@Override
    public String asHeaderValue() {
        if (headerValue != null) {
            return headerValue;
        }
        try (TemporaryThreadLocals tempThreadLocals = TemporaryThreadLocals.acquire()) {
            final StringBuilder builder = tempThreadLocals.stringBuilder();
            builder.append("OAuth ");
            if (!isNullOrEmpty(realm)) {
                appendValue(builder, REALM, realm, true);
            }

            appendValue(builder, OAUTH_CONSUMER_KEY, consumerKey, true);
            appendValue(builder, OAUTH_TOKEN, token, true);
            appendValue(builder, OAUTH_SIGNATURE_METHOD, signatureMethod, true);
            appendValue(builder, OAUTH_SIGNATURE, signature, true);
            appendValue(builder, OAUTH_TIMESTAMP, timestamp, true);
            appendValue(builder, OAUTH_NONCE, nonce, true);
            appendValue(builder, OAUTH_VERSION, version, false);
            for (Entry<String, String> entry : additionals.entrySet()) {
                builder.append(',');
                appendValue(builder, entry.getKey(), entry.getValue(), false);
            }

            return headerValue = builder.toString();
        }
    }
Returns the string that is sent as the value of the {@link HttpHeaderNames#AUTHORIZATION} header.
core/src/main/java/com/linecorp/armeria/common/auth/OAuth1aToken.java