Table of Contents

Session based authentication

Learn how to secure a Micronaut app using Session based authentication.

Authors: Sergio del Amo

Micronaut Version: 2.5.0

1. Getting Started

In this guide you are going to write a Micronaut app with session based authentication.

The following sequence illustrates the authentication flow:

session based auth

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

  • JDK 1.8 or greater installed with JAVA_HOME configured appropriately

3. Solution

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

4. Writing the Application

Create an app using the Micronaut Command Line Interface.

mn create-app example.micronaut.micronautguide --test=spock --lang=kotlin

The previous command creates a micronaut app with the default package example.micronaut in a folder named micronautguide.

If you are using Java or Kotlin and IntelliJ IDEA, make sure you have enabled annotation processing.

annotationprocessorsintellij

4.1. Security Dependency

Add Micronaut’s security dependency to your build file.

Add Micronaut’s JWT security dependency.

build.gradle
kapt("io.micronaut.security:micronaut-security-annotations")
implementation("io.micronaut.security:micronaut-security-session")

4.2. Configuration

Create the next configuration file:

src/main/resources/application.yml
micronaut:
  security:
    authentication: session (1)
    redirect:
      login-success: / (2)
      login-failure: /login/authFailed (3)
1 Set micronaut.security.authentication to session. It sets the necessary beans for login and logout using session based authentication.
2 After the user logs in, redirect them to the Home page.
3 If the login fails, redirect them to /login/authFailed

4.3. 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.AuthenticationException
import io.micronaut.security.authentication.AuthenticationFailed
import io.micronaut.security.authentication.AuthenticationProvider
import io.micronaut.security.authentication.AuthenticationRequest
import io.micronaut.security.authentication.AuthenticationResponse
import io.micronaut.security.authentication.UserDetails
import io.reactivex.BackpressureStrategy
import io.reactivex.Flowable
import io.reactivex.FlowableEmitter
import org.reactivestreams.Publisher
import javax.inject.Singleton

@Singleton (1)
class AuthenticationProviderUserPassword : AuthenticationProvider { (2)
    override fun authenticate(httpRequest: HttpRequest<*>?, authenticationRequest: AuthenticationRequest<*, *>): Publisher<AuthenticationResponse> {
        return Flowable.create({ emitter: FlowableEmitter<AuthenticationResponse> ->
            if (authenticationRequest.identity == "sherlock" && authenticationRequest.secret == "password") {
                val userDetails = UserDetails(authenticationRequest.identity as String, ArrayList())
                emitter.onNext(userDetails)
                emitter.onComplete()
            } else {
                emitter.onError(AuthenticationException(AuthenticationFailed()))
            }
        }, BackpressureStrategy.ERROR)
    }
}
1 To register a Singleton in Micronaut’s application context annotate your class with javax.inject.Singleton
2 A Micronaut’s Authentication Provider implements the interface io.micronaut.security.authentication.AuthenticationProvider

4.4. Apache Velocity

By default, Micronaut’s controllers produce JSON. Usually, you consume those endpoints with a mobile phone application, or a Javascript front end (Angular, React, Vue.js …​). However, to keep this guide simple we are going to produce HTML in our controllers.

In order to do that, we use Apache Velocity.

Velocity is a Java-based template engine. It permits anyone to use a simple yet powerful template language to reference objects defined in Java code.

Add a dependency to Micronaut’s Server Side View Rendering Module and to Velocity:

build.gradle
implementation("io.micronaut.views:micronaut-views-velocity")

Create two velocity templates in src/main/resources/views:

src/main/resources/views/home.vm
<!DOCTYPE html>
<html>
    <head>
        <title>Home</title>
    </head>
    <body>
        #if( $loggedIn )
            <h1>username: <span>$username</span></h1>
        #else
            <h1>You are not logged in</h1>
        #end
        #if( $loggedIn )
            <form action="logout" method="POST">
                <input type="submit" value="Logout"/>
            </form>
        #else
            <p><a href="/login/auth">Login</a></p>
        #end
    </body>
</html>
src/main/resources/views/auth.vm
<!DOCTYPE html>
<html>
    <head>
        #if( $errors )
            <title>Login Failed</title>
        #else
            <title>Login</title>
        #end
    </head>
<body>
    <form action="/login" method="POST">
        <ol>
            <li>
                <label for="username">Username</label>
                <input type="text" name="username" id="username"/>
            </li>
            <li>
                <label for="password">Password</label>
                <input type="password" name="password" id="password"/>
            </li>
            <li>
                <input type="submit" value="Login"/>
            </li>
            #if( $errors )
                <li id="errors">
                    <span style="color: red;">Login Failed</span>
                </li>
            #end
        </ol>
    </form>
</body>
</html>

4.5. Controllers

Create a file named HomeController which resolves the base URL /:

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

import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
import io.micronaut.security.annotation.Secured
import io.micronaut.security.rules.SecurityRule
import io.micronaut.views.View
import java.security.Principal

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

    @Get (3)
    @View("home") (4)
    fun index(principal: Principal?): Map<String, Any> { (5)
        val data = mutableMapOf<String, Any>()
        data["loggedIn"] = (principal != null) as Any
        if (principal != null) {
            data["username"] = principal.name as Any
        }
        return data
    }
}
1 Annotate with io.micronaut.security.Secured to configure security access. Use isAnonymous() expression to allow access to authenticated and unauthenticated users.
2 Annotate with io.micronaut.http.annotation.Controller to designate a class as a Micronaut’s controller.
3 You can specify the HTTP verb for which a controller’s action responds to. To respond to a GET request, use io.micronaut.http.annotation.Get
4 Use View annotation to specify which template would you like to render the response against.
5 If you are authenticated, you can use the java.security.Principal as a parameter type. For parameters which maybe null, use io.micronaut.core.annotation.Nullable.

5. Login Form

Next, create LoginAuthController which renders the login form.

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

import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
import io.micronaut.security.annotation.Secured
import io.micronaut.security.rules.SecurityRule
import io.micronaut.views.View

@Secured(SecurityRule.IS_ANONYMOUS) (1)
@Controller("/login") (2)
class LoginAuthController {

    @Get("/auth") (3)
    @View("auth") (4)
    fun auth(): Map<String, Any> {
        return HashMap()
    }

    @Get("/authFailed") (5)
    @View("auth") (4)
    fun authFailed(): Map<String, Any> {
        return mapOf(Pair("errors", true))
    }
}
1 Annotate with io.micronaut.security.Secured to configure security access. Use isAnonymous() expression for anonymous access.
2 Annotate with io.micronaut.http.annotation.Controller to designate a class as a Micronaut’s controller.
3 Responds to GET requests at /login/auth
4 Use View annotation to specify which template would you like to render the response against.
5 Responds to GET requests at /login/authFailed

6. Tests

We also use Geb, a browser automation solution.

To use Geb, add these dependencies:

build.gradle
testImplementation("org.gebish:geb-spock:4.0")
testImplementation("org.seleniumhq.selenium:htmlunit-driver:2.47.1")

Geb uses the Page concept pattern - The Page Object Pattern gives us a common sense way to model content in a reusable and maintainable way.

Create three pages:

src/test/groovy/example/micronaut/HomePage.groovy
package example.micronaut

import geb.Page

class HomePage extends Page {

    static url = '/'

    static at = { title == 'Home' }

    static content = {
        loginLink { $('a', text: 'Login') }
        logoutButton { $('input', type: 'submit', value: 'Logout') }
        usernameElement(required: false) { $('h1 span', 0) }
    }

    String username() {
        if (usernameElement.empty) {
            return null
        }
        usernameElement.text()
    }

    void login() {
        loginLink.click()
    }

    void logout() {
        logoutButton.click()
    }
}
src/test/groovy/example/micronaut/LoginPage.groovy
package example.micronaut

import geb.Page

class LoginPage extends Page {

    static url = '/login/auth'

    static at = { title.contains 'Login' }

    static content = {
        usernameInput { $('#username') }
        passwordInput { $('#password') }
        submitInput { $('input', type: 'submit') }
        errorsLi(required: false) { $('li#errors') }
    }

    boolean hasErrors() {
        !errorsLi.empty
    }

    void login(String username, String password) {
        usernameInput = username
        passwordInput = password
        submitInput.click()
    }
}
src/test/groovy/example/micronaut/LoginFailedPage.groovy
package example.micronaut

import geb.Page

class LoginFailedPage extends Page {

    static at = { title == 'Login Failed' }

    static url = '/login/authFailed'
}

Create a test which verifies the user authentication flow.

src/test/groovy/example/micronaut/SessionAuthenticationSpec.groovy
@MicronautTest (1)
class SessionAuthenticationSpec extends GebSpec {

    @Inject
    EmbeddedServer embeddedServer (2)

    def "verify session based authentication works"() {
        given:
        browser.baseUrl = "http://localhost:${embeddedServer.port}"

        when:
        to HomePage

        then:
        at HomePage

        when:
        HomePage homePage = browser.page HomePage

        then: 'As we are not logged in, there is no username'
        homePage.username() == null

        when: 'click the login link'
        homePage.login()

        then:
        at LoginPage

        when: 'fill the login form, with invalid credentials'
        LoginPage loginPage = browser.page LoginPage
        loginPage.login('foo', 'foo')

        then: 'the user is still in the login form'
        at LoginPage

        and: 'and error is displayed'
        loginPage.hasErrors()

        when: 'fill the form with wrong credentials'
        loginPage.login('sherlock', 'foo')

        then: 'we get redirected to the home page'
        at LoginFailedPage

        when: 'fill the form with valid credentials'
        loginPage.login('sherlock', 'password')

        then: 'we get redirected to the home page'
        at HomePage

        when:
        homePage = browser.page HomePage

        then: 'the username is populated'
        homePage.username() == 'sherlock'

        when: 'click the logout button'
        homePage.logout()

        then: 'we are in the home page'
        at HomePage

        when:
        homePage = browser.page HomePage

        then: 'but we are no longer logged in'
        homePage.username() == null
    }
}
1 Annotate the class with @MicronautTest to let Micronaut starts the embedded server and inject the beans. More info: https://micronaut-projects.github.io/micronaut-test/latest/guide/index.html.
2 Inject the EmbeddedServer bean.

7. Testing the Application

To run the tests:

$ ./gradlew test
$ open build/reports/tests/test/index.html

8. Running the Application

To run the application use the ./gradlew run command which will start the application on port 8080.

9. Generate a Micronaut app’s Native Image with GraalVM

We are going to use GraalVM, the polyglot embeddable virtual machine, to generate a Native image of our Micronaut application.

Native images compiled with GraalVM ahead-of-time improve the startup time and reduce the memory footprint of JVM-based applications.

Use of GraalVM’s native-image tool is only supported in Java or Kotlin projects. Groovy relies heavily on reflection which is only partially supported by GraalVM.

9.1. Native Image generation

The easiest way to install GraalVM is to use SDKMan.io.

# For Java 8
$ sdk install java 21.1.0.r8-grl

# For Java 11
$ sdk install java 21.1.0.r11-grl

You need to install the native-image component which is not installed by default.

$ gu install native-image

To generate a native image using Gradle run:

$ ./gradlew nativeImage

The native image will be created in build/native-image/application and can be run with ./build/native-image/application

It is also possible to customize the name of the native image or pass additional parameters to GraalVM:

build.gradle
nativeImage {
    args('--verbose')
    imageName('mn-graalvm-application') (1)
}
1 The native image name will now be mn-graalvm-application

10. Next steps

Explore more features with Micronaut Guides.

11. Help with Micronaut

Object Computing, Inc. (OCI) sponsored the creation of this Guide. A variety of consulting and support services are available.

Meet the Team.