How to use the JBang plugin

Run Java source files directly without a build system — JBang compiles and executes them on the fly.

Common properties

containerImage defaults to a JBang image. taskRunner defaults to Docker and can be overridden for other execution environments.

Tasks

Script runs inline Java code defined in the script property — best for short, flow-specific logic. Commands runs JBang commands (e.g., jbang main.java) against source files; use it when your code lives in namespace files shared across flows, or is cloned from a Git repository with a preceding Clone task.

Declare Maven dependencies directly in the source file using JBang's //DEPS directive at the top: //DEPS com.google.guava: guava: 32.0.0-jre. JBang resolves and caches them automatically at runtime — no pom.xml or build.gradle required.

Triggers

ScriptTrigger

Polls on an interval by running an inline JBang script the same way the Script task does, and starts an execution when exitCondition matches. The script runs in a fresh container on every poll, so keep it quick.

Required properties:

• script: inline JBang script body
• exitCondition: either exit N, which matches when the script exits with code N, or a regex (with substring fallback) matched against the vars the script emits with : : {"outputs": {...}}: :

Optional:

• interval: time between polls, defaults to PT60S
• edge: defaults to true, so the trigger fires only when the condition changes from not matching to matching. The previous result is kept in the namespace KV store under a key starting with trigger-edge-. Set to false to fire on every matching poll
• containerImage: defaults to jbangdev/jbang-action
• extension: file extension for the inline script (.java, .jsh, .kt, .groovy, .md), defaults to .java. Because each poll runs in a fresh container without a cached JBang environment, .kt and .groovy scripts incur a compiler cold start (around 25-30s) on every poll, so size interval accordingly
• quiet: runs JBang with --quiet, defaults to true

The trigger outputs are available as {{ trigger.timestamp }}, {{ trigger.condition }}, {{ trigger.exitCode }} and {{ trigger.vars }}. A failed run has no vars, so only an exit N condition can match a failure. Since JBang itself exits with 1 on compile errors or unresolvable //DEPS, prefer a dedicated exit code such as exit 42 for the condition you watch.

CommandsTrigger

Same behavior as ScriptTrigger, but runs a list of commands the way the Commands task does. Required properties are commands and exitCondition; interval, edge and containerImage work as above.