8.0.x FIX: Overriding bean definition for bean 'dispatcherServlet' with a different definition

[codeconsole]

What

ControllersAutoConfiguration defines its own dispatcherServlet (a GrailsDispatcherServlet) and dispatcherServletRegistration beans, but it is not ordered before Spring Boot's DispatcherServletAutoConfiguration. As a result Spring Boot registers its own beans first and Grails overrides them on startup:

INFO  o.s.b.f.s.DefaultListableBeanFactory : Overriding bean definition for bean 'dispatcherServlet' with a different definition:
  replacing [... DispatcherServletAutoConfiguration$DispatcherServletConfiguration ...]
  with      [... ControllersAutoConfiguration ...]
INFO  o.s.b.f.s.DefaultListableBeanFactory : Overriding bean definition for bean 'dispatcherServletRegistration' with a different definition:
  replacing [... DispatcherServletAutoConfiguration$DispatcherServletRegistrationConfiguration ...]
  with      [... ControllersAutoConfiguration ...]

This emits two INFO Overriding bean definition messages and depends on spring.main.allow-bean-definition-overriding to win.

Change

Add DispatcherServletAutoConfiguration to the existing @AutoConfiguration(before = …) list:

@AutoConfiguration(
        before = {DispatcherServletAutoConfiguration.class, HttpEncodingAutoConfiguration.class, WebMvcAutoConfiguration.class},
        after = {GrailsDomainClassAutoConfiguration.class}
)

Grails now registers dispatcherServlet / dispatcherServletRegistration first, so Spring Boot's DefaultDispatcherServletCondition and DispatcherServletRegistrationCondition find the existing beans and back off through their own conditions rather than being overridden.

Why it's safe

• Runtime behavior is unchanged — GrailsDispatcherServlet still handles requests in both cases; only the registration mechanism changes (back-off instead of override).
• Converts an override into idiomatic auto-configuration ordering and removes two INFO log lines, reducing reliance on bean-definition overriding.

Verification

• ./gradlew :grails-controllers:compileGroovy — BUILD SUCCESSFUL.
• Mechanism follows Spring Boot's DefaultDispatcherServletCondition (backs off when a dispatcherServlet-named DispatcherServlet bean already exists).

[testlens-app]

✅ All tests passed ✅

🏷️ Commit: c87af0f
▶️ Tests: 43228 executed
⚪️ Checks: 44/44 completed

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