Simple Token Authorization Flow in Flutter Without a Backend

Learn how to implement a straightforward token-based authorization system in Flutter without relying on a backend server or third-party services. --- This video is based on the question https://stackoverflow.com/q/77768385/ asked by the user 'Aditya Pachchigar' ( https://stackoverflow.com/u/23203672/ ) and on the answer https://stackoverflow.com/a/77768405/ provided by the user 'jesto paul' ( https://stackoverflow.com/u/4140589/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, comments, revision history etc. For example, the original title of the Question was: Authorization in Flutter using token Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Implementing Token Authorization in Flutter Without a Backend Introduction In mobile application development, authorization is a crucial aspect that ensures users can securely access their accounts and perform actions within the app. The common way to handle this is through token-based authentication, where a server issues a token upon successful login. However, what if you are developing a Flutter application without access to a backend server or external services? This guide will guide you through creating a simple token authorization system in such a scenario. Understanding the Problem When building an app that requires user authentication, you typically need a backend to manage user credentials and generate authorization tokens. However, if you find yourself in a situation where: You are not allowed to use any backend servers. You cannot rely on third-party authentication services like Auth0. You need to implement standard login and registration (e.g., no Google sign-in). This can pose a significant challenge. Despite these restrictions, you can still implement a local solution to simulate token generation and storage. Solution Overview Here’s how you can establish a basic token-based authorization flow in Flutter without a backend: Registering Users Generating Tokens Storing Tokens Logging In Authorizing Users Let’s break these steps down further. 1. Registering Users When a user registers, you'll need to securely store their credentials (username and password). For this purpose, you can use the flutter_secure_storage package, which provides a simple way to store data securely. 2. Generating Tokens After successfully registering the user, you need to generate a unique token for them. In real-world applications, this is often accomplished using a JSON Web Token (JWT), but in a basic scenario, you can use a simple unique identifier. A UUID (Universally Unique Identifier) or even a random number generated using Dart's Random class would suffice. 3. Storing Tokens Once you generate the token, store it, associated with the user's credentials, in secure local storage. This will allow you to retrieve it later when the user attempts to log in. 4. Logging In When the user attempts to log in, you’ll check their entered credentials against the stored data. If they match, you retrieve their associated token and allow their access. 5. Authorizing Users After the user logs in, you can store the received token in memory during the app's runtime. You can check for this token to determine whether the user is authorized to perform certain actions within the app. Example Code Implementation Here’s a simple example code snippet demonstrating the registration and login functionality: [[See Video to Reveal this Text or Code Snippet]] Important Notes This approach is very simplified and is meant for educational purposes only. It is not suitable for production use. In a real application, consider securely managing user credentials, using proper encryption, and ideally incorporating a backend to manage authentication properly. Conclusion While implementing a full-fledged token authorization system without a backend can be challenging, a basic approach like the one outlined above can provide a foundation for your app's authorization needs. Remember that this solution is primarily for learning and prototyping. For any production application, integrating proper security measures and a backend server is essential. If you have any questions or need further clarification, feel free to reach out!