Edit code, see changes live. Reclazz hot-swaps Java classes the moment you build. Spring beans refresh, MVC mappings re-scan, caches evict — all in ~50ms. No restart needed.
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Reclazz understands Spring internals. When a class reloads, beans refresh, mappings re-scan, caches evict, and schedulers re-register — automatically.
Automatically destroys and recreates singleton beans after class reload. Your changes take effect immediately without losing application state.
Re-registers @RequestMapping methods when controllers change structurally. New endpoints are available instantly.
Evicts Spring caches for classes with @Cacheable, @CacheEvict, or @CachePut. No stale data after reload.
Cancels and re-registers @Scheduled tasks. Changed cron expressions and fixed-rate schedules apply immediately.
Add or remove methods and fields on the fly with JetBrains Runtime or DCEVM. Go beyond method body changes.
Clears AOP proxy caches for @Aspect classes. Re-registers @EventListener methods. Refreshes @Async processing.
Refreshes Repository beans. Detects @EnableWebSecurity and SecurityConfigurer changes. Full Spring ecosystem support.
Redefines classes in the running JVM via the Instrumentation API. Method body changes apply in ~50ms. Zero downtime.
No telemetry, no analytics, no license server, no outbound requests. Everything runs on your machine. Your code never leaves your environment.
Spring Boot DevTools restarts your entire context. JRebel costs $550+/year. Reclazz is free, open-source, and performs true in-place hot-swap.
| Feature | Reclazz | Spring Boot DevTools | JRebel |
|---|---|---|---|
| Price | Free & open source | Free | $550+/year |
| Reload type | In-place hot-swap | Full context restart | In-place hot-swap |
| Application state | Preserved | Lost on restart | Preserved |
| Reload speed | ~50ms | Seconds | ~50ms |
| Method body changes | ✓ | ✓ (restart) | ✓ |
| Add/remove methods & fields | ✓ (with JBR) | ✓ (restart) | ✓ |
| Spring bean refresh | ✓ | ✓ (restart) | ✓ |
| MVC mapping re-scan | ✓ | ✓ (restart) | ✓ |
| Cache eviction | ✓ | ✓ (restart) | Partial |
| @Scheduled re-register | ✓ | ✓ (restart) | ✗ |
| @EventListener refresh | ✓ | ✓ (restart) | ✗ |
| AOP proxy refresh | ✓ | ✓ (restart) | Partial |
| SAP Commerce support | Purpose-built | ✗ | Generic |
| Open source | ✓ Apache 2.0 | ✓ | ✗ |
Reclazz auto-detects your JDK and configures the right flags. Structural changes work everywhere; JetBrains Runtime additionally makes new members visible to reflection.
--add-opens flags-XX:+AllowEnhancedClassRedefinitionA lightweight Java agent runs inside your application JVM. It watches compiled classes and orchestrates Spring-aware reloading.
These are fundamental JVM and framework limitations that no tool can fully overcome.
Changing superclass or interfaces is a JVM limitation. No tool can work around this — requires a restart.
Adding and removing methods or fields works on any JDK 17+. On a standard JDK the new members live on a hidden companion class, so code that calls them directly sees them, but reflection on the original class and caches built at startup (Hybris ModelService, Jackson) do not until a restart. JetBrains Runtime or DCEVM removes that caveat.
Configuration file changes (application.properties, application.yml, XML bean definitions) are loaded at startup and require a restart.
Adding entirely new @Component classes requires a restart — Spring's component scanning runs at startup. Modifying existing beans works out of the box.
Add the -javaagent flag to your JVM arguments, or install the IntelliJ plugin for automatic injection.
-javaagent:/path/to/reclazz-agent.jar
Start your Spring Boot application normally. Reclazz auto-detects your project layout and begins watching.
mvn spring-boot:run
Change your code, then compile. Reclazz hot-swaps the changes automatically. No restart needed.
mvn compile — or — gradle classes
target/classes (Maven) or build/classes/java/main (Gradle) from the classpath. Just run mvn compile or gradle classes and Reclazz hot-swaps the changes automatically.Spring Boot DevTools restarts take seconds and lose your state. Reclazz reloads in ~50ms and preserves everything. Free and open source.