apache/seatunnel · error · UnsupportedOperationException

File format 'canal_json' does not support reading.

Error message

File format 'canal_json' does not support reading.

What it means

The CANAL_JSON FileFormat enum member only implements a write strategy (CanalJsonWriteStrategy). Calling getReadStrategy() on it throws UnsupportedOperationException because canal-json files cannot be read back as a regular file source format.

Source

Thrown at seatunnel-connectors-v2/connector-file/connector-file-base/src/main/java/org/apache/seatunnel/connectors/seatunnel/file/config/FileFormat.java:148

        @Override
        public WriteStrategy getWriteStrategy(FileSinkConfig fileSinkConfig) {
            return new BinaryWriteStrategy(fileSinkConfig);
        }

        @Override
        public ReadStrategy getReadStrategy() {
            return new BinaryReadStrategy();
        }
    },
    CANAL_JSON("canal_json") {
        @Override
        public WriteStrategy getWriteStrategy(FileSinkConfig fileSinkConfig) {
            return new CanalJsonWriteStrategy(fileSinkConfig);
        }

        @Override
        public ReadStrategy getReadStrategy() {
            throw new UnsupportedOperationException(
                    "File format 'canal_json' does not support reading.");
        }
    },
    DEBEZIUM_JSON("debezium_json") {
        @Override
        public WriteStrategy getWriteStrategy(FileSinkConfig fileSinkConfig) {
            return new DebeziumJsonWriteStrategy(fileSinkConfig);
        }

        @Override
        public ReadStrategy getReadStrategy() {
            throw new UnsupportedOperationException(
                    "File format 'debezium_json' does not support reading.");
        }
    },
    MAXWELL_JSON("maxwell_json") {
        @Override
        public WriteStrategy getWriteStrategy(FileSinkConfig fileSinkConfig) {

View on GitHub (pinned to cf67b549a7)

Solutions

1. Use a format that supports reading (e.g. text, csv, json, parquet, orc) for the file source.
2. Use the MySQL-CDC connector to consume canal-style change data instead of a file source.
3. Wrap the format resolution with a capability check (FileFormat supports getReadStrategy) before selecting the format.
4. If write-only output is what you need, keep canal_json only on sink configs.

Example fix

// before
source {
  LocalFile {
    format = "canal_json"
  }
}
// after
source {
  LocalFile {
    format = "json"
  }
}

FileFormat fmt = FileFormat.valueOf(config.get("format"));
try {
    fmt.getReadStrategy();
} catch (UnsupportedOperationException e) {
    throw new IllegalArgumentException("Format " + fmt + " cannot be used as a file source");
}

boolean isReadable(FileFormat fmt) {
    try { fmt.getReadStrategy(); return true; }
    catch (UnsupportedOperationException e) { return false; }
}

try {
    sourceConfig.getFormat().getReadStrategy();
} catch (UnsupportedOperationException e) {
    log.error("This file format supports writing only; switch to a readable format", e);
    throw new IllegalArgumentException(e);
}

When it happens

Trigger: Configuring a file source (or any code path that resolves a ReadStrategy) with format = "canal_json"; FileFormat.valueOf(...).getReadStrategy() is invoked during source initialization.

Common situations: Copy-pasting a sink config into a source job; assuming CDC JSON formats are bidirectional; docs/examples mismatch across SeaTunnel versions.

Related errors

• File format 'debezium_json' does not support reading.
• File format 'maxwell_json' does not support reading.
• FORMAT_NOT_SUPPORT
• File format 'markdown' does not support writing.
• FILE_TYPE_INVALID

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/5d8378dd83ebb1ad. Report an issue: GitHub.