if err != nil {
		return false, err
	}

	// Handle large OPA responses when OPA URL is of
	// form http://localhost:8181/v1/data/httpapi/authz
	type opaResultAllow struct {
		Result struct {
			Allow bool `json:"allow"`
		} `json:"result"`
	}

	// Handle simpler OPA responses when OPA URL is of
	// form http://localhost:8181/v1/data/httpapi/authz/allow
	type opaResult struct {

from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse


class UnicornException(Exception):
    def __init__(self, name: str):
        self.name = name


app = FastAPI()


@app.exception_handler(UnicornException)
async def unicorn_exception_handler(request: Request, exc: UnicornException):
    return JSONResponse(
        status_code=418,

```JSON
{"message": "Oops! yolo did something. There goes a rainbow..."}
```

/// note | 技術細節

你也可以使用 `from starlette.requests import Request` 與 `from starlette.responses import JSONResponse`。

**FastAPI** 以便利性為由，提供和 `starlette.responses` 相同的介面於 `fastapi.responses`。但大多數可用的回應類型其實直接來自 Starlette。`Request` 也一樣。

///

## 覆寫預設例外處理器 { #override-the-default-exception-handlers }

**FastAPI** 內建了一些預設例外處理器。

    assert response.headers["Content-Encoding"] == "gzip"
    assert int(response.headers["Content-Length"]) < 4000
    response = client.get("/")

client = TestClient(app, root_path="/api/v1")


def test_main():
    response = client.get("/app")
    assert response.status_code == 200
    assert response.json() == {"message": "Hello World", "root_path": "/api/v1"}


def test_openapi():
    response = client.get("/openapi.json")
    assert response.status_code == 200
    assert response.json() == snapshot(
        {
            "openapi": "3.1.0",

def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == snapshot(
        {
            "openapi": "3.1.0",
            "info": {"title": "FastAPI", "version": "0.1.0"},
            "paths": {
                "/a/compute": {
                    "post": {
                        "responses": {
                            "200": {

from fastapi import FastAPI
from fastapi.responses import ORJSONResponse

app = FastAPI()


@app.get("/items/", response_class=ORJSONResponse)
async def read_items():

from fastapi import FastAPI
from fastapi.responses import RedirectResponse

app = FastAPI()


@app.get("/pydantic", response_class=RedirectResponse, status_code=302)
async def redirect_pydantic():

from fastapi import FastAPI
from fastapi.responses import RedirectResponse

app = FastAPI()


@app.get("/teleport")
async def get_teleport() -> RedirectResponse:

    return {"message": "Hello World"}


client = TestClient(app)


def test_app():
    response = client.get("/foo")
    assert response.status_code == 200, response.text


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == snapshot(
        {
            "openapi": "3.1.0",