quarkusio/quarkus · warning · BadRequestException

Malformed quality value.

Error message

Malformed quality value.

What it means

QualityValue.parseAsInteger() validates q-values: 1–5 chars, single-digit form or d.dd form (digit, dot, up to 3 digits). Values failing these structural rules throw this BadRequestException (MALFORMED_VALUE_MESSAGE).

Source

Thrown at independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/request/QualityValue.java:84

    @Override
    public float floatValue() {
        return (float) WEIGHT / 1000f;
    }

    @Override
    public int intValue() {
        return WEIGHT;
    }

    @Override
    public long longValue() {
        return WEIGHT;
    }

    private static int parseAsInteger(String value) {
        int length = value.length();
        if (length == 0 || length > 5)
            throw new BadRequestException(MALFORMED_VALUE_MESSAGE);
        if (length > 1 && value.charAt(1) != '.')
            throw new BadRequestException(MALFORMED_VALUE_MESSAGE);
        int firstCharacter = value.codePointAt(0);
        if (firstCharacter == '1') {
            for (int i = 2; i < length; ++i)
                if (value.charAt(i) != '0')
                    throw new BadRequestException(MALFORMED_VALUE_MESSAGE);
            return 1000;
        } else if (firstCharacter == '0') {
            int weight = 0;
            for (int i = 2; i < 5; ++i) {
                weight *= 10;
                if (i < length) {
                    int digit = value.codePointAt(i) - '0';
                    if (digit < 0 || digit > 9)
                        throw new BadRequestException(MALFORMED_VALUE_MESSAGE);
                    weight += digit;
                }

View on GitHub (pinned to e1c734241f)

Solutions

1. Use a valid q value between 0 and 1: 0, 0.5, 0.999, 1 (max 3 decimal digits)
2. Remove the q parameter entirely to use the default quality
3. Fix the client library that formats quality weights

Example fix

// before
Accept: application/json;q=10
// after
Accept: application/json;q=1.0

boolean isValidQValue(String q) {
    return q != null && q.matches("[01](\.[0-9]{1,3})?");
}

boolean isQualityValue(String v) {
    if (v == null || v.isEmpty() || v.length() > 5) return false;
    return v.matches("[01](\.[0-9]{1,3})?");
}

try {
    QualityValue qv = QualityValue.valueOf(q);
} catch (BadRequestException e) {
    QualityValue qv = QualityValue.DEFAULT;
}

When it happens

Trigger: q= parameter values like '10', '1.2345', '.5', 'q=abc', 'q=2.0' (>1) encountered while parsing Accept-style headers.

Common situations: Clients emitting weights outside 0–1 (e.g. 'q=2'); locale-formatted decimals; hand-written tests with arbitrary strings as q values.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Malformed media type:
• IOException(e)
• OIDC discovery endpoint request failed
• Proxy type HTTP is required
• Response already committed

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/8ef5530e95fefbee. Report an issue: GitHub.