对于以下ajax发布请求Flask(如何使用从flask中的ajax发布的数据?):
$.ajax({
    url: "http://127.0.0.1:5000/foo", 
    type: "POST",
    contentType: "application/json",
    data: JSON.stringify({'inputVar': 1}),
    success: function( data ) { 
        alert( "success" + data );
    }   
});
我收到一个Cross Origin Resource Sharing (CORS)错误:
No 'Access-Control-Allow-Origin' header is present on the requested resource. 
Origin 'null' is therefore not allowed access. 
The response had HTTP status code 500.
我尝试通过以下两种方式解决问题,但似乎没有任何效果。
- 使用Flask-CORS
 
这是Flask处理的扩展CORS,应使跨域AJAX成为可能。
- http://flask-cors.readthedocs.org/en/latest/
 - 如何在Flask和Heroku中启用CORS
 - 应用jwt auth包装器时,flask-cors包装器不起作用。
 - Javascript-所请求的资源上没有“ Access-Control-Allow-Origin”标头
 
我的pythonServer.py使用此解决方案:
from flask import Flask
from flask.ext.cors import CORS, cross_origin
app = Flask(__name__)
cors = CORS(app, resources={r"/foo": {"origins": "*"}})
app.config['CORS_HEADERS'] = 'Content-Type'
@app.route('/foo', methods=['POST','OPTIONS'])
@cross_origin(origin='*',headers=['Content-Type','Authorization'])
def foo():
    return request.json['inputVar']
if __name__ == '__main__':
    app.run()
- 使用特定的Flask装饰器
 
这是Flask官方代码片段,定义了一个装饰器,该装饰器应允许CORS其装饰功能。
- http://flask.pocoo.org/snippets/56/
 - Python Flask跨站点HTTP POST-不适用于特定的允许来源
 - http://chopapp.com/#351l7gc3
 
我的pythonServer.py使用此解决方案:
from flask import Flask, make_response, request, current_app
from datetime import timedelta
from functools import update_wrapper
app = Flask(__name__)
def crossdomain(origin=None, methods=None, headers=None,
                max_age=21600, attach_to_all=True,
                automatic_options=True):
    if methods is not None:
        methods = ', '.join(sorted(x.upper() for x in methods))
    if headers is not None and not isinstance(headers, basestring):
        headers = ', '.join(x.upper() for x in headers)
    if not isinstance(origin, basestring):
        origin = ', '.join(origin)
    if isinstance(max_age, timedelta):
        max_age = max_age.total_seconds()
    def get_methods():
        if methods is not None:
            return methods
        options_resp = current_app.make_default_options_response()
        return options_resp.headers['allow']
    def decorator(f):
        def wrapped_function(*args, **kwargs):
            if automatic_options and request.method == 'OPTIONS':
                resp = current_app.make_default_options_response()
            else:
                resp = make_response(f(*args, **kwargs))
            if not attach_to_all and request.method != 'OPTIONS':
                return resp
            h = resp.headers
            h['Access-Control-Allow-Origin'] = origin
            h['Access-Control-Allow-Methods'] = get_methods()
            h['Access-Control-Max-Age'] = str(max_age)
            if headers is not None:
                h['Access-Control-Allow-Headers'] = headers
            return resp
        f.provide_automatic_options = False
        return update_wrapper(wrapped_function, f)
    return decorator
@app.route('/foo', methods=['GET','POST','OPTIONS'])
@crossdomain(origin="*")
def foo():
    return request.json['inputVar']
if __name__ == '__main__':
    app.run()
您能说明为什么会这样吗?