apache/beam · error · IllegalArgumentException

Unable to serialize row: {row}

Error message

Unable to serialize row: {row}

What it means

RowJsonUtils.rowToJson serializes a Beam Row to a JSON string and wraps JsonProcessingException into IllegalArgumentException('Unable to serialize row: <row>'). Serialization failures are typically Row values that the RowJson serializer cannot represent (see writeValue's unsupported types) or Jackson generation failures.

Source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/util/RowJsonUtils.java:148

    return objectMapper;
  }

  public static Row jsonToRow(ObjectMapper objectMapper, String jsonString) {
    try {
      return objectMapper.readValue(jsonString, Row.class);
    } catch (JsonParseException | JsonMappingException jsonException) {
      throw new UnsupportedRowJsonException("Unable to parse Row", jsonException);
    } catch (IOException e) {
      throw new IllegalArgumentException("Unable to parse json object: " + jsonString, e);
    }
  }

  public static String rowToJson(ObjectMapper objectMapper, Row row) {
    try {
      return objectMapper.writeValueAsString(row);
    } catch (JsonProcessingException e) {
      throw new IllegalArgumentException("Unable to serialize row: " + row, e);
    }
  }
}

View on GitHub (pinned to 12126d8942)

Solutions

1. Check getCause() (JsonProcessingException) for the exact field/value that failed
2. Convert unsupported field types to supported ones (base types, String) before serializing
3. Use a RowJson ObjectMapper configured for Row serialization
4. Catch IllegalArgumentException around rowToJson and skip/re-encode offending rows

Example fix

try {
  String json = RowJsonUtils.rowToJson(mapper, row);
} catch (IllegalArgumentException e) {
  LOG.error("Cannot serialize row: {}", e.getMessage(), e.getCause());
}

// pre-check: ensure all field values map to supported writer types
row.getSchema().getFields().forEach(f -> {
  if (!SUPPORTED_WRITER_TYPES.contains(f.getType().getTypeName())) throw new IllegalStateException("Unsupported: " + f.getName());
});

try { String s = RowJsonUtils.rowToJson(mapper, row); } catch (IllegalArgumentException e) { /* e.getCause() is JsonProcessingException naming the failing field */ }

When it happens

Trigger: rowToJson(objectMapper, row) where the Row contains fields the serializer cannot write (unsupported schema types, illegal values) or a Jackson generation problem occurs mid-write.

Common situations: Rows containing logical/custom types unsupported by the writer; NaN/infinite doubles; schema evolution producing types the serializer switch doesn't cover.

Understand the failure class

Background: "JSON serialization failed", "not JSON serializable", "Failed to serialize": why JSON marshaling errors happen and how to fix them — this error's family across 46 libraries.

Related errors

• Unsupported field type: {type}
• Cannot provide SerializableCoder because {} does not impleme
• Java Serialization may be non-deterministic.
• cannot encode a null String
• cannot encode a null Integer

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/94392c101754a3fc. Report an issue: GitHub.