apache/cassandra · error · InvalidRequestException

Error decoding JSON value for %s: %s

Error message

Error decoding JSON value for %s: %s

What it means

Json.parseJson wraps per-column decode failures in this InvalidRequestException: the JSON value for a recognized column could not be converted to the column's type by spec.type.fromJSONObject. The MarshalException message (e.g. wrong type, out-of-range number, bad format) is appended after the column name.

Source

Thrown at src/java/org/apache/cassandra/cql3/Json.java:304

                // explicit null value from no value
                if (!valueMap.containsKey(spec.name.toString()))
                    continue;

                Object parsedJsonObject = valueMap.remove(spec.name.toString());
                if (parsedJsonObject == null)
                {
                    // This is an explicit user null
                    columnMap.put(spec.name, Constants.NULL_VALUE);
                }
                else
                {
                    try
                    {
                        columnMap.put(spec.name, spec.type.fromJSONObject(parsedJsonObject));
                    }
                    catch (MarshalException exc)
                    {
                        throw new InvalidRequestException(format("Error decoding JSON value for %s: %s", spec.name, exc.getMessage()));
                    }
                }
            }

            if (!valueMap.isEmpty())
            {
                throw new InvalidRequestException(format("JSON values map contains unrecognized column: %s",
                                                         valueMap.keySet().iterator().next()));
            }

            return columnMap;
        }
        catch (IOException exc)
        {
            throw new InvalidRequestException(format("Could not decode JSON string as a map: %s. (String was: %s)", exc.toString(), jsonString));
        }
        catch (MarshalException exc)
        {

View on GitHub (pinned to 88fd0f6a0e)

Solutions

  1. Read the appended MarshalException message for the exact per-column reason
  2. Match JSON value types to schema: quoted strings for timestamps/uuids/durations, numbers within range for numeric columns
  3. Use toJson() on existing rows to see the exact JSON shape Cassandra accepts
  4. Validate payloads against the table schema (SystemSchema/describe) before insert

Example fix

// before
{"created": "2026-09-09T10:00:00Z"} // if timestamp format rejected
// after
{"created": "2026-09-09 10:00:00+0000"} // use Cassandra-accepted format
Defensive patterns

Strategy: try-catch

Validate before calling

// validate one value against its column type before INSERT JSON
spec.type.parse(rawJsonStringForValue); // throws InvalidRequest on mismatch

Try / catch

try { session.execute("INSERT INTO t JSON ?", json); } catch (InvalidRequestException e) { if (e.getMessage().startsWith("Error decoding JSON value for")) { String col = e.getMessage().split("for ")[1].split(":")[0].trim(); throw new IllegalArgumentException("Bad value for column " + col, e); } throw e; }

Prevention

When it happens

Trigger: INSERT INTO t JSON with a value that doesn't match the column type — a string where an int is expected, a malformed timestamp/uuid, a number too large for the column type, an invalid nested collection element.

Common situations: Sending ISO date strings where Cassandra expects its timestamp format; floats for decimal/int columns; JSON numbers exceeding column range; passing objects for non-collection columns; duration/tuple columns given string values in wrong internal format.

Understand the failure class

Background: "failed to unmarshal" / json.Unmarshal errors: why parsing a response into a Go struct fails and how to fix it — this error's family across 23 libraries.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/22055d127d3109e6. Report an issue: GitHub.