Implementation Commit

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">

	<modelVersion>4.0.0</modelVersion>

	<groupId>org.etsi.osl.util</groupId>

	<artifactId>servicespecificationfetcher</artifactId>

	<version>0.0.1-SNAPSHOT</version>

    <!-- Specify the Java version you're using -->

    <properties>

        <maven.compiler.source>17</maven.compiler.source>

        <maven.compiler.target>17</maven.compiler.target>

    </properties>

    <dependencies>

        <!-- Jackson JSON Processor -->

        <dependency>

            <groupId>com.fasterxml.jackson.core</groupId>

            <artifactId>jackson-databind</artifactId>

            <version>2.12.3</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->

        <dependency>

            <groupId>org.slf4j</groupId>

            <artifactId>slf4j-api</artifactId>

            <version>2.0.16</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/ch.qos.logback/logback-classic -->

        <dependency>

            <groupId>ch.qos.logback</groupId>

            <artifactId>logback-classic</artifactId>

            <version>1.5.8</version>

        </dependency>

        <!-- Google Gson -->

        <dependency>

            <groupId>com.google.code.gson</groupId>

            <artifactId>gson</artifactId>

            <version>2.8.6</version>

        </dependency>

        <!-- Your custom library dependency -->

	    <dependency>

	        <groupId>org.etsi.osl</groupId>

	        <artifactId>org.etsi.osl.model.tmf</artifactId>

	        <version>1.0.0</version>

	    </dependency>

    </dependencies>

    <build>

        <plugins>

            <!-- Maven Compiler Plugin -->

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-compiler-plugin</artifactId>

                <version>3.8.1</version>

                <configuration>

                    <source>17</source>

                    <target>17</target>

                </configuration>

            </plugin>

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-jar-plugin</artifactId>

                <version>3.2.0</version>

                <configuration>

                    <archive>

                        <manifest>

                            <mainClass>org.osl.etsi.util.ServiceSpecificationFetcher</mainClass>

                        </manifest>

                    </archive>

                </configuration>

            </plugin>

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-shade-plugin</artifactId>

                <version>3.4.1</version>

                <executions>

                    <execution>

                        <phase>package</phase>

                        <goals>

                            <goal>shade</goal>

                        </goals>

                        <configuration>

                            <createDependencyReducedPom>true</createDependencyReducedPom>

                            <transformers>

                                <!-- Ensures that the manifest specifies the main class -->

                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">

                                    <mainClass>org.osl.etsi.util.ServiceSpecificationFetcher</mainClass> <!-- Fully Qualified Name -->

                                </transformer>

                            </transformers>

                        </configuration>

                    </execution>

                </executions>

            </plugin>

        </plugins>

    </build>

</project>  

package org.osl.etsi.util;

import com.fasterxml.jackson.databind.JsonNode;

import com.fasterxml.jackson.databind.ObjectMapper;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import java.io.IOException;

import java.net.URI;

import java.net.URLEncoder;

import java.net.http.HttpClient;

import java.net.http.HttpRequest;

import java.net.http.HttpResponse;

import java.nio.charset.StandardCharsets;

import java.time.Instant;

import java.util.Properties;

public class KeycloakAuthenticator {

    private static final Logger logger = LoggerFactory.getLogger(KeycloakAuthenticator.class.getName());

    private final Properties config;

    private final HttpClient client;

    private final ObjectMapper objectMapper;

    private String currentToken;

    private long tokenExpiryTime;

    private long tokenRefreshBufferSeconds;

    /**

     * Constructs a KeycloakAuthenticator with the specified configuration file path.

     *

     * @param configFilePath The file path to the configuration properties file.

     * @throws IOException If there is an error loading the configuration file.

     */

    public KeycloakAuthenticator(Properties config) throws IOException {

        this.config = config;

        this.client = HttpClient.newHttpClient();

        this.objectMapper = new ObjectMapper();

        setTokenRefreshBufferSeconds();

    }

    /**

     * Loads the configuration properties from the specified file path.

     *

     * @param configFilePath The file path to the configuration properties file.

     * @return The token refresh buffer time in seconds.

     * @throws IOException If the configuration file cannot be read.

     */

    private void setTokenRefreshBufferSeconds() throws IOException {

        // Load the token refresh buffer time, defaulting to 60 seconds if not specified

        String bufferSecondsStr = this.config.getProperty("token.refresh.buffer.seconds", "60");

        long bufferSeconds;

        try {

            bufferSeconds = Long.parseLong(bufferSecondsStr);

            if (bufferSeconds < 0) {

                throw new NumberFormatException("Buffer seconds cannot be negative.");

            }

        } catch (NumberFormatException ex) {

            logger.warn("Invalid token.refresh.buffer.seconds value: " + bufferSecondsStr + ". Using default of 60 seconds.");

            bufferSeconds = 60;

        }

        logger.info("Token refresh buffer set to " + bufferSeconds + " seconds.");

        this.tokenRefreshBufferSeconds=bufferSeconds;

    }

    /**

     * Retrieves a valid access token. If the current token is expired or not present,

     * it authenticates with Keycloak to obtain a new one.

     *

     * @return A valid access token as a String.

     * @throws IOException          If an I/O error occurs during authentication.

     * @throws InterruptedException If the HTTP request is interrupted.

     */

    public synchronized String getToken() throws IOException, InterruptedException {

        long currentEpochSeconds = Instant.now().getEpochSecond();

        if (currentToken != null && currentEpochSeconds < (tokenExpiryTime - tokenRefreshBufferSeconds)) {

            logger.info("Using cached token. Token expires at " + Instant.ofEpochSecond(tokenExpiryTime));

            return currentToken;

        } else {

            logger.info("Cached token is missing or nearing expiration. Authenticating to obtain a new token.");

            return authenticateAndGetToken();

        }

    }

    /**

     * Authenticates with Keycloak and retrieves a new access token.

     *

     * @return The new access token as a String.

     * @throws IOException          If the authentication request fails.

     * @throws InterruptedException If the HTTP request is interrupted.

     */

    private String authenticateAndGetToken() throws IOException, InterruptedException {

        String keycloakUrl = config.getProperty("keycloak.url");

        String clientId = config.getProperty("client.id");

        String clientSecret = config.getProperty("client.secret");

        String username = config.getProperty("username");

        String password = config.getProperty("password");

        // Validate required properties

        if (keycloakUrl == null || clientId == null || username == null || password == null) {

            String errorMsg = "Missing required configuration properties.";

            logger.error(errorMsg);

            throw new IOException(errorMsg);

        }

        // Build the form data with URL encoding

        String form = buildFormData(clientId, clientSecret, username, password);

        HttpRequest request = HttpRequest.newBuilder()

                .uri(URI.create(keycloakUrl))

                .header("Content-Type", "application/x-www-form-urlencoded")

                .POST(HttpRequest.BodyPublishers.ofString(form))

                .build();

        logger.info("Sending authentication request to Keycloak.");

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

        if (response.statusCode() == 200) {

            JsonNode responseJson = objectMapper.readTree(response.body());

            currentToken = responseJson.get("access_token").asText();

            long expiresIn = responseJson.get("expires_in").asLong();

            tokenExpiryTime = Instant.now().getEpochSecond() + expiresIn;

            logger.info("Authentication successful. Token obtained. Token expires in " + expiresIn + " seconds.");

            return currentToken;

        } else {

            String errorMsg = "Authentication failed: HTTP status " + response.statusCode() + ": " + response.body();

            logger.error(errorMsg);

            throw new IOException(errorMsg);

        }

    }

    /**

     * Builds the URL-encoded form data for the authentication request.

     *

     * @param clientId     The client ID.

     * @param clientSecret The client secret (optional).

     * @param username     The username.

     * @param password     The password.

     * @return The URL-encoded form data as a String.

     * @throws IOException If URL encoding fails.

     */

    private String buildFormData(String clientId, String clientSecret, String username, String password) throws IOException {

        StringBuilder form = new StringBuilder();

        form.append("client_id=").append(urlEncode(clientId));

        if (clientSecret != null && !clientSecret.isEmpty()) {

            form.append("&client_secret=").append(urlEncode(clientSecret));

        }

        form.append("&username=").append(urlEncode(username));

        form.append("&password=").append(urlEncode(password));

        form.append("&grant_type=password");

        return form.toString();

    }

    /**

     * URL-encodes a string using UTF-8 encoding.

     *

     * @param value The string to encode.

     * @return The URL-encoded string.

     * @throws IOException If UTF-8 encoding is not supported.

     */

    private String urlEncode(String value) throws IOException {

        try {

            return URLEncoder.encode(value, StandardCharsets.UTF_8.toString());

        } catch (Exception ex) {

            logger.error("URL encoding failed for value: " + value, ex);

            throw new IOException("URL encoding failed.", ex);

        }

    }

}