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 Java and secure it with JWT.

The following sequence illustrates the authentication flow:

2. What you will need

To complete this guide, you will need the following:

Some time on your hands
A decent text editor or IDE (e.g. IntelliJ IDEA)
JDK 17 or greater installed with JAVA_HOME configured appropriately

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.

Download and unzip the source

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=java \
    --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/java/example/micronaut/AuthenticationProviderUserPassword.java

package example.micronaut;

import io.micronaut.core.annotation.NonNull;
import io.micronaut.core.annotation.Nullable;
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> implements HttpRequestAuthenticationProvider<B> { (2)

    @Override
    public AuthenticationResponse authenticate(
            @Nullable HttpRequest<B> httpRequest,
            @NonNull AuthenticationRequest<String, String> authenticationRequest
    ) {
        return authenticationRequest.getIdentity().equals("sherlock") && authenticationRequest.getSecret().equals("password")
                ? AuthenticationResponse.success(authenticationRequest.getIdentity())
                : 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/java/example/micronaut/HomeController.java

package example.micronaut;

import io.micronaut.http.MediaType;
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)
public class HomeController {

    @Produces(MediaType.TEXT_PLAIN)
    @Get (3)
    public String index(Principal principal) {  (4)
        return principal.getName();
    }
}

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/java/example/micronaut/JwtAuthenticationTest.java

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.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.Test;

import java.text.ParseException;

import static io.micronaut.http.HttpStatus.OK;
import static io.micronaut.http.HttpStatus.UNAUTHORIZED;
import static io.micronaut.http.MediaType.TEXT_PLAIN;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

@MicronautTest (1)
class JwtAuthenticationTest {

    @Inject
    @Client("/")
    HttpClient client; (2)

    @Test
    void accessingASecuredUrlWithoutAuthenticatingReturnsUnauthorized() {
        HttpClientResponseException e = assertThrows(HttpClientResponseException.class, () -> {
            client.toBlocking().exchange(HttpRequest.GET("/").accept(TEXT_PLAIN)); (3)
        });

        assertEquals(UNAUTHORIZED, e.getStatus()); (3)
    }

    @Test
    void uponSuccessfulAuthenticationAJsonWebTokenIsIssuedToTheUser() throws ParseException {
        UsernamePasswordCredentials creds = new UsernamePasswordCredentials("sherlock", "password");
        HttpRequest<?> request = HttpRequest.POST("/login", creds); (4)
        HttpResponse<BearerAccessRefreshToken> rsp = client.toBlocking().exchange(request, BearerAccessRefreshToken.class); (5)
        assertEquals(OK, rsp.getStatus());

        BearerAccessRefreshToken bearerAccessRefreshToken = rsp.body();
        assertEquals("sherlock", bearerAccessRefreshToken.getUsername());
        assertNotNull(bearerAccessRefreshToken.getAccessToken());
        assertTrue(JWTParser.parse(bearerAccessRefreshToken.getAccessToken()) instanceof SignedJWT);

        String accessToken = bearerAccessRefreshToken.getAccessToken();
        HttpRequest<?> requestWithAuthorization = HttpRequest.GET("/")
                .accept(TEXT_PLAIN)
                .bearerAuth(accessToken); (6)
        HttpResponse<String> response = client.toBlocking().exchange(requestWithAuthorization, String.class);

        assertEquals(OK, rsp.getStatus());
        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/java/example/micronaut/AppClient.java

package example.micronaut;

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;

import static io.micronaut.http.HttpHeaders.AUTHORIZATION;
import static io.micronaut.http.MediaType.TEXT_PLAIN;

@Client("/")
public interface AppClient {

    @Post("/login")
    BearerAccessRefreshToken login(@Body UsernamePasswordCredentials credentials);

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

Create a test which uses the previous @Client

src/test/java/example/micronaut/DeclarativeHttpClientWithJwtTest.java

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.Test;

import java.text.ParseException;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertTrue;

@MicronautTest
class DeclarativeHttpClientWithJwtTest {

    @Inject
    AppClient appClient; (1)

    @Test
    void verifyJwtAuthenticationWorksWithDeclarativeClient() throws ParseException {
        UsernamePasswordCredentials creds = new UsernamePasswordCredentials("sherlock", "password");
        BearerAccessRefreshToken loginRsp = appClient.login(creds); (2)

        assertNotNull(loginRsp);
        assertNotNull(loginRsp.getAccessToken());
        assertTrue(JWTParser.parse(loginRsp.getAccessToken()) instanceof SignedJWT);

        String msg = appClient.home("Bearer " + loginRsp.getAccessToken()); (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/java/example/micronaut/LoginIncludesRefreshTokenTest.java

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.Test;

import java.text.ParseException;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertTrue;

@MicronautTest
public class LoginIncludesRefreshTokenTest {

    @Inject
    @Client("/")
    HttpClient client;

    @Test
    void uponSuccessfulAuthenticationUserGetsAccessTokenAndRefreshToken() throws ParseException {
        UsernamePasswordCredentials creds = new UsernamePasswordCredentials("sherlock", "password");
        HttpRequest<?> request = HttpRequest.POST("/login", creds);
        BearerAccessRefreshToken rsp = client.toBlocking().retrieve(request, BearerAccessRefreshToken.class);

        assertEquals("sherlock", rsp.getUsername());
        assertNotNull(rsp.getAccessToken());
        assertNotNull(rsp.getRefreshToken()); (1)

        assertTrue(JWTParser.parse(rsp.getAccessToken()) instanceof 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 -->
<path> (1)
    <groupId>io.micronaut</groupId>
    <artifactId>micronaut-data-processor</artifactId>
</path>
<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/java/example/micronaut/RefreshTokenEntity.java

package example.micronaut;
*/

import io.micronaut.core.annotation.NonNull;
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 jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import java.time.Instant;

@MappedEntity (1)
public class RefreshTokenEntity {

    @Id (2)
    @GeneratedValue (3)
    @NonNull
    private Long id;

    @NonNull
    @NotBlank
    private String username;

    @NonNull
    @NotBlank
    private String refreshToken;

    @NonNull
    @NotNull
    private Boolean revoked;

    @DateCreated (4)
    @NonNull
    @NotNull
    private Instant dateCreated;

    public RefreshTokenEntity() {
    }

    // getters and setters...

    @NonNull
    public Long getId() {
        return id;
    }

    public void setId(@NonNull Long id) {
        this.id = id;
    }

    @NonNull
    public String getUsername() {
        return username;
    }

    public void setUsername(@NonNull String username) {
        this.username = username;
    }

    @NonNull
    public String getRefreshToken() {
        return refreshToken;
    }

    public void setRefreshToken(@NonNull String refreshToken) {
        this.refreshToken = refreshToken;
    }

    @NonNull
    public Boolean getRevoked() {
        return revoked;
    }

    public void setRevoked(@NonNull Boolean revoked) {
        this.revoked = revoked;
    }

    @NonNull
    public Instant getDateCreated() {
        return dateCreated;
    }

    public void setDateCreated(@NonNull Instant dateCreated) {
        this.dateCreated = dateCreated;
    }
}


import io.micronaut.core.annotation.NonNull;
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 jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import java.time.Instant;

@MappedEntity (1)
public class RefreshTokenEntity {

    @Id (2)
    @GeneratedValue (3)
    @NonNull
    private Long id;

    @NonNull
    @NotBlank
    private String username;

    @NonNull
    @NotBlank
    private String refreshToken;

    @NonNull
    @NotNull
    private Boolean revoked;

    @DateCreated (4)
    @NonNull
    @NotNull
    private Instant dateCreated;

    public RefreshTokenEntity() {
    }

    // getters and setters...

}

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/java/example/micronaut/RefreshTokenRepository.java

package example.micronaut;

import io.micronaut.core.annotation.NonNull;
import io.micronaut.data.jdbc.annotation.JdbcRepository;
import io.micronaut.data.repository.CrudRepository;

import jakarta.transaction.Transactional;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import java.util.Optional;

import static io.micronaut.data.model.query.builder.sql.Dialect.H2;

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

    @Transactional
    RefreshTokenEntity save(@NonNull @NotBlank String username,
                            @NonNull @NotBlank String refreshToken,
                            @NonNull @NotNull Boolean revoked); (3)

    Optional<RefreshTokenEntity> findByRefreshToken(@NonNull @NotBlank String refreshToken); (4)

    long updateByUsername(@NonNull @NotBlank String username,
                          boolean revoked); (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/java/example/micronaut/CustomRefreshTokenPersistence.java

package example.micronaut;

import io.micronaut.security.authentication.Authentication;
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;

import java.util.Optional;

import static io.micronaut.security.errors.IssuingAnAccessTokenErrorCode.INVALID_GRANT;

@Singleton (1)
public class CustomRefreshTokenPersistence implements RefreshTokenPersistence {

    private final RefreshTokenRepository refreshTokenRepository;

    public CustomRefreshTokenPersistence(RefreshTokenRepository refreshTokenRepository) { (2)
        this.refreshTokenRepository = refreshTokenRepository;
    }

    @Override
    public void persistToken(RefreshTokenGeneratedEvent event) { (3)
        if (event != null &&
                event.getRefreshToken() != null &&
                event.getAuthentication() != null &&
                event.getAuthentication().getName() != null) {
            String payload = event.getRefreshToken();
            refreshTokenRepository.save(event.getAuthentication().getName(), payload, false); (4)
        }
    }

    @Override
    public Publisher<Authentication> getAuthentication(String refreshToken) {
        return Flux.create(emitter -> {
            Optional<RefreshTokenEntity> tokenOpt = refreshTokenRepository.findByRefreshToken(refreshToken);
            if (tokenOpt.isPresent()) {
                RefreshTokenEntity token = tokenOpt.get();
                if (token.getRevoked()) {
                    emitter.error(new OauthErrorResponseException(INVALID_GRANT, "refresh token revoked", null)); (5)
                } else {
                    emitter.next(Authentication.build(token.getUsername())); (6)
                    emitter.complete();
                }
            } else {
                emitter.error(new 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/java/example/micronaut/UnsignedRefreshTokenTest.java

package example.micronaut;

import io.micronaut.core.type.Argument;
import io.micronaut.http.HttpRequest;
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.Test;

import java.util.Map;
import java.util.Optional;

import static io.micronaut.http.HttpStatus.BAD_REQUEST;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

@MicronautTest
class UnsignedRefreshTokenTest {

    @Inject
    @Client("/")
    HttpClient client;

    @Test
    void accessingSecuredURLWithoutAuthenticatingReturnsUnauthorized() {

        String unsignedRefreshedToken = "foo"; (1)

        Argument<BearerAccessRefreshToken> bodyArgument = Argument.of(BearerAccessRefreshToken.class);
        Argument<Map> errorArgument = Argument.of(Map.class);

        HttpClientResponseException e = assertThrows(HttpClientResponseException.class, () -> {
            client.toBlocking().exchange(
                    HttpRequest.POST("/oauth/access_token", new TokenRefreshRequest(TokenRefreshRequest.GRANT_TYPE_REFRESH_TOKEN, unsignedRefreshedToken)),
                    bodyArgument,
                    errorArgument);
        });
        assertEquals(BAD_REQUEST, e.getStatus());

        Optional<Map> mapOptional = e.getResponse().getBody(Map.class);
        assertTrue(mapOptional.isPresent());

        Map m = mapOptional.get();
        assertEquals("invalid_grant", m.get("error"));
        assertEquals("Refresh token is invalid", m.get("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/java/example/micronaut/RefreshTokenNotFoundTest.java

package example.micronaut;

import io.micronaut.core.type.Argument;
import io.micronaut.http.HttpRequest;
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.Test;

import java.util.Map;
import java.util.Optional;

import static io.micronaut.http.HttpStatus.BAD_REQUEST;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

@MicronautTest
class RefreshTokenNotFoundTest {

    @Inject
    @Client("/")
    HttpClient client;

    @Inject
    RefreshTokenGenerator refreshTokenGenerator;

    @Test
    void accessingSecuredURLWithoutAuthenticatingReturnsUnauthorized() {
        Authentication user = Authentication.build("sherlock");

        String refreshToken = refreshTokenGenerator.createKey(user);
        Optional<String> refreshTokenOptional = refreshTokenGenerator.generate(user, refreshToken);
        assertTrue(refreshTokenOptional.isPresent());

        String signedRefreshToken = refreshTokenOptional.get();  (1)
        Argument<BearerAccessRefreshToken> bodyArgument = Argument.of(BearerAccessRefreshToken.class);
        Argument<Map> errorArgument = Argument.of(Map.class);
        HttpRequest<?> req = HttpRequest.POST("/oauth/access_token", new TokenRefreshRequest(TokenRefreshRequest.GRANT_TYPE_REFRESH_TOKEN, signedRefreshToken));

        HttpClientResponseException e = assertThrows(HttpClientResponseException.class, () -> {
            client.toBlocking().exchange(req, bodyArgument, errorArgument);
        });
        assertEquals(BAD_REQUEST, e.getStatus());

        Optional<Map> mapOptional = e.getResponse().getBody(Map.class);
        assertTrue(mapOptional.isPresent());

        Map m = mapOptional.get();
        assertEquals("invalid_grant", m.get("error"));
        assertEquals("refresh token not found", m.get("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/java/example/micronaut/RefreshTokenRevokedTest.java

package example.micronaut;

import io.micronaut.context.ApplicationContext;
import io.micronaut.core.type.Argument;
import io.micronaut.http.HttpRequest;
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.Test;

import java.util.Collections;
import java.util.Map;
import java.util.Optional;

import static io.micronaut.http.HttpStatus.BAD_REQUEST;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

class RefreshTokenRevokedTest {

    EmbeddedServer embeddedServer = ApplicationContext.run(EmbeddedServer.class, Collections.emptyMap());
    HttpClient client = embeddedServer.getApplicationContext().createBean(HttpClient.class, embeddedServer.getURL());
    RefreshTokenGenerator refreshTokenGenerator = embeddedServer.getApplicationContext().getBean(RefreshTokenGenerator.class);
    RefreshTokenRepository refreshTokenRepository = embeddedServer.getApplicationContext().getBean(RefreshTokenRepository.class);

    @Test
    void accessingSecuredURLWithoutAuthenticatingReturnsUnauthorized() {
        Authentication user = Authentication.build("sherlock");

        String refreshToken = refreshTokenGenerator.createKey(user);
        Optional<String> refreshTokenOptional = refreshTokenGenerator.generate(user, refreshToken);
        assertTrue(refreshTokenOptional.isPresent());

        long oldTokenCount = refreshTokenRepository.count();
        String signedRefreshToken = refreshTokenOptional.get();
        refreshTokenRepository.save(user.getName(), refreshToken, true); (1)
        assertEquals(oldTokenCount + 1, refreshTokenRepository.count());

        Argument<BearerAccessRefreshToken> bodyArgument = Argument.of(BearerAccessRefreshToken.class);
        Argument<Map> errorArgument = Argument.of(Map.class);
        HttpClientResponseException e = assertThrows(HttpClientResponseException.class, () -> {
            client.toBlocking().exchange(
                    HttpRequest.POST("/oauth/access_token", new TokenRefreshRequest(TokenRefreshRequest.GRANT_TYPE_REFRESH_TOKEN, signedRefreshToken)),
                    bodyArgument,
                    errorArgument);
        });
        assertEquals(BAD_REQUEST, e.getStatus());

        Optional<Map> mapOptional = e.getResponse().getBody(Map.class);
        assertTrue(mapOptional.isPresent());

        Map m = mapOptional.get();
        assertEquals("invalid_grant", m.get("error"));
        assertEquals("refresh token revoked", m.get("error_description"));

        refreshTokenRepository.deleteAll();
    }
}

1	Save the token but flag it as revoked

6.3.4. Test Access Token Refresh

src/test/java/example/micronaut/OauthAccessTokenTest.java

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.Test;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;

@MicronautTest(rollback = false)
class OauthAccessTokenTest {

    @Inject
    @Client("/")
    HttpClient client;

    @Inject
    RefreshTokenRepository refreshTokenRepository;

    @Test
    void verifyJWTAccessTokenRefreshWorks() throws InterruptedException {
        String username = "sherlock";

        UsernamePasswordCredentials creds = new UsernamePasswordCredentials(username, "password");
        HttpRequest<?> request = HttpRequest.POST("/login", creds);

        long oldTokenCount = refreshTokenRepository.count();
        BearerAccessRefreshToken rsp = client.toBlocking().retrieve(request, BearerAccessRefreshToken.class);
        Thread.sleep(3_000);
        assertEquals(oldTokenCount + 1, refreshTokenRepository.count());

        assertNotNull(rsp.getAccessToken());
        assertNotNull(rsp.getRefreshToken());

        Thread.sleep(1_000); // sleep for one second to give time for the issued at `iat` Claim to change
        AccessRefreshToken refreshResponse = client.toBlocking().retrieve(HttpRequest.POST("/oauth/access_token",
                new TokenRefreshRequest(TokenRefreshRequest.GRANT_TYPE_REFRESH_TOKEN, rsp.getRefreshToken())), AccessRefreshToken.class); (1)

        assertNotNull(refreshResponse.getAccessToken());
        assertNotEquals(rsp.getAccessToken(), refreshResponse.getAccessToken()); (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…).

Table of Contents

Micronaut JWT Authentication

1. Getting Started

2. What you will need

3. Solution

4. Writing the Application

4.1. Configuration

4.2. Authentication Provider

4.3. Controller

5. Tests

5.1. Use the Micronaut HTTP Client and JWT

6. Issuing a Refresh Token

6.1. Save Refresh Token

6.2. Refresh Controller

6.3. Test Refresh Token

6.3.1. Test Refresh Token Validation

6.3.2. Test Refresh Token Not Found

6.3.3. Test Refresh Token Revocation

6.3.4. Test Access Token Refresh

7. Testing the Application

8. Running the Application

9. Generate a Micronaut Application Native Executable with GraalVM

9.1. GraalVM installation

9.2. Native executable generation

10. Next steps

11. Help with the Micronaut Framework

12. License