FastApi-中间件

# 一、概述

所谓的中间件，其实和我们bottle中的中间件作用是一致。有些方法或操作需要在所有路由之前执行，比如要加一个http访问的拦截器，可以对部分接口API需要授权才能访问的接口进行验证之类的。

FastAPI提供了一个@app.middleware("http")可以做到类似上面的拦截功能。其实和bottle或flask 钩子函数很相似

# 二、示例

示例如下：

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

import time
from fastapi import FastAPI, HTTPException
from fastapi.exceptions import RequestValidationError
from fastapi.responses import PlainTextResponse
from starlette.exceptions import HTTPException as StarletteHTTPException

app = FastAPI()


@app.exception_handler(StarletteHTTPException)
async def http_exception_handler(request, exc):
    return PlainTextResponse(str(exc.detail), status_code=exc.status_code)


@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request, exc):
    return JSONResponse({'mes': '触发了RequestValidationError错误，，错误信息:%s 你妹的错了！' % (str(exc))})


@app.get("/items/{item_id}")
async def read_item(item_id: int):
    return {"item_id": item_id}


@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
    start_time = time.time()
    response = await call_next(request)
    process_time = time.time() - start_time
    response.headers["X-Process-Time"] = str(process_time)
    return response

if __name__ == '__main__':
    uvicorn.run(app='main:app', host="127.0.0.1", port=8000, reload=True, debug=True)