我想编写一个带有 mysql 连接的小身份验证应用程序，但我总是收到此错误，但我需要这种方式。
如果客户端获取/admin(如果他不是管理员)，我想发送响应，如果他是管理员，则应呈现 admin。
app.js
var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var index = require('./routes/index');
const admin = require("./routes/admin");
const session = require("express-session");
var app = express();
app.set("trust proxy", 1);
app.use(session({
secret: "asdf",
resave: false,
cookie: {
maxAge: 120000
},
saveUninitialized: false
}));
function checkIfLoggedin(req,res,next){
if(!(req.originalUrl === "/") && !req.session.loggedIn){
res.redirect('/');
return;
}
next();
};
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');
// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use(checkIfLoggedin);
app.use('/', index);
app.use("/admin", admin);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handler
app.use(function(err, req, res, next) {
// set locals, only providing error in development
res.locals.message = err.message;
res.locals.error = req.app.get('env') === 'development' ? err : {};
// render the error page
res.status(err.status || 500);
res.render('error');
});
module.exports = app;
index.js
var express = require('express');
var router = express.Router();
const bcrypt = require('bcrypt-nodejs');
var dbPassword;
import mysql from "mysql";
//
/* GET home page. */
router.get('/', function(req, res, next) {
res.render('index', {});
});
router.post('/', function(req,res,next) {
console.log("1");
const enteredUsername = req.body.username;
const enteredPassword = req.body.password;
const con = mysql.createConnection({
host: "localhost",
user: "user",
password: "pass",
database: "db"
});
con.query('SELECT * FROM users WHERE username = ?;', [`${enteredUsername}`], (error, results, fields) => {
if (results.length > 0) {
console.log("2");
console.log(error);
let dbPassword = results[0].password;
bcrypt.compare(enteredPassword, dbPassword, (err,response) => {
console.log(err);
console.log(response);
console.log("3");
if (response == true) {
req.session.user = {
userId: results[0].userId,
username: results[0].username,
isAdmin: results[0].isAdmin,
};
req.session.loggedIn = true;
console.log("file");
if (req.session.user.isAdmin) {
res.redirect("/admin");
}
else{
res.redirect("/file/" + req.session.user.userId);
}
}
else{
req.session.loggedIn = false;
console.log("false");
res.send("Wrong password");
}
});
}
else{
res.send("Wrong Data");
}
});
});
module.exports = router;
admin.js
var express = require('express');
var router = express.Router();
/* GET users listing. */
router.get('/', function(req, res, next) {
if (!req.session.user.isAdmin) {
res.send("Du bist kein Admin!");
}
res.render("admin");
});
module.exports = router;
索引.ejs
<!DOCTYPE html>
<html>
<head>
<title>Costufi</title>
<link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
<link type="text/css" rel="stylesheet" href="stylesheets/materialize.min.css" media="screen,projection"/>
</head>
<body>
<main>
<center>
<div class="container">
<div class="z-depth-2" style="display: inline-block; padding: 20px 50px 10px 50px; margin-top: 15%;">
<form class="col s12" action="/" method="post">
<div class="row">
<h4>Login</h4>
<div class="input-field col s12">
<input type="text" name="username" id="username" class="validate">
<label for="username">Username</label>
</div>
</div>
<div class="row">
<div class="input-field col s12">
<input type="password" name="password" id="password" class="validate">
<label for="password">PassworD</label>
</div>
</div>
<div class="row">
<button class="left btn waves-effect waves-light indigo darken-2" type="submit" name="send">Login
<i class="material-icons right">send</i>
</div>
</form>
</div>
</div>
</center>
</main>
<script type="text/javascript" src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<script type="text/javascript" src="js/materialize.min.js"></script>
</body>
</html>
最佳答案
当您尝试向同一请求发送多个响应时，会导致此错误。我没有研究代码中的所有位置，但这里有一个明显的情况:
/* GET users listing. */
router.get('/', function(req, res, next) {
if (!req.session.user.isAdmin) {
res.send("Du bist kein Admin!");
}
res.render("admin");
});
如果您的 if 测试为真，那么您最终会执行 res.send() 和 res.render() 。 res.render() 会触发警告，因为您已经在此连接上发送了响应，并且无法发送另一个响应。您应该将其更改为:
/* GET users listing. */
router.get('/', function(req, res, next) {
if (!req.session.user.isAdmin) {
res.send("Du bist kein Admin!");
} else {
res.render("admin");
}
});
关于javascript - 身份验证系统错误: Can't set headers after they are sent.，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48270822/