Table of Contents

Micronaut JWT Authentication

Learn how to secure a Micronaut application using JWT (JSON Web Token) Authentication.

Authors: Sergio del Amo

Micronaut Version: 4.6.3

1. Getting Started

The Micronaut framework ships with security capabilities based on Json Web Token (JWT). JWT is an IETF standard which defines a secure way to encapsulate arbitrary data that can be sent over unsecure URLs.

In this guide you will create a Micronaut application written in Kotlin and secure it with JWT.

The following sequence illustrates the authentication flow:

jwt bearer token

2. What you will need

To complete this guide, you will need the following:

3. Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can go right to the completed example.

4. Writing the Application

Create an application using the Micronaut Command Line Interface or with Micronaut Launch.

mn create-app example.micronaut.micronautguide \
    --features=security-jwt,data-jdbc,reactor,validation,graalvm \
    --build=maven \
    --lang=kotlin \
    --test=junit
If you don’t specify the --build argument, Gradle with the Kotlin DSL is used as the build tool.
If you don’t specify the --lang argument, Java is used as the language.
If you don’t specify the --test argument, JUnit is used for Java and Kotlin, and Spock is used for Groovy.

The previous command creates a Micronaut application with the default package example.micronaut in a directory named micronautguide.

If you use Micronaut Launch, select Micronaut Application as application type and add security-jwt, data-jdbc, reactor, validation, and graalvm features.

If you have an existing Micronaut application and want to add the functionality described here, you can view the dependency and configuration changes from the specified features, and apply those changes to your application.

Diff

Setup IntelliJ IDEA to develop Micronaut Applications.

4.1. Configuration

Note the following configuration in the generated application.properties:

src/main/resources/application.properties
(1)
micronaut.security.authentication=bearer
(2)
micronaut.security.token.jwt.signatures.secret.generator.secret="${JWT_GENERATOR_SIGNATURE_SECRET:pleaseChangeThisSecretForANewOne}"'
1 Set authentication to bearer to receive a JSON response from the login endpoint.
2 Change this to your own secret and keep it safe (do not store this in your VCS).

4.2. Authentication Provider

To keep this guide simple, create a naive AuthenticationProvider to simulate user’s authentication.

src/main/kotlin/example/micronaut/AuthenticationProviderUserPassword.kt
package example.micronaut

import io.micronaut.http.HttpRequest
import io.micronaut.security.authentication.AuthenticationFailureReason
import io.micronaut.security.authentication.AuthenticationRequest
import io.micronaut.security.authentication.AuthenticationResponse
import io.micronaut.security.authentication.provider.HttpRequestAuthenticationProvider
import jakarta.inject.Singleton

@Singleton (1)
class AuthenticationProviderUserPassword<B> : HttpRequestAuthenticationProvider<B> { (2)

    override fun authenticate(
        httpRequest: HttpRequest<B>?,
        authenticationRequest: AuthenticationRequest<String, String>
    ): AuthenticationResponse {
        return if (authenticationRequest.identity == "sherlock" && authenticationRequest.secret == "password")
            AuthenticationResponse.success(authenticationRequest.identity) else
            AuthenticationResponse.failure(AuthenticationFailureReason.CREDENTIALS_DO_NOT_MATCH)
    }
}
1 Use jakarta.inject.Singleton to designate a class as a singleton.
2 A Micronaut Authentication Provider implements the interface io.micronaut.security.authentication.provider.HttpRequestAuthenticationProvider.

4.3. Controller

Create HomeController which resolves the base URL /:

src/main/kotlin/example/micronaut/HomeController.kt
package example.micronaut

import io.micronaut.http.MediaType.TEXT_PLAIN
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
import io.micronaut.http.annotation.Produces
import io.micronaut.security.annotation.Secured
import io.micronaut.security.rules.SecurityRule
import java.security.Principal

@Secured(SecurityRule.IS_AUTHENTICATED) (1)
@Controller (2)
class HomeController {

    @Produces(TEXT_PLAIN)
    @Get (3)
    fun index(principal: Principal): String = principal.name (4)
}
1 Annotate with io.micronaut.security.Secured to configure secured access. The isAuthenticated() expression will allow access only to authenticated users.
2 Annotate with io.micronaut.http.annotation.Controller to designate the class as a Micronaut controller.
3 You can specify the HTTP verb that a controller action responds to. To respond to a GET request, use the io.micronaut.http.annotation.Get annotation.
4 If a user is authenticated, the Micronaut framework will bind the user object to an argument of type java.security.Principal (if present).

5. Tests

Create a test to verify a user is able to login and access a secured endpoint.

src/test/kotlin/example/micronaut/JwtAuthenticationTest.kt
package example.micronaut

import com.nimbusds.jwt.JWTParser
import com.nimbusds.jwt.SignedJWT
import io.micronaut.http.HttpRequest
import io.micronaut.http.HttpResponse
import io.micronaut.http.HttpStatus.OK
import io.micronaut.http.HttpStatus.UNAUTHORIZED
import io.micronaut.http.MediaType.TEXT_PLAIN
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.http.client.exceptions.HttpClientResponseException
import io.micronaut.security.authentication.UsernamePasswordCredentials
import io.micronaut.security.token.render.BearerAccessRefreshToken
import io.micronaut.test.extensions.junit5.annotation.MicronautTest
import jakarta.inject.Inject
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertNotNull
import org.junit.jupiter.api.Assertions.assertThrows
import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test

@MicronautTest (1)
class JwtAuthenticationTest(@Client("/") val client: HttpClient) { (2)

    @Test
    fun accessingASecuredUrlWithoutAuthenticatingReturnsUnauthorized() {
        val e = assertThrows(HttpClientResponseException::class.java) {
            client.toBlocking().exchange<Any, Any>(HttpRequest.GET<Any>("/").accept(TEXT_PLAIN)) (3)
        }
        assertEquals(UNAUTHORIZED, e.status) (3)
    }

    @Test
    fun uponSuccessfulAuthenticationAJsonWebTokenIsIssuedToTheUser() {
        val creds = UsernamePasswordCredentials("sherlock", "password")
        val request: HttpRequest<*> = HttpRequest.POST("/login", creds) (4)
        val rsp: HttpResponse<BearerAccessRefreshToken> =
            client.toBlocking().exchange(request, BearerAccessRefreshToken::class.java) (5)
        assertEquals(OK, rsp.status)

        val bearerAccessRefreshToken: BearerAccessRefreshToken = rsp.body()
        assertEquals("sherlock", bearerAccessRefreshToken.username)
        assertNotNull(bearerAccessRefreshToken.accessToken)
        assertTrue(JWTParser.parse(bearerAccessRefreshToken.accessToken) is SignedJWT)

        val accessToken: String = bearerAccessRefreshToken.accessToken
        val requestWithAuthorization = HttpRequest.GET<Any>("/")
            .accept(TEXT_PLAIN)
            .bearerAuth(accessToken) (6)
        val response: HttpResponse<String> = client.toBlocking().exchange(requestWithAuthorization, String::class.java)

        assertEquals(OK, rsp.status)
        assertEquals("sherlock", response.body()) (7)
    }
}
1 Annotate the class with @MicronautTest so the Micronaut framework will initialize the application context and the embedded server. More info.
2 Inject the HttpClient bean and point it to the embedded server.
3 When you include the security dependencies, security is considered enabled and every endpoint is secured by default.
4 To login, do a POST request to /login with your credentials as a JSON payload in the body of the request.
5 The Framework makes it easy to bind JSON responses into Java objects.
6 The Framework supports RFC 6750 Bearer Token specification out-of-the-box. We supply the JWT token in the Authorization HTTP Header.
7 Use .body() to retrieve the parsed payload.

5.1. Use the Micronaut HTTP Client and JWT

To access a secured endpoint, you can also use a Micronaut HTTP Client and supply the JWT token in the Authorization header.

First create a @Client with a method home which accepts an Authorization HTTP Header.

src/test/kotlin/example/micronaut/AppClient.kt
package example.micronaut

import io.micronaut.http.HttpHeaders.AUTHORIZATION
import io.micronaut.http.MediaType.TEXT_PLAIN
import io.micronaut.http.annotation.Body
import io.micronaut.http.annotation.Consumes
import io.micronaut.http.annotation.Get
import io.micronaut.http.annotation.Header
import io.micronaut.http.annotation.Post
import io.micronaut.http.client.annotation.Client
import io.micronaut.security.authentication.UsernamePasswordCredentials
import io.micronaut.security.token.render.BearerAccessRefreshToken

@Client("/")
interface AppClient {

    @Post("/login")
    fun login(@Body credentials: UsernamePasswordCredentials): BearerAccessRefreshToken

    @Consumes(TEXT_PLAIN)
    @Get
    fun home(@Header(AUTHORIZATION) authorization: String): String
}

Create a test which uses the previous @Client

src/test/kotlin/example/micronaut/DeclarativeHttpClientWithJwtTest.kt
package example.micronaut

import com.nimbusds.jwt.JWTParser
import com.nimbusds.jwt.SignedJWT
import io.micronaut.security.authentication.UsernamePasswordCredentials
import io.micronaut.security.token.render.BearerAccessRefreshToken
import io.micronaut.test.extensions.junit5.annotation.MicronautTest
import jakarta.inject.Inject
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertNotNull
import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test

@MicronautTest
class DeclarativeHttpClientWithJwtTest {

    @Inject
    lateinit var appClient: AppClient (1)

    @Test
    fun verifyJwtAuthenticationWorksWithDeclarativeClient() {
        val creds: UsernamePasswordCredentials = UsernamePasswordCredentials("sherlock", "password")
        val loginRsp: BearerAccessRefreshToken = appClient.login(creds) (2)

        assertNotNull(loginRsp)
        assertNotNull(loginRsp.accessToken)
        assertTrue(JWTParser.parse(loginRsp.accessToken) is SignedJWT)

        val msg = appClient.home("Bearer ${loginRsp.accessToken}") (3)
        assertEquals("sherlock", msg)
    }
}
1 Inject AppClient bean from the application context.
2 To login, do a POST request to /login with your credentials as a JSON payload in the body of the request.
3 Supply the JWT to the HTTP Authorization header value to the @Client method.

6. Issuing a Refresh Token

Access tokens expire. You can control the expiration with micronaut.security.token.jwt.generator.access-token.expiration. In addition to the access token, you can configure your login endpoint to also return a refresh token. You can use the refresh token to obtain a new access token.

First, add the following configuration:

src/main/resources/application.properties
(1)
micronaut.security.token.jwt.generator.refresh-token.secret="${JWT_GENERATOR_SIGNATURE_SECRET:pleaseChangeThisSecretForANewOne}"'
1 To generate a refresh token your application must have beans of type: RefreshTokenGenerator, RefreshTokenValidator, and RefreshTokenPersistence. We will deal with the latter in the next section. For the generator and validator, Micronaut Security ships with SignedRefreshTokenGenerator. It creates and verifies a JWS (JSON web signature) encoded object whose payload is a UUID with a hash-based message authentication code (HMAC). You need to provide secret to use SignedRefreshTokenGenerator which implements both RefreshTokenGenerator and RefreshTokenValidator.

Create a test to verify the login endpoint responds both access and refresh token:

src/test/kotlin/example/micronaut/LoginIncludesRefreshTokenTest.kt
package example.micronaut

import com.nimbusds.jwt.JWTParser
import com.nimbusds.jwt.SignedJWT
import io.micronaut.http.HttpRequest
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.security.authentication.UsernamePasswordCredentials
import io.micronaut.security.token.render.BearerAccessRefreshToken
import io.micronaut.test.extensions.junit5.annotation.MicronautTest
import jakarta.inject.Inject
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertNotNull
import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test

@MicronautTest
class LoginIncludesRefreshTokenTest(@Client("/") val client: HttpClient) {

    @Test
    fun uponSuccessfulAuthenticationUserGetsAccessTokenAndRefreshToken() {
        val creds = UsernamePasswordCredentials("sherlock", "password")
        val request: HttpRequest<*> = HttpRequest.POST("/login", creds)
        val rsp: BearerAccessRefreshToken = client.toBlocking().retrieve(request, BearerAccessRefreshToken::class.java)

        assertEquals("sherlock", rsp.username)
        assertNotNull(rsp.accessToken)
        assertNotNull(rsp.refreshToken) (1)

        assertTrue(JWTParser.parse(rsp.accessToken) is SignedJWT)
    }
}
1 A refresh token is returned.

6.1. Save Refresh Token

We may want to save a refresh token issued by the application, for example, to revoke a user’s refresh tokens, so that a particular user cannot obtain a new access token, and thus access the application’s endpoints.

Persist the refresh tokens with help of Micronaut Data.

Micronaut Data is a database access toolkit that uses Ahead of Time (AoT) compilation to pre-compute queries for repository interfaces that are then executed by a thin, lightweight runtime layer.

In particular, use Micronaut JDBC

Micronaut Data JDBC is an implementation that pre-computes native SQL queries (given a particular database dialect) and provides a repository implementation that is a simple data mapper between a JDBC ResultSet and an object.

The data-jdbc feature adds the following dependencies:

pom.xml
<!-- Add the following to your annotationProcessorPaths element -->
<annotationProcessorPath> (1)
    <groupId>io.micronaut</groupId>
    <artifactId>micronaut-data-processor</artifactId>
</annotationProcessorPath>
<dependency> (2)
    <groupId>io.micronaut.data</groupId>
    <artifactId>micronaut-data-jdbc</artifactId>
    <scope>compile</scope>
</dependency>
<dependency> (3)
    <groupId>io.micronaut.sql</groupId>
    <artifactId>micronaut-jdbc-hikari</artifactId>
    <scope>compile</scope>
</dependency>
<dependency> (4)
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>
1 Micronaut data is a build time tool. You need to add the build time annotation processor
2 Add the Micronaut Data JDBC dependency
3 Add a Hikari connection pool
4 Add a JDBC driver. Add H2 driver

Create an entity to save the issued Refresh Tokens.

src/main/kotlin/example/micronaut/RefreshTokenEntity.kt
package example.micronaut
*/

import io.micronaut.data.annotation.DateCreated
import io.micronaut.data.annotation.GeneratedValue
import io.micronaut.data.annotation.Id
import io.micronaut.data.annotation.MappedEntity
import java.time.Instant
import jakarta.validation.constraints.NotBlank

@MappedEntity (1)
data class RefreshTokenEntity(

    @field:Id (2)
    @GeneratedValue (3)
    var id: Long? = null,

    @NotBlank
    var username: String,

    @NotBlank
    var refreshToken: String,

    var revoked: Boolean,

    @DateCreated (4)
    var dateCreated: Instant? = null
)


import io.micronaut.data.annotation.DateCreated
import io.micronaut.data.annotation.GeneratedValue
import io.micronaut.data.annotation.Id
import io.micronaut.data.annotation.MappedEntity
import java.time.Instant
import jakarta.validation.constraints.NotBlank

@MappedEntity (1)
data class RefreshTokenEntity(

    @field:Id (2)
    @GeneratedValue (3)
    var id: Long? = null,

    @NotBlank
    var username: String,

    @NotBlank
    var refreshToken: String,

    var revoked: Boolean,

    @DateCreated (4)
    var dateCreated: Instant? = null

)
1 Specifies the entity is mapped to the database
2 Specifies the ID of an entity
3 Specifies that the property value is generated by the database and not included in inserts
4 Allows assigning a data created value (such as a java.time.Instant) prior to an insert

Create a CrudRepository to include methods to peform Create, Read, Updated and Delete operations with the RefreshTokenEntity.

src/main/kotlin/example/micronaut/RefreshTokenRepository.kt
package example.micronaut

import io.micronaut.data.jdbc.annotation.JdbcRepository
import io.micronaut.data.model.query.builder.sql.Dialect.H2
import io.micronaut.data.repository.CrudRepository
import java.util.Optional
import jakarta.transaction.Transactional
import jakarta.validation.constraints.NotBlank

@JdbcRepository(dialect = H2) (1)
interface RefreshTokenRepository : CrudRepository<RefreshTokenEntity, Long> { (2)

    @Transactional
    fun save(@NotBlank username: String,
             @NotBlank refreshToken: String,
             revoked: Boolean): RefreshTokenEntity (3)

    fun findByRefreshToken(@NotBlank refreshToken: String): Optional<RefreshTokenEntity> (4)

    fun updateByUsername(@NotBlank username: String,
                         revoked: Boolean): Long (5)
}
1 The interface is annotated with @JdbcRepository and specifies a dialect of H2 used to generate queries
2 The CrudRepository interface has two generic arguments; the entity type (in this case RefreshTokenEntity) and the ID type (in this case Long)
3 When a new refresh token is issued we will use this method to persist it
4 Before issuing a new access token, we will use this method to check if the supplied refresh token exists
5 We can revoke the refresh tokens of a particular user with this method

6.2. Refresh Controller

Enable the Refresh Controller via configuration and provide an implementation of RefreshTokenPersistence.

To enable the refresh controller, create a bean of type RefreshTokenPersistence which leverages the Micronaut Data repository we coded in the previous section:

src/main/kotlin/example/micronaut/CustomRefreshTokenPersistence.kt
package example.micronaut

import io.micronaut.security.authentication.Authentication
import io.micronaut.security.errors.IssuingAnAccessTokenErrorCode.INVALID_GRANT
import io.micronaut.security.errors.OauthErrorResponseException
import io.micronaut.security.token.event.RefreshTokenGeneratedEvent
import io.micronaut.security.token.refresh.RefreshTokenPersistence
import jakarta.inject.Singleton
import org.reactivestreams.Publisher
import reactor.core.publisher.Flux
import reactor.core.publisher.FluxSink

@Singleton (1)
class CustomRefreshTokenPersistence(private val refreshTokenRepository: RefreshTokenRepository) (2)
    : RefreshTokenPersistence {

    override fun persistToken(event: RefreshTokenGeneratedEvent?) { (3)
        if (event?.refreshToken != null && event.authentication?.name != null) {
            val payload = event.refreshToken
            refreshTokenRepository.save(event.authentication.name, payload, false) (4)
        }
    }

    override fun getAuthentication(refreshToken: String): Publisher<Authentication> {
        return Flux.create({ emitter: FluxSink<Authentication> ->
            val tokenOpt = refreshTokenRepository.findByRefreshToken(refreshToken)
            if (tokenOpt.isPresent) {
                val (_, username, _, revoked) = tokenOpt.get()
                if (revoked) {
                    emitter.error(OauthErrorResponseException(INVALID_GRANT, "refresh token revoked", null)) (5)
                } else {
                    emitter.next(Authentication.build(username)) (6)
                    emitter.complete()
                }
            } else {
                emitter.error(OauthErrorResponseException(INVALID_GRANT, "refresh token not found", null)) (7)
            }
        }, FluxSink.OverflowStrategy.ERROR)
    }
}
1 Use jakarta.inject.Singleton to designate a class as a singleton.
2 Constructor injection of RefreshTokenRepository.
3 When a new refresh token is issued, the application emits an event of type RefreshTokenGeneratedEvent. We listen for it and save the token in the database.
4 The event contains both the refresh token and the user details associated to the token.
5 Throw an exception if the token is revoked.
6 Return the user details associated to the refresh token, e.g. username, roles, attributes, etc.
7 Throw an exception if the token is not found.

6.3. Test Refresh Token

6.3.1. Test Refresh Token Validation

Refresh tokens issued by SignedRefreshTokenGenerator, the default implementation of RefreshTokenGenerator, are signed.

SignedRefreshTokenGenerator implements both RefreshTokenGenerator and RefreshTokenValidator.

The bean of type RefreshTokenValidator is used by the Refresh Controller to ensure the refresh token supplied is valid.

Create a test for this:

src/test/kotlin/example/micronaut/UnsignedRefreshTokenTest.kt
package example.micronaut

import io.micronaut.core.type.Argument
import io.micronaut.http.HttpRequest
import io.micronaut.http.HttpStatus.BAD_REQUEST
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.http.client.exceptions.HttpClientResponseException
import io.micronaut.security.endpoints.TokenRefreshRequest
import io.micronaut.security.token.render.BearerAccessRefreshToken
import io.micronaut.test.extensions.junit5.annotation.MicronautTest
import jakarta.inject.Inject
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertThrows
import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test
import java.util.Optional

@MicronautTest
internal class UnsignedRefreshTokenTest(@Client("/") val client: HttpClient) {

    @Test
    fun accessingSecuredURLWithoutAuthenticatingReturnsUnauthorized() {
        val unsignedRefreshedToken = "foo" (1)
        val bodyArgument = Argument.of(BearerAccessRefreshToken::class.java)
        val errorArgument = Argument.of(Map::class.java)
        val e = assertThrows(HttpClientResponseException::class.java) {
            client.toBlocking().exchange(
                HttpRequest.POST("/oauth/access_token", TokenRefreshRequest(TokenRefreshRequest.GRANT_TYPE_REFRESH_TOKEN, unsignedRefreshedToken)),
                bodyArgument,
                errorArgument)
        }
        assertEquals(BAD_REQUEST, e.status)

        val mapOptional: Optional<Map<*, *>> = e.response.getBody(Map::class.java)
        assertTrue(mapOptional.isPresent)

        val m = mapOptional.get()
        assertEquals("invalid_grant", m["error"])
        assertEquals("Refresh token is invalid", m["error_description"])
    }
}
1 Use an unsigned token

6.3.2. Test Refresh Token Not Found

Create a test to verify that sending a valid refresh token that was not persisted returns HTTP Status 400.

src/test/kotlin/example/micronaut/RefreshTokenNotFoundTest.kt
package example.micronaut

import io.micronaut.core.type.Argument
import io.micronaut.http.HttpRequest
import io.micronaut.http.HttpStatus.BAD_REQUEST
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.http.client.exceptions.HttpClientResponseException
import io.micronaut.security.authentication.Authentication
import io.micronaut.security.token.generator.RefreshTokenGenerator
import io.micronaut.security.endpoints.TokenRefreshRequest
import io.micronaut.security.token.render.BearerAccessRefreshToken
import io.micronaut.test.extensions.junit5.annotation.MicronautTest
import jakarta.inject.Inject
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertThrows
import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test
import java.util.Optional

@MicronautTest
class RefreshTokenNotFoundTest(@Client("/") val client: HttpClient) {

    @Inject
    lateinit var refreshTokenGenerator: RefreshTokenGenerator

    @Test
    fun accessingSecuredURLWithoutAuthenticatingReturnsUnauthorized() {

        val user = Authentication.build("sherlock")
        val refreshToken = refreshTokenGenerator.createKey(user)
        val refreshTokenOptional = refreshTokenGenerator.generate(user, refreshToken)
        assertTrue(refreshTokenOptional.isPresent)

        val signedRefreshToken = refreshTokenOptional.get() (1)
        val bodyArgument = Argument.of(BearerAccessRefreshToken::class.java)
        val errorArgument = Argument.of(MutableMap::class.java)
        val req: HttpRequest<*> = HttpRequest.POST("/oauth/access_token", TokenRefreshRequest(TokenRefreshRequest.GRANT_TYPE_REFRESH_TOKEN, signedRefreshToken))
        val e = assertThrows(HttpClientResponseException::class.java) {
            client.toBlocking().exchange(req, bodyArgument, errorArgument)
        }
        assertEquals(BAD_REQUEST, e.status)

        val mapOptional: Optional<Map<*, *>> = e.response.getBody(Map::class.java)
        assertTrue(mapOptional.isPresent)

        val m = mapOptional.get()
        assertEquals("invalid_grant", m["error"])
        assertEquals("refresh token not found", m["error_description"])
    }
}
1 Supply a signed token which was never saved.

6.3.3. Test Refresh Token Revocation

Generate a valid refresh token, save it but flag it as revoked. Expect a 400.

src/test/kotlin/example/micronaut/RefreshTokenRevokedTest.kt
package example.micronaut

import io.micronaut.context.ApplicationContext
import io.micronaut.core.type.Argument
import io.micronaut.http.HttpRequest
import io.micronaut.http.HttpStatus.BAD_REQUEST
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.exceptions.HttpClientResponseException
import io.micronaut.runtime.server.EmbeddedServer
import io.micronaut.security.authentication.Authentication
import io.micronaut.security.token.generator.RefreshTokenGenerator
import io.micronaut.security.endpoints.TokenRefreshRequest
import io.micronaut.security.token.render.BearerAccessRefreshToken
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertThrows
import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test
import java.util.Optional

internal class RefreshTokenRevokedTest {

    val embeddedServer = ApplicationContext.run(EmbeddedServer::class.java, emptyMap())
    val client = embeddedServer.applicationContext.createBean(HttpClient::class.java, embeddedServer.url)
    val refreshTokenGenerator = embeddedServer.applicationContext.getBean(RefreshTokenGenerator::class.java)
    val refreshTokenRepository = embeddedServer.applicationContext.getBean(RefreshTokenRepository::class.java)

    @Test
    fun accessingSecuredURLWithoutAuthenticatingReturnsUnauthorized() {
        val user = Authentication.build("sherlock")
        val refreshToken = refreshTokenGenerator.createKey(user)
        val refreshTokenOptional = refreshTokenGenerator.generate(user, refreshToken)
        assertTrue(refreshTokenOptional.isPresent)

        val oldTokenCount = refreshTokenRepository.count()
        val signedRefreshToken = refreshTokenOptional.get()
        refreshTokenRepository.save(user.name, refreshToken, true) (1)
        assertEquals(oldTokenCount + 1, refreshTokenRepository.count())

        val bodyArgument = Argument.of(BearerAccessRefreshToken::class.java)
        val errorArgument = Argument.of(Map::class.java)
        val e = assertThrows(HttpClientResponseException::class.java) {
            client.toBlocking().exchange(
                HttpRequest.POST("/oauth/access_token", TokenRefreshRequest(TokenRefreshRequest.GRANT_TYPE_REFRESH_TOKEN, signedRefreshToken)),
                bodyArgument,
                errorArgument)
        }
        assertEquals(BAD_REQUEST, e.status)

        val mapOptional: Optional<Map<*, *>> = e.response.getBody(Map::class.java)
        assertTrue(mapOptional.isPresent)

        val m = mapOptional.get()
        assertEquals("invalid_grant", m["error"])
        assertEquals("refresh token revoked", m["error_description"])

        refreshTokenRepository.deleteAll()
    }
}
1 Save the token but flag it as revoked

6.3.4. Test Access Token Refresh

Login, obtain both access token and refresh token, with the refresh token obtain a different access token:

src/test/kotlin/example/micronaut/OauthAccessTokenTest.kt
package example.micronaut

import io.micronaut.http.HttpRequest
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.security.authentication.UsernamePasswordCredentials
import io.micronaut.security.endpoints.TokenRefreshRequest
import io.micronaut.security.token.render.AccessRefreshToken
import io.micronaut.security.token.render.BearerAccessRefreshToken
import io.micronaut.test.extensions.junit5.annotation.MicronautTest
import jakarta.inject.Inject
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertNotEquals
import org.junit.jupiter.api.Assertions.assertNotNull
import org.junit.jupiter.api.Test

@MicronautTest(rollback = false)
internal class OauthAccessTokenTest(@Client("/") val client: HttpClient) {

    @Inject
    lateinit var refreshTokenRepository: RefreshTokenRepository

    @Test
    fun verifyJWTAccessTokenRefreshWorks() {
        val username = "sherlock"

        val creds = UsernamePasswordCredentials(username, "password")
        val request: HttpRequest<*> = HttpRequest.POST("/login", creds)

        val oldTokenCount = refreshTokenRepository.count()
        val rsp: BearerAccessRefreshToken = client.toBlocking().retrieve(request, BearerAccessRefreshToken::class.java)
        Thread.sleep(3000)
        assertEquals(oldTokenCount + 1, refreshTokenRepository.count())

        assertNotNull(rsp.accessToken)
        assertNotNull(rsp.refreshToken)

        Thread.sleep(1000) // sleep for one second to give time for the issued at `iat` Claim to change
        val refreshResponse = client.toBlocking().retrieve(HttpRequest.POST("/oauth/access_token",
                TokenRefreshRequest(TokenRefreshRequest.GRANT_TYPE_REFRESH_TOKEN, rsp.refreshToken)), AccessRefreshToken::class.java) (1)

        assertNotNull(refreshResponse.accessToken)
        assertNotEquals(rsp.accessToken, refreshResponse.accessToken) (2)

        refreshTokenRepository.deleteAll()
    }
}
1 Make a POST request to /oauth/access_token with the refresh token in the JSON payload to get a new access token
2 A different access token is retrieved.

7. Testing the Application

To run the tests:

./mvnw test

8. Running the Application

To run the application, use the ./mvnw mn:run command, which starts the application on port 8080.

Send a request to the login endpoint:

curl -X "POST" "http://localhost:8080/login" -H 'Content-Type: application/json' -d $'{"username": "sherlock","password": "password"}'
{"username":"sherlock","access_token":"eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJzaGVybG9jayIsIm5iZiI6MTYxNDc2NDEzNywicm9sZXMiOltdLCJpc3MiOiJjb21wbGV0ZSIsImV4cCI6MTYxNDc2NzczNywiaWF0IjoxNjE0NzY0MTM3fQ.cn8bOjlccFqeUQA7x7MnfacMNPjSVAtWP65z1c8eaJc","refresh_token":"eyJhbGciOiJIUzI1NiJ9.NDI1ZjAxZTktYTRmYS00MmU5LTllYjctOWU2ZTNhNTI5YmQ1.RUc2iCfZdPQdwg2U0Nw_LLzZQIIDp5_Is2UWeHVZT7E","token_type":"Bearer","expires_in":3600}

9. Generate a Micronaut Application Native Executable with GraalVM

We will use GraalVM, the polyglot embeddable virtual machine, to generate a native executable of our Micronaut application.

Compiling native executables ahead of time with GraalVM improves startup time and reduces the memory footprint of JVM-based applications.

Only Java and Kotlin projects support using GraalVM’s native-image tool. Groovy relies heavily on reflection, which is only partially supported by GraalVM.

9.1. GraalVM installation

The easiest way to install GraalVM on Linux or Mac is to use SDKMan.io.

Java 21
sdk install java 21.0.5-graal
Java 21
sdk use java 21.0.5-graal

For installation on Windows, or for manual installation on Linux or Mac, see the GraalVM Getting Started documentation.

The previous command installs Oracle GraalVM, which is free to use in production and free to redistribute, at no cost, under the GraalVM Free Terms and Conditions.

Alternatively, you can use the GraalVM Community Edition:

Java 21
sdk install java 21.0.2-graalce
Java 21
sdk use java 21.0.2-graalce

9.2. Native executable generation

To generate a native executable using Maven, run:

./mvnw package -Dpackaging=native-image

The native executable is created in the target directory and can be run with target/micronautguide.

Send the same curl request as before to test that the native executable application works.

10. Next steps

Learn more about JWT Authentication in the official documentation.

11. Help with the Micronaut Framework

The Micronaut Foundation sponsored the creation of this Guide. A variety of consulting and support services are available.

12. License

All guides are released with an Apache license 2.0 license for the code and a Creative Commons Attribution 4.0 license for the writing and media (images…​).