* using the Fess file transformation process with support for various file types.
 *
 * <p>It extends AbstractFessFileTransformer to provide specialized file processing
 * capabilities using the appropriate extractor for each file type.</p>
 */
public class FessFileTransformer extends AbstractFessFileTransformer {
    /**
     * Default constructor.
     */
    public FessFileTransformer() {

 * the standard Fess file transformation process with support for various content types.
 *
 * <p>It extends AbstractFessFileTransformer to provide file-specific transformation
 * capabilities while using the appropriate extractor for each document type.</p>
 */
public class FessStandardTransformer extends AbstractFessFileTransformer {
    /**
     * Default constructor.
     */

## Project Overview

Fess is an Enterprise Search Server built on OpenSearch. It's a Java-based web application that crawls and indexes documents from various sources and provides full-text search capabilities.

## Development Commands

### Setup
```bash
# Download OpenSearch plugins (required before first build)
mvn antrun:run

# Generate DBFlute source code (when schema changes)

import com.esotericsoftware.kryo.io.Input;
import com.esotericsoftware.kryo.io.Output;

/**
 * A serializer class for handling object serialization and deserialization.
 * <p>
 * This class provides serialization capabilities using different serializers,
 * currently supporting Kryo and JavaBin serialization formats. The serializer
 * type is determined by the crawler data serializer configuration.
 * </p>
 * <p>

 * response fields, search fields, facet fields, sort fields, and highlighting.
 * It initializes field mappings from the FessConfig and provides methods to
 * query field properties and capabilities.
 */
public class QueryFieldConfig {

    /**
     * Default constructor.
     */
    public QueryFieldConfig() {
        // Default constructor
    }

    /** Logger instance for this class */

        client.execute(action, request, listener);
    }

    /**
     * Prepares a field capabilities request builder.
     *
     * @param indices the indices to check field capabilities for
     * @return the field capabilities request builder
     */
    @Override
    public FieldCapabilitiesRequestBuilder prepareFieldCaps(final String... indices) {

 *   <li>Content length validation</li>
 *   <li>MIME type detection</li>
 *   <li>Handling of large files through temporary file storage</li>
 *   <li>Object metadata retrieval</li>
 *   <li>Directory listing capabilities</li>
 * </ul>
 *
 * <p>The client handles timeout management for access operations and includes proper
 * resource cleanup mechanisms.
 */
public class GcsClient extends AbstractCrawlerClient {

 * This class extends the base CrawlerThread and provides Fess-specific functionality for
 * crawling and indexing documents, including incremental crawling capabilities, content
 * modification checking, and integration with the Fess search engine backend.
 *
 * <p>Key features include:</p>
 * <ul>
 * <li>Incremental crawling support with last-modified timestamp checking</li>

 *   <li>Content length validation</li>
 *   <li>MIME type detection</li>
 *   <li>Handling of large files through temporary file storage</li>
 *   <li>Object metadata and tags retrieval</li>
 *   <li>Directory listing capabilities</li>
 * </ul>
 *
 * <p>The client handles timeout management for access operations and includes proper
 * resource cleanup mechanisms.
 */
public class S3Client extends AbstractCrawlerClient {

     * Adds the searcher to the searchers list and initializes the executor service
     * if it hasn't been created yet. The executor service is created with a thread pool
     * sized based on configuration or system capabilities.
     *
     * @param searcher the RankFusionSearcher to register
     */
    public void register(final RankFusionSearcher searcher) {
        if (logger.isDebugEnabled()) {