Java App CI/CD + CD Architecture

GitHub source code → Jenkins CI → Docker Hub image registry → GitLab CD with GitLab Agent → Kubernetes deployment with Helm

This diagram shows the full project flow: Jenkins handles CI tasks and pushes the Java/Tomcat image to Docker Hub, then triggers GitLab, and GitLab deploys the selected image tag to the Kubernetes cluster using Helm through GitLab Agent.
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GitHub

Source code repository for the Java web application inside my-java-app/.

Push / Commit
Webhook → Jenkins
🤵
Jenkins CI Pipeline
1. Checkout CodeGitHub repository
2. Maven Build & Testmvn clean test package
3. SonarQube ScanStatic code analysis
4. Quality GatePipeline waits for result
5. Build Docker ImageTomcat image with WAR file
6. Push to Docker HubVersion tag + latest tag
7. Trigger GitLab DeployPipeline Trigger API
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Docker Hub

Stores the built container image for deployment.

ahmad09x/java-app:4
ahmad09x/java-app:latest

Produced by Jenkins

The CD pipeline deploys a specific image tag passed from Jenkins to GitLab.
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GitLab CD Project

Dedicated deployment repository containing Helm chart files and GitLab CI/CD configuration.

Pipeline Trigger Token
.gitlab-ci.yml
Variables: KUBE_CONTEXT, DOCKER_IMAGE, IMAGE_TAG
Helm chart in helm/java-app/

Deployment Logic

GitLab receives the image tag from Jenkins, switches to the GitLab Agent Kubernetes context, and runs helm upgrade --install.
☸️

Kubernetes Cluster

Application is deployed through GitLab Agent and Helm into the target namespace.

GitLab Agent (java-agent)
Helm Deploy / Upgrade
LoadBalancer Service
☕Java App Pod
☕Java App Pod
☕Java App Pod
End-to-end flow: Developer pushes code to GitHub, Jenkins runs Maven tests and SonarQube checks, builds the Tomcat-based Java image, and pushes it to Docker Hub. Jenkins then triggers the GitLab deployment pipeline with the selected image tag. GitLab uses the configured Agent context to connect to Kubernetes and deploys the application using Helm, updating the running pods behind a LoadBalancer service.