Dart

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.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  var 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.
  final jsonAuth = CkJsonObject();

  // 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 = true;
  try {
    jsonAuth.updateString('oauth2.client_id', '!!sharepoint|oauth2|client_id');
  } on ChilkatException {
    success = false;
  }
  if (success) {
    success = true;
    try {
      jsonAuth.updateString('oauth2.client_secret', '!!sharepoint|oauth2|client_secret');
    } on ChilkatException {
      success = false;
    }
  }

  if (success) {
    success = true;
    try {
      jsonAuth.updateString('oauth2.token_endpoint', '!!sharepoint|oauth2|token_endpoint');
    } on ChilkatException {
      success = false;
    }
  }

  if (!success) {
    print(jsonAuth.lastErrorText);
    return;
  }

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

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

  final curl = CkHttpCurl();

  // 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.
  final 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 = true;
  try {
    curl.doYourThing(curlCommand);
  } on ChilkatException {
    success = false;
  }
  if (!success) {
    print(curl.lastErrorText);
    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.
  final statusCode = curl.statusCode;
  if (statusCode != 200) {
    print(curl.responseBodyStr);
    print('status code = $statusCode');
    return;
  }

  // The response body contains the contents of the downloaded file.
  final sbFileContents = CkStringBuilder();
  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 = true;
  try {
    sbFileContents.writeFile('c:/temp/hamlet.json', 'utf-8', false);
  } on ChilkatException {
    success = false;
  }
  if (!success) {
    print(sbFileContents.lastErrorText);
    return;
  }

  print('Success.');
}