Python Falcon - 字尾響應器

為了理解字尾響應器的概念和必要性，讓我們定義一個StudentResource類。它包含一個on_get()響應器，該響應器將學生列表（dict物件）轉換為JSON並作為響應返回。

讓我們再新增一個on_post()響應器，它讀取來自傳入請求的資料，並在列表中新增一個新的dict物件。

import falcon
import json
from waitress import serve
students = [
   {"id": 1, "name": "Ravi", "percent": 75.50},
   {"id": 2, "name": "Mona", "percent": 80.00},
   {"id": 3, "name": "Mathews", "percent": 65.25},
]
class StudentResource:
   def on_get(self, req, resp):
      resp.text = json.dumps(students)
      resp.status = falcon.HTTP_OK
      resp.content_type = falcon.MEDIA_JSON
   def on_post(self, req, resp):
      student = json.load(req.bounded_stream)
      students.append(student)
      resp.text = "Student added successfully."
      resp.status = falcon.HTTP_OK
      resp.content_type = falcon.MEDIA_TEXT

使用Falcon的App物件的add_route()函式，我們添加了/students路由。

app = falcon.App()
app.add_route("/students", StudentResource())

啟動伺服器後，我們可以從HTTPie命令列測試GET和POST請求。

http GET localhost:8000/students
HTTP/1.1 200 OK
Content-Length: 187
Content-Type: application/json
Date: Mon, 18 Apr 2022 06:21:02 GMT
Server: waitress
[
   {
      "id": 1,
      "name": "Ravi",
      "percent": 75.5
   },
   {
      "id": 2,
      "name": "Mona",
      "percent": 80.0
   },
   {
      "id": 3,
      "name": "Mathews",
      "percent": 65.25
   }
]
http POST localhost:8000/students id=4 name="Prachi"
percent=59.90
HTTP/1.1 200 OK
Content-Length: 27
Content-Type: text/plain; charset=utf-8
Date: Mon, 18 Apr 2022 06:20:51 GMT
Server: waitress
Student added successfully.

再次呼叫on_get()確認了新學生資源的新增。

http GET localhost:8000/students
HTTP/1.1 200 OK
Content-Length: 187
Content-Type: application/json
Date: Mon, 18 Apr 2022 06:21:02 GMT
Server: waitress
[
   {
      "id": 1,
      "name": "Ravi",
      "percent": 75.5
   },
   {
      "id": 2,
      "name": "Mona",
      "percent": 80.0
   },
   {
      "id": 3,
      "name": "Mathews",
      "percent": 65.25
   },
   {
      "id": "4",
      "name": "Prachi",
      "percent": "59.90"
   }
]

在此階段，我們希望在StudentResource類中有一個GET響應器方法，該方法從URL中讀取id引數並檢索列表中相應的dict物件。

換句話說，格式為/student/{id}的URL應該與資源類中的GET方法關聯。但顯然，一個類不能有兩個同名的方法。因此，我們定義使用add_route()方法的suffix引數來區分on_get()響應器的兩個定義。

透過指定suffix ='student'，將帶有id引數的路由新增到Application物件。

app.add_route("/students/{id:int}", StudentResource(), suffix='student')

現在，我們可以使用此後綴新增另一個on_get()方法的定義，以便此響應器的名稱為on_get_student()，如下所示：

def on_get_student(self, req, resp, id):
   resp.text = json.dumps(students[id-1])
   resp.status = falcon.HTTP_OK
   resp.content_type = falcon.MEDIA_JSON

新增新路由和on_get_student()響應器後，啟動Waitress伺服器並測試以下URL：

http GET localhost:8000/students/2
HTTP/1.1 200 OK
Content-Length: 42
Content-Type: application/json
Date: Mon, 18 Apr 2022 06:21:05 GMTy
Server: waitress
{
   "id": 2,
   "name": "Mona",
   "percent": 80.0
}

請注意，當客戶端使用適當的請求頭請求URL路由/students/{id:int}時，on_put()響應器（更新資源）和on_delete()響應器（刪除資源）也將被呼叫。

我們已經使用student作為字尾添加了此路由。因此，on_put_student()方法將路徑引數解析為一個整型變數。獲取給定id的專案的JSON表示形式，並使用PUT請求中提供的資料進行更新。

def on_put_student(self, req, resp, id):
   student=students[id-1]
   data = json.load(req.bounded_stream)

   student.update(data)
   resp.text = json.dumps(student)
   resp.status = falcon.HTTP_OK
   resp.content_type = falcon.MEDIA_JSON

on_delete_student()響應器僅刪除DELETE請求中指定的id對應的專案。返回剩餘資源的列表。

def on_delete_student(self, req, resp, id):
   students.pop(id-1)
   resp.text = json.dumps(students)
   resp.status = falcon.HTTP_OK
   resp.content_type = falcon.MEDIA_JSON

我們可以使用HTTPie命令測試API的PUT和DELETE操作：

http PUT localhost:8000/students/2 id=3 name="Mathews"
percent=55
HTTP/1.1 200 OK
Content-Length: 46
Content-Type: application/json
Date: Sat, 18 Apr 2022 10:13:00 GMT
Server: waitress
{
   "id": "3",
   "name": "Mathews",
   "percent": "55"
}
http DELETE localhost:8000/students/2
HTTP/1.1 200 OK
Content-Length: 92
Content-Type: application/json
Date: Sat, 18 Apr 2022 10:18:00 GMT
Server: waitress
[
   {
      "id": 1,
      "name": "Ravi",
      "percent": 75.5
   },
   {
      "id": 3,
      "name": "Mathews",
      "percent": 65.25
   }
]

此API（studentapi.py）的完整程式碼如下：

import falcon
import json
from waitress import serve
students = [
   {"id": 1, "name": "Ravi", "percent": 75.50},
   {"id": 2, "name": "Mona", "percent": 80.00},
   {"id": 3, "name": "Mathews", "percent": 65.25},
]
class StudentResource:
   def on_get(self, req, resp):
      resp.text = json.dumps(students)
      resp.status = falcon.HTTP_OK
      resp.content_type = falcon.MEDIA_JSON
   def on_post(self, req, resp):
      student = json.load(req.bounded_stream)
      students.append(student)
      resp.text = "Student added successfully."
      resp.status = falcon.HTTP_OK
      resp.content_type = falcon.MEDIA_TEXT
   def on_get_student(self, req, resp, id):
      resp.text = json.dumps(students[id-1])
      resp.status = falcon.HTTP_OK
      resp.content_type = falcon.MEDIA_JSON
   def on_put_student(self, req, resp, id):
      student=students[id-1]
      data = json.load(req.bounded_stream)

      student.update(data)

      resp.text = json.dumps(student)
      resp.status = falcon.HTTP_OK
      resp.content_type = falcon.MEDIA_JSON
   def on_delete_student(self, req, resp, id):
      students.pop(id-1)
      print (students)
      resp.text = json.dumps(students)
      resp.status = falcon.HTTP_OK
      resp.content_type = falcon.MEDIA_JSON
app = falcon.App()
app.add_route("/students", StudentResource())
app.add_route("/students/{id:int}", StudentResource(), suffix='student')
if __name__ == '__main__':
   serve(app, host='0.0.0.0', port=8000)