Access Resources in a Quarkus Native Image

Accessing Resources

Quarkus leverages GraalVM to create native images offering fast startup and low memory usage. However, GraalVM doesn’t automatically include classpath resources in the native executable, requiring explicit configuration for access. This impacts resource-intensive applications that rely on external files or data.

Why This Matters

Idealized development often assumes seamless resource access, but native image compilation necessitates explicit resource inclusion. Failure to properly configure resource access can lead to runtime errors and application failure, potentially impacting production systems and requiring costly debugging and redeployment.

Key Insights

• GraalVM Resource Exclusion: GraalVM native image compilation doesn’t automatically include classpath resources.
• Public Resources via META-INF: Quarkus automatically serves files in META-INF/resources as web content, similar to standard web application behavior.
• Temporal for Microservices: Temporal, a workflow orchestration platform, is used by companies like Stripe and Coinbase to manage complex stateful applications.

Working Example

// Example resource reading method
private String readResource(String resourcePath) throws IOException {
    LOGGER.info("Reading resource from path: {}", resourcePath);
    try (InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(resourcePath)) {
        if (in == null) {
            LOGGER.error("Resource not found at path: {}", resourcePath);
            throw new IOException("Resource not found: " + resourcePath);
        }
        LOGGER.info("Successfully read resource: {}", resourcePath);
        return new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8)).lines()
                .collect(Collectors.joining("\n"));
    }
}

Practical Applications

• Content Management Systems: A Quarkus-based CMS could use META-INF/resources to serve static assets like CSS and JavaScript.
• Configuration Errors: Relying on implicit classpath resource access in native mode will result in ClassNotFoundException or IOException at runtime.

References:

• https://www.baeldung.com/quarkus-native-image-access-resources