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Build environment variables for Java in Azure Container Apps

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Azure Container Apps uses Buildpacks to automatically create a container image that allows you to deploy from your source code directly to the cloud. To take control of your build configuration, you can use environment variables to customize parts of your build like the JDK, Maven, and Tomcat. The following article shows you how to configure environment variables to help you take control over builds that automatically create a container for you.

Supported Java build environment variables

Configure JDK

Container Apps use Microsoft Build of OpenJDK to build source code and as the runtime environment. Four LTS JDK versions are supported: 8, 11, 17 and 21.

  • For source code build, the default version is JDK 17.

  • For a JAR file build, the JDK version is read from the file location META-INF\MANIFEST.MF in the JAR, but uses the default JDK version 17 if the specified version isn't available.

Here's a listing of the environment variables used to configure JDK:

Environment variable Description Default
BP_JVM_VERSION Controls the JVM version. 17

Configure Maven

Container Apps supports building Maven-based applications from source.

Here's a listing of the environment variables used to configure Maven:

Build environment variable Description Default
BP_MAVEN_VERSION Sets the major Maven version. Since Buildpacks only ships a single version of each supported line, updates to the buildpack can change the exact version of Maven installed. If you require a specific minor/patch version of Maven, use the Maven wrapper instead. 3
BP_MAVEN_BUILD_ARGUMENTS Defines the arguments passed to Maven. The --batch-mode is prepended to the argument list in environments without a TTY. -Dmaven.test.skip=true --no-transfer-progress package
BP_MAVEN_ADDITIONAL_BUILD_ARGUMENTS Defines extra arguments used (for example, -DskipJavadoc appended to BP_MAVEN_BUILD_ARGUMENTS) to pass to Maven.
BP_MAVEN_ACTIVE_PROFILES Comma separated list of active profiles passed to Maven.
BP_MAVEN_BUILT_MODULE Designates application artifact that contains the module. By default, the build looks in the root module.
BP_MAVEN_BUILT_ARTIFACT Location of the built application artifact. This value supersedes the BP_MAVEN_BUILT_MODULE variable. You can match a single file, multiple files, or a directory through one or more space separated patterns. target/*.[ejw]ar
BP_MAVEN_POM_FILE Specifies a custom location to the project's pom.xml file. This value is relative to the root of the project (for example, /workspace). pom.xml
BP_MAVEN_DAEMON_ENABLED Triggers the installation and configuration of Apache maven-mvnd instead of Maven. Set this value to true if you want to the Maven Daemon. false
BP_MAVEN_SETTINGS_PATH Specifies a custom location to Maven's settings.xml file.
BP_INCLUDE_FILES Colon separated list of glob patterns to match source files. Any matched file is retained in the final image.
BP_EXCLUDE_FILES Colon separated list of glob patterns to match source files. Any matched file is removed from the final image. Any include patterns are applied first, and you can use "exclude patterns" to reduce the files included in the build.
BP_JAVA_INSTALL_NODE Control whether or not a separate Buildpack installs Yarn and Node.js. If set to true, the Buildpack checks the app root or path set by BP_NODE_PROJECT_PATH. The project path looks for either a yarn.lock file, which requires the installation of Yarn and Node.js. If there's a package.json file, then the build only requires Node.js. false
BP_NODE_PROJECT_PATH Direct the project subdirectory to look for package.json and yarn.lock files.

Configure Tomcat

Container Apps supports running war file in Tomcat application server.

Here's a listing of the environment variables used to configure Tomcat:

Build environment variable Description Default
BP_TOMCAT_CONTEXT_PATH The context path where the application is mounted. Defaults to empty (ROOT)
BP_TOMCAT_EXT_CONF_SHA256 The SHA256 hash of the external configuration package.
BP_TOMCAT_ENV_PROPERTY_SOURCE_DISABLED When set to true, the Buildpack doesn't configure org.apache.tomcat.util.digester.EnvironmentPropertySource. This configuration option is added to support loading configuration from environment variables and referencing them in Tomcat configuration files.
BP_TOMCAT_EXT_CONF_STRIP The number of directory levels to strip from the external configuration package. 0
BP_TOMCAT_EXT_CONF_URI The download URI of the external configuration package.
BP_TOMCAT_EXT_CONF_VERSION The version of the external configuration package.
BP_TOMCAT_VERSION Used to configure a specific Tomcat version. Supported Tomcat versions include 8, 9, and 10. 9.*

Configure Cloud Build Service

Here's a listing of the environment variables used to configure a Cloud Build Service:

Build environment variable Description Default
ORYX_DISABLE_TELEMETRY Controls whether or not to disable telemetry collection. false

How to configure Java build environment variables

You can configure Java build environment variables when you deploy Java application source code via CLI command az containerapp up, az containerapp create, or az containerapp update:

az containerapp up \
  --name <CONTAINER_APP_NAME> \
  --source <SOURCE_DIRECTORY> \
  --build-env-vars <NAME=VALUE NAME=VALUE> \
  --resource-group <RESOURCE_GROUP_NAME> \
  --environment <ENVIRONMENT_NAME>

The build-env-vars argument is a list of environment variables for the build, space-separated values in key=value format. Here's an example list you can pass in as variables:

BP_JVM_VERSION=21 BP_MAVEN_VERSION=4 "BP_MAVEN_BUILD_ARGUMENTS=-Dmaven.test.skip=true --no-transfer-progress package"

You can also configure the Java build environment variables when you set up GitHub Actions with Azure CLI in Azure Container Apps.

az containerapp github-action add \
  --repo-url "https://github.com/<OWNER>/<REPOSITORY_NAME>" \
  --build-env-vars <NAME=VALUE NAME=VALUE> \
  --branch <BRANCH_NAME> \
  --name <CONTAINER_APP_NAME> \
  --resource-group <RESOURCE_GROUP> \
  --registry-url <URL_TO_CONTAINER_REGISTRY> \
  --registry-username <REGISTRY_USER_NAME> \
  --registry-password <REGISTRY_PASSWORD> \
  --service-principal-client-id <appId> \
  --service-principal-client-secret <password> \
  --service-principal-tenant-id <tenant> \
  --token <YOUR_GITHUB_PERSONAL_ACCESS_TOKEN>

Next steps

Build and deploy from a repository