clefos/ibmjava repository overview

⁠Building the Image

This Dockerfile expects the IBM Java SDK to have been downloaded into this directory.

You may obtain the SDK from IBM Developerworks⁠

⁠IBM® SDK, Java™ Technology Edition and Docker

Dockerfiles and build scripts for generating various Docker Images related to IBM® SDK, Java™ Technology Edition.

⁠Overview

The images in this repository contain IBM® SDK, Java™ Technology Edition.

Java and all Java-based trademarks and logos are trademarks or registered trademarks of Oracle and/or its affiliates.

⁠Images

There are three types of Docker images here: the Software Developers Kit (SDK), and the Java Runtime Environment (JRE) and a small footprint version of the JRE (SFJ). These images can be used as the basis for custom built images for running your applications.

⁠Small Footprint JRE

The Small Footprint JRE (SFJ⁠) is designed specifically for web developers who want to develop and deploy cloud-based Java applications. Java tools and functions that are not required in the cloud environment, such as the Java control panel, are removed. The runtime environment is stripped down to provide core, essential function that has a greatly reduced disk and memory footprint.

⁠How to use this Image

To run a pre-built jar file with the JRE image, use the following commands:

FROM clefos/ibmjava:jre
RUN mkdir /opt/app
COPY japp.jar /opt/app
CMD ["java", "-jar", "/opt/app/japp.jar"]

You can build and run the Docker Image as shown in the following example:

docker build -t japp .
docker run -it --rm japp

If you want to place the jar file on the host file system instead of inside the container, you can mount the host path onto the container by using the following commands:

FROM clefos/ibmjava:jre
CMD ["java", "-jar", "/opt/app/japp.jar"]

docker build -t japp .
docker run -it -v /path/on/host/system/jars:/opt/app japp

⁠Using the Class Data Sharing feature

IBM SDK, Java Technology Edition provides a feature called Class data sharing⁠. This mechanism offers transparent and dynamic sharing of data between multiple Java virtual machines (JVMs) running on the same host thereby reducing the amount of physical memory consumed by each JVM instance. By providing partially verified classes and possibly pre-loaded classes in memory, this mechanism also improves the start up time of the JVM.

To enable class data sharing between JVMs that are running in different containers on the same host, a common location must be shared between containers. This requirement can be satisfied through the host or a data volume container. When enabled, class data sharing creates a named "class cache", which is a memory-mapped file, at the common location. This feature is enabled by passing the -Xshareclasses option to the JVM as shown in the following Dockerfile example:

FROM clefos/ibmjava:jre
RUN mkdir /opt/shareclasses
RUN mkdir /opt/app
COPY japp.jar /opt/app
CMD ["java", "-Xshareclasses:cacheDir=/opt/shareclasses", "-jar", "/opt/app/japp.jar"]

The cacheDir sub-option specifies the location of the class cache. For example /opt/sharedclasses. When sharing through the host, a host path must be mounted onto the container at the location the JVM expects to find the class cache. For example:

docker build -t japp .
docker run -it -v /path/on/host/shareclasses/dir:/opt/shareclasses japp

When sharing through a data volume container, create a named data volume container that shares a volume.

docker create -v /opt/shareclasses --name classcache japp /bin/true

Then start your JVM container by using --volumes-from flag to mount the shared volume, as shown in the following example:

docker run -it --volumes-from classcache japp

⁠See Also

See the Websphere-Liberty image⁠, which builds on top of this IBM docker image for Java.

⁠License

The Dockerfiles and associated scripts are licensed under the Apache License 2.0⁠.

Licenses for the products installed within the images:

• IBM® SDK, Java™ Technology Edition: International License Agreement for Non-Warranted Programs⁠.
• IBM® SDK, Java™ Technology Edition Version 9 Early Access: International License Agreement for Non-Warranted Programs⁠

⁠Issues

For issues relating specifically to this Docker image, please use the GitHub issue tracker⁠.

For more general issues relating to IBM® SDK, Java™ Technology Edition you can ask questions in the developerWorks forum: IBM Java Runtimes and SDKs⁠.

For general information on Troubleshooting with the SDK, please do take a look at our How Do I ...?⁠ page.