public String get(final String key) {
        TreeCache cache = findFromCache(key);
        if (Objects.isNull(cache)) {
            return getDirectly(key);
        }
        ChildData data = cache.getCurrentData(key);
        if (Objects.isNull(data)) {
            return getDirectly(key);
        }
        return Objects.isNull(data.getData()) ? null : new String(data.getData(), StandardCharsets.UTF_8);
    }
get value for specific key.

@param key zookeeper path
@return value.
shenyu-admin-listener/shenyu-admin-listener-zookeeper/src/main/java/org/apache/shenyu/admin/listener/zookeeper/ZookeeperClient.java