import org.codelibs.fess.crawler.entity.ExtractData;
import org.codelibs.fess.crawler.exception.CrawlerSystemException;
import org.codelibs.fess.crawler.exception.ExtractException;
import org.codelibs.fess.crawler.exception.UnsupportedExtractException;

import jakarta.annotation.Resource;

/**
 * Factory class for managing and retrieving {@link Extractor} instances.
 * This class provides methods to add, retrieve, and manage extractors based on a key.

CrawlingAccessException (checked)   # Runtime crawl errors
  ├─ MaxLengthExceededException
  └─ ChildUrlsException
ExtractException (checked)          # Extraction failures
  └─ UnsupportedExtractException
```

### Thread-Local Storage

```java
// Set (in CrawlerThread)
CrawlingParameterUtil.setCrawlerContext(context);
CrawlingParameterUtil.setUrlQueue(urlQueue);