通过fileget URL访问文件：基于Provider Hosted Application的SharePoint文件处理程序咨询

Hey there! I’ve worked with SharePoint WOPI integrations before, so let’s walk through how to access your file content using that fileget URL you’re receiving from SharePoint.

The fileget URL SharePoint sends you is a direct REST endpoint to retrieve the file’s contents, already pre-populated with a valid access_token for authentication. Here’s how to implement this in your Heroku-hosted add-in:

1. Basic GET Request Implementation #

You can use any HTTP client library (fetch, axios, etc.) to send a GET request to the fileget URL. Here’s a simple example using vanilla JavaScript/fetch (works well in Node.js or browser environments):

async function fetchSharePointFile(fileGetUrl) {
  try {
    // Send the GET request to the WOPI file endpoint
    const response = await fetch(fileGetUrl, {
      method: 'GET',
      headers: {
        // Specify the appropriate Accept header for your custom file type
        // Use 'application/octet-stream' for binary files, or your custom MIME type
        'Accept': 'application/octet-stream'
      }
    });

    // Handle HTTP errors (e.g., expired token, missing file)
    if (!response.ok) {
      throw new Error(`WOPI request failed: ${response.status} - ${response.statusText}`);
    }

    // Process the file content based on your needs
    const content = await response.text(); // Use response.arrayBuffer() for binary files
    return content;
  } catch (error) {
    console.error('Failed to retrieve file:', error);
    // Add your custom error handling logic here (e.g., notify user, retry)
    throw error;
  }
}

2. Critical Things to Keep in Mind for Heroku #

• CORS Configuration: SharePoint’s WOPI endpoints are typically configured to allow requests from trusted Provider Hosted Add-ins, but if you run into CORS errors, verify that your Heroku app’s domain is added to SharePoint’s list of trusted external domains (this is set via the SharePoint Admin Center).
• Token Expiry: The access_token in the fileget URL has a limited lifespan. If you encounter 401 Unauthorized errors, it means the token has expired—you’ll need to trigger a new WOPI session (usually by re-opening the file from SharePoint) to get a fresh token.
• Binary File Handling: If your custom file is binary (not plain text), replace response.text() with response.arrayBuffer() or response.blob() to properly handle the raw data, then parse it according to your file’s format.

3. Error Handling Best Practices #

• Log detailed errors in Heroku: Use Heroku’s logging system to record the fileget URL, response status codes, and error messages—this will make debugging issues like expired tokens or missing files much easier.
• Handle specific HTTP status codes:
  • 401 Unauthorized: Token is invalid/expired; prompt the user to re-open the file.
  • 404 Not Found: The file no longer exists in SharePoint; notify the user accordingly.
  • 500 Internal Server Error: SharePoint encountered an issue; retry the request after a short delay or inform the user.

内容的提问来源于stack exchange，提问作者duwalanise