* purposes, the "count" field, tracking the number of elements, serves as that volatile
     * variable ensuring visibility. This is convenient because this field needs to be read in many
     * read operations anyway:
     *
     * - All (unsynchronized) read operations must first read the "count" field, and should not
     * look at table entries if it is 0.
     *

        final Map<String, Object> source = new LinkedHashMap<>();
        source.put("field\"name", "value");

        final String json = new JsonIndexExportFormatter().format(source, Collections.emptySet());

        assertTrue(json.contains("\"field\\\"name\": \"value\""));
    }

    @Test
    public void test_jsonFormatter_singleField() {

```

Notice how no connect events are fired for the second call. It reused the connection from the first request for dramatically better performance.

### EventListener.Factory

    input.addListener(output, rejectionPropagatingExecutor(executor, output));
    return output;
  }

  /*
   * In certain circumstances, this field might theoretically not be visible to an afterDone() call
   * triggered by cancel(). For details, see the comments on the fields of TimeoutFuture.
   */
  @LazyInit @Nullable ListenableFuture<? extends V> inputFuture;

  private final Object lock = new Object();

  /**
   * The runnable, executor pairs to execute. This acts as a stack threaded through the {@link
   * RunnableExecutorPair#next} field.
   */
  @GuardedBy("lock")
  private @Nullable RunnableExecutorPair runnables;

  @GuardedBy("lock")
  private boolean executed;

  /** Creates a new, empty {@link ExecutionList}. */

                        "uses the unsupported value 'legacy', artifact resolution might fail.");
            }
        }
    }

    // ----------------------------------------------------------------------
    // Field validation
    // ----------------------------------------------------------------------

    /**
     * Asserts:
     * <p/>
     * <ul>
     * <li><code>string.length != null</code>

/**
 * OpenSearchUrlFilterService is an implementation of {@link UrlFilterService} for OpenSearch.
 */
public class OpenSearchUrlFilterService extends AbstractCrawlerService implements UrlFilterService {

    /**
     * Field name for filter type.
     */
    private static final String FILTER_TYPE = "filterType";

    /**
     * Filter type for include filters.
     */
    private static final String INCLUDE = "include";

    /**

### Other notable changes

You can also declare a response using a plain arbitrary `dict`, declaring just the type of the keys and values, without using a Pydantic model.

This is useful if you don't know the valid field/attribute names (that would be needed for a Pydantic model) beforehand.

In this case, you can use `dict`:

{* ../../docs_src/extra_models/tutorial005_py310.py hl[6] *}

## Recap { #recap }

            return 4000;
        }
    }

    /**
     * Parses and validates field filter parameters from the request.
     * Only configured label values are accepted to prevent query injection.
     *
     * @param request the HTTP request
     * @return a map of field names to their validated filter values
     */