apache/flink · error · java.lang.IllegalArgumentException

Union types with more than just a null type are not supporte

Error message

Union types with more than just a null type are not supported yet.

What it means

Error "Union types with more than just a null type are not supported yet." thrown in apache/flink.

Source

Thrown at flink-formats/flink-json/src/main/java/org/apache/flink/formats/json/JsonRowSchemaConverter.java:228

                || node.has(ANY_OF)
                || node.has(NOT)
                || node.has(EXTENDS)
                || node.has(DISALLOW)) {
            throw new IllegalArgumentException(
                    "Union types are such as '"
                            + ALL_OF
                            + "', '"
                            + ANY_OF
                            + "' etc. "
                            + "and extending are not supported yet.");
        }

        // only a type (with null) is supported yet
        final List<TypeInformation<?>> types = new ArrayList<>(typeSet);
        if (types.size() == 0) {
            throw new IllegalArgumentException("No type could be found in node:" + location);
        } else if (types.size() > 2 || (types.size() == 2 && !types.contains(Types.VOID))) {
            throw new IllegalArgumentException(
                    "Union types with more than just a null type are not supported yet.");
        }

        // return the first non-void type or void
        if (types.size() == 2 && types.get(0) == Types.VOID) {
            return types.get(1);
        } else {
            return types.get(0);
        }
    }

    private static TypeInformation<Row> convertObject(
            String location, JsonNode node, JsonNode root) {
        // validate properties
        if (!node.has(PROPERTIES)) {
            return Types.ROW();
        }
        if (!node.isObject()) {

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Address the cause reported by the error message: Union types with more than just a null type are not supported yet.
2. Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry.

Example fix

Correct the condition described ("Union types with more than just a null type are not supported yet.") and rerun the job or command.

When it happens

Trigger: Triggered at runtime when the operation fails because: Union types with more than just a null type are not supported yet.

Common situations: Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: Union types with more than just a null type are not supported yet.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/38bc4668acdb3d68. Report an issue: GitHub.