Java APIs to Get and Update Solr Configuration Files

User Case
SolrCloud stores its configuration files (for example: elevate.xml) in Zookeeper. Usually we need APIs that clients(for example UI) can call to get these configuration files or update.

Related: Build Web Service APIs to Update Solr's Managed Resources (stop words, synonyms)

The Implementation
We use SolrJ's SolrZkClient APIs to get data, make znode, and set znode's data.

public String getConfigData(final String filePath) {
    final ZkStateReader zkStateReader = getZKReader(getSolrClient());
    final String path = normalizeConfigPath(filePath);
    final SolrZkClient zkClient = zkStateReader.getZkClient();
    try {
        return new String(zkClient.getData(path, null, null, true));
    } catch (KeeperException | InterruptedException e) {
        throw new BusinessException(ErrorCode.data_access_error, e, "Failed to get " + path);
    }
}
public void setConfigData(final String filePath, final String data, final boolean createPath,
        final boolean reloadCollection) {
    Validate.notNull(filePath);
    Validate.notNull(data);
    final ZkStateReader zkStateReader = getZKReader(getSolrClient());
    final String path = normalizeConfigPath(filePath);
    final SolrZkClient zkClient = zkStateReader.getZkClient();
    try {
        if (createPath) {
            zkClient.makePath(path, false, true);
        }
        zkClient.setData(path, data.getBytes(), true);

        if (reloadCollection) {
            reloadCollection();
        }
    } catch (KeeperException | InterruptedException e) {
        throw new BusinessException(ErrorCode.data_access_error, e, "Failed to get " + path);
    }
}

public void reloadCollection() {
    try {
        final CollectionAdminRequest.Reload reload = new CollectionAdminRequest.Reload();
        reload.setCollectionName(getSolrClient().getDefaultCollection());
        final CollectionAdminResponse response = reload.process(getSolrClient());
        logger.info(MessageFormat.format("reload collection: {0} rsp: {1}", getSolrClient().getDefaultCollection(),
                response));
        final int status = response.getStatus();
        if (status != 0) {
            throw new BusinessException(ErrorCode.data_access_error,
                    "Failed to reload collection, status: " + status);
        }
    } catch (SolrServerException | IOException e) {
        throw new BusinessException(ErrorCode.data_access_error,
                "Failed to reload collection: " + getSolrClient().getDefaultCollection());
    }
}

public static ZkStateReader getZKReader(final CloudSolrClient solrClient) {
    final ZkStateReader zkReader = solrClient.getZkStateReader();
    if (zkReader == null) {
        // This only happens when we first time call solrClient to do anything
        // Usually we will call solrClient to do something during abolition starts: such as
        // healthCheck, so in most cases, its already connected.
        solrClient.connect();
    }
    return solrClient.getZkStateReader();
}
/**
 * @param filePath
 * @return add prefix to make elevate.xml - /configs/myCollection/elevate.xml
 */
private String normalizeConfigPath(final String filePath) {
    return ZkStateReader.CONFIGS_ZKNODE + "/" + getSolrClient().getDefaultCollection() + "/" + filePath;
}

Resources
Build Web Service APIs to Update Solr's Managed Resources (stop words, synonyms)