Image Overview: maven

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Minimal image with Maven build system.

Download this Image

The image is available on cgr.dev:

docker pull cgr.dev/chainguard/maven:latest

Using Maven

Chainguard Maven images come with different versions of OpenJDK, ensure you choose the correct image tag for your application needs. In these examples we will use a Chainguard Maven image based on OpenJDK 17.

Check the maven version

docker run --rm --platform=linux/amd64 cgr.dev/chainguard/maven:openjdk-17 --version

Examples

SpringBoot

Visit https://start.spring.io

Select the following options:

1. Project: select Maven Project
2. Spring Boot: latest GA version, e.g. 2.7.5
3. Project Metadata: populate your application details
4. Packaging: select your packaging. For this demo, we’ll use jar
5. Java: select Java version, e.g. 17 that matches the OpenJDK image version we are building with
6. Dependencies: choose your dependencies, e.g. Spring Web
7. Generate: Hit that generate button!

Go to your downloaded zip file, unzip

mkdir ~/chainguard-sb
cd chainguard-sb
mv ~/Downloads/demo.zip .
unzip demo.zip
cd demo

You now have your generated Spring Boot application souce code. Now let’s build it.

docker run --platform=linux/amd64 --rm -v ${PWD}:/home/build cgr.dev/chainguard/maven:openjdk-17 clean install

Check to see your compiled jar file

find target -name "*.jar"

You should see…

target/demo-0.0.1-SNAPSHOT.jar

Let’s run the application using the Chainguard OpenJDK JRE image. Note there’s a few things happening here and this is just for test purposes, see section below for more real world scenarios.

Choose the Chainguard OpenJDK JRE image tag that matches your application’s Java version selected when generating your Spring Boot application above.

docker run --platform=linux/amd64 --rm -p 8080:8080 -v ${PWD}/target:/app/ cgr.dev/chainguard/jre:openjdk-17 -jar /app/demo-0.0.1-SNAPSHOT.jar

Now visit the Spring Boot Application in your browser using the same port mapped in the docker command above.

e.g http://localhost:8080/

Note this is the expected Spring Whitelabel error page.

Multistage Dockerfile

The steps above are useful to test Chainguard images however, we can now create a multistage Dockerfile that will build a smaller image to run our demo application.

First create a .dockerignore file so we don’t copy the generated maven ./target folder from the steps above into the multistage docker build. This helps avoid any permission errors during the build.

cat <<EOF >>.dockerignore
target/
EOF

Next create the multistage Dockerfile

cat <<EOF >>Dockerfile
FROM cgr.dev/chainguard/maven:openjdk-17

WORKDIR /home/build

COPY . ./

RUN mvn install

FROM cgr.dev/chainguard/jre:openjdk-17

COPY --from=0 /home/build/target/demo-*.jar /app/demo.jar

CMD ["-jar", "/app/demo.jar"]
EOF

Build your application image

docker build --platform=linux/amd64 -t my-chainguard-springboot-app .

Now run your application

docker run --platform=linux/amd64 --rm -p 8080:8080 my-chainguard-springboot-app

Again visit the Spring Boot Whitelabel page in your browser

e.g. http://localhost:8080/

What’s inside?

Now let’s take a closer look at your newly built image.

Check the size of your image, as this is based on Chainguard images it will only contain the Linux packages required to run your application. The reduces the number of packages that can be affected by CVEs.

docker images | grep my-chainguard-springboot-app

You can also check for vulnerabilities using your favorite scanner.