apache/flink · error · java.lang.RuntimeException

Could not serialize value

Error message

Could not serialize value '%s'.

What it means

Wraps a JsonProcessingException thrown by Jackson while converting the element to JSON bytes; the cause is chained. Typically the element contains a type Jackson cannot serialize (no matching serializer) — the '%s' placeholder echoes the failing element.

Solutions

1. Address the cause reported by the error message: Could not serialize value 'the reported value'.
2. Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry.

Example fix

Correct the condition described ("Could not serialize value 'the reported value'.") and rerun the job or command.

When it happens

Trigger: Triggered at runtime when the operation fails because: Could not serialize value 'the reported value'.

Common situations: Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: Could not serialize value 'the reported value'.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/5287a8aeea00e081. Report an issue: GitHub.

Appendix: source

Thrown at flink-formats/flink-json/src/main/java/org/apache/flink/formats/json/JsonSerializationSchema.java:55

    public JsonSerializationSchema() {
        this(() -> new ObjectMapper());
    }

    public JsonSerializationSchema(SerializableSupplier<ObjectMapper> mapperFactory) {
        this.mapperFactory = mapperFactory;
    }

    @Override
    public void open(InitializationContext context) {
        mapper = mapperFactory.get();
    }

    @Override
    public byte[] serialize(T element) {
        try {
            return mapper.writeValueAsBytes(element);
        } catch (JsonProcessingException e) {
            throw new RuntimeException(
                    String.format("Could not serialize value '%s'.", element), e);
        }
    }
}

View on GitHub (pinned to 2f3c205e92)