在ServerAuthenticationConverter中读取request body后如何保存？

StringBuilder requestBody = new StringBuilder();

@Override
public Mono<Authentication> convert(ServerWebExchange exchange) {
    // 读取request body
    return DataBufferUtils.join(exchange.getRequest().getBody())
            .flatMap(dataBuffer -> {
                byte[] bytes = new byte[dataBuffer.readableByteCount()];
                dataBuffer.read(bytes);
                DataBufferUtils.release(dataBuffer);
                // 将读取到的内容追加到StringBuilder对象中
                requestBody.append(new String(bytes, StandardCharsets.UTF_8));
                return Mono.empty();
            })
            .then(Mono.defer(() -> {
                // 处理request body并返回Authentication对象
                return processRequestBody(requestBody.toString());
            }));
}

private Mono<Authentication> processRequestBody(String requestBody) {
    // 处理request body并返回Authentication对象
    // ...
}