Enable sign-in for Java Tomcat apps using Microsoft Entra ID

This article demonstrates a Java Tomcat app that signs in users to your Microsoft Entra ID tenant using the Microsoft Authentication Library (MSAL) for Java.

The following diagram shows the topology of the app:

The client app uses MSAL for Java (MSAL4J) to sign in users to their own Microsoft Entra ID tenant and obtain an ID token from Microsoft Entra ID. The ID token proves that a user is authenticated with this tenant. The app protects its routes according to the user's authentication status.

Prerequisites

• JDK version 8 or higher
• Maven 3
• A Microsoft Entra ID tenant. For more information, see How to get a Microsoft Entra ID tenant.
• A user account in your own Microsoft Entra ID tenant if you want to work with accounts in your organizational directory only - that is, in single-tenant mode. If you haven't created a user account in your Microsoft Entra ID tenant, you should do so before proceeding. For more information, see How to create, invite, and delete users.
• A user account in any organization's Microsoft Entra ID tenant if you want to work with accounts in any organizational directory - that is, in multitenant mode. You must modify this sample to work with a personal Microsoft account. If you haven't created a user account in your Microsoft Entra ID tenant yet, you should do so before proceeding. For more information, see How to create, invite, and delete users.
• A personal Microsoft account - for example, Xbox, Hotmail, Live, and so on - if you want to work with personal Microsoft accounts.

• Tomcat 9
• Visual Studio Code
• Azure Tools for Visual Studio Code

Recommendations

• Some familiarity with the Java / Jakarta Servlets.
• Some familiarity with Linux/OSX terminal or Windows PowerShell.
• jwt.ms for inspecting your tokens.
• Fiddler for monitoring your network activity and troubleshooting.
• Follow the Microsoft Entra ID Blog to stay up-to-date with the latest developments.

Set up the sample

The following sections show you how to set up the sample application.

Clone or download the sample repository

To clone the sample, open a Bash window and use the following command:

git clone https://github.com/Azure-Samples/ms-identity-msal-java-samples.git
cd 3-java-servlet-web-app/1-Authentication/sign-in

Alternatively, navigate to the ms-identity-msal-java-samples repository, then download it as a .zip file and extract it to your hard drive.

Register the sample application with your Microsoft Entra ID tenant

There's one project in this sample. This section shows you how to register the app.

First, register the app in the Azure portal by following the instructions in Quickstart: Register an application with the Microsoft identity platform.

Then, use the following steps to complete the registration:

1. Navigate to the Microsoft identity platform for developers App registrations page.

2. Select New registration.

3. In the Register an application page that appears, enter the following application registration information:

   • In the Name section, enter a meaningful application name for display to users of the app - for example, java-servlet-webapp-authentication.

   • Under Supported account types, select one of the following options:

     • Select Accounts in this organizational directory only if you're building an application for use only by users in your tenant - that is, a single-tenant application.
     • Select Accounts in any organizational directory if you'd like users in any Microsoft Entra ID tenant to be able to use your application - that is, a multitenant application.
     • Select Accounts in any organizational directory and personal Microsoft accounts for the widest set of customers - that is, a multitenant application that also supports Microsoft personal accounts.
     • Select Personal Microsoft accounts for use only by users of personal Microsoft accounts - for example, Hotmail, Live, Skype, and Xbox accounts.

   • In the Redirect URI section, select Web in the combo-box and enter the following redirect URI: http://localhost:8080/msal4j-servlet-auth/auth/redirect.

4. Select Register to create the application.

5. On the app's registration page, find and copy the Application (client) ID value to use later. You use this value in your app's configuration file or files.

6. On the app's registration page, select Certificates & secrets on the navigation pane to open the page to generate secrets and upload certificates.

7. In the Client secrets section, select New client secret.

8. Type a description - for example, app secret.

9. Select one of the available durations: In 1 year, In 2 years, or Never Expires.

10. Select Add. The generated value is displayed.

11. Copy and save the generated value for use in later steps. You need this value for your code's configuration files. This value isn't displayed again, and you can't retrieve it by any other means. So, be sure to save it from the Azure portal before you navigate to any other screen or pane.

Configure the app to use your app registration

Use the following steps to configure the app:

1. Open the project in your IDE.

2. Open the ./src/main/resources/authentication.properties file.

3. Find the string {enter-your-tenant-id-here}. Replace the existing value with one of the following values:

   • Your Microsoft Entra ID tenant ID if you registered your app with the Accounts in this organizational directory only option.
   • The word organizations if you registered your app with the Accounts in any organizational directory option.
   • The word common if you registered your app with the Accounts in any organizational directory and personal Microsoft accounts option.
   • The word consumers if you registered your app with the Personal Microsoft accounts option.

4. Find the string {enter-your-client-id-here} and replace the existing value with the application ID or clientId of the java-servlet-webapp-authentication application copied from the Azure portal.

5. Find the string {enter-your-client-secret-here} and replace the existing value with the value you saved during the creation of the java-servlet-webapp-authentication app, in the Azure portal.

Build the sample

To build the sample using Maven, navigate to the directory containing the pom.xml file for the sample, and then run the following command:

mvn clean package

This command generates a .war file that you can run on various application servers.

Run the sample

Please confirm webapp properties
AppName : msal4j-servlet-auth-1707209552268
ResourceGroup : msal4j-servlet-auth-1707209552268-rg
Region : centralus
PricingTier : P1v2
OS : Linux
Java Version: Java 11
Web server stack: Tomcat 9.0
Deploy to slot : false
Confirm (Y/N) [Y]: [INFO] Saving configuration to pom.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  37.112 s
[INFO] Finished at: 2024-02-06T08:53:02Z
[INFO] ------------------------------------------------------------------------

<build>
    <plugins>
        <plugin>
            <groupId>com.microsoft.azure</groupId>
            <artifactId>>azure-webapp-maven-plugin</artifactId>
            <version>x.xx.x</version>
            <configuration>
                <schemaVersion>v2</schemaVersion>
                <resourceGroup>your-resourcegroup-name</resourceGroup>
                <appName>your-app-name</appName>
            ...
            </configuration>
        </plugin>
    </plugins>
</build>

az login

mvn package azure-webapp:deploy

Explore the sample

Use the following steps to explore the sample:

1. Notice the signed-in or signed-out status displayed at the center of the screen.
2. Select the context-sensitive button in the corner. This button reads Sign In when you first run the app.
3. On the next page, follow the instructions and sign in with an account in the Microsoft Entra ID tenant.
4. On the consent screen, notice the scopes that are being requested.
5. Notice that the context-sensitive button now says Sign out and displays your username.
6. Select ID Token Details to see some of the ID token's decoded claims.
7. Use the button in the corner to sign out.
8. After signing out, select ID Token Details to observe that the app displays a 401: unauthorized error instead of the ID token claims when the user isn't authorized.

About the code

This sample shows how to use MSAL for Java (MSAL4J) to sign in users into your Microsoft Entra ID tenant. If you'd like to use MSAL4J in your own applications, you must add it to your projects using Maven.

If you want to replicate this sample's behavior, you can copy the pom.xml file and the contents of the helpers and authservlets folders in the src/main/java/com/microsoft/azuresamples/msal4j folder. You also need the authentication.properties file. These classes and files contain generic code that you can use in a wide array of applications. You can copy the rest of the sample as well, but the other classes and files are built specifically to address this sample's objective.

Contents

The following table shows the contents of the sample project folder:

ConfidentialClientApplication

A ConfidentialClientApplication instance is created in the AuthHelper.java file, as shown in the following example. This object helps craft the Microsoft Entra ID authorization URL and also helps exchange the authentication token for an access token.

// getConfidentialClientInstance method
IClientSecret secret = ClientCredentialFactory.createFromSecret(SECRET);
confClientInstance = ConfidentialClientApplication
                     .builder(CLIENT_ID, secret)
                     .authority(AUTHORITY)
                     .build();

The following parameters are used for instantiation:

• The client ID of the app.
• The client secret, which is a requirement for Confidential Client Applications.
• The Microsoft Entra ID Authority, which includes your Microsoft Entra ID tenant ID.

In this sample, these values are read from the authentication.properties file using a properties reader in the Config.java file.

Step-by-step walkthrough

The following steps provide a walkthrough of the app's functionality:

1. The first step of the sign-in process is to send a request to the /authorize endpoint on for your Microsoft Entra ID tenant. The MSAL4J ConfidentialClientApplication instance is used to construct an authorization request URL. The app redirects the browser to this URL, which is where the user signs in.

   final ConfidentialClientApplication client = getConfidentialClientInstance();
   AuthorizationRequestUrlParameters parameters = AuthorizationRequestUrlParameters.builder(Config.REDIRECT_URI, Collections.singleton(Config.SCOPES))
           .responseMode(ResponseMode.QUERY).prompt(Prompt.SELECT_ACCOUNT).state(state).nonce(nonce).build();
   
   final String authorizeUrl = client.getAuthorizationRequestUrl(parameters).toString();
   contextAdapter.redirectUser(authorizeUrl);
   

   The following list describes the features of this code:

   • AuthorizationRequestUrlParameters: Parameters that must be set in order to build an AuthorizationRequestUrl.

   • REDIRECT_URI: Where Microsoft Entra ID redirects the browser - along with the auth code - after collecting the user credentials. It must match the redirect URI in the Microsoft Entra ID app registration in the Azure portal.

   • SCOPES: Scopes are permissions requested by the application. Normally, the three scopes openid profile offline_access suffice for receiving an ID token response.

     You can find a full list of scopes requested by the app in the authentication.properties file. You can add more scopes, such as User.Read.

2. The user is presented with a sign-in prompt by Microsoft Entra ID. If the sign-in attempt is successful, the user's browser is redirected to the app's redirect endpoint. A valid request to this endpoint contains an authorization code.

3. The ConfidentialClientApplication instance then exchanges this authorization code for an ID token and access token from Microsoft Entra ID.

   // First, validate the state, then parse any error codes in response, then extract the authCode. Then:
   // build the auth code params:
   final AuthorizationCodeParameters authParams = AuthorizationCodeParameters
           .builder(authCode, new URI(Config.REDIRECT_URI)).scopes(Collections.singleton(Config.SCOPES)).build();
   
   // Get a client instance and leverage it to acquire the token:
   final ConfidentialClientApplication client = AuthHelper.getConfidentialClientInstance();
   final IAuthenticationResult result = client.acquireToken(authParams).get();
   

   The following list describes the features of this code:

   • AuthorizationCodeParameters: Parameters that must be set in order to exchange the Authorization Code for an ID and/or access token.
   • authCode: The authorization code that was received at the redirect endpoint.
   • REDIRECT_URI: The redirect URI used in the previous step must be passed again.
   • SCOPES: The scopes used in the previous step must be passed again.

4. If acquireToken is successful, the token claims are extracted. If the nonce check passes, the results are placed in context - an instance of IdentityContextData - and saved to the session. The application can then instantiate the IdentityContextData from the session by way of an instance of IdentityContextAdapterServlet whenever it needs access to it, as shown in the following code:

   // parse IdToken claims from the IAuthenticationResult:
   // (the next step - validateNonce - requires parsed claims)
   context.setIdTokenClaims(result.idToken());
   
   // if nonce is invalid, stop immediately! this could be a token replay!
   // if validation fails, throws exception and cancels auth:
   validateNonce(context);
   
   // set user to authenticated:
   context.setAuthResult(result, client.tokenCache().serialize());
   

Protect the routes

For information about how the sample app filters access to routes, see AuthenticationFilter.java. In the authentication.properties file, the app.protect.authenticated property contains the comma-separated routes that only authenticated users can access, as shown in the following example:

# for example, /token_details requires any user to be signed in and does not require special roles claim(s)
app.protect.authenticated=/token_details

Scopes

Scopes tell Microsoft Entra ID the level of access that the application is requesting.

Based on the requested scopes, Microsoft Entra ID presents a consent dialogue to the user upon sign-in. If the user consents to one or more scopes and obtains a token, the scopes-consented-to are encoded into the resulting access_token.

For the scopes requested by the application, see authentication.properties. These three scopes are requested by MSAL and given by Microsoft Entra ID by default.

More information

• Microsoft Authentication Library (MSAL) for Java
• MSAL Java Reference Documentation
• Microsoft identity platform (Microsoft Entra ID for developers)
• Quickstart: Register an application with the Microsoft identity platform
• Understanding Microsoft Entra ID application consent experiences
• Understand user and admin consent
• MSAL code samples