public Boolean exists(final String key) {
        try {
            GetOption option = GetOption.newBuilder()
                    .withPrefix(ByteSequence.from(key, StandardCharsets.UTF_8))
                    .build();
            List<KeyValue> keyValues = client.getKVClient().get(ByteSequence.from(key, StandardCharsets.UTF_8), option).get().getKvs();
            return !keyValues.isEmpty();
        } catch (Exception e) {
            LOG.error("check node exists error", e);
            throw new ShenyuException(e);
        }
    }
check node exists.
@param key node name
@return bool
shenyu-admin-listener/shenyu-admin-listener-etcd/src/main/java/org/apache/shenyu/admin/listener/etcd/EtcdClient.java