IHttpCachePolicy Interface
Provides CHttpModule derived classes access to the setting and getting policy for request caching.
Syntax
class IHttpCachePolicy
Methods
The following table lists the methods exposed by the IHttpCachePolicy class.
| Name | Description |
|---|---|
| AppendVaryByHeader | Appends the header value to the cache policy. |
| AppendVaryByQueryString | Appends the query value to the cache policy. |
| DisableUserCache | Disables user caching for the cache policy. |
| GetKernelCacheInvalidatorSet | Gets a value that indicates whether the kernel cache is invalidated. |
| GetKernelCachePolicy | Returns the cache policy for the kernel. |
| GetUserCachePolicy | Returns the cache policy for the user. |
| GetVaryByHeaders | Returns the custom header values for the cache policy. |
| GetVaryByQueryStrings | Returns the custom query values for the cache policy. |
| GetVaryByValue | Returns the variable value for the cache policy. |
| IsCached | Returns a value that indicates whether the cache policy is enabled. |
| IsUserCacheEnabled | Returns a value that indicates whether user caching is enabled for the cache policy. |
| SetIsCached | Sets a value that indicates that the data is cached. |
| SetKernelCacheInvalidatorSet | Sets a value that indicates that the kernel cache is invalidated. |
| SetVaryByValue | Sets the variable value for the cache policy. |
Properties
This class contains no properties.
Derived Classes
| Name | Description |
|---|---|
| IHttpCachePolicy2 | Provides CHttpModule derived classes access to the setting and getting policy for request caching. |
Remarks
CHttpModule derived classes that register for request or response events receive an IHttpContext pointer as a parameter on the corresponding virtual method.
Example
The following code example demonstrates how to create a global module that listens for RQ_BEGIN_REQUEST and RQ_SEND_RESPONSE events, and then sets IHttpCachePolicy data and returns that data to the browser as an XML document.
#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;
#import "msxml6.dll"
using namespace MSXML2;
// 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 HANDLE to a wstring.
// h: the HANDLE to convert to a wstring.
// return: the HANDLE as a wstring.
static wstring ToString(HANDLE h)
{
// If the HANDLE is NULL, return the "NULL" string.
if (NULL == h)
{
return L"NULL";
}
// If the HANDLE is not valid, return
// the INVALID_HANDLE_VALUE as a string.
if (INVALID_HANDLE_VALUE == h)
{
return L"INVALID_HANDLE_VALUE";
}
// The HANDLE is valid.
return L"valid";
}
// The ToString method converts a FILETIME pointer to a wstring.
// fileTime: the FILETIME pointer to convert to a wstring.
// return: the FILETIME pointer as a wstring.
static wstring ToString(FILETIME* fileTime)
{
// If fileTime is NULL, return the empty string.
if (NULL == fileTime)
{
return L"NULL";
}
// Convert the FILETIME to a local time, and
// then convert that local time to a wstring.
SYSTEMTIME stUTC;
SYSTEMTIME stLocal;
FileTimeToSystemTime(fileTime, &stUTC);
SystemTimeToTzSpecificLocalTime(NULL, &stUTC, &stLocal);
// Create a wstring to return. Note: wsprintf
// can be also used. However, it is more difficult
// to handle both UNICODE and non-UNICODE correctly.
wstring timeString =
ToString(stLocal.wMonth) +
wstring(L"/") +
ToString(stLocal.wDay) +
wstring(L"/") +
ToString(stLocal.wYear) +
wstring(L" ") +
ToString(stLocal.wHour) +
wstring(L":") +
ToString(stLocal.wMinute);
// Return the FILETIME data as a wstring.
return timeString;
}
// The ToString method converts a
// ULARGE_INTEGER pointer to a wstring.
// ui: the ULARGE_INTEGER pointer to convert to a string.
// return: the ULARGE_INTEGER pointer as a string.
static wstring ToString(ULARGE_INTEGER* ui)
{
// Return the empty string if the
// ULARGE_INTEGER pointer is NULL.
if (NULL == ui)
{
return L"NULL";
}
// Return the low-order part to a wstring.
return (ToString(ui->LowPart));
}
// The ToString method converts a PCSTR to a wstring.
// pcstr: the PCSTR to convert to a wstring.
// return: the PCSTR as a wstring.
static wstring ToString(PCSTR pcstr)
{
// Return the empty string
// if the PCSTR is NULL.
if (NULL == pcstr)
{
return L"NULL";
}
// Get the length of the string to copy.
size_t length = strlen(pcstr);
// Create a new double-byte character
// array of length plus 1.
wchar_t* newText = new wchar_t[length+1];
// Copy the source into the sink string.
for (size_t i = 0; i < length; ++i)
{
newText[i] = pcstr[i];
}
// Terminate the string with the NULL character.
newText[length] = '\0';
// Get a wstring from the new double-byte string.
wstring wText = newText;
// Call delete on the newText pointer
// and set this pointer to NULL.
delete[] newText;
newText = NULL;
// Return the wstring copy.
return wText;
}
// The ToString method converts a long to a wstring.
// l: the long value to convert to a wstring.
// return: the long as a wstring.
static wstring ToString(long l)
{
WCHAR str[256];
str[0] = '\0';
_ltow_s(l, str, 256, 10);
return str;
}
// The ToString method converts a DWORD to a wstring.
// d: the DWORD value to convert to a wstring.
// return: the DWORD as a wstring.
static wstring ToString(DWORD d)
{
return ToString((long)d);
}
// The ToString method converts an LPCGUID to a wstring.
// guid: the LPCGUID value to convert to a wstring.
// return: The LPCGUID as a wstring; otherwise, L"" if
// guid is NULL.
static wstring ToString(LPCGUID guid)
{
// If the GUID is NULL, return the empty string.
if (NULL == guid)
{
return L"NULL";
}
// Create a WCHAR array to write the GUID to.
WCHAR guidString[256];
// Initialize the zero-based index of the
// guidString to the null-terminating character
// because the StringFromGUID2 may fail.
guidString[0] = '\0';
// Convert the GUID to a string of the form "{...}".
int characters = StringFromGUID2(*guid, guidString, 256);
// Return the guidString as a wstring.
return guidString;
}
// 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 ToString method converts a USHORT to a wstring.
// u: the USHORT value to convert to a wstring.
// return: the value of u as a wstring.
static wstring ToString(USHORT u)
{
return (ToString((long)u));
}
// The ToString method converts a
// const BYTE pointer to a wstring.
// bytes: the BYTE pointer to convert.
// return: the value of bytes as a wstring.
static wstring ToString(const BYTE* bytes)
{
return (ToString((PCSTR)bytes));
}
// The ToString method converts
// a PCWSTR to a wstring.
// pcwstr: the PCWSTR to convert.
// return: L"NULL" if the pcwstr
// parameter is NULL; otherwise,
// pcwstr converted to a wstring.
static wstring ToString(PCWSTR pcwstr)
{
// If the pcwstr parameter
// is NULL, return L"NULL".
if (NULL == pcwstr)
{
return L"NULL";
}
// Implicitly convert the
// PCWSTR to a wstring.
return pcwstr;
}
};
// 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 CCachePolicyModule method
// is the public constructor for
// the CHttpResponseModule class.
CCachePolicyModule()
{
}
// The CHttpResponseModule method is
// the public virtual destructor for
// the CHttpResponseModule class.
virtual ~CCachePolicyModule()
{
}
// The OnBeginRequest method handles
// request processing when the request
// is first placed into the pipeline.
// This method sets values on the
// IHttpCachePolicy pointer.
// pHttpContext: the IHttpContext pointer.
// pProvider: the IHttpEventProvider pointer.
// return: RQ_NOTIFICATION_CONTINUE.
virtual
REQUEST_NOTIFICATION_STATUS
OnBeginRequest
(
IN IHttpContext* pHttpContext,
IN IHttpEventProvider* 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;
}
// Append the first header value.
policy->AppendVaryByHeader("header1");
// Append the second header value.
policy->AppendVaryByHeader("header2");
// Append the first query string.
policy->AppendVaryByQueryString("query1");
// Append the second query string.
policy->AppendVaryByQueryString("query2");
// Disable the user cache.
policy->DisableUserCache();
// Get the HTTP_CACHE_POLICY for the kernel
// from the IHttpCachePolicy pointer.
HTTP_CACHE_POLICY* kernelPolicy =
policy->GetKernelCachePolicy();
// If the kernelPolicy is not
// NULL then set its values.
if (NULL != kernelPolicy)
{
// Set the kernelPolicy to
// HttpCachePolicyTimeToLive.
kernelPolicy->Policy = HttpCachePolicyTimeToLive;
// Set the seconds to live.
kernelPolicy->SecondsToLive = 2;
}
// Get the HTTP_CACHE_POLICY for the
// user from the IHttpCachePolicy pointer.
HTTP_CACHE_POLICY* userPolicy =
policy->GetUserCachePolicy();
// If the userPolicy is not
// NULL then set its values.
if (NULL != userPolicy)
{
// Set the userPolicy to
// HttpCachePolicyMaximum.
userPolicy->Policy = HttpCachePolicyMaximum;
// Set the seconds to live.
userPolicy->SecondsToLive = 5;
}
// Set the data as cached.
policy->SetIsCached();
// Invalidate the kernel cache.
policy->SetKernelCacheInvalidatorSet();
// Set the VaryByValue value.
policy->SetVaryByValue("vary");
// Return RQ_NOTIFICATION_CONTINUE so that
// other handlers will receive the event.
return RQ_NOTIFICATION_CONTINUE;
}
// 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;
}
try
{
// Create an XML document in memory.
MSXML2::IXMLDOMDocument3Ptr doc
(__uuidof(MSXML2::DOMDocument60));
// Create a response element
// for the root XML element.
MSXML2::IXMLDOMElementPtr responseElement =
doc->createElement(L"response");
// Append the responseElement
// to the XML document.
doc->appendChild(responseElement);
// Create a policyElement element.
MSXML2::IXMLDOMElementPtr policyElement =
CreateElement(policy, doc);
// Append the policyElement
// to the responseElement.
responseElement->appendChild(policyElement);
// Clear the existing response.
response->Clear();
// Set the MIME type to text/xml.
response->SetHeader(
HttpHeaderContentType,
"text/xml",
(USHORT)strlen("text/xml"),
TRUE);
// Get the XML from the document.
_bstr_t xml = doc->xml;
// Add version information
// to the XML string.
string xmlString =
"<?xml version=\"1.0\"?>" + xml;
// Create a writer to write
// the response data to.
CResponseWriter writer(response);
// Write the XML to the
// response stream.
writer.Write(xmlString.c_str());
}
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 AddAttribute method creates a new
// XML attribute and adds it to an XML element.
// name: the name of the attribute.
// text: the text of the attribute.
// element: the XML element to
// append the attribute to.
// doc: the XML document for creating
// elements and attributes.
// return: a new MSXML2::IXMLDOMAttributePtr.
// throws: a _com_error exception.
static MSXML2::IXMLDOMAttributePtr AddAttribute
(
const wstring& name,
const wstring& text,
MSXML2::IXMLDOMElementPtr element,
MSXML2::IXMLDOMDocument3Ptr doc
) throw (_com_error)
{
// Create an attribute with the name.
MSXML2::IXMLDOMAttributePtr attribute =
doc->createAttribute(name.c_str());
// Set the text of the
// attribute to the text value.
attribute->text = text.c_str();
// Add the attribute
// to the passed element.
element->setAttributeNode(attribute);
// Return the new attribute
// to the caller.
return attribute;
}
// The CreateAttribute method creates an
// XML attribute representing the data
// in the HTTP_CACHE_POLICY_TYPE parameter.
// policyType: the HTTP_CACHE_POLICY_TYPE.
// name: the name to give the XML attribute.
// doc: the XML document to use for
// creating elements and attributes.
// return: a new MSXML2::IXMLDOMAttributePtr.
// throws: a _com_error exception.
static MSXML2::IXMLDOMAttributePtr CreateAttribute
(
HTTP_CACHE_POLICY_TYPE policyType,
const wstring& name,
MSXML2::IXMLDOMDocument3Ptr doc
) throw (_com_error)
{
// Create an attribute for the CACHE_OPERATION value.
MSXML2::IXMLDOMAttributePtr policyTypeAttribute =
doc->createAttribute(name.c_str());
// Create an empty string to write the
// value of the HTTP_CACHE_POLICY_TYPE to.
wstring value;
// Write to the value string dependent
// upon the value of the HTTP_CACHE_POLICY_TYPE.
switch (policyType)
{
case HttpCachePolicyNocache:
{
value = L"HttpCachePolicyNocache";
break;
}
case HttpCachePolicyUserInvalidates:
{
value = L"HttpCachePolicyUserInvalidates";
break;
}
case HttpCachePolicyTimeToLive:
{
value = L"HttpCachePolicyTimeToLive";
break;
}
case HttpCachePolicyMaximum:
{
value = L"HttpCachePolicyMaximum";
break;
}
default:
{
value = L"Error";
break;
}
}
// Set the attribute text
// using the value string.
policyTypeAttribute->text = value.c_str();
// Return the new attribute to the caller.
return policyTypeAttribute;
}
// The CreateElement method writes the value
// of an HTTP_CACHE_POLICY to a new XML element.
// cachePolicy: the HTTP_CACHE_POLICY
// pointer to write.
// name: the name to use for the
// HTTP_CACHE_POLICY_TYPE attribute.
// doc: the XML document to use for
// creating elements and attributes.
// return: a new MSXML2::IXMLDOMElementPtr.
// throws: a _com_error exception.
static MSXML2::IXMLDOMElementPtr CreateElement
(
HTTP_CACHE_POLICY* cachePolicy,
const wstring& name,
MSXML2::IXMLDOMDocument3Ptr doc
) throw (_com_error)
{
// Create a new XML element to return.
MSXML2::IXMLDOMElementPtr cachePolicyElement =
doc->createElement(L"cachePolicy");
// If the HTTP_CACHE_POLICY pointer
// is NULL then return.
if (NULL == cachePolicy)
{
return cachePolicyElement;
}
// Get the HTTP_CACHE_POLICY_TYPE from
// the HTTP_CACHE_POLICY pointer.
HTTP_CACHE_POLICY_TYPE policyType =
cachePolicy->Policy;
// Create an XML attribute for the
// HTTP_CACHE_POLICY_TYPE.
MSXML2::IXMLDOMAttributePtr policyTypeAttribute =
CreateAttribute(policyType, name, doc);
// Add the policyTypeAttribute
// to the cachePolicyElement.
cachePolicyElement->setAttributeNode(policyTypeAttribute);
// Get the seconds to live from
// the HTTP_CACHE_POLICY pointer.
ULONG secondsToLiveULONG =
cachePolicy->SecondsToLive;
// Convert the ULONG to a wstring.
wstring secondsToLive =
CConvert::ToString(secondsToLiveULONG);
// Add a secondsToLive attribute
// to the cachePolicyElement.
AddAttribute(L"secondsToLive", secondsToLive,
cachePolicyElement, doc);
// Return the cachePolicyElement
// to the caller.
return cachePolicyElement;
}
// The CreateElement method converts an
// IHttpCachePolicy pointer to an XML element.
// httpCachePolicy: the IHttpCachePolicy
// pointer to convert.
// doc: the XML document to use for
// creating elements and attributes.
static MSXML2::IXMLDOMElementPtr CreateElement
(
IHttpCachePolicy* httpCachePolicy,
MSXML2::IXMLDOMDocument3Ptr doc
) throw (_com_error)
{
// Create an element for the
// IHttpCachePolicy pointer.
MSXML2::IXMLDOMElementPtr httpCachePolicyElement =
doc->createElement(L"httpCachePolicy");
// If the IHttpCachePolicy
// pointer is NULL, return.
if (NULL == httpCachePolicy)
{
return httpCachePolicyElement;
}
// Get the HTTP_CACHE_POLICY
// pointer for the kernel from
// the IHttpCachePolicy pointer.
HTTP_CACHE_POLICY* kernelCachePolicy =
httpCachePolicy->GetKernelCachePolicy();
// Create an XML element for the
// HTTP_CACHE_POLICY pointer.
MSXML2::IXMLDOMElementPtr kernelCacheElement =
CreateElement(kernelCachePolicy, L"kernelPolicy", doc);
// Append the kernelCacheElement to
// the httpCachePolicyElement.
httpCachePolicyElement->appendChild(kernelCacheElement);
// Get the HTTP_CACHE_POLICY
// pointer from the IHttpCachePolicy
// pointer for the user.
HTTP_CACHE_POLICY* userCachePolicy =
httpCachePolicy->GetUserCachePolicy();
// Create an XML element for the
// HTTP_CACHE_POLICY pointer for the user.
MSXML2::IXMLDOMElementPtr userCacheElement =
CreateElement(userCachePolicy, L"userPolicy", doc);
// Append the userCacheElement to
// the httpCachePolicyElement.
httpCachePolicyElement->appendChild(userCacheElement);
// Get the vary-by-headers from
// the IHttpCachePolicy pointer.
PCSTR varyByHeadersPCSTR =
httpCachePolicy->GetVaryByHeaders();
// Convert the vary-by-headers
// to a wstring.
wstring varyByHeaders =
CConvert::ToString(varyByHeadersPCSTR);
// Add a varyByHeaders attribute
// to the httpCachePolicyElement.
AddAttribute(L"varyByHeaders", varyByHeaders,
httpCachePolicyElement, doc);
// Get the vary-by-query string data
// from the IHttpCachePolicy pointer.
PCSTR varyByQueryPCSTR =
httpCachePolicy->GetVaryByQueryStrings();
// Convert the vary-by-query
// string to a wstring.
wstring varyByQuery =
CConvert::ToString(varyByQueryPCSTR);
// Add a varyByQuery attribute to
// the httpCachePolicyElement.
AddAttribute(L"varyByQuery", varyByQuery,
httpCachePolicyElement, doc);
// Get the vary-by-value value from
// the IHttpCachePolicy pointer.
PCSTR varyByValuePCSTR =
httpCachePolicy->GetVaryByValue();
// Convert the vary-by-value
// value to a wstring.
wstring varyByValue =
CConvert::ToString(varyByValuePCSTR);
// Add a varyByValue attribute
// to the httpCachePolicyElement.
AddAttribute(L"varyByValue", varyByValue,
httpCachePolicyElement, doc);
// 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);
// Add an isCached attribute to
// the httpCachePolicyElement.
AddAttribute(L"isCached", isCached,
httpCachePolicyElement, doc);
// Get a value indicating if the user cache
// is enabled from the IHttpCachePolicy pointer.
BOOL isUserCacheEnabledBOOL =
httpCachePolicy->IsUserCacheEnabled();
// Convert the BOOL to a wstring.
wstring isUserCacheEnabled =
CConvert::ToString(isUserCacheEnabledBOOL);
// Add an isUserCacheEnabled attribute
// to the httpCachePolicyElement.
AddAttribute(L"isUserCacheEnabled", isUserCacheEnabled,
httpCachePolicyElement, doc);
// Return the httpCachePolicyElement.
return httpCachePolicyElement;
}
};
// 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_BEGIN_REQUEST | 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);
}
For more information on how to create and deploy a native DLL module, see Walkthrough: Creating a Request-Level HTTP Module By Using Native Code.
The above code writes an XML document that is similar to the following to the response stream:
<?xml version="1.0"?>
<response>
<httpCachePolicy
varyByHeaders="header1,header2"
varyByQuery="query1,query2"
varyByValue="vary"
isCached="true"
isUserCacheEnabled="false">
<cachePolicy
kernelPolicy="HttpCachePolicyUserInvalidates"
secondsToLive="2"/>
<cachePolicy
userPolicy="HttpCachePolicyMaximum"
secondsToLive="5"/>
</httpCachePolicy>
</response>
You can optionally compile the code by using the __stdcall (/Gz) calling convention instead of explicitly declaring the calling convention for each function.
Requirements
| Type | Description |
|---|---|
| Client | - IIS 7.0 on Windows Vista - IIS 7.5 on Windows 7 - IIS 8.0 on Windows 8 - IIS 10.0 on Windows 10 |
| Server | - IIS 7.0 on Windows Server 2008 - IIS 7.5 on Windows Server 2008 R2 - IIS 8.0 on Windows Server 2012 - IIS 8.5 on Windows Server 2012 R2 - IIS 10.0 on Windows Server 2016 Technical Preview |
| Product | - 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 |