Apex Code for Starting a Resumable Session

Oct 13, 2025 by vinooalluri.com 105 views

Introduction

In today's digital landscape, cloud storage has become an essential component of modern applications. Google Drive, with its robust Rest API, has made it possible for developers to integrate cloud storage capabilities into their applications. Salesforce, a leading customer relationship management (CRM) platform, has also made it possible for developers to leverage Google Drive's Rest API using Apex and REST clients. In this article, we will explore the process of creating a resumable upload session using Google Drive's Rest API V3 from Salesforce Apex.

Why Resumable Uploads?

Resumable uploads are a crucial feature in cloud storage, especially when dealing with large files. They allow users to upload files in chunks, which can be resumed from where they left off in case of an interruption. This feature is particularly useful in scenarios where network connectivity is unreliable or when dealing with large files that may take a long time to upload.

Step 1: Start a Resumable Session

To start a resumable session, you need to make a POST request to the start endpoint of the Google Drive Rest API. This endpoint is used to initiate a resumable upload session. The request body should contain the metadata of the file being uploaded, including its name, size, and MIME type.

Apex Code for Starting a Resumable Session

@RestResource(urlMapping='/startResumableSession')
global class StartResumableSession {
    @HttpPost
    global static String startResumableSession() {
        // Set the API endpoint URL
        String endpointUrl = 'https://www.googleapis.com/upload/drive/v3/files?uploadType=resumable';
    // Set the API key
    String apiKey = &#39;YOUR_API_KEY&#39;;
    
    // Set the file metadata
    String fileName = &#39;example.txt&#39;;
    String fileSize = &#39;1024&#39;;
    String mimeType = &#39;text/plain&#39;;
    
    // Create the request body
    String requestBody = &#39;{
        &quot;name&quot;: &quot;&#39; + fileName + &#39;&quot;,
        &quot;size&quot;: &#39; + fileSize + &#39;,
        &quot;mimeType&quot;: &quot;&#39; + mimeType + &#39;&quot;
    }&#39;;
    
    // Make the POST request
    Http http = new Http();
    HttpRequest req = new HttpRequest();
    req.setEndpoint(endpointUrl);
    req.setMethod(&#39;POST&#39;);
    req.setHeader(&#39;Authorization&#39;, &#39;Bearer &#39; + apiKey);
    req.setHeader(&#39;Content-Type&#39;, &#39;application/json&#39;);
    req.setBody(requestBody);
    
    // Send the request and get the response
    HttpResponse res = http.send(req);
    
    // Get the resumable session URL from the response
    String resumableSessionUrl = res.getHeaders().getFirstValue(&#39;Location&#39;);
    
    return resumableSessionUrl;
}

}

Step 2: Save the Resumable Session

Once you have started a resumable session, you need to save the session URL and the session ID. The session URL is used to upload the file in chunks, while the session ID is used to authenticate the upload request.

Apex Code for Saving the Resumable Session

@RestResource(urlMapping='/saveResumableSession')
global class SaveResumableSession {
    @HttpPost
    global static String saveResumableSession(String resumableSessionUrl, String sessionId) {
        // Set the API endpoint URL
        String endpointUrl = 'https://www.googleapis.com/upload/drive/v3/files?uploadType=resumable';
    // Set the API key
    String apiKey = &#39;YOUR_API_KEY&#39;;
    
    // Set the resumable session URL and session ID
    String resumableSessionUrl = &#39;https://example.com/resumable-session&#39;;
    String sessionId = &#39;example-session-id&#39;;
    
    // Create the request body
    String requestBody = &#39;{
        &quot;resumableSessionUrl&quot;: &quot;&#39; + resumableSessionUrl + &#39;&quot;,
        &quot;sessionId&quot;: &quot;&#39; + sessionId + &#39;&quot;
    }&#39;;
    
    // Make the POST request
    Http http = new Http();
    HttpRequest req = new HttpRequest();
    req.setEndpoint(endpointUrl);
    req.setMethod(&#39;POST&#39;);
    req.setHeader(&#39;Authorization&#39;, &#39;Bearer &#39; + apiKey);
    req.setHeader(&#39;Content-Type&#39;, &#39;application/json&#39;);
    req.setBody(requestBody);
    
    // Send the request and get the response
    HttpResponse res = http.send(req);
    
    return res.getHeaders().getFirstValue(&#39;Location&#39;);
}

}

Step 3: Upload the File

Once you have saved the resumable session, you can upload the file in chunks using the resumable session URL and session ID. You need to send a PUT request to the resumable session URL with the file chunk in the request body.

Apex Code for Uploading the File

@RestResource(urlMapping='/uploadFile')
global class UploadFile {
    @HttpPut
    global static String uploadFile(String resumableSessionUrl, String sessionId, Blob fileChunk) {
        // Set the API endpoint URL
        String endpointUrl = 'https://example.com/resumable-session';
    // Set the API key
    String apiKey = &#39;YOUR_API_KEY&#39;;
    
    // Set the resumable session URL and session ID
    String resumableSessionUrl = &#39;https://example.com/resumable-session&#39;;
    String sessionId = &#39;example-session-id&#39;;
    
    // Create the request body
    String requestBody = &#39;{
        &quot;fileChunk&quot;: &#39; + fileChunk + &#39;
    }&#39;;
    
    // Make the PUT request
    Http http = new Http();
    HttpRequest req = new HttpRequest();
    req.setEndpoint(endpointUrl);
    req.setMethod(&#39;PUT&#39;);
    req.setHeader(&#39;Authorization&#39;, &#39;Bearer &#39; + apiKey);
    req.setHeader(&#39;Content-Type&#39;, &#39;application/octet-stream&#39;);
    req.setBody(requestBody);
    
    // Send the request and get the response
    HttpResponse res = http.send(req);
    
    return res.getHeaders().getFirstValue(&#39;Location&#39;);
}

}

Conclusion

In this article, we have explored the process of creating a resumable upload session using Google Drive's Rest API V3 from Salesforce Apex. We have covered the three steps needed to be followed: starting a resumable session, saving the resumable session, and uploading the file. We have also provided Apex code examples for each step to help you implement resumable uploads in your Salesforce application.

Best Practices

When implementing resumable uploads in your Salesforce application, keep the following best practices in mind:

Use a secure API key to authenticate your requests.
Use a robust error handling mechanism to handle any errors that may occur during the upload process.
Use a progress bar or a loading indicator to show the progress of the upload to the user.
Use a retry mechanism to retry the upload in case of any errors that may occur during the upload process.

Introduction

In our previous article, we explored the process of creating a resumable upload session using Google Drive's Rest API V3 from Salesforce Apex. We covered the three steps needed to be followed: starting a resumable session, saving the resumable session, and uploading the file. In this article, we will answer some frequently asked questions (FAQs) related to resumable uploads in Google Drive's Rest API V3 from Salesforce Apex.

Q: What is a resumable upload?

A: A resumable upload is a type of upload that allows you to upload a file in chunks, which can be resumed from where they left off in case of an interruption. This feature is particularly useful in scenarios where network connectivity is unreliable or when dealing with large files that may take a long time to upload.

Q: Why do I need to start a resumable session?

A: You need to start a resumable session to initiate the upload process. This step is necessary to create a resumable session URL and session ID, which are used to authenticate and upload the file.

Q: What is the difference between a resumable session URL and a session ID?

A: The resumable session URL is used to upload the file in chunks, while the session ID is used to authenticate the upload request. The resumable session URL is a unique URL that is generated when you start a resumable session, while the session ID is a unique identifier that is used to authenticate the upload request.

Q: How do I handle errors during the upload process?

A: You can handle errors during the upload process by using a robust error handling mechanism. This can include retrying the upload in case of any errors that may occur during the upload process, or by displaying an error message to the user.

Q: Can I use resumable uploads with other Google Drive APIs?

A: Yes, you can use resumable uploads with other Google Drive APIs, such as the Google Drive API for Android and iOS.

Q: Are there any limitations to resumable uploads?

A: Yes, there are some limitations to resumable uploads. For example, you can only upload files up to 750 MB in size using resumable uploads. Additionally, you can only upload files in chunks of up to 256 MB in size.

Q: How do I implement resumable uploads in my Salesforce application?

A: To implement resumable uploads in your Salesforce application, you can use the Apex code examples provided in our previous article. You will need to create a resumable session, save the resumable session, and upload the file in chunks using the resumable session URL and session ID.

Q: Can I use resumable uploads with other Salesforce APIs?

A: Yes, you can use resumable uploads with other Salesforce APIs, such as the Salesforce REST API and the Salesforce SOAP API.

Conclusion

In this article, we have answered some frequently asked questions (FAQs) related to resumable uploads in Google Drive's Rest API V3 from Salesforce Apex. We have covered topics such as the definition of a resumable upload, the difference between a resumable session URL and a session ID, and how to handle errors during the upload process. By following the best practices and using the Apex code examples provided in our previous article, you can implement resumable uploads in your Salesforce application and provide a seamless experience to your users.

Best Practices

When implementing resumable uploads in your Salesforce application, keep the following best practices in mind:

Use a secure API key to authenticate your requests.
Use a robust error handling mechanism to handle any errors that may occur during the upload process.
Use a progress bar or a loading indicator to show the progress of the upload to the user.
Use a retry mechanism to retry the upload in case of any errors that may occur during the upload process.

By following these best practices and using the Apex code examples provided in our previous article, you can implement resumable uploads in your Salesforce application and provide a seamless experience to your users.