/**
 * This class is an implementation of {@link UrlQueueService}.
 */
public class UrlQueueServiceImpl implements UrlQueueService<UrlQueueImpl<Long>> {

    /**
     * Creates a new UrlQueueServiceImpl instance.
     */
    public UrlQueueServiceImpl() {
        // NOP
    }

    private static final Logger logger = LogManager.getLogger(UrlQueueServiceImpl.class);

    /**
     * The memory data helper.
     */
    @Resource

	<component name="urlQueue" class="org.codelibs.fess.crawler.entity.UrlQueueImpl" instance="prototype" >
	</component>

	<!-- Service -->
	<component name="urlQueueService" class="org.codelibs.fess.crawler.service.impl.UrlQueueServiceImpl" instance="prototype" >
	</component>
	<component name="dataService" class="org.codelibs.fess.crawler.service.impl.DataServiceImpl" instance="prototype" >
	</component>

import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;

/**
 * Test class for {@link UrlQueueServiceImpl}.
 */
public class UrlQueueServiceImplTest extends PlainTestCase {

    @InjectMocks
    private UrlQueueServiceImpl service;

    @Mock
    private MemoryDataHelper dataHelper;

    @Override
    protected void setUp() throws Exception {

import org.codelibs.fess.crawler.service.impl.DataServiceImpl;
import org.codelibs.fess.crawler.service.impl.UrlFilterServiceImpl;
import org.codelibs.fess.crawler.service.impl.UrlQueueServiceImpl;
import org.codelibs.fess.crawler.transformer.impl.FileTransformer;
import org.codelibs.fess.crawler.util.CrawlerWebServer;
import org.dbflute.utflute.core.PlainTestCase;

```

### Services

**UrlQueueService**: URL queue management (FIFO), duplicate detection via `visited()`
**DataService**: Access result persistence, iteration

**Implementations**:
- `UrlQueueServiceImpl`, `DataServiceImpl`: In-memory (default)
- `OpenSearchDataService`: OpenSearch backend (persistent)

### Processing Pipeline

```