/** Property name for maximum total connections setting */
    public static final String MAX_TOTAL_CONNECTION_PROPERTY = "maxTotalConnection";

    /** Property name for time to live time unit setting */
    public static final String TIME_TO_LIVE_TIME_UNIT_PROPERTY = "timeToLiveTimeUnit";

    /** Property name for time to live setting */

```

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

**Key Properties**: `connectionTimeout`, `soTimeout`, `proxyHost`, `proxyPort`, `userAgent`, `robotsTxtEnabled`, `ignoreSslCertificate`, `maxTotalConnection`, `defaultMaxConnectionPerRoute`

### CrawlerClientFactory

Pattern-based client selection (from `crawler/client.xml`):
- `http:.*`, `https:.*` → SwitchableHttpClient
- `file:.*` → FileSystemClient