Migrate from Java 17 to Java 22 (Phases 1-5)

[devin-ai-integration]

Summary

This PR migrates the Springboot-BankApp from Java 17 to Java 22, covering phases 1-5 of the migration plan. The changes update the Java version across build configuration, Docker images, and documentation.

Key changes:

• pom.xml: Updated java.version property from 17 to 22, and maven-compiler-plugin source/target from 1.8 to 22
• Dockerfile: Changed build stage to maven:3.9-eclipse-temurin-22-alpine and runtime stage to eclipse-temurin:22-jre-alpine (note: the originally requested maven:3.8.3-openjdk-22 and openjdk:22-alpine images do not exist on Docker Hub)
• README.md: Updated Jenkins installation instructions to use openjdk-21-jre with a note explaining that openjdk-22-jre is not available in standard Ubuntu repositories
• JAVA22_MIGRATION_NOTES.md: Added comprehensive documentation for staging/production deployment considerations

Updates Since Last Revision

• Fixed pom.xml indentation: Corrected the maven-compiler-plugin section indentation to match the rest of the file
• Updated README.md for openjdk availability: Changed from openjdk-22-jre to openjdk-21-jre since Java 22 is not available via apt in Ubuntu repos. Added a note recommending Eclipse Temurin/Adoptium as an alternative for Java 22.
• Verified Docker build: Successfully built with maven:3.9-eclipse-temurin-22-alpine and eclipse-temurin:22-jre-alpine
• Verified application startup: Application starts successfully with Java 22.0.2 (confirmed via container logs)

Review & Testing Checklist for Human

• Test full application functionality: The Docker build and startup were verified, but full functionality (login, transactions) requires a MySQL database connection - please test end-to-end with the database
• Verify Jenkins pipeline: Run the CI/CD pipeline to confirm it works with the new Java 22 configuration
• Confirm openjdk-21-jre compatibility: The README now recommends openjdk-21-jre for Jenkins since openjdk-22-jre isn't available via apt. Java 21 should run Java 22 compiled code, but verify this works in your environment
• Review JAVA22_MIGRATION_NOTES.md: Check the staging/production deployment guidance before deploying to higher environments

Recommended test plan:

1. Run the Jenkins pipeline to verify CI/CD works
2. Deploy to a staging environment with MySQL
3. Test login, transactions, and other banking functionality
4. Monitor application logs for any Java 22 specific warnings

Notes

The Jenkinsfile and GitOps/Jenkinsfile were reviewed and found to be Java version agnostic (they use shared library functions and don't hardcode Java versions), so no changes were required.

Link to Devin run: https://app.devin.ai/sessions/405849c37f9b4d0e9e7c41bbde831cba
Requested by: Satwik Bebortha (@satwik-cog)

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