What Spring Didn’t Teach You: Becoming a Modern Java Developer with Quarkus

You mastered Spring. You’ve built services, wired beans, and wrestled with configuration. But what if your expertise is holding you back?

Spring has been a faithful companion to Java developers for two decades. But frameworks, like developers, need to evolve. Today’s cloud-native world values startup time, memory efficiency, predictable builds, and dev-friendly tooling over general-purpose flexibility. This is where Quarkus comes in: a modern Java stack built with these priorities in mind.

This isn’t just a feature-by-feature comparison. This is about what Spring never forced you to think about — and why embracing Quarkus can make you a better, more modern developer.

Spring prioritizes abstraction. Quarkus makes the cost of abstraction visible.

Spring famously made Java "enterprise-ready" by abstracting away infrastructure concerns. But with that power came hidden complexity: runtime classpath scanning, reflective bean instantiation, and unpredictable boot sequences.

Quarkus flips the model. It does as much as possible at build time, not runtime. That means faster boot, lower memory, and fewer surprises.

Spring-style bean registration:

@Service
public class GreetingService {
    public String hello() {
        return "Hello from Spring!";
    }
}

Quarkus equivalent:

@ApplicationScoped
public class GreetingService {
    public String hello() {
        return "Hello from Quarkus!";
    }
}

At first glance, these look the same. But Quarkus turns this into a static build-time graph, using Jandex indexing and bytecode analysis. Spring waits until runtime, costing you boot time and reflection overhead.

With Quarkus, you’re not just writing DI-friendly code — you’re thinking about the life cycle of your application.

You were trained to run apps. Quarkus trains you to iterate.

One of the most powerful features of Quarkus is quarkus:dev. It's not a plugin, it's a philosophy: shorten the feedback loop.

• Change code

• Save file

• Quarkus reloads instantly

With Spring, you’re likely restarting the app or using brittle hot-swap tools. Over time, that friction shapes your behavior: fewer experiments, slower iterations.

With Quarkus, the inner loop is so fast that refactoring and testing become second nature.

Configuration as code! Not magic or mystery

Spring’s @Value injection is easy to start with, but as projects grow, it becomes harder to understand where a value comes from. Spring’s property resolution can involve multiple layers (YAML merging, profile activation, environment variables), and debugging the effective value often feels like detective work.

Quarkus solves this cleanly:

• Strong typing via @ConfigProperty, not only string substitution.

• Profiles (like dev, test, prod) are first-class and intuitive.

• Live reload during development means you can update configuration without restarting.

Example – application.properties:

server.timeout=5s
server.port=8080

And in Java:

import java.time.Duration;
import java.util.Optional;

@ConfigProperty(name = "server.timeout")
Duration timeout;

@ConfigProperty(name = "server.port")
Optional<Integer> port;

In this example, timeout is automatically parsed into a Duration, and port is an Optional<Integer>. No manual parsing, no boilerplate.

Need a different timeout for tests? Create an application-test.properties, override server.timeout=1s, and Quarkus will automatically pick it up — no need to navigate Spring’s complex property source precedence rules.

In Quarkus, configuration is explicit, type-safe, and predictable.

Modern REST without extra runtime baggage

Spring Boot uses Spring MVC or WebFlux — both powerful, but heavy in different ways.

Quarkus uses Quarkus REST (based on Jakarta REST) with first-class support for both blocking and non-blocking I/O — without requiring you to choose a different programming model.

Simple REST endpoint in Quarkus:

@Path("/hello")
public class HelloResource {

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        return "Hello from Quarkus!";
    }
}

Want to go reactive later? Just return a Uni<String> instead of a String.

@GET
@Produces(MediaType.TEXT_PLAIN)
public Uni<String> helloAsync() {
    return Uni.createFrom().item("Hello reactive world!");
}

Spring taught you to structure for the JVM. Quarkus teaches you to structure for containers.

Spring Boot apps often assume a monolithic runtime model: auto-scanning, runtime wireups, fat JARs.

Quarkus assumes the opposite: fast startup, small memory footprint, predictable behavior in containers.

Multi-stage Dockerfile for Quarkus app:

FROM quay.io/quarkus/quarkus-micro-image:latest
COPY target/*-runner /work/application
CMD ["./application", "-Dquarkus.http.host=0.0.0.0"]

No tuning required. You get a fast-starting binary or JVM-based app that behaves consistently: even under orchestration.

From Annotations to Actions — Thinking Beyond Decorators

Spring's annotation model works. Until it doesn't. It's common to see classes overloaded with annotations, some of which conflict or depend on runtime context. Quarkus encourages explicitness. You still use annotations, but the behavior is clear and lifecycle-friendly.

@Scheduled(every = "10s")
void doPeriodicTask() {
    System.out.println("Running every 10 seconds");
}

No surprises, no guessing how beans get initialized. It just works — at build time.

Modern Java is more than syntax — it’s about assumptions

You might write Java 17 or 21. But are you writing for the future of Java?

Quarkus encourages:

• Records for DTOs

• CDI scopes that map better to container lifecycles

• Panache for simpler Hibernate models

• Reactive APIs where appropriate, without forcing your entire stack to be reactive

Panache example:

@Entity
public class Person extends PanacheEntity {
    public String name;
    public int age;
}

Query it like this:

Person.find("name", "Alice").firstResult();

Simple. Expressive. And efficient.

Native images are an upgrade — not a requirement

This is where many Spring developers get nervous: "Do I have to use GraalVM to use Quarkus?"

The answer: Absolutely not.

Quarkus runs exceptionally well on the JVM, with fast startup, low memory, and predictable behavior. Most teams adopt Quarkus without touching native builds.

But when you’re ready for cold starts, functions, or edge deployments, Quarkus makes the native path smoother than anything else in Java.

./mvnw package -Dnative

You’ll need GraalVM or Mandrel, but it’s fully integrated. You don’t rewrite your app. You optimize it.

Final thoughts: Spring got you here. Quarkus takes you forward.

Spring gave you the building blocks. But today’s cloud-native Java world is about build-time optimization, container-native behavior, and fast iteration cycles.

Quarkus isn’t just a faster Spring. It’s a different way of thinking about what Java can be.

• Want dev joy?

• Want control over startup time and memory?

• Want to use Java for AI, serverless, or microservices?

Try it now

You don’t have to start with migrating your monolith. Start small:

mvn io.quarkus.platform:quarkus-maven-plugin:3.9.3:create \
  -DprojectGroupId=com.example \
  -DprojectArtifactId=hello-quarkus \
  -DclassName="com.example.HelloResource" \
  -Dpath="/hello"

Then run:

cd hello-quarkus
./mvnw quarkus:dev

Visit http://localhost:8080/hello and see how it feels to develop with the Java platform of the future.

Ready to go further?

Explore the Quarkus getting started guide, check out Dev Services, or try building your first app with Panache and REST.

You're not just learning a new framework — you're learning how modern Java works.