jr-runtime (merged into jr-apputils)

This library was merged into jr-apputils on 2026-10-11: JrApp is there under the package jarrunner.jr.apputils, and its update check became Updater.checkAtMostEvery, inBackground and notice, which ask jr itself so the update rules live in one place. This repository is archived. It was never released on Maven Central.

jr-runtime

Optional library for a Java app launched by a jr exe. io.github.jarrunner:jr-runtime, Java 21, no dependencies.

jr passes the app everything about itself as system properties: every leaf of the exe's embedded jrc-json as io.github.jarrunner.jr.<path> (app.id, app.version, update.url, jvm.vmArgs.0, ...), plus exe (the launcher's path), startMicros and beforeJvmMicros. Those properties are the API; this library only gives them names and types, and adds an update check. An app can use the properties directly and never depend on this.

JrApp

JrApp.launchedByJr(), exe(), exeName(), appId(), appVersion(), updateUrl(), updateChannel() (default stable), config("jvm.mode") for any leaf, configList("app.args") for a list. All empty when the app runs without jr (plain java, an IDE, tests), so calling them unconditionally is safe.

UpdateCheck

Reads the same update file as <exe> -Xjr:update-check and decides by the same rules: releases newest first, this build finds its own app.version by exact match, the channel names the release it should be on, version strings are never compared. Status is CURRENT, NEWER, NOT_CONFIGURED (no jr, or no update.url / app.version) or ERROR.

• check() checks now.
• checkAtMostEvery(Duration) checks at most once per interval, caching the result in ~/.jr/update-check/<app.id>.json. The cache only counts for the same url, version and channel, so after an update the next start checks again. Errors are not cached.
• inBackground(Duration, Consumer<Result>) runs that on a daemon thread, so startup never waits on the network.
• notice(Result) is one line for the user, or null: demo 1.1 is available (this is 1.0): run demo -Xjr:update.

Nothing runs or prints unless the app asks, and installing stays jr's job (-Xjr:update replaces the exe). When and whether to tell the user is the app's decision. For example, a CLI whose stdout is data:

UpdateCheck.inBackground(Duration.ofDays(1), r -> {
    var line = UpdateCheck.notice(r);
    if (line != null && !jsonOutput) System.err.println(line);
});

A window app would show the same Result as a tray message or a line in its about box instead.