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。

To understand the concept and the need of suffixed responders, let us define a StudentResource class. It consists of an on_get() responder that converts the students a list of dict objects to JSON and returns as its response.

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。

Let us also add on_post() responder that reads the data from the incoming request and adds a new dict object in the list.

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。

Using add_route() function of the Falcon’s App object, we add /students route.

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 -

After starting the server, we can test the GET and POST requests from HTTPie command line −

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。

Invoking on_get() again confirms the addition of new students resource.

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。

At this stage, we would like to have a GET responder method in StudentResource class that reads the id parameter from the URL and retrieves a corresponding dict object of from the list.

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。

In other words, the URL of the format /student/{id} should be associated to the GET method in the resource class. But obviously, a class cannot have two methods of same name. Hence, we define to use suffix parameter for the add_route() method to distinguish between the two definitions of on_get() responders.

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

A route with id parameter is added to the Application object by specifying suffix ='student'.

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 -

We can now add another definition of on_get() method with this suffix, so that the name of this responder is on_get_student(), as follows −

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 -

Start the Waitress server after adding the new route and on_get_student() responder and test this URL as follows −

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。

Note that the on_put() responder (to update a resource) and on_delete() responder (to delete a resource) will also get invoked when the URL route /students/{id:int} is requested by the client with appropriate request header.

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。

We have already added this route with student as the suffix. Hence, on_put_student() method parses the path parameter in an integer variable. The JSON representation of the item with given id is fetched and updated with the data provided in the PUT request.

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。

The on_delete_student() responder simply deletes the item with the id specified in the DELETE request. The list of remaining resources is returned.

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 -

We can test the PUT and DELETE operations of the API with HTTPie commands −

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 -

The complete code of this API (studentapi.py) is as under −

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)