必须从 Blob 上传回调请求中调用

Question

我已经在 J​​ava 中为 blobstore API 实现了这个 GWT 示例： https://cloud.google.com/appengine/docs/java/blobstore/

当通过客户端表单（在浏览器内）进行 POST 时，它可以正常工作。

但是，现在我将文件（图像）发送到同一个 /upload 服务处理程序，但来自我的离线程序（不是浏览器）内的 python 请求：

r = requests.post(url+'upload', files= {'myFile': open('fig.jpeg', 'rb')})

我得到以下异常

必须从 blob 上传回调请求中调用

在（服务器端）的第一行：

Map<String, List<BlobKey>> blobs = blobstoreService.getUploads(req);
List<BlobKey> blobKeys = blobs.get("myFile");

我做错了什么？？

Answer 1

找到下面的示例代码来理解flask和python的回调

项目> app.py

import datetime
import time
import requests # to make get and post requests
import json
from flask import Flask, Response, request, render_template  #  request : is not same as requests its flask request on url

app = Flask(__name__)
app.config['JSONIFY_PRETTYPRINT_REGULAR'] = True

# 3. no need to give any url mapping for callback function,
# this will get call once demo() return back to hello() at post request call.
def callbacks(response, *args, **kwargs):
    print(" -- callbacks starts -- : ", datetime.datetime.now().time())

    if response.status_code == 200:
        #print(response.text)
        print(" -- callback end -- : ", datetime.datetime.now().time());
        #return response
        # return Response(response, status=200)   do not return response here this will cause problem when


# 2. on post request call made from hello(): resp = requests.post(......)
@app.route('/demo' , methods=['POST']) # validate request of type methods=['POST']
def demo():
    print("Post request received : ", datetime.datetime.now().time())

    if request.method == 'POST':  # check request of type post
        time.sleep(5)   # some sleep time to check if callback is working
        print("Post response sent to callback : ", datetime.datetime.now().time())
        # return response with data received from request.data  and status = 200
        return Response(request.data, headers={'Content-Type': 'application/json'}, status=200)



# 1. run this file and hit url localhost:5000/  to execute ( GET request)
@app.route('/', methods=['GET'])
def hello():
    print("Hello start : ", datetime.datetime.now().time())
    url = 'http://jsonplaceholder.typicode.com/users';         # url will return json list

    data = requests.get(
                            url=url,
                            headers={'Content-Type': 'application/json'}
                        )   # get request to get json data from url using requests lib

    # check if flask request is get
    if request.method == 'GET':

        # post request to another url /demo with data as a json as argument ,
        # imp : hooks to link callback function once /demo url returns response callback will start execute
        resp = requests.post( url = 'http://localhost:5000/demo',
                              headers = {'Content-Type': 'application/json'},
                              json = data.json(),
                              hooks={'response': callbacks }
                            )

    print("Hello End : ",datetime.datetime.now().time())
    # render with html template with argument as data and result
    return render_template('index.html', result=resp.json(), data=data.json())
    #                OR
    # return Response(response='OK', status=resp.status_code) # return response with 200 or 'OK'


if __name__ == '__main__':
    app.run(debug=False)

创建文件 index.html 并复制以下代码

项目/模板> index.html

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>JSON OUTPUT</title>
    </head>
    <body>
    <table border="1">
        <tr><td>ID</td><td>Name</td><td>Email</td></tr>
            {% for d in data %}
                <tr><td>{{ d['id'] }}</td><td>{{ d['name'] }}</td><td>{{ d['email'] }}</td></tr>
            {% endfor %}
    </table>
    <div>{{ result }}</div>
    </body>
    </html>

使用 cmd 运行 > python app.py

Answer 2

/upload 处理程序并不意味着您可以直接调用，无论是从浏览器还是 python 应用程序。相反，您的应用程序将需要进行两次调用：第一次调用您的服务器以获取临时 URL，然后第二次调用该 URL，该 URL 将直接与 blobstore 连接。您的服务器应使用 blobstoreService.createUploadUrl 生成该临时 URL，如您链接的文档的 this section 的第 1 步所述。

在第二次调用（上传）的过程中，blobstore 将直接调用您的上传处理程序以通知您的应用有关新 blob 的信息。这就是blobstoreService.getUploads(req) 知道如何解释的。

因此，您的 python 应用程序将进行 2 次调用，并且您的服务器还将处理 2 个请求。第一个请求直接来自简单地请求 url 的 python 应用程序。第二个请求将在上传期间发生，但实际上将直接来自 blobstore。