Java Kit¶

JDK 17, 21, and 25 via mise, with Maven and Gradle available as sub-kits.

Activation: Default — added to config on first detection; active when present.

What's Included¶

JDK 17, 21, 25 installed via mise (default: 21)
Maven (via sub-kit) with dependency caching
Gradle (via sub-kit) with dependency caching

Configuration¶

kits:
  java:
    versions: [17, 21, 25]    # which JDK versions to pre-install in the base image
    default-version: "21"     # which JDK is the global default

Option	Type	Default	Description
`versions`	list	`[17, 21, 25]`	JDK versions installed in the base image via mise
`default-version`	string	`"21"`	JDK version to set as the global default

If default-version is not in versions, it is installed in the project image instead of the base image. You can also install additional versions at runtime with mise install java@<version>.

Sub-Kits¶

java/maven¶

Installs Maven via apt. Dependency cache persisted at ~/.m2.

Maven Credentials¶

The java/maven kit can inject credentials from your host's ~/.m2/settings.xml into the container. Rather than mounting the full file, it generates a filtered settings.xml containing only the server entries that your project's pom.xml actually references — so unrelated credentials stay on the host.

Configure credentials under the java kit:

Auto mode (default when credentials are enabled): Asylum reads the pom.xml in your project root, extracts all referenced server IDs (from repositories, pluginRepositories, distributionManagement, and profiles), and injects the matching entries.

kits:
  java:
    credentials: auto

Explicit mode: Specify server IDs directly, bypassing pom.xml discovery. Useful for multi-module projects or when the root pom.xml doesn't declare all repositories.

kits:
  java:
    credentials:
      - nexus-releases
      - nexus-snapshots

Disabling: Set credentials: false to prevent any credential injection.

The filtered settings.xml is mounted read-only at ~/.m2/settings.xml inside the container. If ~/.m2/settings.xml does not exist on the host, or no referenced server IDs match, nothing is mounted. If a server ID is referenced in pom.xml but missing from settings.xml, a comment is added in its place in the generated file.

Credentials are enabled via asylum config (interactive) or by editing .asylum directly. Changes to credentials take effect on the next fresh container start — if a container is already running, use asylum --rebuild to apply them.

java/gradle¶

Installs Gradle via mise. Dependency cache persisted at ~/.gradle.

Version Switching¶

Switch JDK version inside the container:

mise use java@17
mise use java@25

You can also set the version via environment variable in your config:

kits:
  java:
    default-version: "17"

Or detect it automatically from .tool-versions in your project root.

Auto-Detection¶

If your project has a .tool-versions file with a java entry, Asylum reads the version from it and sets it as the default in the container.