I'm trying to use parse's .net client in an mvc web application.
and couldn't find a proper way to inject ParseObject, ParseUser and ParseUser.CurrentUser
what is the nice way of injecting static objects?
web app has a Forms authentication setup.
and ioc container register components or services LifestylePerWebRequest()
my problem occured when I want to update the user object,
only if the ParseUser.CurrentUser logged in we can update. (https://parse.com/docs/dotnet_guide#users-security)
but this is a static object and I get the latest signed in user...
now I'm thinking to create a user2 table in parse and keep all profile data in there...
Is there a better way to go?
public async Task<bool> UpdateUser(string id, string name, string surname)
{
//var user = ParseUser.CurrentUser;
var user = await ParseUser.Query.GetAsync(id);
if (user == null) return await Task.FromResult(false);
user.Name = name;
user.Surname = surname;
await user.SaveAsync();
return await Task.FromResult(true);
}
what is the nice way of injecting static objects?
You hide them behind an application-defined abstraction. You define a narrow interface that describes the functionality that your application needs (and ideally without the interface leaking the external framework). For instance:
public interface IUserRepository
{
// Throws an exception on failure.
void UpdateUser(string id, string name, string surname);
}
Now you can hide the static class behind an implementation of IUserRepository:
public class ParseUserRepository : IUserRepository
{
public void UpdateUser(string id, string name, string surname)
{
// call the static Parse functionality.
}
}
Related
I have a really nasty StackOverflowException in my spring backend, that I need help with. This is not going to be solved easily. I really hope to find some help here.
Most parts of my backend work. I can query my REST interface for models, they are nicely returned by spring-hateoas, GET, PUT and POST operations work. But one exception: When I try to update an existing DelegationModel, then I run into an endless StackOverflowException.
Here is my DelegetionModel.java class. Please mark, that delegation model actually doesn't have any property annotated with #CreatedBy!
#Entity
#Data
#NoArgsConstructor
#RequiredArgsConstructor(suppressConstructorProperties = true) //BUGFIX: https://jira.spring.io/browse/DATAREST-884
#EntityListeners(AuditingEntityListener.class) // this is necessary so that UpdatedAt and CreatedAt are handled.
#Table(name = "delegations")
public class DelegationModel {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
public Long id;
/** Area that this delegation is in */
#NonNull
#NotNull
#ManyToOne
public AreaModel area;
/** reference to delegee that delegated his vote */
#NonNull
#NotNull
#ManyToOne
public UserModel fromUser;
/** reference to proxy that receives the delegation */
#NonNull
#NotNull
#ManyToOne
public UserModel toProxy;
#CreatedDate
#NotNull
public Date createdAt = new Date();
#LastModifiedDate
#NotNull
public Date updatedAt = new Date();
}
As described in the Spring-data-jpa doc I implemented the necessary AuditorAware interface, which loads the UserModel from the SQL DB. I would have expected that this AuditorAware interface is only called for models that have a field annotated with #CreatedBy.
#Component
public class LiquidoAuditorAware implements AuditorAware<UserModel> {
Logger log = LoggerFactory.getLogger(this.getClass()); // Simple Logging Facade 4 Java
#Autowired
UserRepo userRepo;
#Override
public UserModel getCurrentAuditor() {
Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
if (authentication == null || !authentication.isAuthenticated()) {
log.warn("Cannot getCurrentAuditor. No one is currently authenticated");
return null;
}
User principal = (org.springframework.security.core.userdetails.User) authentication.getPrincipal();
UserModel currentlyLoggedInUser = userRepo.findByEmail(principal.getUsername()); // <<<<======= (!)
return currentlyLoggedInUser;
} catch (Exception e) {
log.error("Cannot getCurrentAuditor: "+e);
return null;
}
}
}
Now I update a DelegationModel in my UserRestController. The functional "Scrum User Story" here is:
As a user I want to be able to store a delegation so that I can forward my right to vote to my proxy.
#RestController
#RequestMapping("/liquido/v2/users")
public class UserRestController {
[...]
#RequestMapping(value = "/saveProxy", method = PUT, consumes="application/json")
#ResponseStatus(HttpStatus.CREATED)
public #ResponseBody String saveProxy(
#RequestBody Resource<DelegationModel> delegationResource,
//PersistentEntityResourceAssembler resourceAssembler,
Principal principal) throws BindException
{
[...]
DelegationModel result = delegationRepo.save(existingDelegation);
[...]
}
[...]
}
For some reason, that I cannot see, this actualy calls the AuditorAware implementation above. The problem is now, that my LqiuidoAuditorAware implementation is called again and again in and endless loop. It seems that the query for the UserModel inside LiquidoAuditorAware.java calls the LiquidoAuditorAware again. (Which is unusual, because that is only a read operation from the DB.)
Here is the full ThreadDump as a Gist
All the code can by found in this github repo
I'd really apriciate any help here. I am searching in the dark :-)
The reason for the behavior you see is that the AuditorAware implementation is called from within a JPA #PrePersist/#PreUpdate callback. You now issue a query by calling findByEmail(…), which triggers the dirty-detection again, which in turn causes the flushing to be triggered and thus the invocation of the callbacks.
The recommended workaround is to keep an instance of the UserModel inside the Spring Security User implementation (by looking it up when the UserDetailsService looks up the instance on authentication), so that you don't need an extra database query.
Another (less recommended) workaround could be to inject an EntityManager into the AuditorAware implementation, call setFlushMode(FlushModeType.COMMIT) before the query execution and reset it to FlushModeType.AUTO after that, so that the flush will not be triggered for the query execution.
Problem:
I have webapi serviss where almost every user has its own database instance to connect. So i have to set different connection string for each user. To recognize user i will pass specific Token into header. Regarding on this Token, system has to build and set differenct connection string into Data Access layer constructor (Order in this case)
Question:
Is it possible to pass argument to Ninject or any kind of IoC binder regarding on request header?
IOrders _orders;
public HomeController(IOrders order)
{
_orders = order;
}
Here is an Ninject binding, but as you can guess, HttpContext.Current is null.
private static void RegisterServices(IKernel kernel)
{
var some_value = HttpContext.Current.Request.Headers.GetValues("Token");
kernel.Bind<IOrders>()
.To<Orders>()
.WhenInjectedInto<HomeController>()
.WithConstructorArgument("Token", some_value);
}
Maybe there is much elegant way to do this using Controller Factory ?
I would create a service class that does this lookup for you. then inject this service into the Orders implementation.
public interface IRequestContext {
string ConnectionString {get;}
}
public class HttpHeaderRequestContext : IRequestContext {
public string ConnectionString {
get {
var token = HttpContext.Current.Request.Headers.GetValues("Token");
// .. lookup conn string based on token
}
}
}
public class Orders : IOrders {
public Orders(IRequestContext ctx) {
// create new connection w/ ctx.ConnectionString
}
}
using this method, the lookup of headers and connection strings is abstracted away from the implementation. this makes it easier to test and easier swap out with a different method of obtaining a connection string if the need arises.
After implementing Dave approach, i realized that i could solve this connection string injection by feeding HttpContext.Current into Ninject binding like this:
private static void RegisterServices(IKernel kernel)
{
kernel.Bind<IOrders>()
.To<Orders>()
.WhenInjectedInto<HomeController>()
.WithConstructorArgument("smth", x => {
var token = HttpContext.Current.Request.Headers.Get("Token");
var _db = new SomeDataCxt();
var connStr = _db.DbStringRepository.GetByToken(token);
return connStr;
});
}
I am developing a web application in ASP.NET MVC5.
Like all basic web applications it also has a login page where a user can authenticate himself. Once authenticated I want to store a couple of user-related items in the Session so I don't have to query the database every time to reconstruct the authenticated user.
After having read Mark Seemann's book about Dependency Injection I want to loosely couple all my layers and make sure that everything can easily be replaced.
At the moment my SessionProvider is by default using the Session object, but maybe in the future this could change to another type of storage mechanism.
The approach I have taken is by using Ambient Context which he explained with the TimeProvider example, but I am wondering if this is the right approach for this functionality and if it is thread safe (also for unit testing).
Is my solution proper or how would you implement such a mechanism? This has been in my head for days now so who can help me define the best solution?
Thanks!
public abstract class SessionProvider
{
private static SessionProvider _current;
static SessionProvider()
{
_current = new DefaultSessionProvider();
}
public static SessionProvider Current
{
get { return _current; }
set
{
if (value == null)
{
throw new ArgumentNullException();
}
_current = value;
}
}
public abstract string UserName { get; set; }
}
My local default:
public class DefaultSessionProvider : SessionProvider
{
public override string UserName
{
get { return (string) HttpContext.Current.Session["username"]; }
set { HttpContext.Current.Session["username"] = value; }
}
}
So I have access in my entire solution to my SessionProvider, whether this is a real session object or a database-driven storage mechanism...
SessionProvider.Current.UserName = "myUserName";
Once authenticated I want to store a couple of user-related items in
the Session so I don't have to query the database every time to
reconstruct the authenticated user.
Well, it looks like you're working on some sort of caching mechanism. It doesn't really matter if it's in a Session or in Redis cache, or any other type of cache. And this cache is key-value storage. I would create cache interface, something like that:
interface ICache
{
object this[string key] {get; set;}
}
And create concrete classes. SessionCache in your case:
public SessionCache : ICache
{
private IHttpSessionState _session;
public SessionCache(IHttpSessionState session)
{
_session = session;
}
// ICache implementation goes here...
}
So you'll narrow down the problem to dependency-inject Session object to concrete class (SessionCache). With Ninject you can do something like:
.WithConstructorArgument("session",ninjectContext=>HttpContext.Session);
And after that you can finally make your controllers dependent on ICache.
In your unit tests project you can create another ICache concrete class, something like DummyCache with in-memory cache. So you can test your controllers without sticking to Session object.
I am using the basic Unity MVC Nuget Bootstrapper.
I would like to Inject the currently logged in user into the services I am defining
_container.RegisterType<IDoSomethingService, DoSomethingService>();
such that DoSomethingService gets an ICurrentUser object or some form of resolver.
I am trying to avoid having to make calls like
DoSomethingService.DoSomething(currentUserUsingService,...);
Or in the constructor of all the MVC Controllers also avoiding setting:
DoSomethingService.CurrentUSer = User.Identity.Name;
In my projects I use next:
public interface ICurrentUserService
{
int? GetId();
}
I register next implementation:
public class CurrentUserService: ICurrentUserService
{
public int? GetId()
{
if (!HttpContext.Current.User.Identity.IsAuthenticated)
return null;
return int.Parse(HttpContext.Current.User.Identity.Name);//When auth - id stored in cookie
}
}
_container.RegisterType<ICurrentUserService, CurrentUserService>();
And make my services depends on ICurrentUserService (by using ctor parameter) or pass userId into methods of my services in controllers.
I'm building a multi-tenant web application where for security concerns, we need to have one instance of the database per tenant. So I have a MainDB for authentication and many ClientDB for application data.
I am using Asp.net MVC with Ninject and Fluent nHibernate. I have already setup my SessionFactory/Session/Repositories using Ninject and Fluent nHibernate in a Ninject Module at the start of the application. My sessions are PerRequestScope, as are repositories.
My problem is now I need to instanciate a SessionFactory (SingletonScope) instance for each of my tenants whenever one of them connects to the application and create a new session and necessary repositories for each webrequest. I'm puzzled as to how to do this and would need a concrete example.
Here's the situation.
Application starts : The user of TenantX enters his login info. SessionFactory of MainDB gets created and opens a session to the MainDB to authenticate the user. Then the application creates the auth cookie.
Tenant accesses the application : The Tenant Name + ConnectionString are extracted from MainDB and Ninject must construct a tenant specific SessionFactory (SingletonScope) for that tenant. The rest of the web request, all controllers requiring a repository will be inject with a Tenant specific session/repository based on that tenant's SessionFactory.
How do I setup that dynamic with Ninject? I was originally using Named instance when I had multiple databases but now that the databases are tenant specific, I'm lost...
After further research I can give you a better answer.
Whilst it's possible to pass a connection string to ISession.OpenSession a better approach is to create a custom ConnectionProvider. The simplest approach is to derive from DriverConnectionProvider and override the ConnectionString property:
public class TenantConnectionProvider : DriverConnectionProvider
{
protected override string ConnectionString
{
get
{
// load the tenant connection string
return "";
}
}
public override void Configure(IDictionary<string, string> settings)
{
ConfigureDriver(settings);
}
}
Using FluentNHibernate you set the provider like so:
var config = Fluently.Configure()
.Database(
MsSqlConfiguration.MsSql2008
.Provider<TenantConnectionProvider>()
)
The ConnectionProvider is evaluated each time you open a session allowing you to connect to tenant specific databases in your application.
An issue with the above approach is that the SessionFactory is shared. This is not really a problem if you are only using the first level cache (since this is tied to the session) but is if you decide to enable the second level cache (tied to the SessionFactory).
The recommended approach therefore is to have a SessionFactory-per-tenant (this would apply to schema-per-tenant and database-per-tenant strategies).
Another issue often overlooked is that although the second level cache is tied to the SessionFactory, in some cases the cache space itself is shared (reference). This can be resolved by setting the "regionName" property of the provider.
Below is a working implementation of SessionFactory-per-tenant based on your requirements.
The Tenant class contains the information we need to set up NHibernate for the tenant:
public class Tenant : IEquatable<Tenant>
{
public string Name { get; set; }
public string ConnectionString { get; set; }
public bool Equals(Tenant other)
{
if (other == null)
return false;
return other.Name.Equals(Name) && other.ConnectionString.Equals(ConnectionString);
}
public override bool Equals(object obj)
{
return Equals(obj as Tenant);
}
public override int GetHashCode()
{
return string.Concat(Name, ConnectionString).GetHashCode();
}
}
Since we'll be storing a Dictionary<Tenant, ISessionFactory> we implement the IEquatable interface so we can evaluate the Tenant keys.
The process of getting the current tenant is abstracted like so:
public interface ITenantAccessor
{
Tenant GetCurrentTenant();
}
public class DefaultTenantAccessor : ITenantAccessor
{
public Tenant GetCurrentTenant()
{
// your implementation here
return null;
}
}
Finally the NHibernateSessionSource which manages the sessions:
public interface ISessionSource
{
ISession CreateSession();
}
public class NHibernateSessionSource : ISessionSource
{
private Dictionary<Tenant, ISessionFactory> sessionFactories =
new Dictionary<Tenant, ISessionFactory>();
private static readonly object factorySyncRoot = new object();
private string defaultConnectionString =
#"Server=(local)\sqlexpress;Database=NHibernateMultiTenancy;integrated security=true;";
private readonly ISessionFactory defaultSessionFactory;
private readonly ITenantAccessor tenantAccessor;
public NHibernateSessionSource(ITenantAccessor tenantAccessor)
{
if (tenantAccessor == null)
throw new ArgumentNullException("tenantAccessor");
this.tenantAccessor = tenantAccessor;
lock (factorySyncRoot)
{
if (defaultSessionFactory != null) return;
var configuration = AssembleConfiguration("default", defaultConnectionString);
defaultSessionFactory = configuration.BuildSessionFactory();
}
}
private Configuration AssembleConfiguration(string name, string connectionString)
{
return Fluently.Configure()
.Database(
MsSqlConfiguration.MsSql2008.ConnectionString(connectionString)
)
.Mappings(cfg =>
{
cfg.FluentMappings.AddFromAssemblyOf<NHibernateSessionSource>();
})
.Cache(c =>
c.UseSecondLevelCache()
.ProviderClass<HashtableCacheProvider>()
.RegionPrefix(name)
)
.ExposeConfiguration(
c => c.SetProperty(NHibernate.Cfg.Environment.SessionFactoryName, name)
)
.BuildConfiguration();
}
private ISessionFactory GetSessionFactory(Tenant currentTenant)
{
ISessionFactory tenantSessionFactory;
sessionFactories.TryGetValue(currentTenant, out tenantSessionFactory);
if (tenantSessionFactory == null)
{
var configuration = AssembleConfiguration(currentTenant.Name, currentTenant.ConnectionString);
tenantSessionFactory = configuration.BuildSessionFactory();
lock (factorySyncRoot)
{
sessionFactories.Add(currentTenant, tenantSessionFactory);
}
}
return tenantSessionFactory;
}
public ISession CreateSession()
{
var tenant = tenantAccessor.GetCurrentTenant();
if (tenant == null)
{
return defaultSessionFactory.OpenSession();
}
return GetSessionFactory(tenant).OpenSession();
}
}
When we create an instance of NHibernateSessionSource we set up a default SessionFactory to our "default" database.
When CreateSession() is called we get a ISessionFactory instance. This will either be the default session factory (if the current tenant is null) or a tenant specific session factory. The task of locating the tenant specific session factory is performed by the GetSessionFactory method.
Finally we call OpenSession on the ISessionFactory instance we have obtained.
Note that when we create a session factory we set the SessionFactory name (for debugging/profiling purposes) and cache region prefix (for the reasons mentioned above).
Our IoC tool (in my case StructureMap) wires everything up:
x.For<ISessionSource>().Singleton().Use<NHibernateSessionSource>();
x.For<ISession>().HttpContextScoped().Use(ctx =>
ctx.GetInstance<ISessionSource>().CreateSession());
x.For<ITenantAccessor>().Use<DefaultTenantAccessor>();
Here NHibernateSessionSource is scoped as a singleton and ISession per request.
Hope this helps.
If all the databases are on the same machine, maybe the schema property of class mappings could be used to set the database on a pre-tenant basis.