Trying to use dependency injection with custom NHibernate implementation classes, specifically an IConnectionProvider. The issue is that I need my implementation of IConnectionProvider to use some dependency components ("services" in the .Net DI terminology). If the provider were managed by the DI container, I would just make the dependencies constructor args and be done.
For example:
public class MyConnectionProvider : ConnectionProvider
 {
public MyConnectionProvider(IServiceA serviceA, IServiceB serviceB) {
this.serviceA = serviceA;
this.serviceB = serviceB;
}
public override DbConnection GetConnection() {
// Use serviceA and serviceB to return a DbConnection...
}
}
But the mechanism by which NHibernate instantiates things like IConnectionProvider is reflection, not DI-aware. How can I make a custom impl like this, which requires cooperating services that are managed by the DI container?
The key is to implement the NHibernate interface IObjectsFactory There are some DI-aware implementations of that for Autofac, Spring, and Castle Windsor (discussed here and here). I ended up writing an implementation for Microsoft default DI that looks like this
public class MicrosoftDIObjectsFactory : IObjectsFactory
{
private Lazy<IServiceProvider> sp;
public MicrosoftDIObjectsFactory(Func<IServiceProvider> serviceProviderProvider)
{
sp = new Lazy<IServiceProvider>(serviceProviderProvider);
}
public object CreateInstance(Type type)
{
object instance = sp.Value.GetService(type);
if (instance != null) { return instance; }
return Activator.CreateInstance(type);
}
}
It would be pretty easy to add a cache of un-resolvable types to help performance (avoid repeated lookups in the IServiceProvider).
To set this up, during IServiceCollection initialization, I use code like this:
Environment.ObjectsFactory = new MicrosoftDIObjectsFactory(services.BuildServiceProvider)
Related
I have a controller with the following content (simplified version):
[HttpPost]
public Task<OkResult> Post([FromBody] commonRequest)
{
parser.DoWork(commonRequest);
return Ok();
}
The commonRequest object is populated from the incoming JSON request.
The parser.DoWork method should invoke the creation of a new instance of the class, depending on requestBody.
Here's what it looks like:
public class CommonParser : ICommonParser
{
private readonly ILogger<CommonParser> logger;
private IServiceProvider serviceProvider;
public CommonParser(ILogger<CommonParser> _logger, IServiceProvider _serviceProvider)
{
this.logger = _logger;
this.serviceProvider = _serviceProvider;
}
public void DoWork(CommonRequest commonRequest)
{
ICommonParser parser = (ICommonParser)Activator.CreateInstance(Type.GetType(commonRequest.instance)
, serviceProvider);
parser.DoWork(commonRequest);
}
}
I have three classes whose names are passed through commonRequest.instance. All of these classes implement the ICommonParser interface. Inside these classes, I pass a serviceProvider so that they can get the ILogger inside themselves and use it.
Here is an example constructor of this class:
private readonly ILogger<Parser1> logger;
public Parser1(IServiceProvider serviceProvider)
{
this.logger = serviceProvider.GetRequiredService<ILoggerFactory>().CreateLogger<Parser1>();
}
As a result, I can send only one message in this way. On the second call, I get a message that serviceProvider.GetRequiredServiceILoggerFactory () has been destroyed.
Please tell me what to do in such cases. I think I'm designing wrong.
From Dependency Injection in ASP.NET Core:
Avoid using the service locator pattern. For example, don't invoke
GetService or GetRequiredService to obtain a service instance when you
can use DI instead.
1) register the logger factory or the logger service, in case of the logger factory
services.AddSingleton<ILoggerFactory, LoggerFactory>();
2) use constructor injection to inject logger factory into the constructor
public Parser1(ILoggerFactory loggerFactory)
{
}
3) you might create a new interface for the parsers (parser1, 2, 3). The parsers implement this interface. Register them as services
public interface IParser
{
void DoWork(CommonRequest commonRequest);
}
services.AddTransient<Parser1>(); // implements IParser
services.AddTransient<Parser2>();
This post gives an answer how to resolve classes implementing the same interface. For getting parser with DI you will actually need IServiceProvider:
_serviceProvider.GetService<Parser1>();
I created a project to test the dependency injection offered by Google Guice in my Jax-rs resources, using Resteasy.
My intentions are:
Use multiple #ApplicationPath for the versions of my API. In each class annotated with #ApplicationPath I load a set of classes for the specific version.
Each resource have a #Inject (from Google Guice) in his constructor to inject some services.
I created two classes annotated with #ApplicationPath: ApplicationV1RS and ApplicationV2RS. In both I added the same resources classes (UserResource and HelloResource), only for my test.
My Module is configured like this:
public class HelloModule implements Module
{
public void configure(final Binder binder)
{
binder.bind(IGreeterService.class).to(GreeterService.class);
binder.bind(IUserService.class).to(UserService.class);
}
}
When I call http://localhost:9095/v1/hello/world or http://localhost:9095/v2/hello/world, I receive the same error:
java.lang.RuntimeException: RESTEASY003190: Could not find constructor
for class: org.jboss.resteasy.examples.guice.hello.HelloResource
Well, as I expected, this not works. The Google Guice is not "smart" to instantiate the resource classes using the construtor for me.
But I can't find a way to work. To be really honest, I'm really confuse about how the Google Guice, Jetty and Resteasy play with each other in this scenario.
If I abandon the idea of use #ApplicationPath, my resources work with Google Guice configuring my HelloModule like this:
public class HelloModule implements Module
{
public void configure(final Binder binder)
{
binder.bind(HelloResource.class);
binder.bind(IGreeterService.class).to(GreeterService.class);
binder.bind(UserResource.class);
binder.bind(IUserService.class).to(UserService.class);
}
}
But in this case, I'm passing the control to register my resources (HelloResource and UserResource) to Guice. It's not flexible for me, I can't setup my multiple #ApplicationPath.
So, what I'm missing or not understanding?
I created a project with the problemetic code. Is very easy to setup and test: https://github.com/dherik/resteasy-guice-hello/tree/so-question/README.md
Thanks!
When you have getClasses method in your Application then it tries to create instance for all the registered resources using the default constructor which is missing in our Resources class. One way is to create a default constructor and Inject the dependencies through setter Injection.
And then instead of overriding getClasses in ApplicationV1RS and ApplicationV2RS you override getSingletons. Since Resources can be Singleton.
Below are the changes that I made to make it work the way you want.
ApplicationV1RS.java
#ApplicationPath("v1")
public class ApplicationV1RS extends Application {
private Set<Object> singletons = new HashSet<Object>();
public ApplicationV1RS(#Context ServletContext servletContext) {
}
#Override
public Set<Object> getSingletons() {
Injector injector = Guice.createInjector(new HelloModule());
HelloResource helloResource = injector.getInstance(HelloResource.class);
UserResource userResource = injector.getInstance(UserResource.class);
singletons.add(helloResource);
singletons.add(userResource);
return singletons;
}
}
ApplicationV2RS.java
#ApplicationPath("v2")
public class ApplicationV2RS extends Application {
private Set<Object> singletons = new HashSet<Object>();
public ApplicationV2RS(#Context ServletContext servletContext) {
}
#Override
public Set<Object> getSingletons() {
Injector injector = Guice.createInjector(new HelloModule());
HelloResource helloResource = injector.getInstance(HelloResource.class);
UserResource userResource = injector.getInstance(UserResource.class);
singletons.add(helloResource);
singletons.add(userResource);
return singletons;
}
}
HelloResource.java
#Path("hello")
public class HelloResource {
#Inject
private IGreeterService greeter;
public HelloResource() {
}
#GET
#Path("{name}")
public String hello(#PathParam("name") final String name) {
return greeter.greet(name);
}
}
UserResource.java
#Path("user")
public class UserResource {
#Inject
private IUserService userService;
public UserResource() {
}
#GET
#Path("{name}")
public String hello(#PathParam("name") final String name) {
return userService.getUser(name);
}
}
Add #Singleton to your Service Classes.
Hope it helps.
I have also pushed the code to forked repo. check it out
I want to get one context per request in ASP NET 5/EF 7 app for use it in some methods (not in controller).
Unfortunately I did not find the answer in the documentation
ASP.NET vNext template and examples aspnet/MusicStore
You may use some methods for achieving this purpose.
Using .AddDbContext<ApplicationDbContext>(); method for registering ApplicationDbContext in Dependency Injection system (in ConfigureServices() method), leads to the fact that it registered as Scoped dependence(or in another words "per request"). Thereby you only need get it from Dependency Injection system.
Add your dbContext as parameter of constructor method your class (in which you will use dbContext). Then you have to get this class using Dependency Injection system, e.g added it as parameter of controller's constructor.
public class HabitsController : Controller
{
public HabitsController(HabitService habitService)
{
}
}
public class HabitService
{
private GetHabitsContext _dbContext;
public HabitService(GetHabitsContext dbContext)
{
_dbContext = dbContext;
}
}
But if you don't want to use constructor injection for getting context, you can get necessary dependenses using GetService() method (but you need in ServiceProvider instance for that, in example below, i'am getting it through constructor injection too).
using Microsoft.Framework.DependencyInjection; // for beta 6 and below
using Microsoft.Extensions.DependencyInjection; // for beta 7 and above
public class HabitService
{
private IServiceProvider _serviceProvider;
public HabitService(IServiceProvider serviceProvider)
{
_serviceProvider = serviceProvider;
}
public GetHabit()
{
var dbcontext = _serviceProvider.GetService<ApplicationDbContext>();
}
}
In first method, we can get HabitService through GetService() method too (not through the constructor injection).
using Microsoft.Framework.DependencyInjection; // for beta 6 and below
using Microsoft.Extensions.DependencyInjection; // for beta 7 and above
public class HabitsController : Controller
{
public HabitsController(IServiceProvider serviceProvider)
{
var habitService= serviceProvider.GetService<HabitService>();
}
}
public class HabitService
{
private GetHabitsContext _dbContext;
public HabitService(GetHabitsContext dbContext)
{
_dbContext = dbContext;
}
}
Thanks Tseng for remark:
I should be noted, that it's a pretty bad practice to inject the container into your objects. The container should only be referenced from the composition root and certain type of factories (which are implemented on application level, and not in the domain/business layer)
dbContext in HabitsController and _dbContext in HabitService are different contexts!
I checked, this is the same context.
i have created sigleton session bean which keeps one connection to my mongo database. It works well in jax-rs class when using #EJB annotation - after controller is contructed and bean is injected it calls init method anotated with #PostConstruct.
Then i created similar class, which is implementing SecurityContext. I used same pattern as in controller, but it is not working properly. init() method is never called and EJB instance is always null.
So is there a way to inject EJB to my SecurityContext implemetation ? it works well unless i try to inject and use MongoConnection
my singleton session bean I use to connect mongo database:
#Singleton
#Startup
public class MongoConnection {
#PostConstruct
public void init() {
// initialize properties
}
I use it in JAX-RS controller. it works here, also in classes inherited from EntityController.
Produces(MediaType.APPLICATION_JSON)
public class EntityController extends Application {
#Context
private UriInfo context;
**#EJB
protected MongoConnection connection;**
public EntityController() {
#PostConstruct
void init() {
...
connection.getMongo();
connection.getDatabaseName();
...
}
}
I implemented my own security context, which is looking for loged user roles in mongo database.
public class MongoSecurityContext implements SecurityContext {
**#EJB
private MongoConnection connection;**
public MongoSecurityContext() {
}
#PostConstruct
void init() {
...
connection.getMongo();
connection.getDatabaseName();
...
}
public MongoSecurityContext(ContainerRequestContext requestContext) {
token = requestContext.getHeaderString("token");
}
#Override
public boolean isUserInRole(String roleName) {
//**connection is allways null**, so it returns false;
if (connection == null)
return false;
}
}
EDIT:
I forget, i also have this warning in glassfish 4 console:
A provider extremeteacher.mongo.connection.MongoConnectionEjb registered in SERVER runtime does not implement any provider interfaces applicable in the SERVER runtime. Due to constraint configuration problems the provider extremeteacher.mongo.connection.MongoConnectionEjb will be ignored
EDIT2:
#Provider
#Priority(Priorities.AUTHORIZATION)
public class AuthorizationFilter implements ContainerRequestFilter {
#Override
public void filter(ContainerRequestContext requestContext) {
requestContext.setSecurityContext(new MongoSecurityContext(requestContext)) ;
}
}
Injection does not work for objects created with new because the container is never given control to perform the injection. I recommend moving the #EJB to the filter and passing it to the MongoSecurityContext constructor.
I have a repository like this
public abstract class BaseRepository<TEntity> : IRepository<TEntity> where TEntity : class
{
protected DbContext _dbContext;
public BaseRepository(DbContext dbContext)
{
_dbContext = dbContext;
}
public TEntity GetByKey(object keyValue)
{
// todo
}
}
and a concrete repository like this
public CustomerRepository : BaseRepository<Customer> , ICustomerRepository
{
public CustomerRepository(DbContext context) : base (context) { }
public Customer FindCustomerByKey(string key)
{
_dbContext.Set<Customer>().Find(key);
}
}
I have wcf service like this
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class CustomerSatisfactionService : ICustomerSatisfactionService
{
private ICustomerRepository _customerRepository;
private IHelpDeskRepository _helpdeskRepository;
public AccountService(ICustomerRepository customerRepository,IHelpdeskRepository helpdeskRepository)
{
_customerRepository = customerRepository;
_helpdeskRepository = helpdeskRepository;
}
public void DoSomethingUsingBothRepositories()
{
// start unit of work
// _customerRepository.DoSomething();
// _helpdeskRepository.DoSomething();
// commit unit of work
}
}
and I am using StructureMap for injecting DbContext instances like this
For<DbContext>().Use(() => new MyApplicationContext());
My problem is when a client calls the service, a new CustomerSatisfactionService instance is created, hence new instances of CustomerRepository and HelpdeskRepository are created but with different DbContexts.
I want to implement the unit of work pattern, but in the DoSomethingWithBothRepositories method, the two repositories have different DbContexts.
Is there any way to tell structure map to spin up a DbContext instance on a per call basis?
You must specify lifecycle for your DbContext so that only one instance is created per call. StructureMap doesn't contain build-in lifecycle management for per call WCF but you can find one implementation on this blog.
You need to implement UnitOfWork pattern so that same context is shared amongst entities. Take a look at http://blogs.msdn.com/b/adonet/archive/2009/06/16/using-repository-and-unit-of-work-patterns-with-entity-framework-4-0.aspx for a way to implement it.
I don't know if you need/want StructureMap to control the instantiation of dbcontext, have a look at this reply, UoW and UoW Factory setup dbcontext for the calls that need to be made in the repository.
EF ObjectContext, Service and Repository - Managing context lifetime.