jwtk/jjwt · error · UnsupportedJwtException

The specified SigningKeyResolver implementation does not…

Error message

The specified SigningKeyResolver implementation does not support content JWS signing key resolution.  Consider overriding either the resolveSigningKey(JwsHeader, byte[]) method or, for HMAC algorithms, the resolveSigningKeyBytes(JwsHeader, byte[]) method.

What it means

Error "The specified SigningKeyResolver implementation does not support content JWS signing key resolution. Consider overriding either the resolveSigningKey(JwsHeader, byte[]) method or, for HMAC algorithms, the resolveSigningKeyBytes(JwsHeader, byte[]) method." thrown in jwtk/jjwt.

Solutions

1. Override resolveSigningKey(JwsHeader, byte[]) or resolveSigningKeyBytes(JwsHeader, byte[]) in your SigningKeyResolverAdapter to handle content (payload) JWSs.
2. Use a Claims-specific resolver only when parsing Claims JWSs; for byte-payload JWSs implement the byte[] variants.
3. Consider extending SigningKeyResolverAdapter only for the JWS type you actually parse, or implement SigningKeyResolver directly.

When it happens

Trigger: Thrown at api/src/main/java/io/jsonwebtoken/SigningKeyResolverAdapter.java:118 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of jwtk/jjwt@fb71496164 (2026-09-09). Data as JSON: /api/errors/887d0a44df5fe940. Report an issue: GitHub.

Appendix: source

Thrown at api/src/main/java/io/jsonwebtoken/SigningKeyResolverAdapter.java:118

    public byte[] resolveSigningKeyBytes(JwsHeader header, Claims claims) {
        throw new UnsupportedJwtException("The specified SigningKeyResolver implementation does not support " +
                "Claims JWS signing key resolution.  Consider overriding either the " +
                "resolveSigningKey(JwsHeader, Claims) method or, for HMAC algorithms, the " +
                "resolveSigningKeyBytes(JwsHeader, Claims) method.");
    }

    /**
     * Convenience method invoked by {@link #resolveSigningKey(JwsHeader, byte[])} that obtains the necessary signing
     * key bytes.  This implementation simply throws an exception: if the JWS parsed is a content JWS, you must
     * override this method or the {@link #resolveSigningKey(JwsHeader, byte[])} method instead.
     *
     * @param header  the parsed {@link JwsHeader}
     * @param content the byte array payload
     * @return the signing key bytes to use to verify the JWS signature.
     */
    @SuppressWarnings("unused")
    public byte[] resolveSigningKeyBytes(JwsHeader header, byte[] content) {
        throw new UnsupportedJwtException("The specified SigningKeyResolver implementation does not support " +
                "content JWS signing key resolution.  Consider overriding either the " +
                "resolveSigningKey(JwsHeader, byte[]) method or, for HMAC algorithms, the " +
                "resolveSigningKeyBytes(JwsHeader, byte[]) method.");
    }
}

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