* it must be synchronized externally.
 * </p>
 * <p>
 * For thread-safe usage, wrap with {@link java.util.Collections#synchronizedMap(Map)}:
 * </p>
 * <pre>
 * Map&lt;K, V&gt; syncMap = Collections.synchronizedMap(new LruHashMap&lt;&gt;(100));
 * </pre>
 * <p>
 * Alternatively, for high-concurrency scenarios, consider implementing a custom

    /**
     * Synchronized LRU cache for storing parent URL encodings.
     * Maps session+parent URL keys to their corresponding character encodings.
     */
    Map<String, String> parentEncodingMap = Collections.synchronizedMap(new LruHashMap<>(1000));

    /**
     * Gets the Fess configuration instance.
     *
     * @return the Fess configuration object
     */
    FessConfig getFessConfig();

    /**