annotations on non-public methods is effectively a NO-OP!
A non-exclusive list of solutions:
Move preProcess() to a different EJB, make it public and keep the #Asynchronous annotation
Make preProcess() public and call it from the Controller
If the computation is truly private to the Service and exposing it would break design, and ou don't mind doing a bit more manual work, you can always run async tasks from the container-provided ManagedExecutorService:
#Resource
private ManagedExecutorService managedExecutorService;
Pay attention to the semantics of the thread that executes your code - more specifically to what context values are propagated and what not! Well, you have to pay attention to that for #Asynchronous methods too!
I'm learning .Net Core SignalR and investigating how I could use it with my app live charts. I play with some examples on the net and they all work, but I don't know how to use SignalR with database polling. I'm getting below error:
Cannot access a disposed object ...
I'm assuming it is related to my contex is being disposed after request is completed. I'm using dependency injection.
ChatController
public class ChatController : ControllerBase
{
private IChatService _chatService;
private IChatContext<ChatHub> _hub;
public ChatController(IChatContext<ChatHub> hub, IChatService chatService)
{
_hub = hub;
_chatService = chatService;
}
public IActionResult Get()
{
var timerManager = new TimerManager(() => _hub.Clients.All.SendAsync("transferchatdata", _chatService.ChatDataByProds()));
return Ok(new { Message = "Request Completed" });
}
}
ChatService
public interface IChatService
{
IEnumerable<ChatDataByProd> ChatDataByProds();
}
public class ChatService : IChatService
{
private ChatContext _context;
public ChatService(ChatContext context)
{
_context = context;
}
public IEnumerable<ChatDataByProd> ChatDataByProds()
{
return _context.ChatDataByProds;
}
}
ChatHub
public class ChatHub : Hub
{
}
It seems that you are using a EF Core context that is a scoped lifetime service, which means per-request lifetime in ASP.NET Core. Your ChatService must have a longer lifetime than a HTTP request, and a single instance of the database context would be disposed by the container while you are still holding the reference to it.
Thus, you need to obtain an IServiceProvider container in the ctor of ChatService, and GetService the database context each time when you need to access the database.
I have a multi-layer application that I started writing in ASP.NET Core 1.1 which I'm still learning along the way. I have organized it like previous apps I've done in the Web API, I have host service (net core app), business layer and data layer that is above database. Business and data layers were net core standard libraries, but when I wanted to add entity framework I had to modify data layer to look like net core app, so now I have Startup.cs with configurations there. That allowed me to configure entity framework service and to create migrations in the data layer. But now I have a problem as I wanted to add asp.net identity. Every tutorial on the net is about SPAs that have everything in one project.
I have added identity to Startup.cs and database is generated well
public void ConfigureServices(IServiceCollection services)
{
var connectionString = Configuration.GetConnectionString("DefaultConnection");
services.AddEntityFramework(connectionString);
services.AddMyIdentity();
services.Configure<IdentityOptions>(options =>
{
// Password settings
options.Password.RequireDigit = true;
options.Password.RequiredLength = 8;
options.Password.RequireNonAlphanumeric = false;
options.Password.RequireUppercase = true;
options.Password.RequireLowercase = false;
// Lockout settings
options.Lockout.DefaultLockoutTimeSpan = TimeSpan.FromMinutes(30);
options.Lockout.MaxFailedAccessAttempts = 10;
// User settings
options.User.RequireUniqueEmail = true;
});
}
public void Configure(IApplicationBuilder app)
{
app.UseIdentity();
}
but now I need to use UserManager from a class that is not a Controller and I don't know how to deal with dependency injection.
To explain better, I have an Account controller in my Host Service
[HttpPost]
[Route("Register")]
public async Task<IActionResult> Register([FromBody]RegisterUserDto dto)
{
var result = await Business.Commands.Accounts.Register(dto);
return Ok(result);
}
Business layer just calls the Data layer
public async static Task<ResponseStatusDto> Register(RegisterUserDto dto)
{
// some code here
var identityLogon = await Data.Commands.ApplicationUsers.Register(dto);
// some code here as well
return new ResponseStatusDto();
}
Now the question is, how do I get UserManager in the Data Register method? It's a simple class, it doesn't inherit from a controller, dependency injection is not working for constructors like in the examples found here
Core Identity
public class AccountController : Controller
{
private readonly UserManager<ApplicationUser> _userManager;
private readonly SignInManager<ApplicationUser> _signInManager;
private readonly IEmailSender _emailSender;
private readonly ISmsSender _smsSender;
private static bool _databaseChecked;
private readonly ILogger _logger;
public AccountController(
UserManager<ApplicationUser> userManager,
SignInManager<ApplicationUser> signInManager,
IEmailSender emailSender,
ISmsSender smsSender,
ILoggerFactory loggerFactory)
{
_userManager = userManager;
_signInManager = signInManager;
_emailSender = emailSender;
_smsSender = smsSender;
_logger = loggerFactory.CreateLogger<AccountController>();
}
//
// GET: /Account/Login
So, how do I pass UserManager that is configured in Startup to some random class somewhere in the middleware? I have seen this question, but the answer to just pass null values to UseManager constructor is not working nor I think it's good.
//EDIT as per Set's answer
I have removed all static references, but I'm still not quite there. I have followed this dependency injection instructions, but I'm not sure how to instantiate and call Add method.
I have created an interface
public interface IIdentityTransaction
{
Task<IdentityResult> Add(ApplicationUser appUser, string password);
}
and implemened it
public class IdentityTransaction : IIdentityTransaction
{
private readonly ApplicationDbContext _dbContext;
private readonly UserManager<ApplicationUser> _userManager;
private readonly RoleManager<IdentityRole> _roleManager;
public IdentityTransaction(ApplicationDbContext context, UserManager<ApplicationUser> userManager, RoleManager<IdentityRole> roleManager)
{
_roleManager = roleManager;
_userManager = userManager;
_dbContext = context;
}
public async Task<IdentityResult> Add(ApplicationUser applicationUser, string password)
{
return await _userManager.CreateAsync(applicationUser, password);
}
}
then I injected it to a service collection in Startup.cs
services.AddScoped<IIdentityTransaction, IdentityTransaction>();
but how to call Add method from IdentityTransaction service?
I cannot instantiate it nor use dependency injection on constructor as it just loops my problem. #Set mentioned
or pass UserManager userManager as parameter to method
pass it from where?
I think I'm very close, but I'm missing something.
I have tried using
IIdentityTransaction it = services.GetRequiredService<IIdentityTransaction>();
but services which is IServiceProvider is null, I don't know where to get it from either.
DI in ASP.NET Core works the same for controller and non-controller classes using "constructor injection" approach.
You have the problem as Register method is static, so doesn't have access to instance variables/properties. You need to
make Register method non-static
or pass UserManager<ApplicationUser> userManager as parameter to method
In general, you should avoid using static classes for business logic as they don't help to test your code properly and produce the code coupling. Search via internet/SO and you will find a lot of topics why static is bad.
Use DI to get the instance of Data.Commands.ApplicationUsers class in your controller. If you need only one instance of this class for your application - use singleton lifetime for it.
Update. Again, use constructor injection: modify your "Data Layer" class so it can get the instance of IIdentityTransaction as constructor parameter:
public class YourDataLayerClass : IYourDataLayerClass
{
private IIdentityTransaction _identityTransaction;
public YourDataLayerClass(IIdentityTransaction identityTransaction)
{
_identityTransaction = identityTransaction;
}
public void MethodWhereYouNeedToCallAdd()
{
_identityTransaction.Add(...);
}
}
And idea the same for IYourDataLayerClass instance: register dependency
services.AddScoped<IYourDataLayerClass, YourDataLayerClass>();
and then the class (middleware in your case, if I understand you properly) that depends on it should receive that instance via constructor:
public class YourMiddleware
{
private IYourDataLayerClass _yourDataLayerClass;
public YourMiddleware(IYourDataLayerClass yourDataLayerClass)
{
_yourDataLayerClass = yourDataLayerClass;
}
...
}
Yes you are very close.
First thing, either remove context parameter from the IdentityTransaction constructor as in your code snipped it appears to be useless. Or if you plan to use it later, declare it in the DI container:
services.AddScoped<ApplicationDbContext, ApplicationDbContext>();
Second thing, you simply need to add IIdentityTransaction as a dependency in the controller's constructor, and remove SignInManager and UserManager from its dependencies as eventually you won't use these directly within the controller:
public class AccountController : Controller
{
private readonly IEmailSender _emailSender;
private readonly ISmsSender _smsSender;
private static bool _databaseChecked;
private readonly ILogger _logger;
IIdentityTransaction _identityTransaction;
public AccountController(
IEmailSender emailSender,
ISmsSender smsSender,
ILoggerFactory loggerFactory,
IIdentityTransaction identityTransaction)
{
_emailSender = emailSender;
_smsSender = smsSender;
_logger = loggerFactory.CreateLogger<AccountController>();
_identityTransaction = identityTransaction;
}
If you need an additional business layer (IBusinessLayer) between the controller, same process, declare the class in the DI container at startup, add IIdentityTransaction as a dependency in the business class constructor, and update the controller's dependencies from IIdentityTransaction to IBusinessLayer.
A couple more precisions.
services.AddScoped<IIdentityTransaction, IdentityTransaction>();
This piece of code does NOT inject instances or dependencies. It declares an interface and its associated implementation in the DI container, so it can be injected later when required. Actual instances are injected when the objects that required them are actually created. I.e. the controller gets its dependencies injected when it is instantiated.
IIdentityTransaction it = services.GetRequiredService<IIdentityTransaction>();
What you tried to do here is called the dependency locator pattern, and is often considered as an anti-pattern. You should stick to dependency injection via the constructor, it's much cleaner.
The key is to declare everything in the DI container at startup, even your custom business/data layers classes, never instantiate them yourself anymore, and declare them as required dependencies in any classes' constructor that need them.
If i have a singleton wrapper around a collection in asp.net does it have to be cached or would it's data be persisted across post backs?
Also if another user logs into the app would the app create another instance (of itself) and therefore another instance of the singleton or would it access the same singleton that was created in the first instance?
The actual implementation of the singleton is one of the following:
(Design 1:)
using System;
public sealed class Singleton
{
private static volatile Singleton instance;
private static object syncRoot = new Object();
private Singleton() {}
public static Singleton Instance
{
get
{
if (instance == null)
{
lock (syncRoot)
{
if (instance == null)
instance = new Singleton();
}
}
return instance;
}
}
}
or Design 2:
public sealed class Singleton
{
private static readonly Singleton instance = new Singleton();
private Singleton(){}
public static Singleton Instance
{
get
{
return instance;
}
}
}
A static variable will exist as long as the application is running, until a application restart. It would exist across postbacks and users.
This article shows how to implement a static singleton: http://msdn.microsoft.com/en-us/library/ff650316.aspx
Are there any more requirements on what you are trying to do that would affect the implementation of the singleton?
Singleton is pattern that makes sure there is only one instance for all request. Since you have declared it static it exists for lifetime of the application. And the same instance will be returned to any user requesting the object through your property.