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Java

Overview

OpenShift Container Platform provides S2I builder images for building Java applications. These builder images take your application source or binary artifacts, build the source using Maven, if the source was provided, and assemble the artifacts with any required dependencies to create a new, ready-to-run image containing your Java application. This resulting image can be run on OpenShift Container Platform or run directly with Docker.

The builder images are intended for use with Maven-based Java standalone projects that are run via main class.

Versions

The current version of the Java S2I builder images support OpenJDK 1.8 and 11, Jolokia 1.6.2, and Maven 3.6.

Images

The RHEL 7 and RHEL 8 images are available through the Red Hat Registry.

registry.redhat.io requires authentication. For details on how to configure your environment for registry.redhat.io, see Red Hat Container Registry Authentication.

RHEL 7 based images

$ docker pull registry.redhat.io/redhat-openjdk-18/openjdk18-openshift
$ docker pull registry.redhat.io/openjdk/openjdk-11-rhel7

RHEL 8 based images

$ docker pull registry.redhat.io/ubi8/openjdk-8
$ docker pull registry.redhat.io/ubi8/openjdk-11

To use these images on OpenShift Container Platform, you can either access them directly from the Red Hat Registry or push them into your OpenShift Container Platform container image registry. Additionally, you can create an image stream that points to the image, either in your container image registry or at the external location. Your OpenShift Container Platform resources can then reference the image stream definition.

Build Process

S2I produces ready-to-run images by injecting source code into a container and letting the container prepare that source code for execution. It performs the following steps:

  1. Starts a container from the builder image.

  2. Downloads the application source.

  3. Streams the scripts and application sources into the builder image container.

  4. Runs the assemble script (from the builder image).

  5. Saves the final image.

See S2I Build Process for a detailed overview of the build process.

Configuration

By default, the Java S2I builder image uses Maven to build the project with the following goals and options:

mvn -e -Popenshift -DskipTests -Dcom.redhat.xpaas.repo.redhatga -Dfabric8.skip=true --batch-mode -Djava.net.preferIPv4Stack=true -s /tmp/artifacts/configuration/settings.xml -Dmaven.repo.local=/tmp/artifacts/m2  package

Based on these defaults, the builder image compiles the project and copies all the transitive dependencies into the output directory without running tests. Additionally, if the project has a profile named openshift, it is activated for the build.

You can override these default goals and options by specifying the following environment variables:

Variable name Description

MAVEN_S2I_ARTIFACT_DIRS

Relative paths of source directories to scan for build output, which are copied to DEPLOY_DIR. Defaults to target.

JAVA_MAIN_CLASS

A main class to use as the argument for java. When this environment variable is given, all jar files in JAVA_APP_DIR are added to the classpath and JAVA_LIB_DIR.

MAVEN_ARGS

The arguments that are passed to the mvn command. Defining this variable replaces the defaults, which are -e -Popenshift -DskipTests -Dcom.redhat.xpaas.repo.redhatga package.

MAVEN_ARGS_APPEND

Additional Maven arguments.

This is a selection of the environment variables available for configuring the behavior of the OpenJDK containers. For a comprehensive list, see Java Environment Variables.

Building and Deploying Java Applications

The OpenJDK image stream must first be installed. If you ran a standard installation, the image stream will be present.

The same S2I builder image can be used to build a Java application from source or from binary artifacts.

Building and Deploying from Source

The Java S2I builder image can be used to build an application from source by running oc new-app against a source repository:

$ oc new-app registry.redhat.io/redhat-openjdk-18/openjdk18-openshift~https://github.com/jboss-openshift/openshift-quickstarts --context-dir=undertow-servlet

By default, tests are not run. To build an application and run tests as part of the build, override the default MAVEN_ARGS, as shown in the following command:

$ oc new-app registry.redhat.io/redhat-openjdk-18/openjdk18-openshift~<git_repo_URL> --context-dir=<context_dir> --build-env='MAVEN_ARGS=-e -Popenshift -Dcom.redhat.xpaas.repo.redhatga package'

If a Java project consists of multiple Maven modules, it can be useful to explicitly specify the artifact output directory. Specifying the directory where the Maven project outputs the artifacts enables the S2I build to pick them up.

To specify the modules to build and the artifact output directory, use the following command:

$ oc new-app registry.redhat.io/redhat-openjdk-18/openjdk18-openshift~<git_repo_URL> --context-dir=<context_dir> --build-env='MAVEN_S2I_ARTIFACT_DIRS=relative/path/to/artifacts/dir' --build-env='MAVEN_ARGS=install -pl <groupId>:<artifactId> -am'

Building and Deploying from Binary Artifacts

You can use the Java S2I builder image to build an application using binary artifacts that you provide.

  1. Create a new binary build:

    $ oc new-build --name=<application_name> registry.redhat.io/redhat-openjdk-18/openjdk18-openshift --binary=true

  2. Start a build and specify the path to the binary artifacts on your local machine:

    $ oc start-build <application_name> --from-dir=/path/to/artifacts --follow

  3. Create an application:

    $ oc new-app <application_name>

Java Environment Variables

The following tables provide a comprehensive list of Java environment variables used for configuring the behavior of the OpenJDK containers.

Table 1. Configuration environment variables
Variable name Description Example value

AB_JOLOKIA_CONFIG

If set, uses this file, including path, as Jolokia JVM agent properties, as described in the Jolokia reference manual. If not set, the /opt/jolokia/etc/jolokia.properties is created using the settings as defined in the manual. Otherwise, the rest of the settings in this document are ignored.

/opt/jolokia/custom.properties

AB_JOLOKIA_DISCOVERY_ENABLED

Enable Jolokia discovery. Defaults to false.

true

AB_JOLOKIA_HOST

Host address to bind to. Defaults to 0.0.0.0.

127.0.0.1

AB_JOLOKIA_ID

Agent ID to use. Defaults to $HOSTNAME, which is the container ID.

openjdk-app-1-xqlsj

AB_JOLOKIA_OFF

If set, disables activation of Jolokia, for example, echos an empty value. By default, Jolokia is enabled.

true

AB_JOLOKIA_OPTS

Additional options to be appended to the agent configuration. They should be given in the format key=value,key=value,…​.

backlog=20

AB_JOLOKIA_PASSWORD

Password for basic authentication. By default, authentication is switched off.

mypassword

AB_JOLOKIA_PORT

Port to listen to. Defaults to 8778.

5432

AB_JOLOKIA_USER

User for basic authentication. Defaults to jolokia.

myusername

AB_PROMETHEUS_ENABLE

Enable the use of the Prometheus agent.

true

AB_PROMETHEUS_JMX_EXPORTER_PORT

Port to use for the Prometheus JMX Exporter.

9799

CONTAINER_CORE_LIMIT

A calculated core limit as described in CFS Bandwidth Control.

2

CONTAINER_MAX_MEMORY

Memory limit given to the container.

1024

GC_ADAPTIVE_SIZE_POLICY_WEIGHT

The weighting given to the current GC time versus previous GC times.

90

GC_CONTAINER_OPTIONS

Specify the Java GC to use. The value of this variable should contain the necessary JRE command-line interface options to specify the required GC, which overrides the default of -XX:+UseParallelOldGC.

-XX:+UseG1GC

GC_MAX_HEAP_FREE_RATIO

Maximum percentage of heap free after GC to avoid shrinking.

40

GC_MAX_METASPACE_SIZE

The maximum metaspace size.

100

GC_METASPACE_SIZE

The initial metaspace size.

20

GC_MIN_HEAP_FREE_RATIO

Minimum percentage of heap free after GC to avoid expansion.

20

GC_TIME_RATIO

Specifies the ratio of the time spent outside the garbage collection, for example, the time spent for application execution, to the time spent in the garbage collection.

4

HTTPS_PROXY

The location of the https proxy. This takes precedence over http_proxy and HTTP_PROXY, and is used for both Maven builds and Java runtime.

myuser@127.0.0.1:8080

HTTP_PROXY

The location of the http proxy. This is used for both Maven builds and Java runtime.

127.0.0.1:8080

JAVA_APP_DIR

The directory where the application resides. All paths in your application are relative to this directory.

myapplication/`

JAVA_ARGS

Arguments passed to the java application.

-

JAVA_CLASSPATH

The classpath to use. If not given, the startup script checks for a file JAVA_APP_DIR/classpath and uses its content literally as classpath. If this file does not exist, all jars in the app dir are added. (classes:JAVA_APP_DIR/*).

-

JAVA_DEBUG

If set, remote debugging is switched on. Disabled by default.

true

JAVA_DEBUG_PORT

Port used for remote debugging. Defaults to 5005.

8787

JAVA_DIAGNOSTICS

Set this variable to get some diagnostics information to standard output when things are happening. Disabled by default.

true

JAVA_INITIAL_MEM_RATIO

Used when no -Xms option is given in JAVA_OPTS. This is used to calculate a default initial heap memory based on the maximum heap memory. If used in a container without any memory constraints for the container, this option has no effect. If there is a memory constraint, -Xms is set to a ratio of the -Xmx memory as set here. The default is 25 which means 25% of the -Xmx is used as the initial heap size. You can skip this mechanism by setting this value to 0, in which case no -Xms option is added.

25

JAVA_LIB_DIR

Directory holding the Java jar files and an optional classpath file which holds the classpath as either a single line classpath (colon separated) or with jar files listed line-by-line. If not set, JAVA_LIB_DIR is the same as JAVA_APP_DIR.

-

JAVA_MAIN_CLASS

A main class to use as the argument for java. When this environment variable is given, all jar files in JAVA_APP_DIR are added to the classpath and JAVA_LIB_DIR.

com.example.MainClass

JAVA_MAX_INITIAL_MEM

Used when no -Xms option is given in JAVA_OPTS. This is used to calculate the maximum value of the initial heap memory. If used in a container without any memory constraints for the container, this option has no effect. If there is a memory constraint, -Xms is limited to the value set here. The default is 4096 MB, which means the calculated value of -Xms is never greater than 4096 MB. The value of this variable is expressed in MB.

4096

JAVA_MAX_MEM_RATIO

Used when no -Xmx option is given in JAVA_OPTS. This is used to calculate a default maximal heap memory based on a containers restriction. If used in a container without any memory constraints for the container, this option has no effect. If there is a memory constraint, -Xmx is set to a ratio of the container available memory as set here. The default is 50, which means 50% of the available memory is used as an upper boundary. You can skip this mechanism by setting this value to 0, in which case no -Xmx option is added.

-

JAVA_OPTS

JVM options passed to the java command.

-verbose:class

JAVA_OPTS_APPEND

User specified Java options to be appended to generated options in JAVA_OPTS.

-Dsome.property=foo

LOGGING_SCRIPT_DEBUG

Set to true to enable script debugging. Deprecates SCRIPT_DEBUG.

true

MAVEN_ARGS

Arguments to use when calling Maven, replacing the default package hawt-app:build -DskipTests -e. Be sure to run the hawt-app:build goal when not already bound to the package execution phase, otherwise the startup scripts do not work.

-e -Popenshift -DskipTests -Dcom.redhat.xpaas.repo.redhatga package

MAVEN_ARGS_APPEND

Additional Maven arguments.

-X -am -pl

MAVEN_CLEAR_REPO

If set, the Maven repository is removed after the artifact is built. This is useful for keeping the created application image small, but prevents incremental builds. This variable is overridden by S2I_ENABLE_INCREMENTAL_BUILDS. Defaults to false.

-

MAVEN_LOCAL_REPO

Directory to use as the local Maven repository.

/home/jboss/.m2/repository

MAVEN_MIRRORS

If set, multi-mirror support is enabled, and other MAVEN_MIRROR_* variables are prefixed. For example, DEV_ONE_MAVEN_MIRROR_URL and QE_TWO_MAVEN_MIRROR_URL.

dev-one,qe-two

MAVEN_MIRROR_URL

The base URL of a mirror used for retrieving artifacts.

http://10.0.0.1:8080/repository/internal/

MAVEN_REPOS

If set, multi-repo support is enabled, and other MAVEN_REPO_* variables are prefixed. For example, DEV_ONE_MAVEN_REPO_URL and QE_TWO_MAVEN_REPO_URL.

dev-one,qe-two

MAVEN_S2I_ARTIFACT_DIRS

Relative paths of source directories to scan for build output, which are copied to DEPLOY_DIR. Defaults to target.

target

MAVEN_S2I_GOALS

Space separated list of goals to be run with the maven build. For example, mvn $MAVEN_S2I_GOALS. Defaults to package.

package install

MAVEN_SETTINGS_XML

Location of custom Maven settings.xml file to use.

/home/jboss/.m2/settings.xml

NO_PROXY

A comma separated list of hosts, IP addresses or domains that can be accessed directly. This is used for both Maven builds and Java runtime.

foo.example.com,bar.example.com

S2I_ARTIFACTS_DIR

Location mount for artifacts persisted with save-artifacts script, which are used with incremental builds. This must not be overridden by end users.

${S2I_DESTINATION_DIR}/artifacts}

S2I_DESTINATION_DIR

Root directory for S2I mount, as specified by the io.openshift.s2i.destination label. This must not be overridden by end users.

/tmp

S2I_ENABLE_INCREMENTAL_BUILDS

Do not remove source and intermediate build files so they can be saved for use with future builds. Defaults to true.

true

S2I_IMAGE_SOURCE_MOUNTS

Comma separated list of relative paths in the source directory which should be included in the image. The list can include wildcards, which are expanded using find. By default, the contents of mounted directories are processed similarly to source folders, where the contents of S2I_SOURCE_CONFIGURATION_DIR, S2I_SOURCE_DATA_DIR, and S2I_SOURCE_DEPLOYMENTS_DIR are copied to their respective target directories. Alternatively, if an install.sh file is located in the root of the mount point, it is executed instead. Deprecates CUSTOM_INSTALL_DIRECTORIES.

extras/*

S2I_SOURCE_CONFIGURATION_DIR

Relative path to directory containing application configuration files to be copied over to the product configuration directory, see S2I_TARGET_CONFIGURATION_DIR. Defaults to configuration.

configuration

S2I_SOURCE_DATA_DIR

Relative path to directory containing application data files to be copied over to the product data directory, see S2I_TARGET_DATA_DIR. Defaults to data.

data

S2I_SOURCE_DEPLOYMENTS_DIR

Relative path to directory containing binary files to be copied over to the product deployment directory, see S2I_TARGET_DEPLOYMENTS_DIR. Defaults to deployments.

deployments

S2I_SOURCE_DIR

Location of mount for source code to be built. This must not be overridden by end users.

${S2I_DESTINATION_DIR}/src}

S2I_TARGET_CONFIGURATION_DIR

Absolute path to which files located in S2I_SOURCE_DIR/S2I_SOURCE_CONFIGURATION_DIR are copied.

/opt/eap/standalone/configuration

S2I_TARGET_DATA_DIR

Absolute path to which files located in S2I_SOURCE_DIR/S2I_SOURCE_DATA_DIR are copied.

/opt/eap/standalone/data

S2I_TARGET_DEPLOYMENTS_DIR

Absolute path to which files located in S2I_SOURCE_DIR/S2I_SOURCE_DEPLOYMENTS_DIR are copied. Additionally, this is the directory to which build output is copied.

/deployments

http_proxy

The location of the http proxy. This takes precedence over HTTP_PROXY and is used for both Maven builds and Java runtime.

http://127.0.0.1:8080

https_proxy

The location of the https proxy. This takes precedence over HTTPS_PROXY, http_proxy, and HTTP_PROXY, and is used for both Maven builds and Java runtime.

myuser:mypass@127.0.0.1:8080

no_proxy

A comma separated list of hosts, IP addresses or domains that can be accessed directly. This takes precedence over NO_PROXY and is used for both Maven builds and Java runtime.

*.example.com

prefix_MAVEN_MIRROR_ID

ID to be used for the specified mirror. If omitted, a unique ID is generated.

internal-mirror

prefix_MAVEN_MIRROR_OF

Repository IDs mirrored by this entry. Defaults to external:.

-

prefix_MAVEN_MIRROR_URL

The URL of the mirror.

http://10.0.0.1:8080/repository/internal

prefix_MAVEN_REPO_DIRECTORY_PERMISSIONS

Maven repository directory permissions.

775

prefix_MAVEN_REPO_FILE_PERMISSIONS

Maven repository file permissions.

664

prefix_MAVEN_REPO_HOST

Maven repository host, if not using fully defined URL, falls back to service.

repo.example.com

prefix_MAVEN_REPO_ID

Maven repository ID.

my-repo-id

prefix_MAVEN_REPO_LAYOUT

Maven repository layout.

default

prefix_MAVEN_REPO_NAME

Maven repository name.

my-repo-name

prefix_MAVEN_REPO_PASSPHRASE

Maven repository passphrase.

maven1!

prefix_MAVEN_REPO_PASSWORD

Maven repository password.

maven1!

prefix_MAVEN_REPO_PATH

Maven repository path, if not using fully defined URL, falls back to service.

/maven2/

prefix_MAVEN_REPO_PORT

Maven repository port, if not using fully defined URL, falls back to service.

8080

prefix_MAVEN_REPO_PRIVATE_KEY

Maven repository private key.

${user.home}/.ssh/id_dsa

prefix_MAVEN_REPO_PROTOCOL

Maven repository protocol, if not using fully defined URL, falls back to service.

http

prefix_MAVEN_REPO_RELEASES_CHECKSUM_POLICY

Maven repository releases checksum policy.

warn

prefix_MAVEN_REPO_RELEASES_ENABLED

Maven repository releases enabled.

true

prefix_MAVEN_REPO_RELEASES_UPDATE_POLICY

Maven repository releases update policy.

always

prefix_MAVEN_REPO_SERVICE

Maven repository service to lookup if prefix_MAVEN_REPO_URL is not specified.

buscentr-myapp

prefix_MAVEN_REPO_SNAPSHOTS_CHECKSUM_POLICY

Maven repository snapshots checksum policy.

warn

prefix_MAVEN_REPO_SNAPSHOTS_ENABLED

Maven repository snapshots enabled.

true

prefix_MAVEN_REPO_SNAPSHOTS_UPDATE_POLICY

Maven repository snapshots update policy.

always

prefix_MAVEN_REPO_URL

Maven repository fully defined URL.

http://repo.example.com:8080/maven2/

prefix_MAVEN_REPO_USERNAME

Maven repository username.

mavenUser
Table 2. Configuration environment variables with default values
Variable name Description Value

AB_JOLOKIA_AUTH_OPENSHIFT

Switch on client authentication for OpenShift TLS communication. The value of this parameter can be a relative distinguished name which must be contained in a presented client’s certificate. Enabling this parameter automatically switches Jolokia into https communication mode. The default CA cert is set to /var/run/secrets/kubernetes.io/serviceaccount/ca.crt.

true

AB_JOLOKIA_HTTPS

Switch on secure communication with https. By default, self-signed server certificates are generated if no serverCert configuration is given in AB_JOLOKIA_OPTS.

true

AB_JOLOKIA_PASSWORD_RANDOM

Determines whether a random AB_JOLOKIA_PASSWORD is generated. Set to true to generate a random password. The generated value is written to /opt/jolokia/etc/jolokia.pw.

true

AB_PROMETHEUS_JMX_EXPORTER_CONFIG

Path to configuration to use for the Prometheus JMX Exporter.

/opt/jboss/container/prometheus/etc/jmx-exporter-config.yaml

S2I_SOURCE_DEPLOYMENTS_FILTER

A space separated list of filters to be applied when copying deployments. Defaults to *.

*

Additional resources