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TBD: Modernize to Java 21

Modernize Application to Java 21

Overview

This issue tracks the comprehensive modernization of our application from the current Java version to Java 21 LTS. This upgrade will provide performance improvements, security enhancements, and access to modern language features while ensuring long-term support.

Objectives

  • Upgrade runtime environment to Java 21 LTS
  • Leverage new language features and performance improvements
  • Maintain backward compatibility where possible
  • Improve application security and maintainability
  • Ensure all dependencies are compatible with Java 21

Requirements

1. Environment Setup

  • Update development environments to Java 21
  • Configure CI/CD pipelines for Java 21
  • Update Docker base images to Java 21
  • Verify IDE support for Java 21 features
  • Update deployment environments (staging, production)

2. Build System Updates

  • Update Maven/Gradle configuration
    • Set maven.compiler.source and maven.compiler.target to 21
    • Update Maven compiler plugin to latest version
    • Update Gradle build scripts if applicable
  • Update build scripts and automation tools
  • Verify all build plugins are Java 21 compatible

3. Dependency Management

  • Audit all dependencies for Java 21 compatibility
  • Update Spring Boot to latest Java 21 compatible version
  • Update application frameworks and libraries
  • Replace deprecated dependencies
  • Update test frameworks (JUnit, Mockito, etc.)
  • Check third-party integrations compatibility

4. Code Modernization

Language Features (Java 17-21)

  • Implement Pattern Matching for switch expressions
  • Utilize Record Patterns where applicable
  • Apply Virtual Threads for improved concurrency
  • Use Sequenced Collections for better data handling
  • Leverage String Templates (Preview feature evaluation)
  • Implement Unnamed Patterns and Variables

Code Quality Improvements

  • Replace deprecated APIs with modern alternatives
  • Optimize exception handling with new patterns
  • Improve null safety using modern approaches
  • Refactor legacy code to use modern idioms
  • Update logging frameworks and configurations

5. Performance Optimizations

  • Evaluate Virtual Threads implementation opportunities
  • Optimize garbage collection settings for Java 21
  • Review and update JVM parameters
  • Benchmark performance improvements
  • Profile memory usage and optimize

6. Security Enhancements

  • Review and update security configurations
  • Implement new security features available in Java 21
  • Update cryptographic libraries and algorithms
  • Review TLS configurations and cipher suites
  • Update security scanning tools for Java 21

7. Testing Strategy

  • Update unit tests for Java 21 compatibility
  • Create integration tests for new features
  • Performance testing with Java 21
  • Security testing and vulnerability scanning
  • Backward compatibility testing
  • End-to-end testing in Java 21 environment

8. Documentation Updates

  • Update README with Java 21 requirements
  • Document new language features usage
  • Update deployment documentation
  • Create migration guide for team members
  • Update API documentation if affected
  • Update troubleshooting guides

9. Monitoring and Observability

  • Update application monitoring for Java 21
  • Configure JVM monitoring and alerting
  • Update logging configurations
  • Verify APM tools compatibility
  • Update health check endpoints

10. Database and External Integrations

  • Verify database driver compatibility
  • Test external API integrations
  • Update database connection configurations
  • Verify message queue client compatibility
  • Test caching layer integration

Technical Considerations

Breaking Changes to Address

  • Review usage of deprecated APIs removed in Java 21
  • Update Security Manager usage (deprecated for removal)
  • Address any reflection warnings and compatibility issues
  • Update serialization implementations if needed

New Features to Evaluate

  • Virtual Threads: For high-concurrency scenarios
  • Pattern Matching: For cleaner conditional logic
  • Records: For immutable data carriers
  • Sealed Classes: For controlled inheritance hierarchies

Performance Expectations

  • Improved startup time with Class Data Sharing (CDS)
  • Better garbage collection performance
  • Reduced memory footprint
  • Enhanced concurrent processing capabilities

Risk Assessment

High Risk

  • Third-party library incompatibilities
  • Runtime behavior changes affecting existing functionality
  • Performance regression in specific use cases

Medium Risk

  • Deprecated API usage requiring refactoring
  • Build system configuration complexities
  • CI/CD pipeline adjustments

Low Risk

  • Documentation updates
  • Development environment setup
  • Monitoring configuration updates

Success Criteria

  • Application successfully runs on Java 21 in all environments
  • All existing functionality preserved
  • Performance improvements documented and verified
  • Security posture improved or maintained
  • Team trained on new Java 21 features
  • Comprehensive test coverage maintained
  • Zero critical vulnerabilities introduced

Timeline Estimate

  • Phase 1: Environment setup and dependency audit (1-2 weeks)
  • Phase 2: Core migration and code updates (2-3 weeks)
  • Phase 3: Testing and optimization (1-2 weeks)
  • Phase 4: Documentation and deployment (1 week)

Total Estimated Duration: 5-8 weeks

Acceptance Criteria

  1. Application builds successfully with Java 21
  2. All tests pass without modification or with documented changes
  3. Performance benchmarks meet or exceed baseline
  4. Security scan shows no new vulnerabilities
  5. Deployment pipeline works end-to-end
  6. Team documentation is complete and accessible

Dependencies

  • Infrastructure team for environment updates
  • DevOps team for CI/CD pipeline changes
  • Security team for compliance review
  • QA team for comprehensive testing

Related Issues

  • Link to dependency audit results
  • Link to performance baseline documentation
  • Link to security review requirements