* should be used for crawling the URL, falling back to the default client if no
     * specific rule matches.
     *
     * @param url the URL to get a client for
     * @return the crawler client instance to use for the URL
     */
    @Override
    protected CrawlerClient getClient(final String url) {
        final CrawlingConfigHelper crawlingConfigHelper = ComponentUtil.getCrawlingConfigHelper();

    assertThat(client.webSocket!!.send("Hello!")).isTrue()
    taskFaker.runTasks()
    client.listener.assertFailure(IOException::class.java, "source is closed")

    // A failed write prevents further use of the WebSocket instance.
    assertThat(client.webSocket!!.send("Hello!")).isFalse()
    assertThat(client.webSocket!!.pong("Ping!".encodeUtf8())).isFalse()
  }

  @Test
  fun serverCloseThenWritingPingSucceeds() {

///

### Passo 2: crie uma "instância" de `FastAPI` { #step-2-create-a-fastapi-instance }

{* ../../docs_src/first_steps/tutorial001_py39.py hl[3] *}

Aqui, a variável `app` será uma "instância" da classe `FastAPI`.

Este será o principal ponto de interação para criar toda a sua API.

    assertThrows(IndexOutOfBoundsException.class, () -> iia3.subArray(1, 4));
  }

  /*
   * Whenever an implementation uses `instanceof` on a parameter instance, the test has to know that
   * (so much for "black box") and try instances that both do and don't pass the check. The "don't"
   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(Collection<T> collection) {

        testRule.register(0);
        testRule.register(1);

        List<Rule> rules = ruleManager.getRules();
        assertEquals(3, rules.size());

        // All should be the same instance
        assertSame(testRule, rules.get(0));
        assertSame(testRule, rules.get(1));
        assertSame(testRule, rules.get(2));
    }

    /**
     * Test property changes after registration
     */

        } finally {
            lock.writeLock().unlock();
        }
    }

    /**
     * Register a file with cache for a path
     *
     * @param path file path
     * @param file SmbFile instance
     */
    public void registerFileCache(String path, SmbFile file) {
        if (file != null) {
            fileCache.put(path, new WeakReference<>(file));
        }
    }

    /**

	startTime            time.Time // Start time for window
	expMovingAvg         float64   // Previously calculated exponential moving average
}

// newRateMeasurement creates a new instance of the measurement with the initial start time.
func newRateMeasurement(initTime time.Time) *rateMeasurement {
	return &rateMeasurement{
		startTime: initTime,
	}
}

        assertEquals(strictlyOrderedList, ordering.immutableSortedCopy(nonNullShuffledList));
      }
    }
  }

  /**
   * A means for changing an Ordering into another Ordering. Each instance is responsible for
   * creating the alternate Ordering, and providing a List that is known to be ordered, based on an
   * input List known to be ordered according to the input Ordering.
   */

        assertEquals(strictlyOrderedList, ordering.immutableSortedCopy(nonNullShuffledList));
      }
    }
  }

  /**
   * A means for changing an Ordering into another Ordering. Each instance is responsible for
   * creating the alternate Ordering, and providing a List that is known to be ordered, based on an
   * input List known to be ordered according to the input Ordering.
   */

}
```

Of course, you will probably find much better ways to take advantage of this than formatting JSON. 😉

## Default response class { #default-response-class }

When creating a **FastAPI** class instance or an `APIRouter` you can specify which response class to use by default.

The parameter that defines this is `default_response_class`.