What causes "Java program should be specified a JAR file." in apache/flink?

Add the JAR path as a positional argument: `flink run ./myjob.jar`

apache/flink · error · CliArgsException

Java program should be specified a JAR file.

Error message

Java program should be specified a JAR file.

What it means

Thrown by ProgramOptions.validate() when getJarFilePath() returns null, meaning the user ran `flink run` without specifying a JAR file to execute. Flink needs a main JAR containing the job's entry point. The validation runs after all option parsing is complete, checking the final resolved jarFilePath.

Source

Thrown at flink-clients/src/main/java/org/apache/flink/client/cli/ProgramOptions.java:137

    protected String[] extractProgramArgs(CommandLine line) {
        String[] args =
                line.hasOption(ARGS_OPTION.getOpt())
                        ? line.getOptionValues(ARGS_OPTION.getOpt())
                        : line.getArgs();

        if (args.length > 0 && !line.hasOption(JAR_OPTION.getOpt())) {
            jarFilePath = args[0];
            args = Arrays.copyOfRange(args, 1, args.length);
        }

        return args;
    }

    public void validate() throws CliArgsException {
        // Java program should be specified a JAR file
        if (getJarFilePath() == null) {
            throw new CliArgsException("Java program should be specified a JAR file.");
        }
        if (savepointSettings.getRecoveryClaimMode().equals(RecoveryClaimMode.LEGACY)) {
            System.out.printf(
                    "Warning: The %s restore mode is deprecated, please use %s or"
                            + " %s mode instead.%n",
                    RecoveryClaimMode.LEGACY, RecoveryClaimMode.CLAIM, RecoveryClaimMode.NO_CLAIM);
        }
    }

    public String getJarFilePath() {
        return jarFilePath;
    }

    public String getEntryPointClassName() {
        return entryPointClass;
    }

    public List<URL> getClasspaths() {

View on GitHub (pinned to 2f3c205e92)

Solutions

Add the JAR path as a positional argument: `flink run ./myjob.jar`
Use the -j/--jar option explicitly: `flink run -j ./myjob.jar`
Ensure the JAR path variable in scripts is non-empty before invoking

Example fix

# before
flink run -c com.example.MyJob

# after
flink run -c com.example.MyJob ./target/myjob.jar

Defensive patterns

Strategy: validation

Validate before calling

if (jarFilePath == null || jarFilePath.isBlank()) {
    throw new IllegalArgumentException(
        "A JAR file path is required. Usage: flink run [options] <jarPath>");
}

Prevention

Always include the JAR path as a positional argument in flink run commands
Validate that script variables resolving to the JAR path are non-empty
Use -j/--jar explicitly to avoid ambiguity with options

When it happens

Trigger: Running `flink run` with no positional argument and no -j/--jar option; all arguments consumed by options (e.g., `-p 4 -c MyClass`) with nothing left for the JAR path.

Common situations: User forgets the JAR path; variable in a script that should expand to the JAR path is empty; user runs `flink run -c com.example.Job` but omits the JAR.

Related errors

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/64aa992effde027d. Report an issue: GitHub.