!!! tip
    Notice that the query `token` will be handled by a dependency.

With that you can connect the WebSocket and then send and receive messages:

<img src="/img/tutorial/websockets/image05.png">

## Handling disconnections and multiple clients

When a WebSocket connection is closed, the `await websocket.receive_text()` will raise a `WebSocketDisconnect` exception, which you can then catch and handle like in this example.

    final List<String> lines = Lists.newArrayList();
    LineBuffer lineBuf =
        new LineBuffer() {
          @Override
          protected void handleLine(String line, String end) {
            lines.add(line + end);
          }
        };
    char[] chars = input.toCharArray();
    int off = 0;
    while (off < chars.length) {

from fastapi.testclient import TestClient

from docs_src.handling_errors.tutorial004 import app

client = TestClient(app)


def test_get_validation_error():
    response = client.get("/items/foo")
    assert response.status_code == 400, response.text
    # TODO: remove when deprecating Pydantic v1
    assert (
        # TODO: remove when deprecating Pydantic v1
        "path -> item_id" in response.text

   * Arrays#hashCode(Object[])}. Note that array arguments to this method, with the exception of a
   * single Object array, do not get any special handling; their hash codes are based on identity
   * and not contents.
   *
   * <p>This is useful for implementing {@link Object#hashCode()}. For example, in an object that

Because this code is executed before the application **starts** taking requests, and right after it **finishes** handling requests, it covers the whole application **lifespan** (the word "lifespan" will be important in a second 😉).

from dirty_equals import IsDict
from fastapi.testclient import TestClient

from docs_src.handling_errors.tutorial006 import app

client = TestClient(app)


def test_get_validation_error():
    response = client.get("/items/foo")
    assert response.status_code == 422, response.text
    assert response.json() == IsDict(
        {
            "detail": [
                {
                    "type": "int_parsing",

import org.lastaflute.web.response.ApiResponse;
import org.lastaflute.web.response.JsonResponse;

/**
 * @author jflute
 */
public class FessApiFailureHook implements ApiFailureHook { // #change_it for handling API failure

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

    // ===================================================================================

 */
package org.apache.maven.internal.impl.model;

import java.nio.file.Path;

import org.apache.maven.api.model.Model;
import org.apache.maven.api.services.ModelProblem;

/**
 * Assists in the handling of model problems.
 *
 */
public class ModelProblemUtils {

    /**
     * Creates a user-friendly source hint for the specified model.
     *

## Mounting a **FastAPI** application

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

### Top-level application

First, create the main, top-level, **FastAPI** application, and its *path operations*:

    }

    @Override
    public @Nullable Object[] toArray() {
      return standardToArray();
    }

    @Override
    @SuppressWarnings("nullness") // bug in our checker's handling of toArray signatures
    public <T extends @Nullable Object> T[] toArray(T[] array) {
      return standardToArray(array);
    }

    @Override
    public String toString() {
      return standardToString();