How do I create a globally accessible Context object similar to the HttpContext object?
I want to create a custom class library which I want to reference from a website project. In the website project I want to be able to call the following globally:
ClassLibraryName.Context
I cannot create a global property directly in my classlibrary, so how should this be implemented? (I've seen other applications/products use this approach, one of which is Sitecore which has a custom Sitecore.Context object available)
Edit
Might this be a 'valid' solution?
namespace MyLibrary
{
public class Context
{
public static object ContextualObject
{
get;
set;
}
}
}
Yes, this is not hard to implement, if you always run this class in the context of an ASP.NET application, use this approach:
namespace MyLibrary
{
public class Context
{
public static object ContextualObject
{
get
{
var ctx = System.Web.HttpContext.Current.Items[typeof(Context)];
if (ctx == null)
{
ctx = new Context();
System.Web.HttpContext.Current.Items.Add(typeof(Context), ctx);
}
return ctx;
}
set { System.Web.HttpContext.Current.Items[typeof(Context)] = ctx; }
}
}
}
Essentially wrapping the existing HTTP context to provide your own service. This approach also doesn't store the object while the app lives, it only creates it for the current context, and when that response ends, it will die, and be regenerated during the next lifecycle. If that is not OK, store a static reference to context.
I've used this approach similarly in a class library I have at http://nucleo.codeplex.com, it works well.
HTH.
It depends on the lifetime you want the Context object to have. If you want all clients to use the same context, you can go with a singleton implementation.
If you want the context to be unique for each thread or http request you have to use a per request/thread implementation. One way to implement a per http request implementation would be to have a HttpModule create the object at every BeginRequest event and stick it in the HttpContext Items collection.
public static object ContextualObject
{
get { return HttpContext.Current.Items["MyContext"];}
}
You could create an instance of the object on Session_Start in the Global.asax.
Related
I'm studying blazor server.
Deployed a solution from a standard vs template.
Created two server-side services, TestService1 and TestService2.
In TestService1 i have task
GetMyData()
How can i call with task from TestService2?
If i trying
var serv1 = new TestService1()
i have to fill in all the variables of the constructor that is in TestService1.
What is easiest way?
In line with the comment on your question, the best way to go about this in Blazor is to utilize the built-in dependency injection mechanism.
I assume that your services look like the following:
public class TestService1
{
public object GetMyData()
{
}
}
public class TestService2
{
private readonly TestService1 _testService1 { get; set; }
public class TestService2(TestService1 ts1)
{
_testService1 = ts1;
}
public void DoesSomething()
{
var data = _testService1.GetMyData();
//...
}
}
First, you'd need to register these with Blazor at startup, so in your Startup.cs in the ConfigureServices method, add the following, assuming you have an empty constructor available for TestService1:
services.AddSingleton<TestService1>();
Because you'll need to instantiate an instance of TestService1 into TestService2 to call methods on it, you'll have to handle registration of TestService2 differently since you'll need to procure an instance of TestService1 from the DI service to instantiate it:
services.AddSingleton<TestService2>(s => {
var testService1 = s.GetService<TestService1>();
return new TestService2(testService1);
});
It's possible you may need to scope the services differently (e.g. used scoped instead of singletons). You can read about the differences here.
Now something is presumably calling TestService2 to kick all this off, so let's pretend it's running in a component in your Blazor app. You'd inject TestService2 into the component with the following:
#inject TestService2 _testService2
<h1>Hello!</h1>
#code {
protected override void OnInitialized()
{
_testService2.DoesSomething();
}
}
As part of the initialization then of this component, it'll automatically inject a TestService2 instance (based on the scoping you specified at DI initialization) to your component and will call the DoesSomething method on it. When injected, it looks to DI to instantiate the TestService1 service to the constructor as you've also specified, leaving it free to call that method and the call commences as intended.
Please let me know if you'd like any clarification somewhere!
When using spring-data-rest there is a post processing of Resource classes returned from Controllers (e.g. RepositoryRestControllers). The proper ResourceProcessor is called in the post processing.
The class responsible for this is ResourceProcessorHandlerMethodReturnValueHandler which is part of spring-hateoas.
I now have a project that only uses spring-hateoas and I wonder how to configure ResourceProcessorHandlerMethodReturnValueHandler in such a scenario. It looks like the auto configuration part of it still resides in spring-data-rest.
Any hints on how to enable ResourceProcessorHandlerMethodReturnValueHandler in a spring-hateoas context?
I've been looking at this recently too, and documentation on how to achieve this is non-existent. If you create a bean of type ResourceProcessorInvokingHandlerAdapter, you seem to lose the the auto-configured RequestMappingHandlerAdapter and all its features. As such, I wanted to avoid using this bean or losing the WebMvcAutoConfiguration, since all I really wanted was the ResourceProcessorHandlerMethodReturnValueHandler.
You can't just add a ResourceProcessorHandlerMethodReturnValueHandler via WebMvcConfigurer.addReturnValueHandlers, because what we need to do is actually override the entire list, as is what happens in ResourceProcessorInvokingHandlerAdapter.afterPropertiesSet:
#Override
public void afterPropertiesSet() {
super.afterPropertiesSet();
// Retrieve actual handlers to use as delegate
HandlerMethodReturnValueHandlerComposite oldHandlers = getReturnValueHandlersComposite();
// Set up ResourceProcessingHandlerMethodResolver to delegate to originally configured ones
List<HandlerMethodReturnValueHandler> newHandlers = new ArrayList<HandlerMethodReturnValueHandler>();
newHandlers.add(new ResourceProcessorHandlerMethodReturnValueHandler(oldHandlers, invoker));
// Configure the new handler to be used
this.setReturnValueHandlers(newHandlers);
}
So, without a better solution available, I added a BeanPostProcessor to handle setting the List of handlers on an existing RequestMappingHandlerAdapter:
#Component
#RequiredArgsConstructor
#ConditionalOnBean(ResourceProcessor.class)
public class ResourceProcessorHandlerMethodReturnValueHandlerConfigurer implements BeanPostProcessor {
private final Collection<ResourceProcessor<?>> resourceProcessors;
#Override
public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException {
if (bean instanceof RequestMappingHandlerAdapter) {
RequestMappingHandlerAdapter requestMappingHandlerAdapter = (RequestMappingHandlerAdapter) bean;
List<HandlerMethodReturnValueHandler> handlers =
requestMappingHandlerAdapter.getReturnValueHandlers();
HandlerMethodReturnValueHandlerComposite delegate =
handlers instanceof HandlerMethodReturnValueHandlerComposite ?
(HandlerMethodReturnValueHandlerComposite) handlers :
new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers);
requestMappingHandlerAdapter.setReturnValueHandlers(Arrays.asList(
new ResourceProcessorHandlerMethodReturnValueHandler(delegate,
new ResourceProcessorInvoker(resourceProcessors))));
return requestMappingHandlerAdapter;
}
else return bean;
}
}
This has seemed to work so far...
How to pass global variable to a referenced assembly?
I am modifying an asp.net app. It is required to log all Employee (the current user of the website) actions like saving a new customer or update invoice data. The UI layer is calling a referenced assembly BLL.dll.
I want to pass current Emplyee to the referenced assembly. The passed Employee should be shared accross all static methods in that dll. It should be thread safe because the Employee can be changed accross requests.
I can't expose static field in the BLL because the Employee is stored in session state.
I need something not static, Global, accessible by both assemblies (UI layer and BLL.dll), and thread safe.
I am thinking about using some variable stored in current thread object. but I don't know what exactly I should do??
Any workarrounds ??
Thanks
Basically you need something in your BLL that can get the reference. You can use a strategy pattern with an interface.
// IN BLL.dll
public interface IEmployeeContextImplementation
{
Employee Current { get; }
}
public static EmployeeContext
{
private static readonly object ImplementationLock = new object();
private static IEmployeeContextImplementation Implementation;
public static void SetImplementation(IEmployeeContextImplementation impl)
{
lock(ImplementationLock)
{
Implementation = impl;
}
}
public static Employee Current { get { return Implementation.Current; }
}
Then in your web app, implement IEmployeeContextImplementation with the session state and call SetImplementation only once in application start.
However, Session state is only good enough for within the context of a request. If you need it to go on a different thread, you will have to explicitly pass it to a different thread.
Sorry if this is stupid question, because I'm a bit confused about .NET remoting and distributed object.
I want to write a webservice, and in one of its methods, I want user to pass one my object's instance as parameter. It will greatly reduces number of parameters, and help user call this method more effectively. I create some class, but when distributing them to client, only class name remains, all properties and methods are gone, just like this
public class CameraPackages
{
private readonly List<CameraPackage> _packages;
public CameraPackages()
{
_packages = new List<CameraPackage>();
}
public void AddNewCamera(CameraPackage package)
{
_packages.Add(package);
}
public void RemoveCamera(CameraPackage package)
{
if(_packages.Contains(package))
_packages.Remove(package);
else
throw new ArgumentException();
}
}
into this: (in Reference.cs)
[System.CodeDom.Compiler.GeneratedCodeAttribute("System.Xml", "2.0.50727.3082")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(Namespace="http://tempuri.org/")]
public partial class CameraPackages {
}
How can I do to allow user use my object?
Thank you so much.
Web Services will only serialise public properties, so you can't do that (in that way) using web services.
You will need to manage your list of objects client side, then send the data in a transfer object (a class with just properties).
Have a look at this.
I'm trying to work out how to complete my implementation of the Repository pattern in an ASP.NET web application.
At the moment, I have a repository interface per domain class defining methods for e.g. loading and saving instances of that class.
Each repository interface is implemented by a class which does the NHibernate stuff. Castle Windsor sorts out the DI of the class into the interface according to web.config. An example of an implemented class is provided below:
public class StoredWillRepository : IStoredWillRepository
{
public StoredWill Load(int id)
{
StoredWill storedWill;
using (ISession session = NHibernateSessionFactory.OpenSession())
{
storedWill = session.Load<StoredWill>(id);
NHibernateUtil.Initialize(storedWill);
}
return storedWill;
}
public void Save(StoredWill storedWill)
{
using (ISession session = NHibernateSessionFactory.OpenSession())
{
using (ITransaction transaction = session.BeginTransaction())
{
session.SaveOrUpdate(storedWill);
transaction.Commit();
}
}
}
}
As pointed out in a previous thread, the repository class needs to accept an unit of work container (i.e. ISession) rather than instantiating it in every method.
I anticipate that the unit of work container will be created by each aspx page when needed (for example, in a property).
How do I then specify that this unit of work container instance is to be passed into the constructor of StoredWillRepository when Windsor is creating it for me?
Or is this pattern completely wrong?
Thanks again for your advice.
David
I have a persistence framework built on top of NHibernate that is used in a few Web apps. It hides the NH implementation behind an IRepository and IRepository<T> interface, with the concrete instances provided by Unity (thus I could in theory swap out NHibernate for, say, Entity Framework fairly easily).
Since Unity doesn't (or at least the version I'm using doesn't) support the passing in of constructor parameters other than those that are dependency injections themselves, passing in an extant NH ISession isn't possible; but I do want all objects in the UOW to share the same ISession.
I solve this by having a controlling repository class that manages access to the ISession on a per-thread basis:
public static ISession Session
{
get
{
lock (_lockObject)
{
// if a cached session exists, we'll use it
if (PersistenceFrameworkContext.Current.Items.ContainsKey(SESSION_KEY))
{
return (ISession)PersistenceFrameworkContext.Current.Items[NHibernateRepository.SESSION_KEY];
}
else
{
// must create a new session - note we're not caching the new session here... that's the job of
// BeginUnitOfWork().
return _factory.OpenSession(new NHibernateInterceptor());
}
}
}
}
In this example, PersistenceFrameworkContext.Current.Items accesses an IList<object> that is stored either ThreadStatic if not in a Web context, or within HttpContext.Current.Items if it is in a Web context (to avoid thread-pool problems). The first call to the property instantiates the ISession from the stored factory instance, subsequent calls just retrieve it from storage. The locking will slow things down slightly but not as much as just locking an appdomain-scoped static ISession instance.
I then have BeginUnitOfWork and EndUnitOfWork methods to take care of the UOW - I have specifically disallowed nested UOWs because frankly they were a pain to manage.
public void BeginUnitOfWork()
{
lock (_lockObject)
{
if (PersistenceFrameworkContext.Current.Items.ContainsKey(SESSION_KEY))
EndUnitOfWork();
ISession session = Session;
PersistenceFrameworkContext.Current.Items.Add(SESSION_KEY, session);
}
}
public void EndUnitOfWork()
{
lock (_lockObject)
{
if (PersistenceFrameworkContext.Current.Items.ContainsKey(SESSION_KEY))
{
ISession session = (ISession)PersistenceFrameworkContext.Current.Items[SESSION_KEY];
PersistenceFrameworkContext.Current.Items.Remove(SESSION_KEY);
session.Flush();
session.Dispose();
}
}
}
Finally, a pair of methods provide access to the domain-type-specific repositories:
public IRepository<T> For<T>()
where T : PersistentObject<T>
{
return Container.Resolve<IRepository<T>>();
}
public TRepository For<T, TRepository>()
where T : PersistentObject<T>
where TRepository : IRepository<T>
{
return Container.Resolve<TRepository>();
}
(Here, PersistentObject<T> is a base class providing ID and Equals support.)
Access to a given repository is thus in the pattern
NHibernateRepository.For<MyDomainType>().Save();
This is then facaded over such that you can use
MyDomainType.Repository.Save();
Where a given type has a specialised repository (ie needs more than it can get from IRepository<T>) then I create an interface deriving from IRepository<T>, an extending implementation inheriting from my IRepository<T> implementation, and in the domain type itself I override the static Repository property using new
new public static IUserRepository Repository
{
get
{
return MyApplication.Repository.For<User, IUserRepository>();
}
}
(MyApplication [which is called something less noddy in the real product] is a facade class which takes care of supplying the Repository instance via Unity so you have no dependency on the specific NHibernate repository implementation within your domain classes.)
This gives me full pluggability via Unity for the repository implementation, easy access to the repository in code without jumping through hoops, and transparent, per-thread ISession management.
There's lots more code than just what's above (and I've simplified the example code a great deal), but you get the general idea.
MyApplication.Repository.BeginUnitOfWork();
User user = User.Repository.FindByEmail("wibble#wobble.com");
user.FirstName = "Joe"; // change something
user.LastName = "Bloggs";
// you *can* call User.Repository.Save(user), but you don't need to, because...
MyApplication.Repository.EndUnitOfWork();
// ...causes session flush which saves the changes automatically
In my Web app, I have session-per-request, so BeginUnitOfWork and EndUnitOfWork get called in BeginRequest and EndRequest respectively.
I have a pretty similar structure to yours, and here's how I solve your question:
1) To specify my container on each method, I have a separate class ("SessionManager") which I then invoke via a static property. By doing so, here's an example using my Save implementation:
private static ISession NHibernateSession
{
get { return SessionManager.Instance.GetSession(); }
}
public T Save(T entity)
{
using (var transaction = NHibernateSession.BeginTransaction())
{
ValidateEntityValues(entity);
NHibernateSession.Save(entity);
transaction.Commit();
}
return entity;
}
2) My container is not created on each ASPX page. I instantiate all of my NHibernate goodness on the global.asax page.
** A few more things spring up **
3) You don't need to have a helper to instantiate the Load. You might as well use Get instead of Load. More information # Difference between Load and Get.
4) Using your current code, you would have to repeat pretty much the same code for each domain object you need (StoredWillRepository, PersonRepository, CategoryRepository, etc..?), which seems like a drag. You could very well use a generic class to operate over NHibernate, like:
public class Dao<T> : IDao<T>
{
public T SaveOrUpdate(T entity)
{
using (var transaction = NHibernateSession.BeginTransaction())
{
NHibernateSession.SaveOrUpdate(entity);
transaction.Commit();
}
return entity;
}
}
In my implementation, I could then use something like:
Service<StoredWill>.Instance.SaveOrUpdate(will);
Technically, the answer to my question is to use the overload of container.Resolve which allows you to specify the constructor argument as an anonymous type:
IUnitOfWork unitOfWork = [Code to get unit of work];
_storedWillRepository = container.Resolve<IStoredWillRepository>(new { unitOfWork = unitOfWork });
But let's face it, the answers provided by everyone else have been much more informative.