apache/seatunnel · error · IllegalArgumentException

Unsupported MQTT sink format:

Error message

Unsupported MQTT sink format: 

What it means

Thrown by createSerializationSchema in MqttSinkWriter when the configured sink 'format' does not match any supported serialization schema (e.g. json/text). Only formats with a builder case in the switch are accepted. IllegalArgumentException means the config value is not part of the supported set.

Source

Thrown at seatunnel-connectors-v2/connector-mqtt/src/main/java/org/apache/seatunnel/connectors/seatunnel/mqtt/sink/MqttSinkWriter.java:254

            options.setPassword(password.toCharArray());
        }
        return options;
    }

    private static SerializationSchema createSerializationSchema(
            SeaTunnelRowType rowType, ReadonlyConfig config) {
        String format = config.get(MqttSinkOptions.FORMAT);
        switch (format.toLowerCase()) {
            case "json":
                return new JsonSerializationSchema(rowType);
            case "text":
                String delimiter = config.get(MqttSinkOptions.FIELD_DELIMITER);
                return TextSerializationSchema.builder()
                        .seaTunnelRowType(rowType)
                        .delimiter(delimiter)
                        .build();
            default:
                throw new IllegalArgumentException("Unsupported MQTT sink format: " + format);
        }
    }
}

View on GitHub (pinned to cf67b549a7)

Solutions

1. Set format to one of the supported sink values exactly as handled in MqttSinkWriter (e.g. json, text)
2. Check docs/en for connector-mqtt sink format options and allowed values
3. Fix typos and match casing exactly as the option expects
4. If you need a new format, add a case in createSerializationSchema with the appropriate schema builder

Example fix

// before
format = csv
// after
format = text
# or
format = json

Set<String> supported = Set.of("json", "text");
if (!supported.contains(format.trim().toLowerCase())) {
  throw new IllegalArgumentException("Unsupported MQTT sink format: " + format);
}

null

null

When it happens

Trigger: Setting format in the MQTT sink config to a value other than those handled by the switch (default branch reached), causing MqttSinkWriter construction to fail immediately.

Common situations: Typo in format (e.g. 'jsonl', 'csv'); copying a format value valid for other connectors; casing assumptions — the sink switch may be case-sensitive even when docs show lowercase.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Unsupported MQTT source format: ${format}
• UNSUPPORTED_DATA_TYPE
• UNSUPPORTED_DATA_TYPE
• Invalid endpoint: %s, expected format host:port
• Invalid endpoint port in endpoint: %s

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/b61e7aea76e95719. Report an issue: GitHub.