Python | Flask 解决跨域问题

Python | Flask 解决跨域问题

系列文章目录

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目录

• 系列文章目录
• 前言
• 使用步骤
  • 1. 引入库
  • 2. 配置
    • 1. 使用 CORS函数 配置全局路由
    • 2. 使用 @cross_origin 来配置单行路由
  • 配置参数说明
• 总结
• 参考

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前言

我靠，又跨域了

使用步骤

1. 引入库

pip install flask-cors

2. 配置

flask-cors 有两种用法，一种为全局使用，一种对指定的路由使用

1. 使用 CORS函数 配置全局路由

from flask import Flask, request
from flask_cors import CORS

app = Flask(__name__)
CORS(app, supports_credentials=True)

其中 CORS 提供了一些参数帮助我们定制一下操作。

常用的我们可以配置 origins、methods、allow_headers、supports_credentials

所有的配置项如下：

:param resources:
    The series of regular expression and (optionally) associated CORS
    options to be applied to the given resource path.

    If the argument is a dictionary, it's keys must be regular expressions,
    and the values must be a dictionary of kwargs, identical to the kwargs
    of this function.

    If the argument is a list, it is expected to be a list of regular
    expressions, for which the app-wide configured options are applied.

    If the argument is a string, it is expected to be a regular expression
    for which the app-wide configured options are applied.

    Default : Match all and apply app-level configuration

:type resources: dict, iterable or string

:param origins:
    The origin, or list of origins to allow requests from.
    The origin(s) may be regular expressions, case-sensitive strings,
    or else an asterisk

    Default : '*'
:type origins: list, string or regex

:param methods:
    The method or list of methods which the allowed origins are allowed to
    access for non-simple requests.

    Default : [GET, HEAD, POST, OPTIONS, PUT, PATCH, DELETE]
:type methods: list or string

:param expose_headers:
    The header or list which are safe to expose to the API of a CORS API
    specification.

    Default : None
:type expose_headers: list or string

:param allow_headers:
    The header or list of header field names which can be used when this
    resource is accessed by allowed origins. The header(s) may be regular
    expressions, case-sensitive strings, or else an asterisk.

    Default : '*', allow all headers
:type allow_headers: list, string or regex

:param supports_credentials:
    Allows users to make authenticated requests. If true, injects the
    `Access-Control-Allow-Credentials` header in responses. This allows
    cookies and credentials to be submitted across domains.

    :note: This option cannot be used in conjuction with a '*' origin

    Default : False
:type supports_credentials: bool

:param max_age:
    The maximum time for which this CORS request maybe cached. This value
    is set as the `Access-Control-Max-Age` header.

    Default : None
:type max_age: timedelta, integer, string or None

:param send_wildcard: If True, and the origins parameter is `*`, a wildcard
    `Access-Control-Allow-Origin` header is sent, rather than the
    request's `Origin` header.

    Default : False
:type send_wildcard: bool

:param vary_header:
    If True, the header Vary: Origin will be returned as per the W3
    implementation guidelines.

    Setting this header when the `Access-Control-Allow-Origin` is
    dynamically generated (e.g. when there is more than one allowed
    origin, and an Origin than '*' is returned) informs CDNs and other
    caches that the CORS headers are dynamic, and cannot be cached.

    If False, the Vary header will never be injected or altered.

    Default : True
:type vary_header: bool

2. 使用 @cross_origin 来配置单行路由

from flask import Flask, request
from flask_cors import cross_origin

app = Flask(__name__)

@app.route('/')
@cross_origin(supports_credentials=True)
def hello():
    name = request.args.get("name", "World")
    return f'Hello, {name}!'

其中 cross_origin 和 CORS 提供一些基本相同的参数。

常用的我们可以配置 origins、methods、allow_headers、supports_credentials

所有的配置项如下：

:param origins:
    The origin, or list of origins to allow requests from.
    The origin(s) may be regular expressions, case-sensitive strings,
    or else an asterisk

    Default : '*'
:type origins: list, string or regex

:param methods:
    The method or list of methods which the allowed origins are allowed to
    access for non-simple requests.

    Default : [GET, HEAD, POST, OPTIONS, PUT, PATCH, DELETE]
:type methods: list or string

:param expose_headers:
    The header or list which are safe to expose to the API of a CORS API
    specification.

    Default : None
:type expose_headers: list or string

:param allow_headers:
    The header or list of header field names which can be used when this
    resource is accessed by allowed origins. The header(s) may be regular
    expressions, case-sensitive strings, or else an asterisk.

    Default : '*', allow all headers
:type allow_headers: list, string or regex

:param supports_credentials:
    Allows users to make authenticated requests. If true, injects the
    `Access-Control-Allow-Credentials` header in responses. This allows
    cookies and credentials to be submitted across domains.

    :note: This option cannot be used in conjuction with a '*' origin

    Default : False
:type supports_credentials: bool

:param max_age:
    The maximum time for which this CORS request maybe cached. This value
    is set as the `Access-Control-Max-Age` header.

    Default : None
:type max_age: timedelta, integer, string or None

:param send_wildcard: If True, and the origins parameter is `*`, a wildcard
    `Access-Control-Allow-Origin` header is sent, rather than the
    request's `Origin` header.

    Default : False
:type send_wildcard: bool

:param vary_header:
    If True, the header Vary: Origin will be returned as per the W3
    implementation guidelines.

    Setting this header when the `Access-Control-Allow-Origin` is
    dynamically generated (e.g. when there is more than one allowed
    origin, and an Origin than '*' is returned) informs CDNs and other
    caches that the CORS headers are dynamic, and cannot be cached.

    If False, the Vary header will never be injected or altered.

    Default : True
:type vary_header: bool

:param automatic_options:
    Only applies to the `cross_origin` decorator. If True, Flask-CORS will
    override Flask's default OPTIONS handling to return CORS headers for
    OPTIONS requests.

    Default : True
:type automatic_options: bool

配置参数说明

参数	类型	Head	默认	说明
resources	字典、迭代器或字符串	无	全部	配置允许跨域的路由接口
origins	列表、字符串或正则表达式	Access-Control-Allow-Origin	*	配置允许跨域访问的源
methods	列表、字符串	Access-Control-Allow-Methods	[GET, HEAD, POST, OPTIONS, PUT, PATCH, DELETE]	配置跨域支持的请求方式
expose_headers	列表、字符串	Access-Control-Expose-Headers	None	自定义请求响应的Head信息
allow_headers	列表、字符串或正则表达式	Access-Control-Request-Headers	*	配置允许跨域的请求头
supports_credentials	布尔值	Access-Control-Allow-Credentials	False	是否允许请求发送cookie
max_age	timedelta、整数、字符串	Access-Control-Max-Age	None	预检请求的有效时长

总结

在 flask 的跨域配置中，我们可以使用 flask-cors 来进行配置，其中 CORS 函数 用来做全局的配置, @cross_origin 来实现特定路由的配置

参考

• https://flask-cors.readthedocs.io/en/latest/