[[webflux-versioning]]
= API Versioning
:page-section-summary-toc: 1

[.small]#xref:web/webmvc-versioning.adoc[See equivalent in the Servlet stack]#

Spring WebFlux supports API versioning. This section provides an overview of the support
and underlying strategies.

Please, see also related content in:

- Use xref:web/webflux/controller/ann-requestmapping.adoc#webflux-ann-requestmapping-version[API Versions]
to map requests to annotated controller methods
- Configure API versioning in xref:web/webflux/config.adoc#webflux-config-api-version[WebFlux Config]



[[webflux-versioning-strategy]]
== ApiVersionStrategy
[.small]#xref:web/webmvc-versioning.adoc#mvc-versioning-strategy[See equivalent in the Servlet stack]#

This strategy holds all application preferences about how to manage versioning.
It delegates to xref:#webflux-versioning-resolver[ApiVersionResolver] to resolve versions
from requests, and to xref:#webflux-versioning-parser[ApiVersionParser] to parse raw version
values into `Comparable<?>`. It also helps to xref:#webflux-versioning-validation[validate]
request versions.

NOTE: `ApiVersionStrategy` helps to map requests to `@RequestMapping` controller methods,
and is initialized by the WebFlux config. Typically, applications do not interact directly with it.




[[webflux-versioning-resolver]]
== ApiVersionResolver
[.small]#xref:web/webmvc-versioning.adoc#mvc-versioning-resolver[See equivalent in the Servlet stack]#

This strategy resolves the API version from a request. The WebFlux config provides built-in
options to resolve from a header, a request parameter, or from the URL path.
You can also use a custom `ApiVersionResolver`.




[[webflux-versioning-parser]]
== ApiVersionParser
[.small]#xref:web/webmvc-versioning.adoc#mvc-versioning-parser[See equivalent in the Servlet stack]#

This strategy helps to parse raw version values into `Comparable<?>`, which helps to
compare, sort, and select versions. By default, the built-in `SemanticApiVersionParser`
parses a version into `major`, `minor`, and `patch` integer values. Minor and patch
values are set to 0 if not present.




[[webflux-versioning-validation]]
== Validation
[.small]#xref:web/webmvc-versioning.adoc#mvc-versioning-validation[See equivalent in the Servlet stack]#

If a request version is not supported, `InvalidApiVersionException` is raised resulting
in a 400 response. By default, the list of supported versions is initialized from declared
versions in annotated controller mappings. You can add to that list, or set it explicitly
to a fixed set of versions (i.e. ignoring declared ones) through the MVC config.

By default, a version is required when API versioning is enabled, but you can turn that
off in which case the highest available version is used. You can also specify a default
version. `MissingApiVersionException` is raised resulting in a 400 response when a
version is required but not present.




[[webflux-versioning-mapping]]
== Request Mapping
[.small]#xref:web/webmvc-versioning.adoc#mvc-versioning-mapping[See equivalent in the Servlet stack]#

`ApiVersionStrategy` supports the mapping of requests to annotated controller methods.
See xref:web/webflux/controller/ann-requestmapping.adoc#webflux-ann-requestmapping-version[API Versions]
for more details.