如何在浏览器中的 Node.js 中显示 MySQL 数据库中的数据

Question

我想在我的浏览器中显示数据库数据..我的文件 connection.js 是

var mysql = require('mysql');

var conn = mysql.createConnection({
    host: "localhost",
    user: "root",
    password: "0000",
    database: "select_country"
});
conn.connect(function (err) {
    if (err) throw err;
    console.log('Database is connected successfully ??????!');
});
module.exports = conn;

我的 app.js 是：

const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;
const mysql = require('./MySql/database');

//create a server object:
const server = http.createServer(function (req, res) {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    mysql.query("SELECT * FROM country", function (err, result, fields) {
        if (err) throw err;
        console.log('All Countries are :-');
        res.write(result); //write a response to the client
    });

    res.write('Hello World'); //write a response to the client
    res.end(); //end the response
}); //the server object listens on port 8080

server.listen(port, hostname, () => {
    console.log(`Server running at http://${hostname}:${port}/`);
});

错误：抛出错误； // 未处理的 'error' 事件,,,, Error [ERR_STREAM_WRITE_AFTER_END]: write after end

Answer 1

您只能在mysql.query()的回调函数mysql.query()您的响应写入客户端。

换句话说，你的程序会立即运行这两行

res.write('Hello World'); //write a response to the client
res.end(); //end the response

在 MySQL 获取其数据之前，回调运行。 您的res.end()结束输出。 因此，稍后，当回调运行时，它会尝试将res.write()写入已经结束的流。

因此，将这两行移到您的回调中。 尝试这个

    mysql.query("SELECT * FROM country", function (err, result, fields) {
        if (err) throw err;
        res.write('Hello World'); //write a response to the client
        console.log('All Countries are :-');
        res.write(result); //write a response to the client
        res.end(); //end the response
    });