Can I able to access appSettings section in my ASP.NET web.config file from a method in another referenced Class Library project when it is called as a new Thread?
I'm accessing the setting through a property as
private static string TempXmlFolder
{
get
{
return System.Web.HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["ReceiptTempPath"] ?? "~/Receipts/TempXML");
}
}
There is an extension method for the matter to generate the receipt.
internal static void GenerateReceipt(this IMatter matter)
{
try
{
string XmlFile = TempXmlFolder + "/Rec_" + matter.MatterID + ".xml";
// ...
// Generating receipt from the matter contents
// ...
// Saving generated receipt
}
catch (Exception ex)
{
ex.WriteLog();
}
}
I'm calling the receipt generation as a new thread from the class library like
Thread printThread = new Thread(new ThreadStart(this.GenerateReceipt));
// To avoid exception 'The calling thread must be STA, because many UI components require this' (Using WPF controls in receipt generation function)
printThread.SetApartmentState(ApartmentState.STA);
printThread.Start();
// ...
// Do another stuffs
// ...
// Wait to generate receipt to complete
printThread.Join();
But since the HttpContext.Current is null inside the Thread, I'm not able to access the current web server configuration file.
Can you suggest there any way other than passing the current HttpContext to the Thread? If no, what are the things I've to take care to keep thread safety?
Edit #1
Currently I'm passing the HttpContext to the thread like
System.Web.HttpContext currentContext = System.Web.HttpContext.Current;
Thread printThread = new Thread(() => this.GenerateReceipt(currentContext));
and in the function,
internal static void GenerateReceipt(this IMatter matter, System.Web.HttpContext htCont)
{
string TempXmlFolder = htCont.Server.MapPath(ConfigurationManager.AppSettings["ReceiptTempPath"] ?? "~/Receipts/TempXML");
//...
Pass the TempXmlFolder into the thread. Don't rely on HttpContext.Current. Alternatively, pass the value of HttpContext.Current to the thread and calculate the value of TempXmlFolder later.
You can pass the value using any way you want. Maybe a field or a local variable that you capture with a lambda.
Related
Friends tell me what is the core meaning of init parameter in case of a servlet.
I know that how to initialize it in a web.xml but I don't know what is the actual purpose of it why it is required? Please tell me with a good example.
The Javadoc says: "A convenience method which can be overridden so that there's no need to call super.init(config)."
The init method's main purpose is to allow customization while you are initializing the servlet.
The simplest implementation is when you don't want to do any customization according to your application you can always call super.init method.
To understand meaning of what different init params can be there and how init method is useful:
Imagine a system Of BookManagement system, here for adding books and removing books from db you will be needing Database connection over which you can access the data. Now as Servlet's init method is called for the first request and database connection also needs be created only once(or n number of time if doing connection pooling) then initializing the database connection is something that you should do in init method.
A code snippet from Softlab example , let's assume that getInitParameter method reads the databaseUrl and other properties from web.xml
public class DBServlet ... {
Connection connection = null;
public void init() throws ServletException {
// Open a database connection to prepare for requests
try {
databaseUrl = getInitParameter("databaseUrl");
... // get user and password parameters the same way
connection = DriverManager.getConnection(databaseUrl,
user, password);
} catch(Exception e) {
throw new UnavailableException (this,
"Could not open a connection to the database");
}
}
...
}
One more example of counting the number of time servlet was accessed: https://docstore.mik.ua/orelly/java-ent/servlet/ch03_03.htm
So in Summary: To do customization like read the initial values of variable or to initialize resources(like db connection) you can use init method.
Below is the source code of init methods :
public void init(ServletConfig config)throws ServletException
{
this.config = config;
int();
}
public void init() throws ServletException;
It is recommended to override to init() method, not init(ServletConfig).
When overriding init(ServletConfig), the first thing that must be done is to call:
super.init(config);
If you do this then calling directly to getServletContext() in your method will no longer result in an NPE.
I have a following code example that is used in ASP.NET MVC application.
The purpose of this code is to create "fire and forget" request for queuing some long running operation.
public JsonResult SomeAction() {
HttpContext ctx = HttpContext.Current;
Task.Run(() => {
HttpContext.Current = ctx;
//Other long running code here.
});
return Json("{ 'status': 'Work Queued' }");
}
I know this is not a good way for handling HttpContext.Current in asynchronous code, but currently our implementation not allows us to do something else.
I would like to understand how much this code is dangerous...
The question: Is it theoretically possible that setting the HttpContext inside Task.Run, will set the context to totally another request?
I think yes, but I'm not sure. How I understand it:
Request1 is handled with Thread1 from thread pool, then while Thread1 is handling absolutelly another request (Request2), the code inside Task.Run will set context from Request1 to Request2.
Maybe I am wrong, but my knowledge of ASP.NET internals not allows me to understand it correctly.
Thanks!
Let me bump a little internals on you:
public static HttpContext Current
{
get { return ContextBase.Current as HttpContext; }
set { ContextBase.Current = value; }
}
internal class ContextBase
{
internal static object Current
{
get { return CallContext.HostContext; }
set { CallContext.HostContext = value; }
}
}
public static object HostContext
{
get
{
var executionContextReader = Thread.CurrentThread.GetExecutionContextReader();
object hostContext = executionContextReader.IllogicalCallContext.HostContext;
if (hostContext == null)
{
hostContext = executionContextReader.LogicalCallContext.HostContext;
}
return hostContext;
}
set
{
var mutableExecutionContext = Thread.CurrentThread.GetMutableExecutionContext();
if (value is ILogicalThreadAffinative)
{
mutableExecutionContext.IllogicalCallContext.HostContext = null;
mutableExecutionContext.LogicalCallContext.HostContext = value;
return;
}
mutableExecutionContext.IllogicalCallContext.HostContext = value;
mutableExecutionContext.LogicalCallContext.HostContext = null;
}
}
So
var context = HttpContext.Current;
is equal to (pseudocode)
var context = CurrentThread.HttpContext;
and inside your Task.Run something like this happens
CurrentThread.HttpContext= context;
Task.Run will start new task with thread from thread pool. So you're telling that your new thread "HttpContext property" is reference to starter thread "HttpContext property" - so far so good (well with all the NullReference/Dispose exceptions you'll be facing after your starter thread finishes). Problem is if inside your
//Other long running code here.
You have statement like
var foo = await Bar();
Once you hit await, your current thread is returned to thread pool, and after IO finishes you grab new thread from thread pool - wonder what its "HttpContext property" is, right ? I don't know :) Most probably you'll end with NullReferenceException.
The issue you will run into here is that the HttpContext will dispose when the request is complete. Since you aren't awaiting the result of the Task.Run, you are essentially creating a race condition between the disposal of the HttpContext and it's usage within the task.
I'm pretty sure that the only issue your task will run into is a NullReferenceException or an ObjectDisposedException. I don't see any way where you could accidentally steal another request's context.
Also, unless you are handling & logging exceptions within your task, your fire and forget will throw and you'll never know about it.
Check out HangFire or consider using a message queue for processing backend jobs from a separate process.
We have an ASP.Net 4 / MVC 3 hybrid web application which uses NInject 3 and (Fluent) NHibernate 3.2. DB is SQL Server 2008 R2. Server is 6-core 28 GB Windows 2008 64-bit server.
Our customer has recently started testing the site using a spidering tool. As soon as the site experiences the load produced by the spider, our log starts to fill up with exceptions.
We see a variety of errors from NHibernate, including some of the following:
NHibernate.TransactionException: Commit failed with SQL exception ---> System.Data.SqlClient.SqlException: The transaction operation cannot be performed because there are pending requests working on this transaction.
System.Data.SqlClient.SqlException (0x80131904): The server failed to resume the transaction. Desc:410000050f. The transaction active in this session has been committed or aborted by another session.
System.NullReferenceException: Object reference not set to an instance of an object. at System.Data.SqlClient.SqlInternalTransaction.GetServerTransactionLevel()....
NHibernate.Exceptions.GenericADOException: could not execute native bulk manipulation query:exec [Stats.InsertListingStatsList] #ListingStats =:ListingStats[SQL: exec [Stats.InsertListingStatsList] #ListingStats =#p0] ---> System.Data.SqlClient.SqlException: New request is not allowed to start because it should come with valid transaction descriptor.
to give just four examples. All have a similar flavour - they all seem to relate to the management of transactions by ADO.Net as the substrate of NHibernate.
Now, some details of our NH implementation:
SessionFactory is static;
SessionFactory uses AdoNetTransactionFactory;
ISession is in request scope, and stored in the HttpContext.Items collection;
Repositories are also in request scope;
We are now using config.CurrentSessionContext();
Each call to our generic repository uses a transaction
Here are two methods from our repository.
public T GetById<T>(int id)
{
using (var t = Session.BeginTransaction())
{
var entity = Session.Get<T>(id);
t.Commit();
return entity;
}
}
public void Add<T>(T entity)
{
using (var t = Session.BeginTransaction())
{
Session.Save(entity);
t.Commit();
}
}
My question is simple: what is going wrong? What is causing these apparent conflicts between transactions, or between the various data-related operations that our domain instigates as it de/hydrates our domain?
UPDATE: here is our full configuration:
public FluentConfiguration BuildConfiguration(string connectionString)
{
var sqlConfig = MsSqlConfiguration.MsSql2008.ConnectionString(connectionString).AdoNetBatchSize(30);
var config = Fluently.Configure().Database(sqlConfig);
var entityMapping = AutoMap.AssemblyOf<User>(new AutomappingConfiguration())
.UseOverridesFromAssemblyOf<UserMappingOverride>()
.AddMappingsFromAssemblyOf<TableNamingConvention>()
.Conventions.AddFromAssemblyOf<TableNamingConvention>();
var cqrsMapping = AutoMap.AssemblyOf<AdvertView>(new QueryAutomappingConfiguration())
.UseOverridesFromAssemblyOf<AdvertViewMappingOverride>();
config.Mappings(c => c.AutoMappings.Add(entityMapping));
config.Mappings(c => c.AutoMappings.Add(cqrsMapping));
config.Mappings(c => c.HbmMappings.AddFromAssemblyOf<AdvertView>());
config.ExposeConfiguration(c => c.SetProperty(Environment.TransactionStrategy, typeof(AdoNetTransactionFactory).FullName));
config.CurrentSessionContext<WebSessionContext>();
return config;
}
More code for you guys and gals. Here is the relevant section of our IoC Container configuration.
var domainEntityBootstrapper = new DomainEntitySessionBootStrapper("Domain", "NHibernate.ISession.Domain", _enableLucine, HttpContextItemsProvider);
Bind<ISessionFactory>().ToMethod(domainEntityBootstrapper.CreateSessionFactory).InSingletonScope().Named(domainEntityBootstrapper.Name);
Bind<ISession>().ToMethod(domainEntityBootstrapper.GetSession).InRequestScope();
var queryBootstrapper = new QueryEntitySessionBootStrapper("Query", "NHibernate.ISession.Query", HttpContextItemsProvider);
Bind<ISessionFactory>().ToMethod(queryBootstrapper.CreateSessionFactory).InSingletonScope().Named(queryBootstrapper.Name);
Bind<ISession>().ToMethod(queryBootstrapper.GetSession).WhenInjectedInto(typeof (QueryExecutor)).InRequestScope();
and here is the code from the GetSession() method of the base class for these SessionBootstrappers (please note that the CreateSessionFactory method calls the BuildConfiguration method above and then calls BuildSessionFactory()).
public virtual ISession GetSession(IContext context)
{
var items = GetHttpContextItems();
var session = default(ISession);
var sessionExists = items.Contains(SessionKey);
if (!sessionExists)
{
session = context.Kernel.Get<ISessionFactory>(Name).OpenSession();
items.Add(SessionKey, session);
}
else
{
session = (ISession)items[SessionKey];
}
return session;
}
// a Func which serves access to the HttpContext.Current.Items collection
private Func<IDictionary> GetHttpContextItems { get; set; }
Please note that we use two sessions, one for ordinary domain de/hydration and one for CQRS, hence the pair of bindings in the Container.
The error messages indicate that you are not managing transactions correctly. I think the root cause is that you are handling transactions in the repository methods which in my opinion is a very poor design. Your repositories should have an ISession injected into their constructors, and your controllers should have any repositories they are dependent upon injected into their constructors. It's easy to wire this all up with Ninject. With this approach you can use transaction-per-request or (much better imo) manage the transaction in the action methods.
Here's how I'm setting up NHibernate with Ninject in NinjectWebCommon. The root cause of your problem may be that you are binding the ISession in request scope and storing it in HttpContext, which is unnecessary. I am also confused why you have two sets of bindings for Domain and Query.
private static void RegisterServices(IKernel kernel)
{
kernel.Bind<ISessionFactory>().ToProvider(new SessionFactoryProvider()).InSingletonScope();
kernel.Bind<ISession>().ToProvider(new SessionProvider()).InRequestScope();
}
private class SessionFactoryProvider : Provider<ISessionFactory>
{
protected override ISessionFactory CreateInstance(IContext context)
{
// create and configure the session factory
// I have a utility class to do this so the code isn't shown
return nhibernateHelper.BuildSessionFactory();
}
}
private class SessionProvider : Provider<ISession>
{
protected override ISession CreateInstance(IContext context)
{
var sessionFactory = context.Kernel.Get<ISessionFactory>();
var session = sessionFactory.OpenSession();
session.FlushMode = FlushMode.Commit;
return session;
}
}
A sample controller action using a transaction. Managing transactions outside of the repositories is important for several reasons:
Allows multiple repositories to participate in a transaction
Allows the controller to set the transaction boundaries (unit of work)
Allows lazy loads to occur in the transaction
Transactions are needed for read operations if second level caching is used. Even if it caching isn't used I think it's a best practice
public ActionResult EditDocuments(int id, string name)
{
using (var txn = _session.BeginTransaction())
{
var summary = _characterizationRepository
.GetCharacterization(id)
.AsCharacterizationSummaryView()
.ToFutureValue();
var documents = _characterizationRepository
.GetCharacterization(id)
.SelectMany(c => c.Documents)
.OrderBy(d => d.FileName)
.AsDocumentSelectView(true)
.ToFuture();
if (summary.Value == null)
{
throw new NotFoundException(_characterizationRepository.ManualId, "Characterization", id);
}
CheckSlug(name, summary.Value.Title);
var model = new DocumentSectionEditView()
{
CharacterizationSummary = summary.Value,
Documents = documents.ToArray()
};
txn.Commit();
return View(model);
}
}
It seems you are using the wrong context manager, check if you are using the WebSessionContext. This context manager will bind your session to the httpcontext of the current call instead of the thread. What happens now under load (the spider), when you are using the ThreadStaticSessionContext, session will 'jump' to an other 'call'.
I want to write a unit test that verifies my route registration and ControllerFactory so that given a specific URL, a specific controller will be created. Something like this:
Assert.UrlMapsToController("~/Home/Index",typeof(HomeController));
I've modified code taken from the book "Pro ASP.NET MVC 3 Framework", and it seems it would be perfect except that the ControllerFactory.CreateController() call throws an InvalidOperationException and says This method cannot be called during the application's pre-start initialization stage.
So then I downloaded the MVC source code and debugged into it, looking for the source of the problem. It originates from the ControllerFactory looking for all referenced assemblies - so that it can locate potential controllers. Somewhere in the CreateController call-stack, the specific trouble-maker call is this:
internal sealed class BuildManagerWrapper : IBuildManager {
//...
ICollection IBuildManager.GetReferencedAssemblies() {
// This bails with InvalidOperationException with the message
// "This method cannot be called during the application's pre-start
// initialization stage."
return BuildManager.GetReferencedAssemblies();
}
//...
}
I found a SO commentary on this. I still wonder if there is something that can be manually initialized to make the above code happy. Anyone?
But in the absence of that...I can't help notice that the invocation comes from an implementation of IBuildManager. I explored the possibility of injecting my own IBuildManager, but I ran into the following problems:
IBuildManager is marked internal, so I need some other authorized derivation from it. It turns out that the assembly System.Web.Mvc.Test has a class called MockBuildManager, designed for test scenarios, which is perfect!!! This leads to the second problem.
The MVC distributable, near as I can tell, does not come with the System.Web.Mvc.Test assembly (DOH!).
Even if the MVC distributable did come with the System.Web.Mvc.Test assembly, having an instance of MockBuildManager is only half the solution. It is also necessary to feed that instance into the DefaultControllerFactory. Unfortunately the property setter to accomplish this is also marked internal (DOH!).
In short, unless I find another way to "initialize" the MVC framework, my options now are to either:
COMPLETELY duplicate the source code for DefaultControllerFactory and its dependencies, so that I can bypass the original GetReferencedAssemblies() issue. (ugh!)
COMPLETELY replace the MVC distributable with my own build of MVC, based on the MVC source code - with just a couple internal modifiers removed. (double ugh!)
Incidentally, I know that the MvcContrib "TestHelper" has the appearance of accomplishing my goal, but I think it is merely using reflection to find the controller - rather than using the actual IControllerFactory to retrieve a controller type / instance.
A big reason why I want this test capability is that I have made a custom controller factory, based on DefaultControllerFactory, whose behavior I want to verify.
I'm not quite sure what you're trying to accomplish here. If it's just testing your route setup; you're way better off just testing THAT instead of hacking your way into internals. 1st rule of TDD: only test the code you wrote (and in this case that's the routing setup, not the actual route resolving technique done by MVC).
There are tons of posts/blogs about testing a route setup (just google for 'mvc test route'). It all comes down to mocking a request in a httpcontext and calling GetRouteData.
If you really need some ninja skills to mock the buildmanager: there's a way around internal interfaces, which I use for (LinqPad) experimental tests. Most .net assemblies nowadays have the InternalsVisibleToAttribute set, most likely pointing to another signed test assembly. By scanning the target assembly for this attribute and creating an assembly on the fly that matches the name (and the public key token) you can easily access internals.
Mind you that I personally would not use this technique in production test code; but it's a nice way to isolate some complex ideas.
void Main()
{
var bm = BuildManagerMockBase.CreateMock<MyBuildManager>();
bm.FileExists("IsCool?").Dump();
}
public class MyBuildManager : BuildManagerMockBase
{
public override bool FileExists(string virtualPath) { return true; }
}
public abstract class BuildManagerMockBase
{
public static T CreateMock<T>()
where T : BuildManagerMockBase
{
// Locate the mvc assembly
Assembly mvcAssembly = Assembly.GetAssembly(typeof(Controller));
// Get the type of the buildmanager interface
var buildManagerInterface = mvcAssembly.GetType("System.Web.Mvc.IBuildManager",true);
// Locate the "internals visible to" attribute and create a public key token that matches the one specified.
var internalsVisisbleTo = mvcAssembly.GetCustomAttributes(typeof (InternalsVisibleToAttribute), true).FirstOrDefault() as InternalsVisibleToAttribute;
var publicKeyString = internalsVisisbleTo.AssemblyName.Split("=".ToCharArray())[1];
var publicKey = ToBytes(publicKeyString);
// Create a fake System.Web.Mvc.Test assembly with the public key token set
AssemblyName assemblyName = new AssemblyName();
assemblyName.Name = "System.Web.Mvc.Test";
assemblyName.SetPublicKey(publicKey);
// Get the domain of our current thread to host the new fake assembly
var domain = Thread.GetDomain();
var assemblyBuilder = domain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.RunAndSave);
moduleBuilder = assemblyBuilder.DefineDynamicModule("System.Web.Mvc.Test", "System.Web.Mvc.Test.dll");
AppDomain currentDom = domain;
currentDom.TypeResolve += ResolveEvent;
// Create a new type that inherits from the provided generic and implements the IBuildManager interface
var typeBuilder = moduleBuilder.DefineType("Cheat", TypeAttributes.NotPublic | TypeAttributes.Class, typeof(T), new Type[] { buildManagerInterface });
Type cheatType = typeBuilder.CreateType();
// Magic!
var ret = Activator.CreateInstance(cheatType) as T;
return ret;
}
private static byte[] ToBytes(string str)
{
List<Byte> bytes = new List<Byte>();
while(str.Length > 0)
{
var bstr = str.Substring(0, 2);
bytes.Add(Convert.ToByte(bstr, 16));
str = str.Substring(2);
}
return bytes.ToArray();
}
private static ModuleBuilder moduleBuilder;
private static Assembly ResolveEvent(Object sender, ResolveEventArgs args)
{
return moduleBuilder.Assembly;
}
public virtual bool FileExists(string virtualPath) { throw new NotImplementedException(); }
public virtual Type GetCompiledType(string virtualPath) { throw new NotImplementedException(); }
public virtual ICollection GetReferencedAssemblies() { throw new NotImplementedException(); }
public virtual Stream ReadCachedFile(string fileName) { throw new NotImplementedException(); }
public virtual Stream CreateCachedFile(string fileName) { throw new NotImplementedException(); }
}
I'm adding ASP.NET routing to an older webforms app. I'm using a custom HttpHandler to process everything. In some situations I would like to map a particular path back to an aspx file, so I need to just pass control back to the default HttpHandler for asp.net.
The closest I've gotten is this
public void ProcessRequest(HttpContext context) {
// .. when we decide to pass it on
var handler = new System.Web.UI.Page();
handler.ProcessRequest(context);
MemoryStream steam = new MemoryStream();
StreamWriter writer = new StreamWriter(stream);
HtmlTextWriter htmlWriter = new HtmlTextWriter(writer);
handler.RenderControl(htmlWriter);
// write headers, etc. & send stream to Response
}
It doesn't do anything, there's nothing output to the stream. MS's documentation for System.Web.UI.Page (as an IHttpHandler) say something to the effect of "do not call the ProcessRequest method. It's for internal use."
From looking around it seems like you can do this with MVC, e.g. : MvcHttpHandler doesn't seem to implement IHttpHandler
There is also this thing System.Web.UI.PageHandlerFactory which appears that it would just produce a Page handler for an aspx file, but it's internal and I can't use it directly.
This page: http://msdn.microsoft.com/en-us/library/bb398986.aspx refers to the "default asp.net handler" but does not identify a class or give any indication how one might use it.
Any ideas on how I can do this? Is it possible?
Persistence pays off! This actually works, and since this information seems to be available pretty much nowhere I thought I'd answer my own question. Thanks to Robert for this post on instantiating things with internal constructors, this is the key.
http://www.rvenables.com/2009/08/instantiating-classes-with-internal-constructors/
public void ProcessRequest(HttpContext context) {
// the internal constructor doesn't do anything but prevent you from instantiating
// the factory, so we can skip it.
PageHandlerFactory factory =
(PageHandlerFactory)System.Runtime.Serialization.FormatterServices
.GetUninitializedObject(typeof(System.Web.UI.PageHandlerFactory));
string newTarget = "default.aspx";
string newQueryString = // whatever you want
string oldQueryString = context.Request.QueryString.ToString();
string queryString = newQueryString + oldQueryString!="" ?
"&" + newQueryString :
"";
// the 3rd parameter must be just the file name.
// the 4th parameter should be the physical path to the file, though it also
// works fine if you pass an empty string - perhaps that's only to override
// the usual presentation based on the path?
var handler = factory.GetHandler(context, "GET",newTarget,
context.Request.MapPath(context,newTarget));
// Update the context object as it should appear to your page/app, and
// assign your new handler.
context.RewritePath(newTarget , "", queryString);
context.Handler = handler;
// .. and done
handler.ProcessRequest(context);
}
... and like some small miracle, an aspx page processes & renders completely in-process without the need to redirect.
I expect this will only work in IIS7.
I'm you're using Routing in webforms you should be able to just add an ignore route for the specific .aspx files you want. This will then be handled by the default HttpHandler.
http://msdn.microsoft.com/en-us/library/dd505203.aspx
Another option is to invert the logic by handling the cases in which you do NOT want to return the default response and remap the others to your own IHttpHandler. Whenever myCondition is false, the response will be the "default". The switch is implemented as an IHttpModule:
public class SwitchModule: IHttpModule
{
public void Init(HttpApplication context)
{
context.PostAuthenticateRequest += app_PostAuthenticateRequest;
}
void app_PostAuthenticateRequest(object sender, EventArgs e)
{
// Check for whatever condition you like
if (true)
HttpContext.Current.RemapHandler(new CustomHandler());
}
public void Dispose()
}
internal class CustomHandler: IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
context.Response.Write("hallo");
}
public bool IsReusable { get; }
}