Using Google Drive API with Spring Boot: How to Properly Authenticate Users

Learn how to effectively use the `Google Drive API` in your Spring Boot application by exchanging ID tokens for access tokens. This guide provides a clear step-by-step guide.
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Accessing Google Drive API Using Spring Boot

Google Drive provides a powerful API that allows developers to interact with users' files in a seamless manner. However, integrating this API into your Spring Boot Java application can be tricky, especially when it comes to authenticating users. In this post, we will explore how to list the logged user's files on Google Drive using their idToken and properly handle authentication tokens.

The Challenge

Imagine you’ve implemented the Google login flow successfully in your Spring Boot application. You ask users for permission to access their Google Drive, and then you retrieve their authentication token. Yet, when you attempt to use this token to call the Google Drive API, you encounter an error similar to the following:

[[See Video to Reveal this Text or Code Snippet]]

This error signifies that you are trying to use an idToken, which is not acceptable for accessing the Google Drive API. Let's understand how to resolve this issue.

Understanding idToken vs AccessToken

What is an ID Token?

An idToken is a signed JWT (JSON Web Token) that contains user profile information. It's primarily used for user authentication but not for accessing APIs on behalf of a user.

What is an Access Token?

An Access Token is used to authorize an application to interact with user data in Google APIs. This token has a different authentication mechanism and is what you need to call the Google Drive API.

Solution: Exchange ID Token for Access Token

To successfully call the Google Drive API, you need to use an Access Token. The recommended way to get this token in a Spring Boot application is to use Spring's OAuth2AuthorizedClientService.

Here’s how you can do this step-by-step:

Step 1: Inject OAuth2AuthorizedClientService

Add a field in your controller for the OAuth2AuthorizedClientService.

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Modify Your Controller Method

You will need to modify your controller method to swap the idToken for an Access Token. Here’s the updated code:

[[See Video to Reveal this Text or Code Snippet]]

Important Notes:

Ensure you have correctly configured the OAuth2AuthorizedClientService bean in your Spring security configuration.

Handle exceptions to prevent your application from crashing due to an invalid state.

Conclusion

Providing seamless access to the Google Drive API in your Spring Boot application is straightforward once you understand how to handle authentication tokens correctly. By using OAuth2AuthorizedClientService to exchange the idToken for an Access Token, you can successfully make API calls to Google Drive on behalf of your users.

By following the steps outlined in this guide, you're well on your way to building a robust Spring Boot application that can integrate with Google services effectively.

If you have any questions or need further assistance, feel free to leave a comment below!