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

[devin-ai-integration]

Summary

This PR upgrades the Spring Boot BankApp from Java 17 to Java 22 across all configuration files, Docker images, and documentation.

Changes made:

• pom.xml: Updated java.version to 22, fixed maven-compiler-plugin source/target from 1.8 to 22, upgraded Spring Boot parent from 3.3.3 to 3.4.0
• Dockerfile: Updated builder stage to maven:3.9-eclipse-temurin-22 and runtime stage to eclipse-temurin:22-jre-alpine
• README.md & README-K8S.md: Updated Jenkins installation to use Eclipse Temurin (Adoptium) repository for Java 22 (since openjdk-22-jre is not available in Ubuntu apt repositories)
• kubernetes/bankapp-deployment.yml: Updated container image tag to java22

Updates since last revision

• Fixed Docker images to use verified existing tags:
  • Builder: maven:3.9-eclipse-temurin-22 (previously referenced non-existent maven:3.8.3-openjdk-22)
  • Runtime: eclipse-temurin:22-jre-alpine (previously referenced non-existent openjdk:22-alpine)
• Updated Jenkins installation docs to use Eclipse Temurin repository with temurin-22-jdk package instead of unavailable openjdk-22-jre

Review & Testing Checklist for Human

• Build Docker image locally: Run docker build -t bankapp:java22 . to verify the image builds successfully with the new base images
• Test application startup: Run the container and verify the Spring Boot application starts correctly with Java 22
• Build and push Docker image: After merging, build and push to trainwithshubham/bankapp-eks:java22 before deploying to Kubernetes

Recommended test plan:

1. Build Docker image locally: docker build -t bankapp:java22 .
2. Run container: docker run -p 8080:8080 bankapp:java22 (will fail without MySQL, but should show Spring Boot startup)
3. After merge, push image and deploy to EKS

Notes

• The maven-compiler-plugin version (3.8.0) is retained but may benefit from an upgrade for better Java 22 support
• The Kubernetes deployment references trainwithshubham/bankapp-eks:java22 which needs to be built and pushed after this PR is merged
• Local Maven build was not verified (dev environment has Java 21); Docker build will handle Java 22 compilation
• Snyk security check shows 1 pre-existing vulnerability (not introduced by this PR)

Link to Devin run: https://app.devin.ai/sessions/e4614558bfff42e0adbb5e24bba87f63
Requested by: Satwik Bebortha (@satwik-cog)

[devin-ai-integration]

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