if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/")
async def create_item(item: Item, x_token: Annotated[str, Header()]) -> Item:
    if x_token != fake_secret_token:

        raise InternalError(
            f"The portal gun is too dangerous to be owned by {username}"
        )
    if item_id != "plumbus":
        raise HTTPException(
            status_code=404, detail="Item not found, there's only a plumbus here"
        )

        raise InternalError(
            f"The portal gun is too dangerous to be owned by {username}"
        )
    if item_id != "plumbus":
        raise HTTPException(
            status_code=404, detail="Item not found, there's only a plumbus here"
        )

@app.get("/items/{item_id}")
def get_item(item_id: str, username: str = Depends(get_username)):
    if item_id not in data:
        raise HTTPException(status_code=404, detail="Item not found")
    item = data[item_id]
    if item["owner"] != username:
        raise OwnerError(username)

    Request request = new Request.Builder()
            .url(url)
            .build();
    try (Response response = client.newCall(request).execute()) {
      assertTrue(response.code() == 200 || response.code() == 404);
      assertEquals(Protocol.HTTP_2, response.protocol());

      for (Certificate c: response.handshake().peerCertificates()) {
        X509Certificate x = (X509Certificate) c;
        System.out.println(x.getSubjectDN());

The status codes in the 400 range mean that there was an error from the client.

Remember all those **"404 Not Found"** errors (and jokes)?

## Use `HTTPException` { #use-httpexception }

To return HTTP responses with errors to the client you use `HTTPException`.

### Import `HTTPException` { #import-httpexception }

これは `dict` を受け取り、キーは各レスポンスのステータスコード（例: `200`）、値は各レスポンスの情報を含む別の `dict` です。

それぞれのレスポンス `dict` には、`response_model` と同様に Pydantic モデルを格納する `model` キーを含められます。

FastAPI はそのモデルから JSON Schema を生成し、OpenAPI の適切な場所に含めます。

例えば、ステータスコード `404` と Pydantic モデル `Message` を持つ別のレスポンスを宣言するには、次のように書けます:

{* ../../docs_src/additional_responses/tutorial001_py310.py hl[18,22] *}

/// note | 備考

`JSONResponse` を直接返す必要がある点に注意してください。

///

/// info | 情報

    response = client.post("/users/rick")
    assert response.status_code == 405, response.text


def test_invalid_path_doesnt_match():
    response = client.post("/usersx/rick")
    assert response.status_code == 404, response.text


def test_websocket():
    with client.websocket_connect("/items/portal-gun") as websocket:
        data = websocket.receive_json()

app = FastAPI()

items = {"foo": "The Foo Wrestlers"}


@app.get("/items/{item_id}")
async def read_item(item_id: str):
    if item_id not in items:
        raise HTTPException(status_code=404, detail="Item not found")

app = FastAPI()

items = {"foo": "The Foo Wrestlers"}


@app.get("/items-header/{item_id}")
async def read_item_header(item_id: str):
    if item_id not in items:
        raise HTTPException(
            status_code=404,
            detail="Item not found",
            headers={"X-Error": "There goes my error"},
        )