apache/iceberg · error · JsonToMapException

parsing binary value threw exception for

Error message

parsing binary value threw exception for ${fieldName}

What it means

extractBytes wraps the Jackson node binary decoding (`node.binaryValue()`) in a try/catch and rethrows any exception as JsonToMapException noting the field name. It means the JSON node could not be decoded as a Base64 binary value for a BYTES-typed field.

Solutions

Ensure the JSON value for the field is valid Base64-encoded binary data.
Base64-encode the bytes on the producing side before sending.
Change the field's schema type to STRING if the data is actually textual.

Example fix

// before
{"payload": "not-valid-base64!!"}
// after
{"payload": "aGVsbG8="}

Defensive patterns

Strategy: validation

Validate before calling

// Validate Base64 before producing/sending the record
try { java.util.Base64.getDecoder().decode(rawValue); } catch (IllegalArgumentException e) { /* fix payload upstream */ }

Type guard

boolean isBase64(String s) { try { java.util.Base64.getDecoder().decode(s); return true; } catch (IllegalArgumentException e) { return false; } }

Try / catch

try { ... } catch (org.apache.iceberg.connect.transforms.JsonToMapException e) { log.error("Bytes field invalid at " + e.getMessage(), e); /* route to DLQ */ }

Prevention

Always Base64-encode BYTES fields on the producing side
Validate payloads with a JSON schema including base64 content encoding
Watch for producers changing field encoding without versioning

When it happens

Trigger: extractValue routes a BYTES-typed field to extractBytes and the Jackson JsonNode is not valid Base64 binary data (e.g. an arbitrary string or malformed base64), causing node.binaryValue() to throw.

Common situations: JSON payloads where a bytes field contains a plain string or non-Base64-encoded data; producers changed encoding; hand-crafted test payloads with invalid Base64.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/cfff7e65b14e9f56. Report an issue: GitHub.

Appendix: source

Thrown at kafka-connect/kafka-connect-transforms/src/main/java/org/apache/iceberg/connect/transforms/JsonToMapUtils.java:276

      default:
        throw new JsonToMapException(
            String.format("Unexpected type %s for field %s", type, fieldName));
    }
    return obj;
  }

  private static Object extractBytes(JsonNode node, String fieldName) {
    Object obj;
    try {
      if (node.isBigInteger()) {
        obj = new BigDecimal(node.bigIntegerValue());
      } else if (node.isBigDecimal()) {
        obj = node.decimalValue();
      } else {
        obj = node.binaryValue();
      }
    } catch (Exception e) {
      throw new JsonToMapException(
          String.format("parsing binary value threw exception for %s", fieldName), e);
    }
    return obj;
  }

  private static List<Object> populateArray(
      JsonNode node, Schema schema, String fieldName, List<Object> acc) {
    if (schema.type() == Schema.Type.ARRAY) {
      node.elements()
          .forEachRemaining(
              arrayNode -> {
                List<Object> nestedList = Lists.newArrayList();
                acc.add(populateArray(arrayNode, schema.valueSchema(), fieldName, nestedList));
              });
    } else {
      node.elements()
          .forEachRemaining(
              arrayEntry -> acc.add(extractValue(arrayEntry, schema.type(), fieldName)));

View on GitHub (pinned to 86d9c8fc54)