apache/seatunnel · error · IllegalArgumentException

Expected List type but got:

Error message

Expected List type but got: 

What it means

AerospikeSinkWriter.convertValue requires that fields configured as Aerospike LIST type implement Iterable; otherwise it throws IllegalArgumentException 'Expected List type but got: <class>'. The check guarantees the value can be stored as an Aerospike list without additional conversion.

Solutions

1. Fix the sink field's AEROSPIKE type to match the actual incoming type
2. Use a transform (or source schema change) so the field is delivered as a List/Iterable
3. Unwrap JSON strings into arrays upstream before the sink
4. Read value.getClass() in the message to see the real type delivered

Example fix

// before
field { name = tags type = { data_type = LIST } } // upstream sends Object[]
// after: wrap upstream
Object[] raw = ...;
List<Object> tags = Arrays.asList(raw); // deliver Iterable

Object v = row.getField(idx);
if (!(v instanceof Iterable)) throw new IllegalArgumentException("field 'tags' must be Iterable for LIST, got " + v.getClass());

boolean isIterable(Object v) { return v instanceof Iterable; }

try { writer.write(row); } catch (AerospikeConnectorException e) { if (e.getCause() instanceof IllegalArgumentException && e.getCause().getMessage().startsWith("Expected List type")) { /* convert to List upstream */ } }

When it happens

Trigger: A record field configured with AEROSPIKE data type LIST contains an object that is not an Iterable (e.g. a String, byte[], or Map-as-array edge cases) when write() invokes convertValue.

Common situations: Source emits arrays as Object[] or JSON strings instead of List; schema mismatch between upstream connector array representation and sink LIST expectation; type declared LIST while data is scalar.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Expected Array type but got:
• List type requires List value, got
• Map in list writing not yet implemented
• Unsupported data format type:
• Unsupported timestamp type:

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/c3701bf9659fd9d7. Report an issue: GitHub.

Appendix: source

Thrown at seatunnel-connectors-v2/connector-aerospike/src/main/java/org/apache/seatunnel/connectors/seatunnel/aerospike/sink/AerospikeSinkWriter.java:218

                    return ((Number) value).doubleValue();
                }
                return Double.parseDouble(value.toString());
            case BOOLEAN:
                if (value instanceof Boolean) {
                    return value;
                }
                return Boolean.parseBoolean(value.toString());
            case BYTEARRAY:
                if (value.getClass().isArray()) {
                    return value;
                }
                throw new IllegalArgumentException(
                        "Expected Array type but got: " + value.getClass());
            case LIST:
                if (value instanceof Iterable) {
                    return value;
                }
                throw new IllegalArgumentException(
                        "Expected List type but got: " + value.getClass());
            default:
                throw new IllegalArgumentException("Unsupported AEROSPIKE data type: " + dataType);
        }
    }

    private long parseDateTimeString(String datetime) {
        try {
            return LocalDateTime.parse(datetime)
                    .atZone(ZoneId.systemDefault())
                    .toInstant()
                    .toEpochMilli();
        } catch (DateTimeParseException e) {
            try {
                return Instant.parse(datetime).toEpochMilli();
            } catch (DateTimeParseException ex) {
                throw new IllegalArgumentException("Unsupported datetime format: " + datetime);
            }

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