*
 * @see HcHttpClient
 */
public class Hc4HttpClient extends HcHttpClient {

    /** Logger instance for this class */
    private static final Logger logger = LogManager.getLogger(Hc4HttpClient.class);

    /**
     * Constructs a new Hc4HttpClient.
     */
    public Hc4HttpClient() {
        // Default constructor
    }

### HTTP Client Architecture

```
SwitchableHttpClient (extends FaultTolerantClient)
    ├── Hc5HttpClient (default) - Apache HttpComponents 5.x
    └── Hc4HttpClient (fallback) - Apache HttpComponents 4.x

HcHttpClient (abstract base class)
    ├── Hc4HttpClient
    └── Hc5HttpClient
```

Switch via system property: `-Dfess.crawler.http.client=hc4` or `hc5` (default)

 * The client implementation is selected based on the system property {@code fess.crawler.http.client}.
 *
 * <p>Supported values:</p>
 * <ul>
 *   <li>{@code hc4} - Use Apache HttpComponents 4.x ({@link Hc4HttpClient})</li>
 *   <li>{@code hc5} or not set - Use Apache HttpComponents 5.x ({@link Hc5HttpClient}) - default</li>
 * </ul>
 *
 * <p>This class extends {@link FaultTolerantClient} to provide automatic retry functionality

		<property name="soTimeout">30000</property>
	</component>

	<!-- HC4 (Alternative - for backward compatibility) -->
	<component name="internalHc4HttpClient" class="org.codelibs.fess.crawler.client.http.Hc4HttpClient"
		instance="prototype">
		<property name="connectionTimeout">15000</property>
		<property name="soTimeout">30000</property>
	</component>
	<component name="httpClient"