In this post Compare Spring WebFlux Vs Spring MVC in depth. Learn their differences in performance, scalability, thread model, and use cases.
π Table of Contents:
- Introduction
- Core Philosophy
- Threading Model
- Programming Style
- Performance and Scalability
- Streaming and Real-Time Support
- Testing Differences
- Use Cases
- When to Choose Which?
- Final Thoughts
π 1. Introduction
Spring Framework offers two major web stacks:
- Spring MVC (imperative, blocking)
- Spring WebFlux (reactive, non-blocking)
Choosing between them depends on application needs, traffic volume, and team expertise. Letβs explore how they differ.
π§ 2. Core Philosophy
| Aspect | Spring MVC | Spring WebFlux |
|---|---|---|
| Style | Imperative (Blocking) | Reactive (Non-blocking) |
| Design | Servlet-based | Reactive Streams-based |
| API Model | @RestController + ResponseEntity | @RestController + Mono/Flux |
𧡠3. Threading Model
Spring MVC:
- Uses Servlet API and a thread-per-request model.
- Requires a pool of threads (e.g., Tomcat with 200 threads).
- Threads block on IO (e.g., DB call), making it inefficient for high-load async tasks.
Spring WebFlux:
- Built on Reactor and Netty (non-blocking).
- Uses event loop model with very few threads.
- Threads do not block while waiting for IO.
π Implication: WebFlux is more scalable in IO-bound systems.
π§βπ» 4. Programming Style
Spring MVC:
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@GetMapping("/hello") public String hello() { return "Hello"; } |
WebFlux:
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@GetMapping("/hello") public Mono<String> hello() { return Mono.just("Hello"); } |
WebFlux requires understanding of Mono and Fluxβreactive types from Project Reactor.
π 5. Performance and Scalability
| Feature | Spring MVC | Spring WebFlux |
|---|---|---|
| Startup | Faster | Slightly Slower |
| Throughput | Limited (due to threads) | High with fewer resources |
| Latency | Can be higher under load | Low even with high concurrency |
π Verdict: WebFlux handles high concurrent traffic more efficiently.
π‘ 6. Streaming and Real-Time Support
Spring WebFlux is superior for real-time streaming, such as:
- Server-Sent Events (SSE)
- WebSockets
- Data streaming pipelines
Spring MVC can simulate these with hacks, but lacks native reactive support.
π§ͺ 7. Testing Differences
| Area | Spring MVC | WebFlux |
|---|---|---|
| Mocking | MockMvc | WebTestClient |
| Assertions | Synchronous assertEquals | StepVerifier, async handlers |
| Time Control | Limited | Virtual time support |
WebFlux tests require deeper knowledge of async testing techniques.
π§ 8. Use Cases
β Use Spring MVC if:
- Your team is familiar with servlet-style coding.
- The app is small to medium with synchronous logic.
- You already use synchronous libraries (JDBC, REST clients).
β Use Spring WebFlux if:
- Your app needs high concurrency and scalability.
- You’re building real-time apps (chat, dashboards, etc.).
- You use reactive DBs (R2DBC, Reactive MongoDB).
π 9. When to Choose Which?
| Criteria | Recommended Stack |
|---|---|
| Low concurrency | Spring MVC |
| High scalability / Reactive DB | Spring WebFlux |
| Legacy integration | Spring MVC |
| Real-time features | Spring WebFlux |
| Short-term delivery | Spring MVC |
π‘ Tip: Avoid WebFlux just for performance unless youβre handling tens of thousands of concurrent requests.
β 10. Final Thoughts
Both Spring MVC and Spring WebFlux are powerful. MVC is tried-and-tested for standard apps, while WebFlux excels in modern, scalable, non-blocking applications.
The key is to align your choice with your team skills, infrastructure needs, and business goals.