---
title: Containerize a Java application
linkTitle: Containerize your app
weight: 10
keywords: java, containerize, initialize, maven, build
description: Learn how to containerize a Java application.
aliases:
  - /language/java/build-images/
  - /language/java/run-containers/
  - /language/java/containerize/
  - /guides/language/java/containerize/
---

## Prerequisites

- You have installed the latest version of [Docker Desktop](/get-started/get-docker.md).
  Docker adds new features regularly and some parts of this guide may
  work only with the latest version of Docker Desktop.

* You have a [Git client](https://git-scm.com/downloads). The examples in this
  section use a command-line based Git client, but you can use any client.

## Overview

This section walks you through containerizing and running a Java
application.

## Get the sample applications

Clone the sample application that you'll be using to your local development machine. Run the following command in a terminal to clone the repository.

```console
$ git clone https://github.com/spring-projects/spring-petclinic.git
```

The sample application is a Spring Boot application built using Maven. For more details, see `readme.md` in the repository.

## Initialize Docker assets

Now that you have an application, you can create the necessary Docker assets to
containerize your application. You can use Docker Desktop's built-in Docker Init
feature to help streamline the process, or you can manually create the assets.

{{< tabs >}}
{{< tab name="Use Docker Init" >}}

Inside the `spring-petclinic` directory, run the `docker init` command. `docker
init` provides some default configuration, but you'll need to answer a few
questions about your application. Refer to the following example to answer the
prompts from `docker init` and use the same answers for your prompts.

The sample application already contains Docker assets. You'll be prompted to overwrite the existing Docker assets. To continue with this guide, select `y` to overwrite them.

```console
$ docker init
Welcome to the Docker Init CLI!

This utility will walk you through creating the following files with sensible defaults for your project:
  - .dockerignore
  - Dockerfile
  - compose.yaml
  - README.Docker.md

Let's get started!

WARNING: The following Docker files already exist in this directory:
  - docker-compose.yml
? Do you want to overwrite them? Yes
? What application platform does your project use? Java
? What's the relative directory (with a leading .) for your app? ./src
? What version of Java do you want to use? 21
? What port does your server listen on? 8080
```

In the previous example, notice the `WARNING`. `docker-compose.yaml` already
exists, so `docker init` overwrites that file rather than creating a new
`compose.yaml` file. This prevents having multiple Compose files in the
directory. Both names are supported, but Compose prefers the canonical
`compose.yaml`.

{{< /tab >}}
{{< tab name="Manually create assets" >}}

If you don't have Docker Desktop installed or prefer creating the assets
manually, you can create the following files in your project directory.

Create a file named `Dockerfile` with the following contents.

```dockerfile {collapse=true,title=Dockerfile}
# syntax=docker/dockerfile:1

# Comments are provided throughout this file to help you get started.
# If you need more help, visit the Dockerfile reference guide at
# https://docs.docker.com/go/dockerfile-reference/

# Want to help us make this template better? Share your feedback here: https://forms.gle/ybq9Krt8jtBL3iCk7

################################################################################

# Create a stage for resolving and downloading dependencies.
FROM eclipse-temurin:21-jdk-jammy as deps

WORKDIR /build

# Copy the mvnw wrapper with executable permissions.
COPY --chmod=0755 mvnw mvnw
COPY .mvn/ .mvn/

# Download dependencies as a separate step to take advantage of Docker's caching.
# Leverage a cache mount to /root/.m2 so that subsequent builds don't have to