// Null-safety: return null for blank templates
        // Early return is safe here as no resources have been allocated yet
        if (StringUtil.isBlank(template)) {
            if (logger.isDebugEnabled()) {
                logger.debug("Template is blank, returning null");
            }
            return null;
        }

        // Null-safety: use empty map if paramMap is null

    .error(throwable -> { /* handle error */ });
```

---

## Important Notes

### Thread Safety
- **Suggester**: Thread-safe for queries
- **SuggestIndexer**: Thread-safe for indexing
- **SuggestSettings**: NOT thread-safe for modifications

### Performance
- Use batch operations for indexing (100-500 items)
- Don't call `refresh()` too frequently

 * <p>
 * <strong>Thread-Safety:</strong> This class is <strong>NOT thread-safe</strong>.
 * It extends {@link LinkedHashMap} without synchronization. If multiple threads access
 * an instance concurrently, and at least one thread modifies the map structurally,
 * it must be synchronized externally.
 * </p>
 * <p>
 * For thread-safe usage, wrap with {@link java.util.Collections#synchronizedMap(Map)}:
 * </p>

**Template Method**: `AbstractCrawlerClient`, `AbstractExtractor` - common logic with overrides
**DI**: LastaFlute container with `@Resource` and XML config

### Core Principles

**Thread Safety**:
- `AtomicLong` for counters (`CrawlerContext.accessCount`)
- `volatile` for status flags
- Synchronized blocks for critical sections
- Thread-local storage via `CrawlingParameterUtil`

**Resource Management**:

import org.dbflute.utflute.core.PlainTestCase;

/**
 * Test class for {@link Handler} and its inner class {@link Handler.GcsURLConnection}.
 * This test covers URL parsing, connection state management, and thread-safety.
 */
public class HandlerTest extends PlainTestCase {
    @Override
    protected void setUp() throws Exception {
        super.setUp();
        new StandardCrawlerContainer();
    }

    /**

import org.dbflute.utflute.core.PlainTestCase;

/**
 * Test class for {@link Handler} and its inner class {@link Handler.StorageURLConnection}.
 * This test covers URL parsing, connection state management, and thread-safety.
 */
public class HandlerTest extends PlainTestCase {
    @Override
    protected void setUp() throws Exception {
        super.setUp();
        new StandardCrawlerContainer();
    }

    /**

 *   <li>{@link DataService} - The service for managing access results.</li>
 * </ul>
 *
 * <p>Each parameter is stored in a ThreadLocal variable to ensure thread safety.</p>
 *
 * <p>Usage example:</p>
 * <pre>
 * {@code
 * UrlQueue<?> urlQueue = CrawlingParameterUtil.getUrlQueue();
 * CrawlingParameterUtil.setUrlQueue(newUrlQueue);
 *

                    }
                    return exitValue;
                }
            } else {
                // This is a secondary timeout, a safety net.
                logger.warn("{} is unresponsive and could not be terminated within the safety timeout.", getName());
                if (!task.isExecuted()) {
                    task.run();
                }
            }

    protected static final String JAVABIN = "javabin";

    /** Constant for Kryo serializer type. */
    protected static final String KRYO = "kryo";

    /** ThreadLocal container for Kryo instances to ensure thread safety. */
    protected final ThreadLocal<Kryo> kryoThreadLocal;

    /**
     * Constructs a new DataSerializer.
     * <p>
     * Initializes the ThreadLocal Kryo instances with appropriate configuration.

 * <pre>
 * {@code
 * String escapedXml = XmlUtil.escapeXml("<tag>value</tag>");
 * Map<String, Object> dataMap = XmlUtil.getDataMap(accessResultData);
 * }
 * </pre>
 *
 * <h2>Thread Safety:</h2>
 * <p>
 * This class is thread-safe as it does not maintain any state.
 * </p>
 *
 * <h2>Dependencies:</h2>
 * <ul>
 *   <li>org.apache.logging.log4j.Logger</li>
 *   <li>org.apache.logging.log4j.LogManager</li>