Python Falcon 简明教程

Python Falcon - Suffixed Responders

为了理解概念和后缀响应者的需求，让我们定义一个 StudentResource 类。它包含一个 on_get() 响应者，它将学生列表转换 dict 对象为 JSON 并返回作为其响应。

我们还添加 on_post() 响应器，它从传入请求中读取数据并在列表中添加一个新的 dict 对象。

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‘s App 对象的 add_route() 函数，我们添加 /students 路由。

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

在启动服务器后，我们可以从 HTTPie 命令行测试 GET 和 POST 请求 -

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.

再次调用 on_get() 来确认添加了新的学生资源。

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"
   }
]

在这一阶段，我们希望在 StudentResource 类中有一个 GET 响应器方法，该方法从 URL 中读取 id 参数并从列表中检索相应的 dict 对象。

换句话说，格式为 /student/{id} 的 URL 应当与资源类中的 GET 方法相关联。但显然，一个类不能有两个相同名称的方法。因此，我们定义对 add_route() 方法使用 suffix 参数来区分 on_get() 响应器的两个定义。

通过指定 suffix ='student' ，将一个带有 id 参数的路由添加到 Application 对象。

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

我们现在可以添加 on_get() 方法的另一个定义和此后缀，以便此响应器的名称为 on_get_student() 如下 -

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

在添加新路由和 on_get_student() 响应器后启动 Waitress 服务器，并按如下方式测试此 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
}

请注意，当客户端在使用适当的请求头请求 URL 路由 /students/{id:int} 时， on_put() 响应器（用于更新资源）和 on_delete() 响应器（用于删除资源）也将被调用。

我们已经添加了此路由，学生作为后缀。因此， on_put_student() 方法将路径参数解析为整数变量。给定 id 的项目的 JSON 表示形式被获取并使用 PUT 请求中提供的数据进行更新。

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() 响应器只是删除了 DELETE 请求中指定 id 的项目。返回剩余资源的列表。

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

我们可以使用 HTTPie 命令测试 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 ) 的完整代码如下 -

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)