OpenAPITools/openapi-generator · error · IllegalArgumentException

Unsupported query collection format: {collectionFormat}

Error message

Unsupported query collection format: {collectionFormat}

What it means

Error "Unsupported query collection format: {collectionFormat}" thrown in OpenAPITools/openapi-generator.

Source

Thrown at modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppBoostBeastClientCodegen.java:303

            return codegenParameter;
        }

        String collectionDelimiter;
        switch (codegenParameter.collectionFormat) {
            case "csv":
                collectionDelimiter = ",";
                break;
            case "ssv":
                collectionDelimiter = "%20";
                break;
            case "tsv":
                collectionDelimiter = "%09";
                break;
            case "pipes":
                collectionDelimiter = "%7C";
                break;
            default:
                throw new IllegalArgumentException(
                        "Unsupported query collection format: " + codegenParameter.collectionFormat);
        }
        codegenParameter.vendorExtensions.put(
                X_CODEGEN_QUERY_COLLECTION_DELIMITER, collectionDelimiter);
        return codegenParameter;
    }

    private String queryCollectionDelimiter(Parameter.StyleEnum style) {
        if (style == Parameter.StyleEnum.SPACEDELIMITED) {
            return "%20";
        }
        if (style == Parameter.StyleEnum.PIPEDELIMITED) {
            return "%7C";
        }
        return ",";
    }

    private void addContainerPropertyNames(List<CodegenProperty> properties) {

View on GitHub (pinned to fcec517be3)

Solutions

1. Use a supported query collection format (e.g. csv, ssv, tsv, pipes) in the parameter definition.

When it happens

Trigger: Thrown when a query parameter in the spec uses a collectionFormat that the C++ Boost.Beast client generator does not support. Change the parameter's collectionFormat to a supported one (e.g. csv).

Common situations: See trigger scenarios.

AI-assisted analysis of OpenAPITools/openapi-generator@fcec517be3 (2026-08-22). Data as JSON: /api/errors/c59c6c1054675ccd. Report an issue: GitHub.