/** Configuration key for crawler clients used in parameter maps */
    protected static final String CRAWLER_CLIENTS = "crawlerClients";

    /** HTTP status code for Not Found */
    private static final int HTTP_STATUS_NOT_FOUND = 404;

    /** HTTP status code for OK */
    private static final int HTTP_STATUS_OK = 200;

    /**

     * @param client The CrawlerClient instance.
     */
    @Override
    public void addClient(final String regex, final CrawlerClient client) {
        factory.addClient(regex, client);
    }

    /**
     * Adds a client to the wrapped factory at a specific position.
     * @param regex The regular expression for the client.
     * @param client The CrawlerClient instance.

     */
    public CrawlerClient getClient(final String urlKey) {
        if (StringUtil.isBlank(urlKey)) {
            return null;
        }

        for (final Map.Entry<Pattern, CrawlerClient> entry : clientMap.entrySet()) {
            final Matcher matcher = entry.getKey().matcher(urlKey);
            if (matcher.matches()) {
                return entry.getValue();
            }

    }

    /**
     * Closes the underlying CrawlerClient and releases any resources associated with it.
     *
     * @throws Exception if an error occurs during the close operation
     */
    @Override
    public void close() throws Exception {
        client.close();
    }

    /**
     * Returns the underlying CrawlerClient.
     * @return The CrawlerClient instance.
     */

└── fess-crawler-opensearch/   # OpenSearch backend
```

### Key Design Patterns

**Factory**: `CrawlerClientFactory`, `ExtractorFactory` - protocol/format-specific component selection
**Strategy**: `CrawlerClient`, `Extractor`, `Transformer` - pluggable implementations
**Builder**: `RequestDataBuilder`, `ExtractorBuilder` - fluent construction
**Template Method**: `AbstractCrawlerClient`, `AbstractExtractor` - common logic with overrides

                    config.initializeClientFactory(() -> ComponentUtil.getComponent(CrawlerClientFactory.class));
            final CrawlerClient client = crawlerClientFactory.getClient(url);
            if (client == null) {
                throw new ThumbnailGenerationException("No CrawlerClient: " + configId + ", url: " + url);
            }
            String u = url;
            for (int i = 0; i < maxRedirectCount; i++) {

        final CrawlerClient client = mock(CrawlerClient.class);
        when(clientFactory.getClient("http://example.com/")).thenReturn(client);

        // Use reflection to access protected method
        final java.lang.reflect.Method method = CrawlerThread.class.getDeclaredMethod("getClient", String.class);
        method.setAccessible(true);

import org.codelibs.core.io.CloseableUtil;
import org.codelibs.core.lang.StringUtil;
import org.codelibs.core.lang.SystemUtil;
import org.codelibs.fess.crawler.builder.RequestDataBuilder;
import org.codelibs.fess.crawler.client.CrawlerClient;
import org.codelibs.fess.crawler.client.CrawlerClientFactory;
import org.codelibs.fess.crawler.container.CrawlerContainer;
import org.codelibs.fess.crawler.entity.AccessResult;

import jakarta.annotation.Resource;

/**
 * Abstract base class for CrawlerClient implementations.
 * Provides common functionality for handling initialization parameters,
 * content length checks, and default method implementations.
 * It defines the basic structure and configuration options for crawler clients.
 */
public abstract class AbstractCrawlerClient implements CrawlerClient {

		<property name="soTimeout">30000</property>
	</component>
	<component name="httpClient"
		class="org.codelibs.fess.crawler.client.FaultTolerantClient" instance="prototype">
		<property name="crawlerClient">internalHttpClient</property>
		<property name="maxRetryCount">5</property>
		<property name="retryInterval">500</property>
	</component>

	<component name="fsClient"