IHttpCachePolicy::IsCached-Methode
Gibt einen Wert zurück, der angibt, ob die Cacherichtlinie aktiviert ist.
Syntax
virtual BOOL IsCached(
VOID
) const = 0;
Parameter
Diese Methode nimmt zwei Parameter entgegen.
Rückgabewert
true , wenn Daten zwischengespeichert werden; falseandernfalls .
Bemerkungen
Von CHttpModule abgeleitete Klassen, die sich für Anforderungs- oder Antwortereignisse registrieren, erhalten einen IHttpContext-Zeiger als Parameter für die entsprechende virtual Methode. Rufen Sie die IHttpContext::GetResponse-Methode , dann die IHttpResponse::GetCachePolicy-Methode und schließlich die IsCached Methode auf, um zu überprüfen, ob die Daten zwischengespeichert werden.
IsCached Das Verhalten hängt von der Implementierung ab. Sie sollten die folgenden Informationen als Richtlinie verwenden, aber sie sind möglicherweise nicht in allen Szenarien korrekt:
Der aktuelle Standardimplementierer der IHttpCachePolicy-Schnittstelle deklariert einen
privatebooleschen Wert, der bei der Erstellung mit initialisiertfalsewird. Wenn die SetIsCached-Methode aufgerufen wird, wird dieser boolesche Wert auftruefestgelegt. NachdemSetIsCachedaufgerufen wurde, gibt es keine Methode zum Zurücksetzen dieses booleschen Werts auffalse.IsCachedgibt den Wert dieses booleschen Werts zurück.
Beispiel
Im folgenden Codebeispiel wird veranschaulicht, wie Sie ein globales Modul erstellen, das auf RQ_BEGIN_REQUEST und RQ_SEND_RESPONSE Ereignisse lauscht. Das Modul ruft dann einen IHttpCachePolicy Zeiger ab und schreibt Cacheinformationen in den Antwortdatenstrom.
#pragma warning( disable : 4290 )
#pragma warning( disable : 4530 )
#define _WINSOCKAPI_
#include <windows.h>
#include <sal.h>
#include <tchar.h>
#include <httptrace.h>
#include <httpserv.h>
#include <httpcach.h>
#include <string>
using namespace std;
// The CConvert class mirrors the Convert class that is
// defined in the .NET Framework. It converts primitives
// and other data types to wstring types.
class CConvert
{
public:
// The ToString method converts a BOOL to a wstring.
// b: the BOOL value to convert to a wstring.
// return: L"true" for true; otherwise, L"false" for false.
static wstring ToString(BOOL b)
{
return (b) ? L"true" : L"false";
}
// The ToByteString converts a double-byte
// character string to a single-byte string.
// str: the double-byte string to convert.
// return: a single-byte string copied from str.
static string ToByteString(const wstring& str)
{
// Get the length of the
// double-byte string.
size_t length = str.length();
// Create a temporary char pointer.
char* byteChar = new char[length+1];
byteChar[0] = '\0';
// Copy the double-byte character string
// into the single-byte string.
size_t charsReturned = 0;
wcstombs_s(&charsReturned, byteChar,
length+1, str.c_str(), length+1);
// Create a string to return.
string retString = byteChar;
// Delete the temporary string and
// set that string to NULL.
delete[] byteChar;
byteChar = NULL;
// Return the single-byte string.
return retString;
}
};
// The CResponseWriter class writes
// text to the response stream.
class CResponseWriter
{
public:
// Creates the CResponseWriter class.
// response: the IHttpResponse
// pointer to write to.
// throws: a _com_error exception if
// the IHttpResponse pointer is NULL.
CResponseWriter(IHttpResponse* response)
throw (_com_error)
{
// If the response is NULL,
// throw an exception.
if (NULL == response)
{
ThrowOnFail(E_INVALIDARG);
}
// Set the internal response.
m_response = response;
}
// The destructor for the CResponseWriter
// class. The CResponseWriter method
// sets the IHttpResponse pointer to NULL.
virtual ~CResponseWriter()
{
m_response = NULL;
}
// The Write method writes the
// PCSTR to the response stream.
// pszValue: the PCSTR to write.
// throws: a _com_error if the
// Write method fails.
void Write
(
PCSTR pszValue
) throw (_com_error)
{
// The string must not be
// NULL, and its length must
// be greater than 0.
if ((NULL == pszValue) ||
(strlen(pszValue) < 1))
{
// Throw an invalid argument
// exception.
ThrowOnFail(E_INVALIDARG);
}
// Create a data chunk structure.
HTTP_DATA_CHUNK dataChunk;
// Set the chunk to a chunk in memory.
dataChunk.DataChunkType =
HttpDataChunkFromMemory;
// Set the chunk to
// the pszValue parameter.
dataChunk.FromMemory.pBuffer =
(PVOID)pszValue;
// Set the chunk size
// to the pszValue length.
dataChunk.FromMemory.BufferLength =
(USHORT)strlen(pszValue);
// Declare and initialize OUT
// parameters for the WriteEntityChunks
// method.
DWORD pcbSent = 0;
BOOL pfCompletionExpected = FALSE;
// Write the entity chunks to
// the response stream.
HRESULT hr =
m_response->WriteEntityChunks
(&dataChunk,
1,
FALSE,
FALSE,
&pcbSent,
&pfCompletionExpected);
// Throw an exception if the call
// to WriteEntityChunks is not a
// success.
ThrowOnFail(hr);
}
// The WriteLine method writes a string
// and newline characters to the response steam.
// pszValue: the PCSTR string to write.
// throws: a _com_error if the PCSTR
// or the newline characters are not
// written to the response stream.
void WriteLine
(
PCSTR pszValue
) throw (_com_error)
{
// Try to write the pszValue parameter.
Write(pszValue);
// Try to write the newline characters.
Write("\r\n");
}
// Convenience method that writes a name
// and value pair to the response stream.
// name: the name of the parameter.
// value: the value of the parameter.
// throws: a _com_error exception if
// the response stream is not written.
void WriteLine
(
const wstring& name,
const wstring& value
) throw (_com_error)
{
// Convert the UNICODE strings
// to mutlibyte strings.
string nameMulti =
CConvert::ToByteString(name);
string valueMulti =
CConvert::ToByteString(value);
// Create the string to write.
string writeString =
nameMulti +
string(": ") +
valueMulti;
// Write the line to
// the response stream.
WriteLine(writeString.c_str());
}
// Tests an HRESULT for success.
// hr: the HRESULT value to inspect.
// throws: a _com_error if the HRESULT
// parameter is not S_OK.
static void ThrowOnFail(HRESULT hr)
{
if (FAILED(hr))
{
_com_error ce(hr);
throw ce;
}
}
private:
// Specify the IHttpResponse
// pointer to write to.
IHttpResponse* m_response;
};
// The CCachePolicyModule is a CHttpModule
// class that handles response processing
// by updating the IHttpCachePolicy pointer
// and writing that IHttpCachePolicy data
// to the response stream.
class CCachePolicyModule : public CHttpModule
{
public:
// The CHttpResponseModule method is
// the public virtual destructor for
// the CHttpResponseModule class.
virtual ~CCachePolicyModule()
{
}
// The OnSendResponse method is the method
// supporting the RQ_SEND_RESPONSE event type.
// pHttpContext: the current IHttpContext pointer.
// pProvider: the current IHttpEventProvider pointer.
// return: RQ_NOTIFICATION_FINISH_REQUEST if the
// IHttpCachePolicy data is written. Otherwise,
// RQ_NOTIFICATION_CONTINUE.
virtual
REQUEST_NOTIFICATION_STATUS
OnSendResponse
(
IN IHttpContext* pHttpContext,
IN ISendResponseProvider* pProvider
)
{
// Return if the IHttpContext
// pointer is NULL.
if (NULL == pHttpContext)
{
return RQ_NOTIFICATION_CONTINUE;
}
// Get the IHttpResponse pointer
// from the IHttpContext pointer.
IHttpResponse* response =
pHttpContext->GetResponse();
// Return if the IHttpResponse
// pointer is NULL.
if (NULL == response)
{
return RQ_NOTIFICATION_CONTINUE;
}
// Get the IHttpCachePolicy pointer
// from the IHttpResponse pointer.
IHttpCachePolicy* policy =
response->GetCachePolicy();
// Return if the IHttpCachePolicy
// pointer is NULL.
if (NULL == policy)
{
return RQ_NOTIFICATION_CONTINUE;
}
// Wrap calls in one try-catch statement
// because a CResponseWriter might throw
// a _com_error exception.
try
{
// Create a CResponseWriter using
// the IHttpResponse pointer.
CResponseWriter writer(response);
// Clear the existing response stream.
response->Clear();
// Set the response header to plain text.
HRESULT hr =
response->SetHeader(HttpHeaderContentType,
"text/plain",
(USHORT)strlen("text/plain"),
TRUE);
// Throw an excepion if the
// SetHeader method failed.
CResponseWriter::ThrowOnFail(hr);
// Write the IHttpCachePolicy pointer
// data to the response stream.
Write(policy, writer);
}
catch(_com_error& ce)
{
// Set the error status
// using the COM exception.
response->SetStatus(500,
"OnSendResponse",
0, ce.Error());
// Continue processing.
return RQ_NOTIFICATION_CONTINUE;
}
// Finish the request because
// the response is written.
return RQ_NOTIFICATION_FINISH_REQUEST;
}
protected:
// The Write method writes IHttpCachePolicy
// pointer data to the response stream.
// httpCachePolicy: the IHttpCachePolicy
// pointer to write to the stream.
// writer: the CResponseWriter writer
// for writing to the response stream.
// throws: a _com_error exception.
static void Write
(
IHttpCachePolicy* httpCachePolicy,
CResponseWriter& writer
) throw (_com_error)
{
// If the IHttpCachePolicy
// pointer is NULL, return.
if (NULL == httpCachePolicy)
{
return;
}
// Get a value indicating if
// the user data is cached.
BOOL isCachedBOOL =
httpCachePolicy->IsCached();
// Convert the BOOL to a wstring.
wstring isCached =
CConvert::ToString(isCachedBOOL);
// Write the user cache information
// to the response streasm.
writer.WriteLine(L"Is Cached", isCached);
}
};
// The CCachePolicyFactory class implements the
// IHttpModuleFactory interface and creates a new
// CCachePolicyModule pointer and registers that
// pointer for request and response events.
class CCachePolicyFactory : public IHttpModuleFactory
{
public:
// The RegisterCHttpModule method creates a new
// CCachePolicyFactory pointer and sets this new
// CCachePolicyFactory pointer as the IHttpModuleFactory
// pointer on the IHttpModuleRegistrationInfo pointer.
// dwServerVersion: the current server version.
// pModuleInfo: the current
// IHttpModuleRegistrationInfo pointer.
// pGlobalInfo: the current IHttpServer pointer.
// return: the value returned from the the call
// to the SetRequestNotifications on the
// IHttpModuleRegistrationInfo pointer.
static HRESULT RegisterCHttpModule
(
DWORD dwServerVersion,
IHttpModuleRegistrationInfo* pModuleInfo,
IHttpServer* pGlobalInfo
)
{
// Create a new CCachePolicyFactory pointer.
CCachePolicyFactory* policyFactory =
new CCachePolicyFactory;
// Test for NULL on the new
// CCachePolicyFactory pointer.
if (NULL == policyFactory)
{
// Return an out-of-memory error
// code if moduleFactory is NULL.
return HRESULT_FROM_WIN32(ERROR_NOT_ENOUGH_MEMORY);
}
// Set the request notifications for RQ_SEND_RESPONSE
// messages on the new CCachePolicyFactory pointer.
return pModuleInfo->SetRequestNotifications
(policyFactory,
RQ_SEND_RESPONSE,
0);
}
// The GetHttpModule method creates a new
// CCachePolicyModule pointer and sets the
// new CCachePolicyModule on the ppModule parameter.
// ppModule: the new CHttpResponseModule pointer to return.
// pAllocator: currently unused.
// return: ERROR_NOT_ENOUGH_MEMORY if the
// heap is exhausted; otherwise, S_OK.
virtual
HRESULT
GetHttpModule
(
OUT CHttpModule** ppModule,
IN IModuleAllocator* pAllocator
)
{
// Call the UNREFERENCED_PARAMETER macro
// with the IModuleAllocator pointer, because
// this parameter is currently unused.
UNREFERENCED_PARAMETER(pAllocator);
// Set the dereferenced ppModule
// to a new CHttpResponseModule pointer.
(*ppModule) = new CCachePolicyModule;
// If the new CHttpResponseModule is
// NULL, return an error indicating
// that heap memory is exhausted.
if (NULL == (*ppModule))
{
return HRESULT_FROM_WIN32(ERROR_NOT_ENOUGH_MEMORY);
}
// Return S_OK.
return S_OK;
}
// The Terminate method
// calls delete on this.
virtual
void
Terminate()
{
delete this;
}
protected:
// The CCachePolicyFactory method is
// the protected constructor for the
// CCachePolicyFactory class.
CCachePolicyFactory()
{
}
// The CCachePolicyFactory method is
// the protected virtual destructor for
// the CCachePolicyFactory class.
virtual ~CCachePolicyFactory()
{
}
private:
};
// The RegisterModule method is the
// main entry point for the DLL.
// dwServerVersion: the current server version.
// pModuleInfo: the current
// IHttpModuleRegistrationInfo pointer.
// pGlobalInfo: the current IHttpServer pointer.
// return: the value returned by calling the
// CCachPolicyFactory::RegisterCHttpModule method.
HRESULT
__stdcall
RegisterModule(
DWORD dwServerVersion,
IHttpModuleRegistrationInfo* pModuleInfo,
IHttpServer* pGlobalInfo
)
{
return CCachePolicyFactory::RegisterCHttpModule
(dwServerVersion,
pModuleInfo,
pGlobalInfo);
}
Weitere Informationen zum Erstellen und Bereitstellen eines nativen DLL-Moduls finden Sie unter Exemplarische Vorgehensweise: Erstellen eines Request-Level HTTP-Moduls mithilfe von nativem Code.
Der obige Code schreibt Daten, die den folgenden ähneln, in den Antwortdatenstrom:
Is Cached: false
Sie können den Code optional kompilieren, indem Sie die __-stdcall (/Gz) Aufrufkonvention verwenden, anstatt die Aufrufkonvention für jede Funktion explizit zu deklarieren.
Anforderungen
| type | BESCHREIBUNG |
|---|---|
| Client | – IIS 7.0 unter Windows Vista – IIS 7.5 unter Windows 7 – IIS 8.0 unter Windows 8 – IIS 10.0 unter Windows 10 |
| Server | – IIS 7.0 unter Windows Server 2008 – IIS 7.5 unter Windows Server 2008 R2 – IIS 8.0 unter Windows Server 2012 – IIS 8.5 unter Windows Server 2012 R2 – IIS 10.0 unter Windows Server 2016 |
| Produkt | – IIS 7.0, IIS 7.5, IIS 8.0, IIS 8.5, IIS 10.0 - IIS Express 7.5, IIS Express 8.0, IIS Express 10.0 |
| Header | Httpserv.h |