Granting authorization to the API with Java

Heading over to Java, you will need to grant authorization to the API. Begin by creating a new Maven project and configure your pom.xml file, by doping the following.

• Go to https://mvnrepository.com/ and search for json then select JSON In Java.

• Select the latest version.

• Select Maven and copy the displayed dependency.

• Go back to your IDE and paste that dependency into your pom.xml file.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>JavaClient</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.json/json -->
        <dependency>
            <groupId>org.json</groupId>
            <artifactId>json</artifactId>
            <version>20240303</version>
        </dependency>
    </dependencies>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

</project>

Troubleshooting

Case 1. The text within the dependency is red

Step 1: Check that you have Maven installed.

• Go to Settings, find Plugins and make sure Maven is under the installed build tools.
• Go to Build, Execution, Deployment > Build Tools > Maven, if the Use settings from .mvn/maven.config box is selected, deselect it.

Step 2: Create a new Java Class called FetchToken.

• Import these libraries.

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.util.Base64;
import org.json.JSONObject;

• Within the public class FetchToken, create the TOKEN_URL, CLIENT_ID and CLIENT_SECRET variables (fill in the fields with your own values).

public class FetchToken {

    private static final String TOKEN_URL = "http://your-openiam-instance/idp/oauth2/token";
    private static final String CLIENT_ID = "your client id";
    private static final String CLIENT_SECRET = "your secret id";

• Create the function public static String getToken() for obtaining an auth token.

public static String getToken() throws IOException, InterruptedException {
   HttpClient client = HttpClient.newHttpClient();
   String authHeader = Base64.getEncoder().encodeToString((CLIENT_ID + ":" + CLIENT_SECRET).getBytes());

   HttpRequest request = HttpRequest.newBuilder()
           .uri(URI.create(TOKEN_URL))
           .header("Authorization", "Basic " + authHeader)
           .header("Content-Type", "application/x-www-form-urlencoded")
           .POST(HttpRequest.BodyPublishers.ofString("grant_type=client_credentials"))
           .build();

   HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

   if (response.statusCode() == 200) {
       JSONObject jsonResponse = new JSONObject(response.body());
       String accessToken = jsonResponse.optString("access_token", null);
       if (accessToken == null) {
           System.out.println("Error: Access token not found in the response");
       }
       return accessToken;
   } else {
       System.out.printf("Error: %d, %s%n", response.statusCode(), response.body());
       return null;
   }
}

• In main, create a String accessToken that will call getToken() and print it out. Note: printing out the token is not necessary but will confirm that your program is working as intended.

public static void main(String[] args) {
   try {
       String accessToken = getToken();
       if (accessToken != null) {
           System.out.println("Access Token: " + accessToken);
       }
   } catch (IOException | InterruptedException e) {
       e.printStackTrace();
   }
}

An example of the full code is given below.

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.util.Base64;
import org.json.JSONObject;

public class FetchToken {

   private static final String TOKEN_URL = "http://localhost.openiam.com:8080/idp/oauth2/token";
   private static final String CLIENT_ID = "89CF108C07274048AE42DEBD251F2ABA";
   private static final String CLIENT_SECRET = "fdc3f1658731bd812105c841e07a8ceece72d553089d5d7e8e19e101b3f3652c";

   public static void main(String[] args) {
       try {
           String accessToken = getToken();
           if (accessToken != null) {
               System.out.println("Access Token: " + accessToken);
           }
       } catch (IOException | InterruptedException e) {
           e.printStackTrace();
       }
   }

   public static String getToken() throws IOException, InterruptedException {
       HttpClient client = HttpClient.newHttpClient();
       String authHeader = Base64.getEncoder().encodeToString((CLIENT_ID + ":" + CLIENT_SECRET).getBytes());

       HttpRequest request = HttpRequest.newBuilder()
               .uri(URI.create(TOKEN_URL))
               .header("Authorization", "Basic " + authHeader)
               .header("Content-Type", "application/x-www-form-urlencoded")
               .POST(HttpRequest.BodyPublishers.ofString("grant_type=client_credentials"))
               .build();

       HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

       if (response.statusCode() == 200) {
           JSONObject jsonResponse = new JSONObject(response.body());
           String accessToken = jsonResponse.optString("access_token", null);
           if (accessToken == null) {
               System.out.println("Error: Access token not found in the response");
           }
           return accessToken;
       } else {
           System.out.printf("Error: %d, %s%n", response.statusCode(), response.body());
           return null;
       }
   }
}

After running FetchToken, if working properly, the output should be similar to this:
Access Token: 9Hc58KWwqKwPmlDXeeHj6kBwp3xswhxA3XLB91FoYtGpAi1kASi.TJ-IETfTedAfiwyUMsu.gOpV4e4wB-kub-