Migrating from Spring Boot to Quarkus: A Practical Guide

Spring Boot has long been the go-to framework for building enterprise-grade Java applications. But as cloud-native development becomes the norm, developers are increasingly looking toward lightweight, fast-startup alternatives like Quarkus. This guide provides a hands-on approach to migrating from Spring Boot to Quarkus, highlighting key differences, migration strategies, and real-world tips.

Spring Boot has long been a favorite for building Java microservices, but Quarkus is emerging as a compelling alternative with faster startup times, lower memory usage, and seamless integration with GraalVM. This guide provides a step-by-step roadmap for migrating your Spring Boot application to Quarkus.

Why Consider Migrating?

Faster Startup: Ideal for serverless and container-based environments.
Lower Memory Footprint: Great for cloud-native applications.
GraalVM Native Image Support: Enables near-instantaneous execution.

Step 1: Evaluate Your Dependencies

Quarkus supports many Spring APIs, but not all. Use the quarkus-spring-api extensions to see what can be reused. Evaluate third-party dependencies for native compatibility.

Step 2: Set Up a New Quarkus Project

You can scaffold a new project using the Quarkus CLI or web generator.

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

Step 3: Migrate Configuration

Spring's application.properties maps easily to Quarkus, though some keys differ. For example:

# Spring Boot
server.port=8080

# Quarkus
quarkus.http.port=8080

Step 4: Convert Spring Annotations

@RestController ➝ @Path + @GET, @POST (JAX-RS)
@Service ➝ @ApplicationScoped
@Autowired ➝ @Inject

Step 5: Replace Spring Features with Quarkus Equivalents

Spring Data ➝ Panache or Hibernate ORM with REST Data
Spring Security ➝ Quarkus Security
Spring Scheduler ➝ @Scheduled from Quarkus Scheduler

Step 6: Build a Native Image

Quarkus makes native compilation simple:

./mvnw package -Pnative

This creates a standalone executable with fast cold-start performance.

Challenges to Watch Out For

Limited support for complex Spring Boot libraries
Dependency injection differences (CDI vs Spring DI)
Quarkus extensions may not cover every Spring use case

Step-by-Step Migration Strategy

Analyze Your Spring Boot App: List dependencies and features like Spring Data, Web, Security, etc.
Setup a New Quarkus Project: Use mvn io.quarkus:quarkus-maven-plugin or code.quarkus.io
Map Spring Features: Replace Spring-specific libraries with Quarkus extensions
Adjust Configuration: Convert application.properties or YAML settings to Quarkus equivalents
Rewrite Annotations: Replace Spring annotations (e.g., @RestController, @Service)
Database Layer: Migrate from Spring Data to Panache or Hibernate with JPA
Testing and Validation: Use @QuarkusTest and native testing

Common Pitfalls

Spring-specific magic (auto-wiring, bean scanning) doesn’t always translate directly
Third-party library compatibility
Native builds may require additional configuration (especially reflection)

Conclusion

While Spring Boot remains a powerful choice, Quarkus offers compelling advantages for modern cloud-native applications. With careful planning and stepwise migration, you can take advantage of Quarkus' speed, memory efficiency, and excellent container/Kubernetes support. Happy migrating!