C++

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.

C++

#include <CkJsonObject.h>
#include <CkHttpCurl.h>
#include <CkStringBuilder.h>

void ChilkatSample(void)
    {
    bool 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.
    CkJsonObject jsonAuth;

    // 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.put_EnableSecrets(true);

    success = jsonAuth.UpdateString("oauth2.client_id","!!sharepoint|oauth2|client_id");
    if (success == true) {
        success = jsonAuth.UpdateString("oauth2.client_secret","!!sharepoint|oauth2|client_secret");
    }

    if (success == true) {
        success = jsonAuth.UpdateString("oauth2.token_endpoint","!!sharepoint|oauth2|token_endpoint");
    }

    if (success == false) {
        std::cout << jsonAuth.lastErrorText() << "\r\n";
        return;
    }

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

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

    CkHttpCurl curl;

    // 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.
    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.
    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.
    curl.AddOutput("getSite","id","site_id");

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

    // Now list the contents of the Documents document library.
    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.
    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.
    const char *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) {
        std::cout << curl.lastErrorText() << "\r\n";
        return;
    }

    // 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.
    int statusCode = curl.get_StatusCode();
    if (statusCode != 200) {
        std::cout << curl.responseBodyStr() << "\r\n";
        std::cout << "status code = " << statusCode << "\r\n";
        return;
    }

    // The response body contains the contents of the downloaded file.
    CkStringBuilder sbFileContents;
    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) {
        std::cout << sbFileContents.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Success." << "\r\n";
    }