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Discover effective solutions to `Keycloak` class collision errors when running web applications in both embedded and normal Jetty instances.
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This video is based on the question https://stackoverflow.com/q/49738610/ asked by the user 'Cloud' ( https://stackoverflow.com/u/2139325/ ) and on the answer https://stackoverflow.com/a/66155570/ provided by the user 'bogdanc' ( https://stackoverflow.com/u/4343189/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Resolve Keycloak Class Collision Issues in Embedded Jetty

When developing web applications that leverage authentication and authorization through Keycloak, you might encounter conflicts between dependencies, particularly when running your application in different environments. A common issue arises when using an embedded Jetty server alongside a standard Jetty deployment, leading to a frustrating ClassCastException. In this post, we'll explore this issue and provide a structured approach to resolve it effectively.

Understanding the Problem

The Conflict

The problem typically manifests in the following error message:

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This error indicates that there are two different copies of the KeycloakSecurityContext class being loaded - one from the keycloak-jetty-adapter and another from the keycloak-core dependency.

The Cause

The duplication of these classes usually arises from conflicting dependencies within your project. If both the Keycloak core and adapter dependencies are included without proper configuration, you may run into these collisions, leading to runtime exceptions.

Step-by-Step Solution

To resolve this issue with Keycloak in your Jetty setup, follow these organized steps:

Step 1: Manage Your Dependencies

Download and Place Keycloak Adapters:

Download the necessary Keycloak adapters from the official Keycloak website.

Place these adapters in the lib directory of your Jetty installation (e.g., tomcat/lib or wildfly/lib), ensuring they are available at runtime.

Adjust Your Maven Configuration:

Open your pom.xml file and specify the Keycloak adapter dependency without versions. This allows the dependencies needed for compiling the project to be provided by the container during runtime. This method prevents version mismatches that often lead to class collisions.

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Step 2: Configure Your Development Environment

IntelliJ IDEA Settings:

If you’re using IntelliJ IDEA, ensure that you can access Keycloak-specific classes. Go to File - Project Structure (CTRL + Shift + Alt + S), then under Libraries, add the JAR files that you previously placed in the Jetty lib folder. This will allow your development environment to properly reference these classes.

Step 3: Test Your Setup

Run Your Application: After making these adjustments, run your web application both in your embedded Jetty configuration and in the standard Jetty instance. Make sure to conduct thorough testing to confirm that the ClassCastException is resolved.

Build and Deploy: Ensure your application builds correctly and deploys successfully without any dependency issues. If problems persist, double-check your dependency management configurations.

Conclusion

Class collisions in Keycloak can be a frustrating yet common issue when working with embedded and traditional Jetty instances. By effectively managing your dependencies and configuring your development environment, you can resolve these conflicts and ensure that your application runs smoothly.

If you encounter any further difficulties or have additional questions, feel free to reach out in the comments below or explore the rich community around Keycloak for more support.