What causes "Field '{name}' has a null value in the JSON object." in apache/beam?

Use ACCEPT_MISSING_OR_NULL nullBehavior to accept both absent keys and JSON nulls.

apache/beam · error · UnsupportedRowJsonException

Field '{name}' has a null value in the JSON object.

Error message

Field '{name}' has a null value in the JSON object.

What it means

RowJson's extractor throws UnsupportedRowJsonException when nullBehavior is REQUIRE_MISSING but the field is present with an explicit JSON null value. This enforces the opposite strictness of error 708: nulls must be represented by absence, not by JSON null. Raised in extractJsonNodeValue during deserialization.

Source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/util/RowJson.java:296

      if (fieldValue.type().getNullable()) {
        if (!fieldValue.isJsonValuePresent()) {
          switch (this.nullBehavior) {
            case ACCEPT_MISSING_OR_NULL:
            case REQUIRE_MISSING:
              return null;
            case REQUIRE_NULL:
              throw new UnsupportedRowJsonException(
                  "Field '" + fieldValue.name() + "' is not present in the JSON object.");
          }
        }

        if (fieldValue.isJsonNull()) {
          switch (this.nullBehavior) {
            case ACCEPT_MISSING_OR_NULL:
            case REQUIRE_NULL:
              return null;
            case REQUIRE_MISSING:
              throw new UnsupportedRowJsonException(
                  "Field '" + fieldValue.name() + "' has a null value in the JSON object.");
          }
        }
      } else {
        // field is not nullable
        if (!fieldValue.isJsonValuePresent()) {
          throw new UnsupportedRowJsonException(
              "Non-nullable field '" + fieldValue.name() + "' is not present in the JSON object.");
        } else if (fieldValue.isJsonNull()) {
          throw new UnsupportedRowJsonException(
              "Non-nullable field '" + fieldValue.name() + "' has value null in the JSON object.");
        }
      }

      if (fieldValue.isRowType()) {
        return jsonObjectToRow(fieldValue);
      }

View on GitHub (pinned to 12126d8942)

Solutions

Use ACCEPT_MISSING_OR_NULL nullBehavior to accept both absent keys and JSON nulls.
Change the producer to omit the key instead of writing null.
Pre-process JSON to drop null-valued keys before deserialization.

Example fix

// before
{"user": null}  // with nullBehavior(REQUIRE_MISSING) -> throws
// after
{}  // omit the key, or switch to ACCEPT_MISSING_OR_NULL

Defensive patterns

Strategy: try-catch

Validate before calling

Iterator<Map.Entry<String, JsonNode>> it = json.fields();
while (it.hasNext()) {
  if (it.next().getValue().isNull()) it.remove(); // drop explicit nulls before convert
}

Try / catch

try {
  Row row = jsonToRow.convert(json);
} catch (UnsupportedRowJsonException e) {
  LOG.warn("Unexpected JSON null: {}", e.getMessage());
  row = convertWithLenientNullBehavior(json); // ACCEPT_MISSING_OR_NULL
}

Prevention

Don't use REQUIRE_MISSING with producers that serialize nulls as JSON null.
Strip null-valued keys before deserialization or use ACCEPT_MISSING_OR_NULL.
Align null conventions (absence vs explicit null) between producer and consumer.
Cover null-field fixtures in deserialization tests.

When it happens

Trigger: Deserializing JSON containing {"field": null} while RowJson is configured with nullBehavior=REQUIRE_MISSING for that field.

Common situations: Producers that serialize Java nulls as JSON null instead of omitting keys; mismatch between the chosen strict null policy and the producer's convention; hand-written test fixtures using null.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/dcd7ab0a04d13603. Report an issue: GitHub.