6.17 API Versioning

Since 1.1.x, Micronaut supports API versioning via a dedicated @Version annotation.

The following example demonstrates how to version an API:

Versioning an API

import io.micronaut.core.version.annotation.Version;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
@Controller("/versioned")
class VersionedController {
    @Version("1") (1)
    @Get("/hello")
    String helloV1() {
        return "helloV1";
    }
    @Version("2") (2)
    @Get("/hello")
    String helloV2() {
        return "helloV2";
    }

Versioning an API

import io.micronaut.core.version.annotation.Version
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
@Controller("/versioned")
class VersionedController {
    @Version("1") (1)
    @Get("/hello")
    String helloV1() {
        "helloV1"
    }
    @Version("2") (2)
    @Get("/hello")
    String helloV2() {
        "helloV2"
    }

Versioning an API

import io.micronaut.core.version.annotation.Version
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
@Controller("/versioned")
internal class VersionedController {
    @Version("1") (1)
    @Get("/hello")
    fun helloV1(): String {
        return "helloV1"
    }
    @Version("2") (2)
    @Get("/hello")
    fun helloV2(): String {
        return "helloV2"
    }

You should then enabling versioning by setting micronaut.router.versioning.enabled to true in application.yml:

Enabling Versioning

micronaut:
    router:
        versioning:
            enabled: true

By default Micronaut has 2 out-of-the-box strategies for resolving the version that are based on an HTTP header named X-API-VERSION or a request parameter named api-version, however this is configurable. A full configuration example can be seen below:

Configuring Versioning

micronaut:
    router:
        versioning:
            enabled: true (1)
            parameter:
                enabled: false (2)
                names: 'v,api-version' (3)
            header:
                enabled: true (4)
                names: (5)
                    - 'X-API-VERSION'
                    - 'Accept-Version'

If this is not enough you can also implement the RequestVersionResolver interface which receives the HttpRequest and can implement any strategy you choose.

Default Version

It is possible to supply a default version through configuration.

Configuring Default Version

micronaut:
    router:
        versioning:
            enabled: true
            default-version: 3 (1)

A route will not be matched if the following conditions are met:

• The default version is configured

• No version is found in the request

• The route defines a version

• The route version does not match the default version

If the incoming request specifies a version then the default version has no effect.

Versioning Client Requests

Micronaut’s Declarative HTTP client also supports automatic versioning of outgoing requests via the @Version annotation.

By default if you annotate a client interface with @Version the value supplied to the annotation will be included using the X-API-VERSION header.

For example:

import io.micronaut.core.version.annotation.Version;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.client.annotation.Client;
import io.reactivex.Single;
@Client("/hello")
@Version("1") (1)
public interface HelloClient {
    @Get("/greeting/{name}")
    String sayHello(String name);
    @Version("2")
    @Get("/greeting/{name}")
    Single<String> sayHelloTwo(String name); (2)
}

import io.micronaut.core.version.annotation.Version
import io.micronaut.http.annotation.Get
import io.micronaut.http.client.annotation.Client
import io.reactivex.Single
@Client("/hello")
@Version("1") (1)
interface HelloClient {
    @Get("/greeting/{name}")
    String sayHello(String name)
    @Version("2")
    @Get("/greeting/{name}")
    Single<String> sayHelloTwo(String name) (2)
}

import io.micronaut.core.version.annotation.Version
import io.micronaut.http.annotation.Get
import io.micronaut.http.client.annotation.Client
import io.reactivex.Single
@Client("/hello")
@Version("1") (1)
interface HelloClient {
    @Get("/greeting/{name}")
    fun sayHello(name : String) : String
    @Version("2")
    @Get("/greeting/{name}")
    fun sayHelloTwo(name : String) : Single<String>  (2)
}

The default behaviour for how the version is sent for each call can be configured with DefaultClientVersioningConfiguration:

🔗

For example to use Accept-Version as the header name:

Configuring Client Versioning

micronaut:
    http:
        client:
            versioning:
                default:
                    headers:
                        - 'Accept-Version'
                        - 'X-API-VERSION'

The default key is used to refer to the default configuration. You can specify client specific configuration by using the value passed to @Client (typically the service ID). For example:

Configuring Versioning

micronaut:
    http:
        client:
            versioning:
                greeting-service:
                    headers:
                        - 'Accept-Version'
                        - 'X-API-VERSION'

The above uses a key called greeting-service which can be used to configure a client annotated with @Client('greeting-service').