apache/flink · error · IllegalArgumentException

Cannot parse ApplicationID from "{hexString}". The expected

Error message

Cannot parse ApplicationID from "{hexString}". The expected format is [0-9a-fA-F]{32}, e.g. fd72014d4c864993a2e5a9287b4a9c5d.

What it means

Thrown by ApplicationID.fromHexString when the input cannot be decoded into the 16-byte (128-bit) identifier. ApplicationID is a fixed-size AbstractID; its hex form must be exactly 32 hex characters. Any malformed input (wrong length, non-hex chars, null) causes StringUtils.hexStringToByte to throw, which is wrapped into this IllegalArgumentException with the offending value.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/ApplicationID.java:102

    public static ApplicationID fromByteBuffer(ByteBuffer buf) {
        long lower = buf.getLong();
        long upper = buf.getLong();
        return new ApplicationID(lower, upper);
    }

    /**
     * Parses an ApplicationID from the given string.
     *
     * @param hexString string representation of an ApplicationID
     * @return Parsed ApplicationID
     * @throws IllegalArgumentException if the ApplicationID could not be parsed from the given
     *     string
     */
    public static ApplicationID fromHexString(String hexString) {
        try {
            return new ApplicationID(StringUtils.hexStringToByte(hexString));
        } catch (Exception e) {
            throw new IllegalArgumentException(
                    "Cannot parse ApplicationID from \""
                            + hexString
                            + "\". The expected format is "
                            + "[0-9a-fA-F]{32}, e.g. fd72014d4c864993a2e5a9287b4a9c5d.",
                    e);
        }
    }
}

View on GitHub (pinned to 2f3c205e92)

Solutions

Validate the input with a regex ^[0-9a-fA-F]{32}$ before calling fromHexString, and trim whitespace.
If reading from an external source, strip prefixes/suffixes and confirm length == 32.
Generate IDs only via new ApplicationID() and persist the result of toString()/toHexString(); never hand-build the string.

Example fix

// before
ApplicationID id = ApplicationID.fromHexString(raw);
// after
String hex = raw == null ? "" : raw.trim();
if (!hex.matches("[0-9a-fA-F]{32}")) {
    throw new IllegalArgumentException("Invalid ApplicationID: " + raw);
}
ApplicationID id = ApplicationID.fromHexString(hex);

Defensive patterns

Strategy: validation

Validate before calling

String hex = hexString == null ? "" : hexString.trim();
if (!hex.matches("[0-9a-fA-F]{32}")) {
    throw new IllegalArgumentException("Invalid ApplicationID hex: " + hexString);
}
ApplicationID id = ApplicationID.fromHexString(hex);

Type guard

public static boolean isValidApplicationIdHex(String s) {
    return s != null && s.trim().matches("[0-9a-fA-F]{32}");
}

Try / catch

try { ApplicationID id = ApplicationID.fromHexString(raw); }
catch (IllegalArgumentException e) { /* log bad input, reject */ }

Prevention

Only persist IDs produced by toString()/toHexString(); never hand-build.
Trim and regex-validate external strings before parsing.
Keep a single helper that both validates and parses.

When it happens

Trigger: Calling ApplicationID.fromHexString(badString) where badString is null, shorter/longer than 32 chars, or contains non-hex characters. Also triggered by round-trip errors when serializing an ApplicationID through a system that truncated or re-encoded the string.

Common situations: Parsing an ApplicationID from a REST response, log line, or environment variable that has surrounding whitespace or a prefix; copying an ID that lost characters;混淆 between ApplicationID and JobID hex formats.

Related errors

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/89469963165be7d7. Report an issue: GitHub.