**Tags:** "Hello World" Examples · Java # Java Hello World [Java](https://www.java.com) Hello World recipe running on [Zerops](https://zerops.io), backed by a [PostgreSQL](https://www.postgresql.org) database. Built with [Spring Boot](https://spring.io/projects/spring-boot), the recipe demonstrates the full Zerops integration pattern: idempotent schema migration, database-backed health check, and ready-made environment configurations spanning the entire development lifecycle. ### Available Environments - [AI Agent](https://app.zerops.io/recipes/java-hello-world.md?environment=ai-agent) - [Remote (CDE)](https://app.zerops.io/recipes/java-hello-world.md?environment=remote-cde) - [Local](https://app.zerops.io/recipes/java-hello-world.md?environment=local) - [Stage](https://app.zerops.io/recipes/java-hello-world.md?environment=stage) - **Small Production** ← current - [Highly-available Production](https://app.zerops.io/recipes/java-hello-world.md?environment=highly-available-production) ### Services in this Environment **Services:** - **core** (core:single@2) - Containers: 1 × Shared Core, 0.00 GB RAM, 0 GB Disk - **app** (ubuntu/java@21) :8080 - Containers: 2 × Shared Core, 0.75 GB RAM, 1 GB Disk - Repository: [zerops-recipe-apps/java-hello-world-app](https://github.com/zerops-recipe-apps/java-hello-world-app) - **db** (postgresql:single@18) :5432, :6432 - Containers: 1 × Shared Core, 1.25 GB RAM, 1 GB Disk **Total Resources:** 4 containers, 2.75 GB RAM, 3 GB Disk ### One-Click Deploy (Import YAML) Use this YAML with `zcli project import` to deploy this environment: ```yaml # Small production environment offers a production-ready setup # optimized for moderate throughput. project: name: java-hello-world-small-prod services: # Production app — always running on at least 2 containers # for availability and distribution across incoming requests. # Zerops pulls source and zerops.yaml from the 'buildFromGit' # public repo as the initial template. For production, replace # 'buildFromGit' with 'zcli push' or connect a git branch so # deploys are triggered by your own release workflow. # The readiness check at '/' in zerops.yaml verifies each new # container before the project balancer routes traffic to it, # enabling zero-downtime rolling updates. # For a custom domain, point your DNS to the project balancer # and configure the domain in the Zerops dashboard. - hostname: app type: java@21 zeropsSetup: prod buildFromGit: https://github.com/zerops-recipe-apps/java-hello-world-app enableSubdomainAccess: true minContainers: 2 verticalAutoscaling: minRam: 0.5 minFreeRamGB: 0.25 # PostgreSQL single-node database for production. It provides # automatic encrypted backups by default. For production traffic, # consider switching to HA mode for multi-node replication, # or implement a dedicated backup strategy. # Priority 10 ensures the database is ready before any app # container starts, preventing connection errors during scaling. - hostname: db type: postgresql:single@18 profile: oltp-production priority: 10 ``` --- ## Next Steps After deploying one of the environments and getting to know Zerops, you have two paths to choose from: 1. **Template Flow** — Clone our GitHub repositories and use the whole recipe as a template 2. **Integrate Flow** — If you already have an existing application on a similar stack, integrate the recipe setup with your application Select a flow: [Template Flow](https://app.zerops.io/recipes/java-hello-world.md?environment=small-production&guideFlow=template) or [Integrate Flow](https://app.zerops.io/recipes/java-hello-world.md?environment=small-production&guideFlow=integrate) Both flows are shown below: ## How to take over the Small Production environment ### 📦 Clone the template repositories Fork or clone the following repositories to your local machine or GitHub account: - [zerops-recipe-apps/java-hello-world-app](https://github.com/zerops-recipe-apps/java-hello-world-app) ### 1. Find your service name Many commands and configurations need the exact name of your service. You can find it in the Zerops Dashboard. - Open your project in the Zerops Dashboard. - In the project overview, find the service you want to manage. - Use this exact name whenever a command or pipeline configuration asks for ``. Zerops GUI: Locating the Service Name ### 2. Configure deployment pipeline Go to Service Settings > Pipelines & CI/CD Settings in the Zerops Dashboard and connect your repository. For production, use a trigger on new tags. This keeps deployments intentional and tied to a specific version. You can also add a regex filter, such as `^v[0-9]+\.[0-9]+\.[0-9]+$`, if you want to allow only semantic version tags. Zerops GUI: Triggers Alternatively, add `zcli push` to your existing CI/CD pipeline if you want full control over when deployments happen. Learn more about pipeline triggers: https://docs.zerops.io/features/pipeline ### 3. Deploy to production Create and push a new Git tag to deploy a specific version of your app: ```bash git tag -a v1.0.0 -m "Release version 1.0.0" git push origin v1.0.0 ``` > [!TIP] > Open the pipeline detail in the Zerops Dashboard to check the build progress and verify that all steps finish successfully. ### 4. Configure autoscaling Review the autoscaling settings for your runtime services and databases in Service Settings > Automatic Scaling Configuration in the Zerops Dashboard. Zerops GUI: Autoscaling configuration The most important settings are: ```yaml verticalAutoscaling: minRam: 1 minFreeRamGB: 0.5 minFreeRamPercent: 20 ``` > [!CAUTION] > Pay attention to `minFreeRamGB`. This value tells Zerops when to scale RAM vertically. Adjust it based on your app’s real memory needs. RAM scales up immediately, while CPU scales after two consecutive measurements below the threshold. > [!TIP] > Run a quick stress test with a tool like hey before real users arrive. This helps you see how your app behaves under load and tune the autoscaling settings. ### 5. Set up your domain To send real traffic to your app, configure public HTTP access in Service Settings > Public Access & Internal Ports in the Zerops Dashboard. Add your custom domain and point your DNS records to the Zerops IPs shown in the dashboard: Zerops GUI: Public access and custom domain ```text Type Name Content TTL A example.com Auto AAAA example.com Auto ``` For wildcard domains, add a CNAME record for SSL validation. Check the public access documentation: https://docs.zerops.io/features/access > [!TIP] > When changing DNS records for production, start with a low TTL value. Make sure SSL certificates are active before you disable the fallback Zerops subdomain. Once everything works, you can disable the Zerops subdomain so all traffic goes through your custom domain. --- ### 🎉 You are good to go! Your application is live in production and the core setup is complete. The following sections are optional. They cover extra production features such as log forwarding, backups, and diagnostic access. You can stop here and come back later when you need them. --- ### 6. Set up log forwarding (Optional) To send logs to an external service, go to Project Settings > Log Forwarding & Logs Overview in the Zerops Dashboard. You can forward logs to services like Better Stack, Papertrail, or your own self-hosted solution. Learn more about log forwarding: https://docs.zerops.io/references/logging ### 7. Configure database backups (Optional) Manage automated encrypted backups in Service Settings > Backups in the Zerops Dashboard. By default, backups run daily between 00:00 and 01:00 UTC. Before a major deployment, create a manual protected backup: ```bash zcli backup create --tags pre-deploy,protected ``` Read the backup documentation for more options: https://docs.zerops.io/features/backup ### 8. Set up diagnostic access (Optional) Use zCLI and VPN access when you need to inspect or maintain services directly. For runtime services: ```bash zcli vpn up ssh .zerops ``` For databases, connect through the VPN to reach the project’s private network, or set up secure direct IP access for your database admin tools. Check the VPN documentation: https://docs.zerops.io/references/cli/commands#vpn-up ## How to integrate app with Zerops ### 1. Adding `zerops.yaml` The main application configuration file you place at the root of your repository, it tells Zerops how to build, deploy and run your application. ```yaml # The 'prod' setup compiles an optimized Spring Boot fat JAR # for deployment. The 'dev' setup ships source code alongside # the pre-built JAR so developers can SSH in, edit files, and # rebuild freely using the pre-installed mvn and java tools. zerops: - setup: prod build: base: java@21 # Compile and package the Spring Boot fat JAR. # '-DskipTests' is intentional — integration tests # belong in CI pipelines, not in the Zerops build # container. Maven 3.9 is pre-installed on java@21. buildCommands: - mvn clean package -DskipTests # One file covers both the app and migration entry points. # ZIP layout in pom.xml enables PropertiesLauncher, which # reads -Dloader.main at runtime to switch between them. deployFiles: - target/app.jar # Maven resolves dependencies into ~/.m2 (outside the build # directory). 'cache: true' snapshots the build container # image — including ~/.m2 — so subsequent builds skip # downloading the dependency graph from Maven Central. cache: true # Zerops runs the readiness check after each new runtime # container starts and before it receives traffic from the # project balancer. Containers that fail are replaced, # not promoted. deploy: readinessCheck: httpGet: port: 8080 path: / run: base: java@21 # Run the migration exactly once per deployed version. # 'zsc execOnce ${appVersionId}' ensures a single container # executes even when minContainers > 1 — others wait. # In initCommands (not buildCommands) so migration and # new code are always deployed together atomically. # # PropertiesLauncher (ZIP layout) reads -Dloader.main # to invoke Migrate.main() directly — no Spring context # is created, just a plain JDBC connection. initCommands: - zsc execOnce ${appVersionId} -- java -Dloader.main=io.zerops.recipe.Migrate -jar target/app.jar ports: - port: 8080 httpSupport: true # Env vars follow '{hostname}_{credential}' — for the 'db' # service: db_hostname, db_port, db_user, db_password. # DB_NAME matches the database name Zerops creates (same # as the service hostname). envVariables: DB_NAME: db DB_HOST: ${db_hostname} DB_PORT: ${db_port} DB_USER: ${db_user} DB_PASS: ${db_password} start: java -jar target/app.jar - setup: dev build: base: java@21 # Build the fat JAR during the build phase so that # target/app.jar is available for the initCommands # migration and for quick test runs after SSH. buildCommands: - mvn clean package -DskipTests # Deploy source for editing and the compiled JAR for # running migrations and the app. target/ is excluded # to avoid shipping hundreds of MB of build artifacts — # only app.jar is needed. Developers rebuild with # 'mvn package' or run directly with 'mvn spring-boot:run'. deployFiles: - ./src - ./pom.xml - ./zerops.yaml - target/app.jar cache: true run: base: java@21 # Migration runs identically to prod — same JAR, # same zsc execOnce guard. initCommands: - zsc execOnce ${appVersionId} -- java -Dloader.main=io.zerops.recipe.Migrate -jar target/app.jar ports: - port: 8080 httpSupport: true envVariables: DB_NAME: db DB_HOST: ${db_hostname} DB_PORT: ${db_port} DB_USER: ${db_user} DB_PASS: ${db_password} # Dev container stays idle. SSH in and use the pre-installed # tools: 'mvn spring-boot:run' for hot-reload development, # or 'java -jar target/app.jar' to run the compiled binary. # Database is already migrated and ready when you connect. start: zsc noop --silent ``` ### 🎯 What's next? **Deploy other environments** — Ready to scale? Deploy additional environments for different stages of your workflow: - [AI Agent](https://app.zerops.io/recipes/java-hello-world.md?environment=ai-agent) - [Remote (CDE)](https://app.zerops.io/recipes/java-hello-world.md?environment=remote-cde) - [Local](https://app.zerops.io/recipes/java-hello-world.md?environment=local) - [Stage](https://app.zerops.io/recipes/java-hello-world.md?environment=stage) - [Highly-available Production](https://app.zerops.io/recipes/java-hello-world.md?environment=highly-available-production) ## Knowledge Base ### Platform Reference - [Routing & Domains](https://docs.zerops.io/features/access) - [Scaling](https://docs.zerops.io/features/scaling) - [Environment Variables](https://docs.zerops.io/features/env-variables) - [CLI (zcli)](https://docs.zerops.io/references/cli) ### Service Type Reference **Java** - [Build & Deploy](https://docs.zerops.io/java/how-to/build-pipeline) - [Customize Runtime](https://docs.zerops.io/java/how-to/customize-runtime) **PostgreSQL** - [Connect](https://docs.zerops.io/postgresql/how-to/connect) - [Backup & Restore](https://docs.zerops.io/postgresql/how-to/backup) - [Manage](https://docs.zerops.io/postgresql/how-to/manage) - [Scale](https://docs.zerops.io/postgresql/how-to/scale) --- ## Related Recipes - [Bun Hello World](https://app.zerops.io/recipes/bun-hello-world.md) - [Go Hello World](https://app.zerops.io/recipes/go-hello-world.md) - [Zerops showcase](https://app.zerops.io/recipes/zerops-showcase.md) - [Deno Hello World](https://app.zerops.io/recipes/deno-hello-world.md)