apache/seatunnel · error · UnsupportedOperationException

Unsupported convert ${value.getClass()} to byte[], typeDefin

Error message

Unsupported convert ${value.getClass()} to byte[], typeDefine: ${typeDefine}

What it means

The typeDefine-aware convertBytes overload supports byte[], ByteBuffer, and String inputs; anything else triggers this UnsupportedOperationException. The typeDefine gives context about the expected BytesType column. It fires when a value routed to BYTES conversion is none of the three supported classes.

Source

Thrown at seatunnel-api/src/main/java/org/apache/seatunnel/api/table/converter/BasicDataConverter.java:370

    default String convertString(LocalTime value) {
        return value.toString();
    }

    default String convertString(LocalDateTime value) {
        return value.toString();
    }

    default byte[] convertBytes(T typeDefine, Object value) throws UnsupportedOperationException {
        if (value instanceof byte[]) {
            return (byte[]) value;
        }
        if (value instanceof ByteBuffer) {
            return convertBytes((ByteBuffer) value);
        }
        if (value instanceof String) {
            return convertBytes(typeDefine, (String) value);
        }
        throw new UnsupportedOperationException(
                "Unsupported convert "
                        + value.getClass()
                        + " to byte[], typeDefine: "
                        + typeDefine);
    }

    default byte[] convertBytes(T typeDefine, String value) {
        return convertBytes(value);
    }

    default byte[] convertBytes(Object value) throws UnsupportedOperationException {
        if (value instanceof byte[]) {
            return (byte[]) value;
        }
        if (value instanceof ByteBuffer) {
            return convertBytes((ByteBuffer) value);
        }
        if (value instanceof String) {

View on GitHub (pinned to cf67b549a7)

Solutions

Convert the value to byte[] yourself first (e.g. ByteString.toByteArray(), or serialize the POJO with an agreed format).
If the value is a wrapper like protobuf ByteString, call its toByteArray() before conversion.
Override convertBytes in your converter to handle the offending class.
Check the schema: if the data is really an integer or string, use the appropriate SqlType instead of BYTES.

Example fix

// before
converter.convertBytes(bytesType, protoByteString);
// after
converter.convertBytes(bytesType, protoByteString.toByteArray());

Defensive patterns

Strategy: type-guard

Validate before calling

if (!(value instanceof byte[]) && !(value instanceof ByteBuffer) && !(value instanceof String)) {
    throw new IllegalArgumentException("convertBytes expects byte[]/ByteBuffer/String, got " + value.getClass());
}

Type guard

boolean isBytesConvertible(Object v) {
    return v instanceof byte[] || v instanceof ByteBuffer || v instanceof String;
}

Try / catch

try {
    return converter.convertBytes(bytesType, value);
} catch (UnsupportedOperationException e) {
    LOG.warn("Bytes conversion failed for {}: {}", value.getClass(), e.getMessage());
    return null;
}

Prevention

Convert wrapper byte containers (ByteString, ByteBuf) to byte[] before conversion.
Use BYTES SqlType only for genuinely binary data.
Agree on encoding when passing Strings that represent bytes (Base64 vs raw).
Unit-test conversions with representative upstream types.

When it happens

Trigger: Calling convertBytes(typeDefine, value) — or convert(...) with a BYTES SqlType column — with an Integer, List of Bytes, POJO, InputStream, or other non-byte[]/ByteBuffer/String object.

Common situations: Upstream returns a boxed numeric or a protobuf ByteString instead of byte[]; passing a Base64 string where raw bytes were expected (works, since String is handled, but a wrapper object does not); deserialized collections of bytes.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/94523464fa64bb8d. Report an issue: GitHub.