问题描述

我正在创建一个发布应用程序，它需要使用 React 和 MySQL 数据库之间的通信来来回发送信息.使用 Express 作为我的 JS 服务器.服务器代码如下:

const express = require('express');const bodyParser = require('body-parser');const mysql = 要求('mysql');const cors = 要求('cors');常量连接 = mysql.createConnection({主机:'本地主机'，用户:'root'，密码 : ''，数据库:'文章数据库'，端口:3300，socketPath: '/Applications/XAMPP/xamppfiles/var/mysql/mysql.sock'});//初始化应用常量应用程序 = 快递()；app.use(cors());appl.post('/articletest', function(req, res) {var art = req.body;var query = connection.query("INSERT INTO article SET ?", art,功能(错误，水库){})})//https://expressjs.com/en/guide/routing.htmlapp.get('/comments', function (req, res) {//连接.connect();connection.query('SELECT * FROM items', function (error, results,字段){if (error) 抛出错误；别的 {返回 res.json({数据:结果})};});//连接.end();});//启动服务器app.listen(3300, () => {console.log('监听 3300 端口');});

我的 React 类如下所示:

class Profile 扩展 React.Component {构造函数(道具){超级(道具)；这个.state = {标题: ''，作者: ''，文本: ''}}处理提交(){//在提交表单时，发送一个带有数据的 POST 请求到// 服务器.fetch('http://localhost:3300/articletest', {正文:JSON.stringify(this.state)，缓存:'无缓存'，凭据:'同源'，标题:{内容类型":应用程序/json"},方法:'POST'，模式:'cors'，重定向:'关注'，推荐人:'无推荐人'，}).then(函数(响应){控制台日志(响应)；if (response.status === 200) {警报(已保存")；} 别的 {alert('问题保存');}});}使成为() {返回 (
<表单提交={() =>this.handleSubmit()}><输入类型=文本"占位符=标题"onChange={e=>this.setState({ title: e.target.value} )}/><input type="text" placeholder="author" onChange={e =>this.setState({ author: e.target.value} )}/><textarea type="text" placeholder="text" onChange={e =>this.setState({ text: e.target.value} )}/><输入类型="提交"/></表格></div>);}}

我在在线教程中找到的相当标准的东西.我可以搜索我的数据库并显示获取的信息没问题，但反过来不行.当我尝试从 <form> 标记获取输入时，没有任何内容插入到我的数据库中，而是出现此错误:

[错误] Fetch API 无法加载http://localhost:3000/static/js/0.chunk.js 由于访问控制检查.错误:您提供的错误不包含堆栈跟踪.未处理的承诺拒绝:TypeError:取消

我知道这与访问控制有关，但由于我已经在使用 cors 并且可以成功地从数据库中检索数据，所以我不确定我做错了什么.任何建议将不胜感激.提前谢谢你.

您需要通过首先验证您的服务点是否已启用 CORS 来隔离问题.为了只关注 CORS 功能，我将暂时删除 MySQL 代码.

const express = require('express');const bodyParser = require('body-parser');const cors = 要求('cors');常量应用程序 = 快递()；app.use(cors());app.get('/', function(req, res){变种根 = {};root.status = '成功';root.method = '索引';var json = JSON.stringify(root);res.send(json);});app.post('/cors', function(req, res) {变种根 = {};root.status = '成功';root.method = 'cors';var json = JSON.stringify(root);res.send(json);})//启动服务器app.listen(3300, () => {console.log('监听 3300 端口');});

如果您有服务器在端口 3300 上侦听，请在终端上运行以下 PREFLIGHT 命令.

curl -v -H "来源:https://example.com" -H访问控制请求标头:X-自定义标头"-H访问控制请求方法:POST"-X 选项http://localhost:3300

如果预检请求成功，响应应包括 Access-Control-Allow-Origin、Access-Control-Allow-Methods 和 Access-Control-Allow-Headers

现在运行 POST 方法.

curl -v -H "来源:https://example.com" -H "X-Custom-Header: 值" -X 发布http://localhost:3300/cors

如果发布请求成功，响应应包括访问控制允许来源

如果一切正常，您的服务器就可以了.然后，您需要从您的 iOS 应用程序中尝试 post 方法.

注意.我也会怀疑在本地主机上使用 cors.我会将 127.0.0.1 映射到域，然后让应用程序使用该域.如果您使用的是 Linux 或 Mac，则修改/etc/hosts.对于 Windows，它是 c:windowssystem32driversetchosts

I am creating a publishing application that needs to use communication between React and MySQL database to send information back and forth. Using Express as my JS server. The server code looks as follows:

const express = require('express');
const bodyParser = require('body-parser');
const mysql = require('mysql');
const cors = require('cors');
const connection = mysql.createConnection({
   host     : 'localhost',
   user     : 'root',
   password : '',
   database : 'ArticleDatabase',
   port: 3300,
   socketPath: '/Applications/XAMPP/xamppfiles/var/mysql/mysql.sock'
  });

// Initialize the app
const app = express();
app.use(cors());

appl.post('/articletest', function(req, res) {
   var art = req.body;
   var query = connection.query("INSERT INTO articles SET ?", art,    
      function(err, res) {
         })
   })

// https://expressjs.com/en/guide/routing.html
app.get('/comments', function (req, res) {
// connection.connect();

connection.query('SELECT * FROM articles', function (error, results,  
  fields) {
    if (error) throw error;
    else {
         return res.json({
            data: results
         })
    };
});

//    connection.end();
});

// Start the server
app.listen(3300, () => {
   console.log('Listening on port 3300');
 });

And my React class looks as follows:

class Profile extends React.Component {
constructor(props) {
    super(props);
    this.state = {
        title: '',
        author: '',
        text: ''
    }
}

handleSubmit() {
    // On submit of the form, send a POST request with the data to the  
    //  server.
    fetch('http://localhost:3300/articletest', {
        body: JSON.stringify(this.state),
        cache: 'no-cache',
        credentials: 'same-origin',
        headers: {
            'content-type': 'application/json'
        },
        method: 'POST',
        mode: 'cors',
        redirect: 'follow',
        referrer: 'no-referrer',
    })
        .then(function (response) {
            console.log(response);
            if (response.status === 200) {
                alert('Saved');
            } else {
                alert('Issues saving');
            }
        });
}

render() {
   return (
    <div>
      <form onSubmit={() => this.handleSubmit()}>
        <input type = "text" placeholder="title" onChange={e =>  
           this.setState({ title: e.target.value} )} />
        <input type="text" placeholder="author" onChange={e => 
          this.setState({ author: e.target.value} )}  />
        <textarea type="text" placeholder="text" onChange={e => 
          this.setState({ text: e.target.value}  )} />
        <input type="Submit" />
      </form>
   </div>
   );
  }
}

So fairly standard stuff that I found in online tutorials. I can search my database and display fetched info no problem, but not the other way around. When I try to take input from the <form> tag nothing is inserted into my database but instead I get this error:

[Error] Fetch API cannot load    
http://localhost:3000/static/js/0.chunk.js due to access control 
checks.
Error: The error you provided does not contain a stack trace.
Unhandled Promise Rejection: TypeError: cancelled

I understand that this has something to do with access control but since I am already using cors and can successfully retrieve data from the database, I am not sure what I am doing wrong. Any suggestions will be greatly appreciated. Thank you in advance.

You'll need to isolate the problem by first verifying that your service point is CORS Enabled. In order to focus solely on CORS functionality, I would remove the MySQL code temporarily.

const express = require('express');
const bodyParser = require('body-parser');
const cors = require('cors');

const app = express();
app.use(cors());

app.get('/', function(req, res){
  var root = {};
  root.status = 'success';
  root.method = 'index';
  var json = JSON.stringify(root);
  res.send(json);
});

app.post('/cors', function(req, res) {
  var root = {};
  root.status = 'success';
  root.method = 'cors';
  var json = JSON.stringify(root);
  res.send(json);
})

// Start the server
app.listen(3300, () => {
   console.log('Listening on port 3300');
 });

One you have server listening on port 3300, run the following PREFLIGHT command at the terminal.

curl -v 
-H "Origin: https://example.com" 
-H "Access-Control-Request-Headers: X-Custom-Header" 
-H "Acess-Control-Request-Method: POST" 
-X OPTIONS 
http://localhost:3300

If the preflight request is successful, the response should include Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers

Now run the POST method.

curl -v 
-H "Origin: https://example.com" 
-H "X-Custom-Header: value" 
-X POST 
http://localhost:3300/cors

If the post request is successful, the response should include Access-Control-Allow-Origin

If everything looks good, your server is okay. You then need to try the post method from your iOS app.

NOTE. I would also be suspicious of using cors on localhost. I would map 127.0.0.1 to a domain and then have the app use that domain instead. If you are on Linux or Mac, you modify /etc/hosts. For Windows it's c:windowssystem32driversetchosts

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