How to use Google Drive API as files source for comparing documents

These days Cloud services are very popular. It means that lots of people use them to store documents, photos and other files. In this situation you may need opportunity to compare files directly from Google Drive, without a need to download and save them locally. You can easily do it combining GroupDocs.Comparison API together with Google Drive API.

Configuring Google API

In order to use Google API you must have Google account. Here we will not describe how to register it. You can find out required steps on Google documentation page. Nevertheless, below are steps, needed to use Google Drive API in your project.

Creating Google Cloud Platform project and activating Drive API

  1. Open Google Cloud Platform Dashboard

  2. Click Select a project to open list of projects

  3. In order to create a project, click NEW PROJECT

  4. Enter project name and click Create

  5. Click Enable APIs and services to enable Google Drive API

  6. Find Google Drive API, select it and click Enable on the opened page

  1. Open Credentials page and check that selected project is correct

  2. Click Create Credentials and select OAuth client ID

  3. Click Configure Consent Screen button

  4. Select User Type and click Create

  5. Fill App information and click Save and continue

  6. Click Add or remove scopes to configure credential scopes.

  7. On the Update selected scopes screen check needed scopes. You can use filters to search scopes. After selecting all needed scopes, click Update button

  8. Click Save and continue to go to the next step

  9. Add users using Add users button and click Save and continue

  10. Click Back to dashboard to finish configuration

Creating Google Drive API credentials

  1. Open Credentials page and check that selected project is correct

  2. Click Create Credentials and select OAuth client ID

  3. Select application type as Desktop app, enter its name and click Create

  4. Now, copy and save your Client ID, Client secret and of course download and save JSON file, that will be used to access Google Drive API

Configuring project to use Google Drive API with Comparison API

To use Google Drive API as a file storage of Comparison API you need to add some libraries and repository to the project.

Connect GroupDocs repository

Creating Google Drive API objects

First, we need JSON factory, that will be used for communication with Google server

Secondly, we need to create transport object

After that we must create client secrets object. It is the place, where we will use json file that was downloaded after creating API credentials

Next step is to create authorization flow that will be used for authorization request. A little details about options:

  • DriveScopes.DRIVE - is a scope that was enabled while creating API credentials
  • "/Path/To/Directory/To/Save/Tokens" - The tokens directory is needed to save authorization tokens. You can remove this line, but in this way Google API will ask for authorization each time.

Now we will request authorization. It will open Google authorization page in default web browser, where you can grand access to the application. More information can be found on Google Documentation page.

Finally, we build an object that will be used to access Google Drive files

Get list of files using Google Drive API

To print list of files which are on your Google Drive, execute next code

Here is an example of the output:

- 1hRgws-lLWMlloSZioaVpKJGKt687KHL7  GroupDocs_Demo.pdf (51911 bytes)
- 22k0Uyt_bBoN96LJhL3iKlKHlhLKjhw2O  GroupDocs_Demo_Word.docx (12044 bytes)
- 33Kk0yt_bBoN96LJhL3iKlKHlhLKjhw2O  GroupDocs_Demo_Word.docx (12044 bytes)
- 80UMm8vRQ637H7hJHkjHKh7JKJL96tm56  GroupDocs_Demo_Image.png (78398 bytes)
- 1qwRjo4Nu0LKHlLhlLKjlk798761tuFJP  GroupDocs_Demo_Photo.jpg (3186063 bytes)

In the output each line is one file. It’s ID, name and size. You can use this information to show files to a user. There are lots on data, that can be got for each file. More information can be found on Google Documentation page. For code samples below we will use two of IDs above. Keep in mind, your files will have other IDs, so running code below don’t forget to change IDs.

Comparing Documents directly from Google Drive

GroupDocs.Comparison for Java is a modern, powerful and flexible library that can be used in any Java, Kotlin or other Java compatible projects. You can use it to compare Word, Excel, Presentation documents, photos, images, diagrams, code files, and other supported file formats. Comparison library has lots of settings, as generating summary page, accepting/rejecting changes, comparing more than two documents (multi comparing), generating document preview images, changing comparison sensitivity and changes highlighting styles. More information about settings can be found in the documentation. On our GitHub page you can find samples of integrating Comparison library with different frameworks, as Spring, Dropwizard, Kotlin Compose Desktop and so on.

Saving Result Document Locally

You can easily compare dwo documents, which are located on your Google Drive saving result document locally or saving it into Java stream and use it whatever you want. Keep in mind that 1ZSDTUZArzuwYab0GUbXEoSX_b9kt2mk0 and 1mKk0yt_bBoN9K9mm-3iGXLxfTzkrdw2O are IDs got in the previous steps. For you, they will be different.

In output console you will see path to the result document.

Saving Result Document to Google Drive

Below you can see the code that will compare documents directly from Google Drive. Output files will be uploaded to Google Drive without saving locally anything. After that, you can open Google Drive page in web browser and see result document, for example, using Google Docs.

In output console you will see ID, name and size of uploaded document.

Get a Free API License

Lots of settings, as summary page, sensitivity of comparison and so on are available only with license. You can get a free temporary license in order to use the API without the evaluation limitations.


Reading this article you learned the way to use Google Drive API as a file storage for GroupDocs.Comparison library that gives you lots of opportunities. You can find samples of using Google Drive API inside Spring and Dropwizard applications on GitHub page which you can modify and use as a core of your own application for comparing photos, code files, PowerPoint, Excel, Word and other supported file formats.

For more details, options, and examples, you can go through the documentation and GitHub repository. Reach us on the forum for your queries.

See also