没有“访问控制允许来源”标头出现在所请求的资源。 [Django的反应的设置](No '

试图通过调用反应的Django的API。但CORS似乎并没有正常工作。

settings.py（Django的）

ALLOWED_HOSTS = ['*']
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'oauth2_provider',
    'rest_framework',
    'accounts',
    'products',
    'corsheaders',
]
MIDDLEWARE = [
    'corsheaders.middleware.CorsMiddleware',
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'oauth2_provider.middleware.OAuth2TokenMiddleware',
]
CORS_ORIGIN_ALLOW_ALL = True

在chrome浏览器API，

GET /products/view/
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

[
    {
        "id": 5,
        "name": "product_updated",
        "image": "...",
        "cost": "50.00",
        "avail_quantity": 100,
        "desc": "Good",
        "rating": "3.60",
        "users_rated": 100
    },
    {
        "id": 14,
        "name": "Dark Coffee",
        "image": "...",
        "cost": "50.00",
        "avail_quantity": 100,
        "desc": "Good",
        "rating": "3.60",
        "users_rated": 100
    }
]

反应组分：

import React, { Component } from 'react'

class Dashboard extends Component {

  constructor(props) {
    super(props)
    this.state = {
      text: '127.0.0.1:8000',
      productList: []
    }
     this.fetchProducts = this.fetchProducts.bind(this)
  }

 fetchProducts(){
     fetch(`http://127.0.0.1:8000/products/view`, {
         method: "GET",
          }).then(res=> res.json())
            .then(res=> {
              console.log(res, typeof res, res.length)
            this.setState({productList: res})
          })
      console.log(this.state.productList)
}


 componentWillMount(){
    this.fetchProducts()
 }

render() {
  var list = []
  for (let i = this.state.productList.length-1; i >= 0; i--) {
        list.push(<li>{this.state.productList[i].name}</li>)
        console.log(list)
      }
  return (
    <div className="dashboard">

    <h1>Welcome To Bear State Coffee!</h1>
    <h3>Products: </h3>
    <ul>
      {list}
    </ul>

    </div>
  )
}
}

export default Dashboard

控制台上反应服务器上运行仪表板

无法加载http://127.0.0.1:8000/products/view ：从“重定向http://127.0.0.1:8000/products/view ”到' http://127.0.0.1:8000/products/view/ “已被封锁的CORS政策：否‘访问控制允许来源’标头出现在所请求的资源。原产地“ 的http：//本地主机：3000 ”因此不允许访问。如果一个不透明的响应提供您的需求，设置请求的模式，以“无CORS”获取禁用CORS的资源。本地主机/：1未捕获（在承诺）类型错误：无法抓取

编辑：设置从浏览器的响应（ http://127.0.0.1:8000/products/view/ ）

OPTIONS /products/view/
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "name": "Products",
    "description": "GET: For viewing all products",
    "renders": [
        "application/json",
        "text/html"
    ],
    "parses": [
        "application/json",
        "application/x-www-form-urlencoded",
        "multipart/form-data"
    ]
}

一种解决方法：

使用Chrome扩展允许控制允许原产地
使用代理服务器：而不是访问http://127.0.0.1:8000/products/view ，使用像代理https://cors-anywhere.herokuapp.com/作为前缀： https://cors-anywhere.herokuapp.com/http://127.0.0.1:8000/products/view