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20. Java 21 transition
Ilkka Seppälä edited this page Mar 27, 2024
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To migrate the Java codebase from Java 17 to Java 21 and to start leveraging the new features of Java 21 effectively, we need a structured technical implementation plan. This plan will guide the team through a series of steps, ensuring a smooth transition while maintaining code integrity and functionality. Here's the detailed technical implementation plan:
- Understand the new features, enhancements, and deprecated features in Java 21.
- Identify any removed APIs and features that might impact the current codebase.
- Use tools like jdeprscan from JDK to scan the code for any uses of deprecated APIs.
- Review custom and third-party dependencies for compatibility with Java 21.
- Download and install JDK 21 on development environment.
- Ensure that all environment variables and PATH settings are updated to point to JDK 21.
- Update the maven-compiler-plugin in the pom.xml file to use Java 21, setting both the source and target to 21.
- Validate and update other Maven plugins and dependencies for Java 21 compatibility.
- Update the GitHub Actions workflow configurations to use JDK 21 for builds.
- Ensure that all CI steps are compatible with Java 21.
- Use IDE tools or other utilities to automatically update code to use Java 21 features where applicable, such as var type inference, switch expressions, and text blocks.
- Manually refactor critical sections of the code that require a nuanced understanding of the new Java 21 features or changes.
- Pay special attention to concurrency updates, API changes, and any feature that could significantly impact performance or functionality.
- Replace deprecated APIs with their recommended Java 21 alternatives.
- For any removed APIs, find or implement suitable replacements.
- Run all existing unit and integration tests to ensure that the migration has not introduced any regressions.
- Update tests to cover new code paths and features used from Java 21.
- Conduct performance testing to identify any potential bottlenecks introduced by the migration.
- Compare key performance indicators (KPIs) before and after migration to ensure no degradation.
- Test the application on all supported platforms to ensure compatibility with Java 21.
- Update technical documentation to reflect the migration to Java 21 and any significant code changes or new patterns employed.
- Identify and prioritize Java 21 features that could benefit the project, such as new APIs, language enhancements, and performance improvements.
- Develop a plan to incrementally adopt these features in a way that aligns with project goals and timelines.
- Continuously refactor the codebase to adopt Java 21 features where they can bring improvements in readability, maintainability, performance, or security.
Migrating to Java 21 is a significant endeavor that requires careful planning, execution, and validation. By following this technical implementation plan, the team will be well-equipped to manage the transition effectively, minimize disruptions, and leverage new Java features to enhance the project's value.