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Visual FoxPro

SharePoint -- Get Server Form Digest Value

Demonstrates how to get a server form digest value to be placed in the X-RequestDigest HTTP request header for POST, PUT, MERGE, and DELETE requests. A form digest value is typically valid for 1800 seconds (i.e. 30 minutes). This example persists the value to a file, and only requests a new form digest value if the existing one is near expiration.

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LOCAL lnSuccess
LOCAL loFac
LOCAL loXml
LOCAL loDtExpire
LOCAL loDtNow
LOCAL lcFormDigestXmlFile
LOCAL lnTNow
LOCAL lnTExpire
LOCAL loHttp
LOCAL lcSavedAccept
LOCAL loResp
LOCAL loXml2
LOCAL lnTimeoutInSec

lnSuccess = 0

* This requires the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

* First, let's see if we already have a persisted form digest value
* that hasn't yet expired.
loFac = CreateObject('Chilkat.FileAccess')
loXml = CreateObject('Chilkat.Xml')

* My example code (below) persists the form digest XML in this format:
* 
* 	<savedFormDigestValue>
* 	<d:ExpireDateTime>2017-04-12T20:46:39Z</d:ExpireDateTime>
* 	<d:FormDigestValue>0x3059FFB920651834540F3E6792EA73F5746B302E953FF4E808E485DB1E6C2836C7CF924644995F092453B02A94DE14A7962674B7B16780AF16EAFB8C246BCDC7,12 Apr 2017 17:08:22 -0000</d:FormDigestValue>
* 	</savedFormDigestValue>
* 

loDtExpire = CreateObject('Chilkat.CkDateTime')
loDtNow = CreateObject('Chilkat.CkDateTime')

lcFormDigestXmlFile = "qa_data/sharepoint/savedFormDigestValue.xml"
IF (loFac.FileExists(lcFormDigestXmlFile) = 1) THEN

    loXml.LoadXmlFile(lcFormDigestXmlFile)

    * Get the expire date/time
    loDtExpire.SetFromTimestamp(loXml.GetChildContent("d:ExpireDateTime"))

    * Get the current date/time
    loDtNow.SetFromCurrentSystemTime()

    * Get both times as Unix time values
    lnTNow = loDtNow.GetAsUnixTime(0)
    lnTExpire = loDtExpire.GetAsUnixTime(0)

    * If tNow >= tExpire, then fall through.
    * Otherwise, just use the cached digest value.
    IF (lnTNow < lnTExpire) THEN
        ? "Cached digest value is not yet expired."
        ? "X-RequestDigest: " + loXml.GetChildContent("d:FormDigestValue")
        RELEASE loFac
        RELEASE loXml
        RELEASE loDtExpire
        RELEASE loDtNow
        CANCEL
    ENDIF

ENDIF

* If we got to this point, the cached digest value either does not exist, or expired.

loHttp = CreateObject('Chilkat.Http')

* If SharePoint Windows classic authentication is used, then set the 
* Login, Password, LoginDomain, and NtlmAuth properties.
loHttp.Login = "SHAREPOINT_USERNAME"
loHttp.Password = "SHAREPOINT_PASSWORD"
loHttp.LoginDomain = "SHAREPOINT_NTLM_DOMAIN"
loHttp.NtlmAuth = 1

* The more common case is to use SharePoint Online authentication (via the SPOIDCRL cookie).
* If so, do not set Login, Password, LoginDomain, and NtlmAuth, and instead
* establish the cookie as shown at SharePoint Online Authentication

* When creating, updating, and deleting SharePoint entities, we'll need
* to first get the server's form digest value to send in the X-RequestDigest header.
* This can be retrieved by making a POST request with an empty body to
* http://<site url>/_api/contextinfo and extracting the value of the
* d:FormDigestValue node in the XML that the contextinfo endpoint returns.

* Apparently, SharePoint needs an "Accept" request header equal to "application/xml",
* otherwise SharePoint will return an utterly incomprehensible and useless error message.
lcSavedAccept = loHttp.Accept
loHttp.Accept = "application/xml"

* Note: The last argument ("utf-8") is meaningless here because the body is empty.
loResp = CreateObject('Chilkat.HttpResponse')
lnSuccess = loHttp.HttpStr("POST","https://SHAREPOINT_HTTPS_DOMAIN/_api/contextinfo","","utf-8","application/xml",loResp)
IF (lnSuccess = 0) THEN
    ? loHttp.LastErrorText
    RELEASE loFac
    RELEASE loXml
    RELEASE loDtExpire
    RELEASE loDtNow
    RELEASE loHttp
    RELEASE loResp
    CANCEL
ENDIF

* Restore the default Accept header
loHttp.Accept = lcSavedAccept

IF (loResp.StatusCode <> 200) THEN
    * A response status code not equal to 200 indicates failure.
    ? "Response status code = " + STR(loResp.StatusCode)
    ? "Response body:"
    ? loResp.BodyStr
    RELEASE loFac
    RELEASE loXml
    RELEASE loDtExpire
    RELEASE loDtNow
    RELEASE loHttp
    RELEASE loResp
    CANCEL
ENDIF

loXml.LoadXml(loResp.BodyStr)

* The response XML looks like this:

* <?xml version="1.0" encoding="utf-8" ?>
* <d:GetContextWebInformation xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns:georss="http://www.georss.org/georss" xmlns:gml="http://www.opengis.net/gml" m:type="SP.ContextWebInformation">
*     <d:FormDigestTimeoutSeconds m:type="Edm.Int32">1800</d:FormDigestTimeoutSeconds>
*     <d:FormDigestValue>0x3059FFB920651834540F3E6792EA73F5746B302E953FF4E808E485DB1E6C2836C7CF924644995F092453B02A94DE14A7962674B7B16780AF16EAFB8C246BCDC7,12 Apr 2017 17:08:22 -0000</d:FormDigestValue>
*     <d:LibraryVersion>15.0.4569.1000</d:LibraryVersion>
*     <d:SiteFullUrl>https://SHAREPOINT_HTTPS_DOMAIN</d:SiteFullUrl>
*     <d:SupportedSchemaVersions m:type="Collection(Edm.String)">
*         <d:element>14.0.0.0</d:element>
*         <d:element>15.0.0.0</d:element>
*     </d:SupportedSchemaVersions>
*     <d:WebFullUrl>https://SHAREPOINT_HTTPS_DOMAIN</d:WebFullUrl>
* </d:GetContextWebInformation>
* 

* Cache the digest value, and also an expiration time.  If this code is run again
* before the digest expires, we'll just get it from the file.
loXml2 = CreateObject('Chilkat.Xml')

loXml2.Tag = "savedFormDigestValue"
loXml2.NewChild2("d:FormDigestValue",loXml.GetChildContent("d:FormDigestValue"))

lnTimeoutInSec = loXml.GetChildIntValue("d:FormDigestTimeoutSeconds")
? "Timeout in seconds = " + STR(lnTimeoutInSec)

* Convert this to an expire timestamp.
* Let's make it expire 30 seconds prior to the actual timeout, just to be safe.
IF (lnTimeoutInSec > 30) THEN
    lnTimeoutInSec = lnTimeoutInSec - 30
ENDIF

loDtExpire.SetFromCurrentSystemTime()
loDtExpire.AddSeconds(lnTimeoutInSec)
loXml2.NewChild2("d:ExpireDateTime",loDtExpire.GetAsTimestamp(0))

* Persist the digest and expire time to a file.
loXml2.SaveXml(lcFormDigestXmlFile)

? "Here is the new form digest value:"
? "X-RequestDigest: " + loXml.GetChildContent("d:FormDigestValue")

RELEASE loFac
RELEASE loXml
RELEASE loDtExpire
RELEASE loDtNow
RELEASE loHttp
RELEASE loResp
RELEASE loXml2