Xbase++
Download a File from a SharePoint Documents Library

This example shows how to use Chilkat's HttpCurl class to download a file from the root of a SharePoint Documents document library. The example demonstrates how HttpCurl automatically resolves the SharePoint site name to a site ID, finds the drive ID for the Documents library, locates the file by name, and then downloads the file content using Microsoft Graph.
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LOCAL nSuccess
LOCAL oJsonAuth
LOCAL oCurl
LOCAL cCurlCommand
LOCAL nStatusCode
LOCAL oSbFileContents

nSuccess := 0

//  This example downloads a file named "hamlet.json" from the root of the SharePoint
//  Documents document library.
//  
//  The example demonstrates how HttpCurl can automatically resolve all of the
//  information needed to locate and download a file:
//  
//    site_name            -> site_id
//    site_id              -> document_library_id
//    document_library_id  -> file_id
//    file_id              -> file content
//  
//  The application only provides the SharePoint site name and the desired
//  filename.  HttpCurl automatically executes the required Microsoft Graph
//  requests to obtain the remaining values.

nSuccess := 0

//  --------------------------------------------------------------------------------------------------------
//  Before running this example, create an Azure App Registration and grant it
//  the Microsoft Graph permissions required to access SharePoint.
//  
//  The application will authenticate using OAuth2 Client Credentials.
//  See:
//  How to Create SharePoint App Registration for OAuth 2.0 Client Credentials
//  --------------------------------------------------------------------------------------------------------

//  Build a JSON authentication configuration.
//  HttpCurl will use this information to automatically obtain OAuth2 access tokens.
oJsonAuth := CreateObject("Chilkat.JsonObject")

//  Enable secret lookup.
//  
//  Instead of hard-coding sensitive values such as the client ID,
//  client secret, and token endpoint, secret specification strings
//  are used.  Chilkat automatically retrieves the actual values from
//  Windows Credential Manager (Windows) or Apple Keychain (macOS).
//  
//  See:
//  Secret Specification Strings
oJsonAuth:EnableSecrets := 1

nSuccess := oJsonAuth:UpdateString("oauth2.client_id", "!!sharepoint|oauth2|client_id")
IF (nSuccess == 1)
    nSuccess := oJsonAuth:UpdateString("oauth2.client_secret", "!!sharepoint|oauth2|client_secret")
ENDIF

IF (nSuccess == 1)
    nSuccess := oJsonAuth:UpdateString("oauth2.token_endpoint", "!!sharepoint|oauth2|token_endpoint")
ENDIF

IF (nSuccess == 0)
    ? oJsonAuth:LastErrorText
    oJsonAuth:destroy()
    RETURN
ENDIF

//  Request Microsoft Graph permissions that were granted to the application.
oJsonAuth:UpdateString("oauth2.scope", "https://graph.microsoft.com/.default")

//  ---------------------------------------------------------------------------------------------------

oCurl := CreateObject("Chilkat.HttpCurl")

//  Associate the OAuth2 configuration with HttpCurl.
//  
//  When the request is executed, Chilkat automatically obtains an access token
//  if needed and adds the Authorization: Bearer header to the HTTP request.
oCurl:SetAuth(oJsonAuth)

//  Define values that are already known.
//  
//  These variables are referenced in curl commands using
//  {{variable_name}} substitution syntax.
oCurl:SetVar("sharepoint_hostname", "example.sharepoint.com")
oCurl:SetVar("site_name", "test")

//  The first step is to obtain the Microsoft Graph site ID.
//  
//  The application only knows the SharePoint site name, so define
//  a function that can retrieve the site information.
oCurl:AddFunction("getSite", "GET https://graph.microsoft.com/v1.0/sites/root:/sites/{{site_name}}")

//  Extract the site's ID and store it in the HttpCurl variable named site_id.
oCurl:AddOutput("getSite", "id", "site_id")

//  The next step is to find the Documents document library.
//  
//  Microsoft Graph refers to document libraries as "drives".
oCurl:AddFunction("getDrives", "GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives")

//  Search the returned drives for the one named "Documents"
//  and save its drive ID in the document_library_id variable.
oCurl:AddOutput2("getDrives", "value", "name", "Documents", 1, "id", "document_library_id")

//  Now list the contents of the Documents document library.
oCurl:AddFunction("getFiles", "GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives/{{document_library_id}}/root/children")

//  Search the returned files for an item named "hamlet.json"
//  and save its Microsoft Graph item ID in the file_id variable.
oCurl:AddOutput2("getFiles", "value", "name", "hamlet.json", 1, "id", "file_id")

//  This is the target request.
//  
//  GET -L https://graph.microsoft.com/v1.0/drives/{{document_library_id}}/items/{{file_id}}/content
//  
//  The /content endpoint returns the actual contents of the file.
//  
//  The -L option instructs HttpCurl to follow the redirect returned by
//  Microsoft Graph.  The Graph API typically responds with a redirect
//  to the actual file download URL.
cCurlCommand := "GET -L https://graph.microsoft.com/v1.0/drives/{{document_library_id}}/items/{{file_id}}/content"

//  Execute the request.
//  
//  HttpCurl examines the target request and determines that both
//  document_library_id and file_id are required.
//  
//  To obtain these values, it automatically builds and executes
//  the following dependency chain:
//  
//    1) getSite      -> site_id
//    2) getDrives    -> document_library_id
//    3) getFiles     -> file_id
//    4) download     -> file content
//  
//  The final response returned by DoYourThing is the downloaded
//  file content from the target request.
nSuccess := oCurl:DoYourThing(cCurlCommand)
IF (nSuccess == 0)
    ? oCurl:LastErrorText
    oJsonAuth:destroy()
    oCurl:destroy()
    RETURN
ENDIF

//  A successful Graph response should return HTTP 200.
//  Any other status code typically indicates an authentication,
//  permission, site lookup, document library lookup, or file lookup error.
nStatusCode := oCurl:StatusCode
IF (nStatusCode != 200)
    ? oCurl:ResponseBodyStr
    ? "status code = " + Str(nStatusCode)
    oJsonAuth:destroy()
    oCurl:destroy()
    RETURN
ENDIF

//  The response body contains the contents of the downloaded file.
oSbFileContents := CreateObject("Chilkat.StringBuilder")
oCurl:GetResponseSb(oSbFileContents)

//  Optionally save the downloaded content to a local file.
//  
//  The third argument controls whether the file is appended.
//  Passing ckfalse causes the file to be overwritten if it already exists.
nSuccess := oSbFileContents:WriteFile("c:/temp/hamlet.json", "utf-8", 0)
IF (nSuccess == 0)
    ? oSbFileContents:LastErrorText
    oJsonAuth:destroy()
    oCurl:destroy()
    oSbFileContents:destroy()
    RETURN
ENDIF

? "Success."

oJsonAuth:destroy()
oCurl:destroy()
oSbFileContents:destroy()