quarkusio/quarkus · error · UncheckedIOException

Unable to copy json config file from ${jsonPath} to ${thinJa

Error message

Unable to copy json config file from ${jsonPath} to ${thinJarDirectory}

What it means

NativeImageSourceJarBuilder wraps an IOException in an UncheckedIOException when copying a native-image JSON config file (e.g. from native-image properties/config) into the thin jar directory fails. The copy creates the thinJarDirectory then copies the JSON file, and any filesystem failure is rethrown with this descriptive message.

Source

Thrown at core/deployment/src/main/java/io/quarkus/deployment/pkg/jar/NativeImageSourceJarBuilder.java:125

    /**
     * This is done in order to make application specific native image configuration files available to the native-image tool
     * without the user needing to know any specific paths.
     * The files that are copied don't end up in the native image unless the user specifies they are needed, all this method
     * does is copy them to a convenient location
     */
    private static void copyJsonConfigFiles(ApplicationArchivesBuildItem applicationArchivesBuildItem, Path thinJarDirectory)
            throws IOException {
        for (Path root : applicationArchivesBuildItem.getRootArchive().getRootDirectories()) {
            try (Stream<Path> stream = Files.find(root, 1, IsJsonFilePredicate.INSTANCE)) {
                stream.forEach(new Consumer<Path>() {
                    @Override
                    public void accept(Path jsonPath) {
                        try {
                            Files.createDirectories(thinJarDirectory);
                            Files.copy(jsonPath, thinJarDirectory.resolve(jsonPath.getFileName().toString()));
                        } catch (IOException e) {
                            throw new UncheckedIOException(
                                    "Unable to copy json config file from " + jsonPath + " to " + thinJarDirectory,
                                    e);
                        }
                    }
                });
            }
        }
    }

    private static class IsJsonFilePredicate implements BiPredicate<Path, BasicFileAttributes> {

        private static final BiPredicate<Path, BasicFileAttributes> INSTANCE = new IsJsonFilePredicate();

        @Override
        public boolean test(Path path, BasicFileAttributes basicFileAttributes) {
            return basicFileAttributes.isRegularFile() && path.toString().endsWith(".json");
        }
    }

View on GitHub (pinned to e1c734241f)

Solutions

Check file permissions on the source JSON file and the target build directory and ensure they are readable/writable.
Verify the jsonPath file exists (not deleted between configuration and packaging) and is a regular file.
Free disk space and run ./mvnw clean, then rebuild the native image source jar.

Example fix

// before (config file missing)
quarkus.native.additional-build-args=-H:ResourceConfigurationFiles=missing.json
// after (ensure file exists and is readable)
ls -l src/main/resources/reflect-config.json
quarkus.native.additional-build-args=-H:ResourceConfigurationFiles=src/main/resources/reflect-config.json

Defensive patterns

Strategy: try-catch

Validate before calling

Path json = Path.of("src/main/resources/reflect-config.json");
if (!Files.isRegularFile(json) || !Files.isReadable(json)) {
    throw new IllegalStateException("Native-image config JSON missing or unreadable: " + json);
}
if (!Files.isWritable(targetDir)) {
    throw new IllegalStateException("Thin jar directory not writable: " + targetDir);
}

Try / catch

try {
    Files.copy(jsonPath, thinJarDirectory.resolve(jsonPath.getFileName().toString()));
} catch (IOException e) {
    throw new IllegalStateException("Failed to copy native-image JSON config " + jsonPath + " to " + thinJarDirectory
        + ": check permissions, disk space, and that the source file exists", e);
}

Prevention

Verify all native-image JSON config paths exist before building.
Keep target/ free of stale locks and ensure sufficient disk space.
Check directory write permissions before running native packaging builds.

When it happens

Trigger: Building the native image source jar with additional native-image JSON config files while the filesystem fails: thinJarDirectory cannot be created or the source jsonPath is unreadable (permissions, missing file, disk full, path is a directory).

Common situations: Read-only target/ directory; stale build processes locking files on Windows; a configured native-image config JSON path pointing to a file that was removed; insufficient disk space.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/d44d9b0625023732. Report an issue: GitHub.