HttpWebRequest.BeginGetResponse(AsyncCallback, Object) Méthode
Définition
Important
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Démarre une requête asynchrone adressée à une ressource Internet.
public:
override IAsyncResult ^ BeginGetResponse(AsyncCallback ^ callback, System::Object ^ state);public override IAsyncResult BeginGetResponse (AsyncCallback callback, object state);public override IAsyncResult BeginGetResponse (AsyncCallback? callback, object? state);override this.BeginGetResponse : AsyncCallback * obj -> IAsyncResultPublic Overrides Function BeginGetResponse (callback As AsyncCallback, state As Object) As IAsyncResultParamètres
- callback
- AsyncCallback
Délégué AsyncCallback.
- state
- Object
Objet d'état de cette requête.
Retours
IAsyncResult qui fait référence à la requête asynchrone d’une réponse.
Exceptions
Le flux est déjà utilisé par un appel précédent à BeginGetResponse(AsyncCallback, Object).
- ou -
TransferEncoding est défini sur une valeur, et SendChunked a pour valeur false.
- ou -
Le nombre de threads du pool de threads est insuffisant.
Method a pour valeur GET ou HEAD, et ContentLength est supérieur à zéro ou SendChunked a pour valeur true.
- ou -
KeepAlive a la valeur true, AllowWriteStreamBuffering a la valeur false, et ContentLength a la valeur -1, SendChunked a la valeur false et Method a la valeur POST ou PUT.
- ou -
La HttpWebRequest a un corps d’entité, mais la méthode BeginGetResponse(AsyncCallback, Object) est appelée sans que soit appelée la méthode BeginGetRequestStream(AsyncCallback, Object).
- ou -
Le ContentLength est supérieur à zéro, mais l’application n’écrit pas toutes les données promises.
Abort() a déjà été appelé.
Exemples
L’exemple de code suivant utilise la BeginGetResponse méthode pour effectuer une requête asynchrone pour une ressource Internet.
Notes
Dans le cas de requêtes asynchrones, il incombe à l’application cliente d’implémenter son propre mécanisme de délai d’attente. L’exemple de code suivant montre comment procéder.
#using <System.dll>
using namespace System;
using namespace System::Net;
using namespace System::IO;
using namespace System::Text;
using namespace System::Threading;
public ref class RequestState
{
private:
// This class stores the State of the request.
const int BUFFER_SIZE;
public:
StringBuilder^ requestData;
array<Byte>^BufferRead;
HttpWebRequest^ request;
HttpWebResponse^ response;
Stream^ streamResponse;
RequestState()
: BUFFER_SIZE( 1024 )
{
BufferRead = gcnew array<Byte>(BUFFER_SIZE);
requestData = gcnew StringBuilder( "" );
request = nullptr;
streamResponse = nullptr;
}
};
ref class HttpWebRequest_BeginGetResponse
{
public:
static ManualResetEvent^ allDone = gcnew ManualResetEvent( false );
literal int BUFFER_SIZE = 1024;
literal int DefaultTimeOut = 120000; // 2 minute timeout
// Abort the request if the timer fires.
static void TimeoutCallback( Object^ state, bool timedOut )
{
if ( timedOut )
{
HttpWebRequest^ request = dynamic_cast<HttpWebRequest^>(state);
if ( request != nullptr )
{
request->Abort();
}
}
}
static void RespCallback( IAsyncResult^ asynchronousResult )
{
try
{
// State of request is asynchronous.
RequestState^ myRequestState = dynamic_cast<RequestState^>(asynchronousResult->AsyncState);
HttpWebRequest^ myHttpWebRequest = myRequestState->request;
myRequestState->response = dynamic_cast<HttpWebResponse^>(myHttpWebRequest->EndGetResponse( asynchronousResult ));
// Read the response into a Stream object.
Stream^ responseStream = myRequestState->response->GetResponseStream();
myRequestState->streamResponse = responseStream;
// Begin the Reading of the contents of the HTML page and print it to the console.
IAsyncResult^ asynchronousInputRead = responseStream->BeginRead( myRequestState->BufferRead, 0, BUFFER_SIZE, gcnew AsyncCallback( ReadCallBack ), myRequestState );
return;
}
catch ( WebException^ e )
{
Console::WriteLine( "\nRespCallback Exception raised!" );
Console::WriteLine( "\nMessage: {0}", e->Message );
Console::WriteLine( "\nStatus: {0}", e->Status );
}
allDone->Set();
}
static void ReadCallBack( IAsyncResult^ asyncResult )
{
try
{
RequestState^ myRequestState = dynamic_cast<RequestState^>(asyncResult->AsyncState);
Stream^ responseStream = myRequestState->streamResponse;
int read = responseStream->EndRead( asyncResult );
// Read the HTML page and then print it to the console.
if ( read > 0 )
{
myRequestState->requestData->Append( Encoding::ASCII->GetString( myRequestState->BufferRead, 0, read ) );
IAsyncResult^ asynchronousResult = responseStream->BeginRead( myRequestState->BufferRead, 0, BUFFER_SIZE, gcnew AsyncCallback( ReadCallBack ), myRequestState );
return;
}
else
{
Console::WriteLine( "\nThe contents of the Html page are : " );
if ( myRequestState->requestData->Length > 1 )
{
String^ stringContent;
stringContent = myRequestState->requestData->ToString();
Console::WriteLine( stringContent );
}
Console::WriteLine( "Press any key to continue.........." );
Console::ReadLine();
responseStream->Close();
}
}
catch ( WebException^ e )
{
Console::WriteLine( "\nReadCallBack Exception raised!" );
Console::WriteLine( "\nMessage: {0}", e->Message );
Console::WriteLine( "\nStatus: {0}", e->Status );
}
allDone->Set();
}
};
int main()
{
try
{
// Create a HttpWebrequest object to the desired URL.
HttpWebRequest^ myHttpWebRequest = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "http://www.contoso.com" ));
/**
* If you are behind a firewall and you do not have your browser proxy setup
* you need to use the following proxy creation code.
// Create a proxy object.
WebProxy* myProxy = new WebProxy();
// Associate a new Uri object to the _wProxy object, using the proxy address
// selected by the user.
myProxy.Address = new Uri(S"http://myproxy");
// Finally, initialize the Web request object proxy property with the _wProxy
// object.
myHttpWebRequest.Proxy=myProxy;
***/
// Create an instance of the RequestState and assign the previous myHttpWebRequest
// object to its request field.
RequestState^ myRequestState = gcnew RequestState;
myRequestState->request = myHttpWebRequest;
// Start the asynchronous request.
IAsyncResult^ result = dynamic_cast<IAsyncResult^>(myHttpWebRequest->BeginGetResponse( gcnew AsyncCallback( HttpWebRequest_BeginGetResponse::RespCallback ), myRequestState ));
// this line impliments the timeout, if there is a timeout, the callback fires and the request becomes aborted
ThreadPool::RegisterWaitForSingleObject( result->AsyncWaitHandle, gcnew WaitOrTimerCallback( HttpWebRequest_BeginGetResponse::TimeoutCallback ), myHttpWebRequest, HttpWebRequest_BeginGetResponse::DefaultTimeOut, true );
// The response came in the allowed time. The work processing will happen in the
// callback function.
HttpWebRequest_BeginGetResponse::allDone->WaitOne();
// Release the HttpWebResponse resource.
myRequestState->response->Close();
}
catch ( WebException^ e )
{
Console::WriteLine( "\nMain Exception raised!" );
Console::WriteLine( "\nMessage: {0}", e->Message );
Console::WriteLine( "\nStatus: {0}", e->Status );
Console::WriteLine( "Press any key to continue.........." );
}
catch ( Exception^ e )
{
Console::WriteLine( "\nMain Exception raised!" );
Console::WriteLine( "Source : {0} ", e->Source );
Console::WriteLine( "Message : {0} ", e->Message );
Console::WriteLine( "Press any key to continue.........." );
Console::Read();
}
}
using System;
using System.Net;
using System.IO;
using System.Text;
using System.Threading;
public class RequestState
{
// This class stores the State of the request.
const int BUFFER_SIZE = 1024;
public StringBuilder requestData;
public byte[] BufferRead;
public HttpWebRequest request;
public HttpWebResponse response;
public Stream streamResponse;
public RequestState()
{
BufferRead = new byte[BUFFER_SIZE];
requestData = new StringBuilder("");
request = null;
streamResponse = null;
}
}
class HttpWebRequest_BeginGetResponse
{
public static ManualResetEvent allDone= new ManualResetEvent(false);
const int BUFFER_SIZE = 1024;
const int DefaultTimeout = 2 * 60 * 1000; // 2 minutes timeout
// Abort the request if the timer fires.
private static void TimeoutCallback(object state, bool timedOut) {
if (timedOut) {
HttpWebRequest request = state as HttpWebRequest;
if (request != null) {
request.Abort();
}
}
}
static void Main()
{
try
{
// Create a HttpWebrequest object to the desired URL.
HttpWebRequest myHttpWebRequest= (HttpWebRequest)WebRequest.Create("http://www.contoso.com");
/**
* If you are behind a firewall and you do not have your browser proxy setup
* you need to use the following proxy creation code.
// Create a proxy object.
WebProxy myProxy = new WebProxy();
// Associate a new Uri object to the _wProxy object, using the proxy address
// selected by the user.
myProxy.Address = new Uri("http://myproxy");
// Finally, initialize the Web request object proxy property with the _wProxy
// object.
myHttpWebRequest.Proxy=myProxy;
***/
// Create an instance of the RequestState and assign the previous myHttpWebRequest
// object to its request field.
RequestState myRequestState = new RequestState();
myRequestState.request = myHttpWebRequest;
// Start the asynchronous request.
IAsyncResult result=
(IAsyncResult) myHttpWebRequest.BeginGetResponse(new AsyncCallback(RespCallback),myRequestState);
// this line implements the timeout, if there is a timeout, the callback fires and the request becomes aborted
ThreadPool.RegisterWaitForSingleObject (result.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), myHttpWebRequest, DefaultTimeout, true);
// The response came in the allowed time. The work processing will happen in the
// callback function.
allDone.WaitOne();
// Release the HttpWebResponse resource.
myRequestState.response.Close();
}
catch(WebException e)
{
Console.WriteLine("\nMain Exception raised!");
Console.WriteLine("\nMessage:{0}",e.Message);
Console.WriteLine("\nStatus:{0}",e.Status);
Console.WriteLine("Press any key to continue..........");
}
catch(Exception e)
{
Console.WriteLine("\nMain Exception raised!");
Console.WriteLine("Source :{0} " , e.Source);
Console.WriteLine("Message :{0} " , e.Message);
Console.WriteLine("Press any key to continue..........");
Console.Read();
}
}
private static void RespCallback(IAsyncResult asynchronousResult)
{
try
{
// State of request is asynchronous.
RequestState myRequestState=(RequestState) asynchronousResult.AsyncState;
HttpWebRequest myHttpWebRequest=myRequestState.request;
myRequestState.response = (HttpWebResponse) myHttpWebRequest.EndGetResponse(asynchronousResult);
// Read the response into a Stream object.
Stream responseStream = myRequestState.response.GetResponseStream();
myRequestState.streamResponse=responseStream;
// Begin the Reading of the contents of the HTML page and print it to the console.
IAsyncResult asynchronousInputRead = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
return;
}
catch(WebException e)
{
Console.WriteLine("\nRespCallback Exception raised!");
Console.WriteLine("\nMessage:{0}",e.Message);
Console.WriteLine("\nStatus:{0}",e.Status);
}
allDone.Set();
}
private static void ReadCallBack(IAsyncResult asyncResult)
{
try
{
RequestState myRequestState = (RequestState)asyncResult.AsyncState;
Stream responseStream = myRequestState.streamResponse;
int read = responseStream.EndRead( asyncResult );
// Read the HTML page and then print it to the console.
if (read > 0)
{
myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.BufferRead, 0, read));
IAsyncResult asynchronousResult = responseStream.BeginRead( myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
return;
}
else
{
Console.WriteLine("\nThe contents of the Html page are : ");
if(myRequestState.requestData.Length>1)
{
string stringContent;
stringContent = myRequestState.requestData.ToString();
Console.WriteLine(stringContent);
}
Console.WriteLine("Press any key to continue..........");
Console.ReadLine();
responseStream.Close();
}
}
catch(WebException e)
{
Console.WriteLine("\nReadCallBack Exception raised!");
Console.WriteLine("\nMessage:{0}",e.Message);
Console.WriteLine("\nStatus:{0}",e.Status);
}
allDone.Set();
}
Imports System.Net
Imports System.IO
Imports System.Text
Imports System.Threading
Public Class RequestState
' This class stores the State of the request.
Private BUFFER_SIZE As Integer = 1024
Public requestData As StringBuilder
Public BufferRead() As Byte
Public request As HttpWebRequest
Public response As HttpWebResponse
Public streamResponse As Stream
Public Sub New()
BufferRead = New Byte(BUFFER_SIZE) {}
requestData = New StringBuilder("")
request = Nothing
streamResponse = Nothing
End Sub
End Class
Class HttpWebRequest_BeginGetResponse
Public Shared allDone As New ManualResetEvent(False)
Private BUFFER_SIZE As Integer = 1024
Private DefaultTimeout As Integer = 2 * 60 * 1000
' 2 minutes timeout
' Abort the request if the timer fires.
Private Shared Sub TimeoutCallback(state As Object, timedOut As Boolean)
If timedOut Then
Dim request As HttpWebRequest = state
If Not (request Is Nothing) Then
request.Abort()
End If
End If
End Sub
Shared Sub Main()
Try
' Create a HttpWebrequest object to the desired URL.
Dim myHttpWebRequest As HttpWebRequest = WebRequest.Create("http://www.contoso.com")
' Create an instance of the RequestState and assign the previous myHttpWebRequest
' object to its request field.
Dim myRequestState As New RequestState()
myRequestState.request = myHttpWebRequest
Dim myResponse As New HttpWebRequest_BeginGetResponse()
' Start the asynchronous request.
Dim result As IAsyncResult = CType(myHttpWebRequest.BeginGetResponse(New AsyncCallback(AddressOf RespCallback), myRequestState), IAsyncResult)
' this line implements the timeout, if there is a timeout, the callback fires and the request aborts.
ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, New WaitOrTimerCallback(AddressOf TimeoutCallback), myHttpWebRequest, myResponse.DefaultTimeout, True)
' The response came in the allowed time. The work processing will happen in the
' callback function.
allDone.WaitOne()
' Release the HttpWebResponse resource.
myRequestState.response.Close()
Catch e As WebException
Console.WriteLine(ControlChars.Lf + "Main Exception raised!")
Console.WriteLine(ControlChars.Lf + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Lf + "Status:{0}", e.Status)
Console.WriteLine("Press any key to continue..........")
Catch e As Exception
Console.WriteLine(ControlChars.Lf + "Main Exception raised!")
Console.WriteLine("Source :{0} ", e.Source)
Console.WriteLine("Message :{0} ", e.Message)
Console.WriteLine("Press any key to continue..........")
Console.Read()
End Try
End Sub
Private Shared Sub RespCallback(asynchronousResult As IAsyncResult)
Try
' State of request is asynchronous.
Dim myRequestState As RequestState = CType(asynchronousResult.AsyncState, RequestState)
Dim myHttpWebRequest As HttpWebRequest = myRequestState.request
myRequestState.response = CType(myHttpWebRequest.EndGetResponse(asynchronousResult), HttpWebResponse)
' Read the response into a Stream object.
Dim responseStream As Stream = myRequestState.response.GetResponseStream()
myRequestState.streamResponse = responseStream
' Begin the Reading of the contents of the HTML page and print it to the console.
Dim asynchronousInputRead As IAsyncResult = responseStream.BeginRead(myRequestState.BufferRead, 0, 1024, New AsyncCallback(AddressOf ReadCallBack), myRequestState)
Return
Catch e As WebException
Console.WriteLine(ControlChars.Lf + "RespCallback Exception raised!")
Console.WriteLine(ControlChars.Lf + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Lf + "Status:{0}", e.Status)
End Try
allDone.Set()
End Sub
Private Shared Sub ReadCallBack(asyncResult As IAsyncResult)
Try
Dim myRequestState As RequestState = CType(asyncResult.AsyncState, RequestState)
Dim responseStream As Stream = myRequestState.streamResponse
Dim read As Integer = responseStream.EndRead(asyncResult)
' Read the HTML page and then print it to the console.
If read > 0 Then
myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.BufferRead, 0, read))
Dim asynchronousResult As IAsyncResult = responseStream.BeginRead(myRequestState.BufferRead, 0, 1024, New AsyncCallback(AddressOf ReadCallBack), myRequestState)
Return
Else
Console.WriteLine(ControlChars.Lf + "The contents of the Html page are : ")
If myRequestState.requestData.Length > 1 Then
Dim stringContent As String
stringContent = myRequestState.requestData.ToString()
Console.WriteLine(stringContent)
End If
Console.WriteLine("Press any key to continue..........")
Console.ReadLine()
responseStream.Close()
End If
Catch e As WebException
Console.WriteLine(ControlChars.Lf + "ReadCallBack Exception raised!")
Console.WriteLine(ControlChars.Lf + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Lf + "Status:{0}", e.Status)
End Try
allDone.Set()
End Sub
End Class
Remarques
La BeginGetResponse méthode démarre une demande asynchrone de réponse de la ressource Internet. La méthode de rappel asynchrone utilise la EndGetResponse méthode pour retourner le réel WebResponse.
Un ProtocolViolationException est levée dans plusieurs cas lorsque les propriétés définies sur la HttpWebRequest classe sont en conflit. Cette exception se produit si une application définit la ContentLength propriété et la propriété sur trueSendChunked , puis envoie une requête HTTP GET. Cette exception se produit si une application tente d’envoyer des blocs à un serveur qui prend uniquement en charge le protocole HTTP 1.0, où cela n’est pas pris en charge. Cette exception se produit si une application tente d’envoyer des données sans définir la ContentLength propriété ou si est false lorsque la SendChunked mise en mémoire tampon est désactivée et sur une connexion keepalive (la KeepAlive propriété est true).
Si un WebException est levée, utilisez les Response propriétés et Status de l’exception pour déterminer la réponse du serveur.
La BeginGetResponse méthode nécessite l’exécution de certaines tâches d’installation synchrones (résolution DNS, détection de proxy et connexion de socket TCP, par exemple) avant que cette méthode ne devienne asynchrone. Par conséquent, cette méthode ne doit jamais être appelée sur un thread d’interface utilisateur, car cela peut prendre beaucoup de temps (jusqu’à plusieurs minutes selon les paramètres réseau) pour effectuer les tâches d’installation synchrones initiales avant qu’une exception pour une erreur ne soit levée ou que la méthode réussisse.
Pour en savoir plus sur le pool de threads, consultez Le pool de threads managés.
Notes
Votre application ne peut pas combiner des méthodes synchrones et asynchrones pour une demande particulière. Si vous appelez la BeginGetRequestStream méthode, vous devez utiliser la BeginGetResponse méthode pour récupérer la réponse.
Notes
Ce membre génère des informations de traçage lorsque vous activez le traçage réseau dans votre application. Pour plus d’informations, consultez Suivi réseau dans le .NET Framework.
S’applique à
Voir aussi
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