apache/pulsar · error · IllegalArgumentException

The value of ${paramName} can't be empty

Error message

The value of ${paramName} can't be empty

What it means

ValueValidationUtil.emptyCheck rejects null/empty string CLI parameters with 'The value of <param> can't be empty'. It guards mandatory textual options (topic names, cluster names, subjects) so the tool fails fast at argument validation instead of sending a degenerate request to the broker.

Source

Thrown at pulsar-cli-utils/src/main/java/org/apache/pulsar/cli/ValueValidationUtil.java:47

            throw new IllegalArgumentException(paramName + " cannot be bigger than <" + maxValue + ">!");
        }
    }

    public static void positiveCheck(String paramName, long value) {
        if (value <= 0) {
            throw new IllegalArgumentException(paramName + " cannot be less than or equal to <0>!");
        }
    }

    public static void positiveCheck(String paramName, int value) {
        if (value <= 0) {
            throw new IllegalArgumentException(paramName + " cannot be less than or equal to <0>!");
        }
    }

    public static void emptyCheck(String paramName, String value) {
        if (StringUtils.isEmpty(value)) {
            throw new IllegalArgumentException("The value of " + paramName + " can't be empty");
        }
    }

    public static void minValueCheck(String name, Long value, long min) {
        if (value < min) {
            throw new IllegalArgumentException(name + " cannot be less than <" + min + ">!");
        }
    }
}

View on GitHub (pinned to 820761864e)

Solutions

1. Supply the required non-empty value for the named parameter.
2. In scripts, guard with : "${TOPIC:?TOPIC is required}" or [ -n "$TOPIC" ] before invoking the CLI.
3. Check quoting so the value isn't swallowed as an empty argument.
4. Trim the value — whitespace-only strings also fail the emptiness check.

Example fix

// before (TOPIC unset)
pulsar-admin topics delete "$TOPIC"
// after
echo "TOPIC=${TOPIC:?must be set}"
pulsar-admin topics delete "$TOPIC"

public static String requireNonEmpty(String name, String value) {
    if (value == null || value.trim().isEmpty()) {
        throw new IllegalArgumentException(name + " is required and cannot be empty");
    }
    return value.trim();
}
// shell: : "${TOPIC:?TOPIC is required}" before invoking the CLI

try {
    tool.run(args);
} catch (IllegalArgumentException e) {
    if (e.getMessage() != null && e.getMessage().contains("can't be empty")) {
        System.err.println("Missing required argument: " + e.getMessage());
    } else throw e;
}

When it happens

Trigger: Calling emptyCheck(paramName, value) where value is null or StringUtils.isEmpty(value) is true — e.g. an unset shell variable producing an empty --topic argument.

Common situations: Shell scripts with unset/empty variables interpolated as empty flags; quoting mistakes dropping the argument; whitespace-only strings that read as non-empty to the user.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• ${paramName} cannot be bigger than <${maxValue}>!
• ${paramName} cannot be less than or equal to <0>!
• ${name} cannot be less than <${min}>!
• Number of messages should be zero or positive.
• byte string cannot be empty

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/fcb74ff51c6a3e0d. Report an issue: GitHub.