How to get the authorization code in spring-authorization-server using a single endpoint call? – Spring

The Problem:

A developer is using Spring Boot 3, Spring Security 6, and Spring Boot Auth Server to build an OAuth 2 authorization server. They want to obtain the authorization code through an endpoint call without having to manually navigate through a browser and input login credentials. The goal is to retrieve the authorization code directly using a tool like Postman or a Java HTTP client class, bypassing the need for a user interface. The developer seeks a solution to accomplish this.

The Solutions:

Solution 1: Client Credentials Flow

• The Authorization Code Grant is designed for user authentication and requires a browser.
• If you want to avoid using a browser, you can use the Client Credentials Flow.
• This flow is intended for applications, not users, and provides an access token directly to the client without user interaction.
• It’s important to note that the Client Credentials Flow is less secure than the Authorization Code Grant as it doesn’t involve user authentication.
• To use the Client Credentials Flow, you can send a POST request to the /oauth/token endpoint with the following parameters:

grant_type=client_credentials
client_id={your_client_id}
client_secret={your_client_secret}

• This will return an access token that you can use to access protected resources.

Example using Java and Postman:

• This example demonstrates how to obtain an access token using the Client Credentials Flow in Java and Postman:

Java:

import com.google.gson.JsonObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;

public class ClientCredentialsFlow {

    public static void main(String[] args) throws IOException {
        // Set your client ID and client secret
        String clientId = "your_client_id";
        String clientSecret = "your_client_secret";

        // Set the URL of your authorization server
        URL url = new URL("http://localhost:8080/oauth/token");

        // Create a POST request and set the appropriate headers
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("POST");
        connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

        // Construct the request body
        String body = "grant_type=client_credentials&client_id=" + clientId + "&client_secret=" + clientSecret;

        // Send the request and parse the response
        OutputStream outputStream = connection.getOutputStream();
        outputStream.write(body.getBytes(StandardCharsets.UTF_8));
        outputStream.close();

        BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        String line;
        StringBuilder response = new StringBuilder();

        while ((line = reader.readLine()) != null) {
            response.append(line);
        }
        reader.close();

        // Extract the access token from the response
        JsonObject jsonResponse = new Gson().fromJson(response.toString(), JsonObject.class);
        String accessToken = jsonResponse.get("access_token").getAsString();

        // Use the access token to access protected resources
        // ...

    }
}

Postman:

1. Open Postman and create a new POST request.
2. Set the URL to your authorization server’s /oauth/token endpoint.
3. In the "Headers" tab, set the following headers:
   • Content-Type: application/x-www-form-urlencoded
4. In the "Body" tab, set the following form data:
   • grant_type: client_credentials
   • client_id:
   • client_secret:
5. Send the request.
6. You will receive a response containing an access token that you can use to access protected resources.

Video Explanation:

The following video, titled "Getting Started with Spring Authorization Server - YouTube", provides additional insights and in-depth exploration related to the topics discussed in this post.

The Spring Authorization Server project provides support for OAuth 2.1 Authorization Framework, OpenID Connect Core 1.0, and the numerous ...