在 ReactJS 中获取 onComponentDidMount 期间出现 CORS 错误答案

【问题标题】：CORS error during fetch onComponentDidMount in ReactJS在 ReactJS 中获取 onComponentDidMount 期间出现 CORS 错误
【发布时间】：2020-08-24 11:23:09
【问题描述】：

在 reactjs 中获取 api 数据时，我得到一个空页面作为输出。

回购：https://github.com/te3t0/building-small-blog

我可能是 reactjs 的新手，我得到一个空页面，即使数据被完美地获取。如果有人能在我做错的地方帮助我，那就太好了。非常感谢您。

endpoint_url : http://localhost:8000/api/blog_list

api 数据：

[
    {
        "id": 1,
        "url": "http://localhost:8000/api/blog_detail/brown",
        "title": "brown",
        "slug": "brown",
        "image": "http://localhost:8000/media/blog/image_2.jpg",
        "description": "",
        "created_on": "2020-05-08T15:20:53Z",
        "status": true,
        "category": [
            1
        ]
    },
    {
        "id": 2,
        "url": "http://localhost:8000/api/blog_detail/black",
        "title": "black",
        "slug": "black",
        "image": "http://localhost:8000/media/blog/loc.png",
        "description": "",
        "created_on": "2020-05-08T17:14:31Z",
        "status": true,
        "category": [
            2
        ]
    }
]

./src/Base.js

export default class App extends Component{

  state = {
    bloglist:[]
  };

  componentDidMount(){
    this.fetchData()
  }

  fetchData = async () => {
    try{
      const response = await fetch("http://localhost:8000/api/blog_list");
      const jsonResponse = await response.json()
      this.setState({bloglist:jsonResponse})
    }
    catch(error){
      console.log(error)
    }
  }

  render(){
    const {bloglist} = this.state
    if(!bloglist){
      return (
        <div>
          <h1>loading...</h1>
        </div>
      )
    }

    return (
      {
        bloglist.map(bloglist => (
          <h3 class="mb-2">
            <a href="single.html">{bloglist.title}</a>
          </h3>
          <p class="mb-4">{bloglist.description}</p>
          ))
      }
    )
  }
}

【问题讨论】：

添加指向您的存储库的链接
“空白页”是什么意思？
这是我的存储库--> github.com/te3t0/building-small-blog@DenisTsoi
通常我在获取数据时得到一个空白页。我没有得到预期的结果。 @GalAbra
应用程序正在获得GET http://localhost:8000/api/blog_list net::ERR_FAILED - 来自Access to fetch at 'http://localhost:8000/api/blog_list' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

标签： javascript django reactjs

【解决方案1】：

由于这是您的第一篇文章 - 在调试问题方面存在一些问题。

对于像您提出的问题这样的较大问题 - 它有助于提供错误来自开发者控制台工具以及远程存储库源。

例如

GET http://localhost:8000/api/blog_list net::ERR_FAILED

'http://localhost:8000/api/blog_list' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled

从那里 - 通过包含 remote repository - 我能够通过 How can I enable CORS on Django REST Framework 了解更多信息

这导致了以下答案：

pip install django-cors-headers
添加已安装的应用程序

INSTALLED_APPS = (
    ...
    'corsheaders',
    ...
)

添加中间件

MIDDLEWARE_CLASSES = (
    ...
    'corsheaders.middleware.CorsMiddleware',  
    'django.middleware.common.CommonMiddleware',  
    ...
)

CORS_ORIGIN_ALLOW_ALL = True # If this is used then `CORS_ORIGIN_WHITELIST` will not have any effect
CORS_ALLOW_CREDENTIALS = True
CORS_ORIGIN_WHITELIST = [
    'http://localhost:3000',
] # If this is used, then not need to use `CORS_ORIGIN_ALLOW_ALL = True`
CORS_ORIGIN_REGEX_WHITELIST = [
    'http://localhost:3000',
]

【讨论】：