apache/flink · error · FlinkException

No JAR found on classpath. Please provide a JAR explicitly.

Error message

No JAR found on classpath. Please provide a JAR explicitly.

What it means

Thrown by extractJobClassNameFromFileClasspath when the classpath being scanned (system classpath or URL classpath) contains no JAR file at all, so an entry class cannot be auto-detected for application mode. It fires when the user submits an application without an explicit job/jar and Flink cannot infer one.

Solutions

1. Address the cause reported by the error message: No JAR found on classpath. Please provide a JAR explicitly.
2. Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry.

Example fix

Correct the condition described ("No JAR found on classpath. Please provide a JAR explicitly.") and rerun the job or command.

When it happens

Trigger: Triggered at runtime when the operation fails because: No JAR found on classpath. Please provide a JAR explicitly.

Common situations: Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: No JAR found on classpath. Please provide a JAR explicitly.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/371eb6a6d22a91bf. Report an issue: GitHub.

Appendix: source

Thrown at flink-clients/src/main/java/org/apache/flink/client/deployment/application/FromClasspathEntryClassInformationProvider.java:164

        return extractJobClassNameFromFileClasspath(extractSystemClasspath());
    }

    private static String extractJobClassFromUrlClasspath(Iterable<URL> classpath)
            throws IOException, FlinkException {
        final List<File> jarFilesFromClasspath =
                StreamSupport.stream(classpath.spliterator(), false)
                        .map(url -> new File(url.getFile()))
                        .filter(f -> isJarFilename(f.getName()))
                        .collect(Collectors.toList());
        return extractJobClassNameFromFileClasspath(jarFilesFromClasspath);
    }

    private static String extractJobClassNameFromFileClasspath(Iterable<File> classpath)
            throws FlinkException, IOException {
        try {
            return JarManifestParser.findOnlyEntryClass(classpath).getEntryClass();
        } catch (NoSuchElementException e) {
            throw new FlinkException(
                    "No JAR found on classpath. Please provide a JAR explicitly.", e);
        } catch (IllegalArgumentException e) {
            throw new FlinkException(
                    "Multiple JAR archives with entry classes found on classpath. Please provide an entry class name.",
                    e);
        }
    }

    private static boolean isJarFilename(String filename) {
        return filename.endsWith(".jar");
    }
}

View on GitHub (pinned to 2f3c205e92)