Packaging OpenJDK 8 applications in containers

OpenJDK 8

Red Hat Developer Customer Content Services

Abstract

OpenJDK is a Red Hat offering on the Red Hat Enterprise Linux platform. The Packaging OpenJDK 8 applications in containers guide provides an overview of this product and explains how to package the applications in a container.

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Chapter 1. OpenJDK applications in containers

OpenJDK images have default startup scripts that automatically detect application JAR files and launch Java. The script’s behavior can be customized using environment variables. For more information, see /help.md in the container.

The OpenJDK applications in the /deployments directory of the OpenJDK image are run when the image loads.

Note

Containers that contain OpenJDK applications are not automatically updated with security updates. Ensure that you update these images at least once every three months.

Application JAR files can be fat JARs or thin JARs.

  • Fat JARs contain all of the application’s dependencies.

  • Thin JARs reference other JARs that contain some, or all, of the application’s dependencies.

    Thin JARs are only supported if:

    • They have a flat classpath.
    • All dependencies are JARs that are in the /deployments directory.

Chapter 2. Deploying OpenJDK applications in containers

You can deploy OpenJDK applications in containers and have them run when the container is loaded.

Procedure

  • Copy the application JAR to the /deployments directory in the image JAR file.

    For example, the following shows a brief Dockerfile that adds an application called testubi.jar to the OpenJDK 8 UBI8 image: 

    FROM registry.access.redhat.com/ubi8/openjdk-8

COPY target/testubi.jar /deployments/testubi.jar

Chapter 3. Updating OpenJDK container images

To ensure that an OpenJDK container with Java applications includes the latest security updates, rebuild the container.

Procedure

  1. Pull the base OpenJDK image.

  2. Deploy the OpenJDK application. For more information, see Deploying OpenJDK applications in containers.

    The OpenJDK container with the OpenJDK application is updated.

Additional resources

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