Sunsetting legacy config classes

_posts/2025-07-03-legacy-config-classes-sunsetting.adoc

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+---
+layout: post
+title: 'Sunsetting legacy config classes'
+date: 2025-07-03
+tags: release
+synopsis: 'After having migrated the whole Quarkus code base and Quarkiverse extensions to @ConfigMapping interfaces in Quarkus 3.19, we announce the sunsetting of legacy config classes.'
+author: gsmet
+---
+
+After having migrated the whole Quarkus code base and Quarkiverse extensions to @ConfigMapping interfaces in Quarkus 3.19,
+we announce the sunsetting of legacy config classes.
+
+== Some history
+
+In 2022, we introduced in Quarkus a new configuration infrastructure for extensions based on interfaces annotated with `@ConfigMapping`.
+They were a replacement for the legacy config classes that were used in Quarkus extensions,
+which came with several issues and were specific to extensions (you couldn't use them in applications).
+
+The new `@ConfigMapping` infrastructure unified extension and application configuration on the same infrastructure.
+
+In Quarkus 3.19k, released late February this year, we moved all the core extensions to this new infrastructure (except for some classes that were kept for compatibility purposes)
+and deprecated the legacy config classes support, together with dropping close to all the existing config classes: we kept a few for compatibility reasons.
+
+The extension annotation processor was also modified to require a specific option `-AlegacyConfigRoot=true`.
+
+The plan has always been to sunset the legacy config classes so that we could remove all the machinery related to it,
+and offer a single unified configuration mechanism.
+
+== Current state
+
+The current state of the public Quarkus ecosystem is the following:
+
+- All the Core extensions are using the new ``@ConfigMapping``-based infrastructure.
+- All the Quarkiverse extensions have been updated to use the new ``@ConfigMapping``-based infrastructure (except for `quarkus-logging-json` but we have a https://github.com/quarkiverse/quarkus-logging-json/pull/345[pull request ready]).
+- Some other extensions participating to the Ecosystem CI have also been updated such as https://persistence.blazebit.com/[Blaze-Persistence].
+
+We know some of you also develop custom extensions so we highly recommend moving your custom extensions to `@ConfigMapping` as soon as possible, if not already done.
+
+You can find more information about it in https://quarkus.io/guides/writing-extensions#configuration[our documentation] and a ton of examples in the https://github.com/search?q=repo%3Aquarkusio%2Fquarkus%20%40ConfigMapping&type=code[Quarkus Core repository] or the https://github.com/search?q=org%3Aquarkiverse+%40ConfigMapping&type=code[Quarkiverse extensions].
+
+If you have any questions while migrating, please ask them in https://github.com/quarkusio/quarkus/discussions/categories/q-a[GitHub Discussions], we will be happy to help.
+
+== Coming in 3.25
+
+In 3.25, we will throw an error when the extension annotation processor is used with `-AlegacyConfigRoot=true`.
+
+**It won't be possible to build an extension containing legacy config classes with Quarkus 3.25 anymore.**
+
+== Coming in 3.26
+
+In 3.26, we will remove all support for legacy config classes, meaning they won't work anymore.
+**If one of the extensions of your application is using any legacy config class, your application won't build.**
+
+Note that since 3.19.4, you get a warning if any of the extensions in your application is using legacy config classes.
+
+We will also drop all the compatibility classes we kept until then:
+
+- `GlobalDevServicesConfig`: use `DevServicesConfig` instead
+- `HttpConfiguration`: use `VertxHttpConfig` instead
+- `HttpBuildTimeConfig`: use `VertxHttpBuildTimeConfig` instead
+
+== Feedback and questions
+
+If you have any feedback or questions regarding this change, please either use https://github.com/quarkusio/quarkus/discussions/categories/q-a[GitHub Discussions] or the https://groups.google.com/g/quarkus-dev[quarkus-dev Google groups].
+
+== Come Join Us
+
+We value your feedback a lot so please report bugs, ask for improvements... Let's build something great together!
+
+If you are a Quarkus user or just curious, don't be shy and join our welcoming community:
+
+ * provide feedback on https://github.com/quarkusio/quarkus/issues[GitHub];
+ * craft some code and https://github.com/quarkusio/quarkus/pulls[push a PR];
+ * discuss with us on https://quarkusio.zulipchat.com/[Zulip] and on the https://groups.google.com/d/forum/quarkus-dev[mailing list];
+ * ask your questions on https://stackoverflow.com/questions/tagged/quarkus[Stack Overflow].