(Xojo Plugin) Download a File from a SharePoint Documents Library

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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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Dim success As Boolean
success = False

// 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.

success = False

// --------------------------------------------------------------------------------------------------------
// 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.
Dim jsonAuth As New 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
jsonAuth.EnableSecrets = True

success = jsonAuth.UpdateString("oauth2.client_id","!!sharepoint|oauth2|client_id")
If (success = True) Then
    success = jsonAuth.UpdateString("oauth2.client_secret","!!sharepoint|oauth2|client_secret")
End If

If (success = True) Then
    success = jsonAuth.UpdateString("oauth2.token_endpoint","!!sharepoint|oauth2|token_endpoint")
End If

If (success = False) Then
    System.DebugLog(jsonAuth.LastErrorText)
    Return
End If

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

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

Dim curl As New 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.
success = curl.SetAuth(jsonAuth)

// Define values that are already known.
// 
// These variables are referenced in curl commands using
// {{variable_name}} substitution syntax.
curl.SetVar "sharepoint_hostname","example.sharepoint.com"
curl.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.
success = curl.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.
success = curl.AddOutput("getSite","id","site_id")

// The next step is to find the Documents document library.
// 
// Microsoft Graph refers to document libraries as "drives".
success = curl.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.
success = curl.AddOutput2("getDrives","value","name","Documents",True,"id","document_library_id")

// Now list the contents of the Documents document library.
success = curl.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.
success = curl.AddOutput2("getFiles","value","name","hamlet.json",True,"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.
Dim curlCommand As String
curlCommand = "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.
success = curl.DoYourThing(curlCommand)
If (success = False) Then
    System.DebugLog(curl.LastErrorText)
    Return
End If

// 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.
Dim statusCode As Int32
statusCode = curl.StatusCode
If (statusCode <> 200) Then
    System.DebugLog(curl.ResponseBodyStr)
    System.DebugLog("status code = " + Str(statusCode))
    Return
End If

// The response body contains the contents of the downloaded file.
Dim sbFileContents As New Chilkat.StringBuilder
success = curl.GetResponseSb(sbFileContents)

// 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.
success = sbFileContents.WriteFile("c:/temp/hamlet.json","utf-8",False)
If (success = False) Then
    System.DebugLog(sbFileContents.LastErrorText)
    Return
End If

System.DebugLog("Success.")