Using non-modular libraries

JDesk apps are JPMS modules, but many useful Java libraries still ship without a module-info (they are automatic modules). If your :app module requires such a library directly, the build fails — error: module not found: org.eclipse.lsp4j — because Gradle puts a project's automatic-module dependency on the classpath, not the module path, and it also does not package: jlink/jpackage only accept explicit modules, so the runtime image can't include an automatic module either. The fix is the same for both problems.

Give the library a real module descriptor#

Use the extra-java-module-info plugin to synthesize a module-info for the dependency at build time — turning the automatic module into a proper named module that resolves on the module path and links into the jpackage image:

plugins {
    id("dev.jdesk.application")
    id("org.gradlex.extra-java-module-info") version "1.+"
}

extraJavaModuleInfo {
    failOnMissingModuleInfo = false            // leave already-modular deps untouched
    module("org.eclipse.lsp4j:org.eclipse.lsp4j", "org.eclipse.lsp4j") {
        exportAllPackages()
        requires("java.logging")               // LSP4J uses java.util.logging
        // requiresTransitive("org.eclipse.lsp4j.jsonrpc")  // for its transitive deps
    }
}

Then requires org.eclipse.lsp4j; in your module-info.java resolves in ./gradlew run and in the packaged app, with no automatic-module warnings.

When a dependency won't cooperate#

Some libraries fight modularization (split packages, reflection, native .so loading from the jar). If synthesizing a descriptor is impractical, run the tool as a separate process and talk to it over a pipe/stdio or loopback — the same pattern a language server or a Node-based sidecar uses. That keeps the JPMS runtime image clean and sidesteps the packaging constraint entirely; ship the sidecar binary alongside the app image.

Rule of thumb#

• Modular dependency → just requires it.
• Automatic module you can describe → extra-java-module-info; works in dev and in the package.
• Stubborn / non-Java tool → run it out-of-process as a sidecar.