如何解决发送到客户端后无法设置标头将会话数据表达为 ejs html
我遇到以下问题：每次访问用户个人资料页面（见下文）时，我都会在控制台中收到此错误：
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at new NodeError (node:internal/errors:329:5)
at ServerResponse.setHeader (node:_http_outgoing:573:11)
at ServerResponse.header (C:\Users\Lyrdum\Desktop\Projects\app\node_modules\express\lib\response.js:771:10)
at ServerResponse.send (C:\Users\Lyrdum\Desktop\Projects\app\node_modules\express\lib\response.js:170:12)
at C:\Users\Lyrdum\Desktop\Projects\app\app.js:36:9
at Layer.handle_error (C:\Users\Lyrdum\Desktop\Projects\app\node_modules\express\lib\router\layer.js:71:5)
at trim_prefix (C:\Users\Lyrdum\Desktop\Projects\app\node_modules\express\lib\router\index.js:315:13)
at C:\Users\Lyrdum\Desktop\Projects\app\node_modules\express\lib\router\index.js:284:7
at Function.process_params (C:\Users\Lyrdum\Desktop\Projects\app\node_modules\express\lib\router\index.js:335:12)
at next (C:\Users\Lyrdum\Desktop\Projects\app\node_modules\express\lib\router\index.js:275:10)
我认为问题出在 ejs 语法上，因为我从 express-session 获取数据并使用 ejs 语法在 html 文件中打印（例如：,)，我不知道还能做什么，如果有人有更好的主意或一些提示/技巧会很有用，还是谢谢！
快速路线：
const express = require("express");
const User = require("./user");
const router = express.Router();
const user = new User();
var online = "undefined";
// Get
router.get("/login",(req,res,next) => {
if (req.session.user) {
online = req.session.user.username;
res.redirect("/profile");
}
res.render("login",{ user: req.session.user });
});
router.get("/register",next) => {
if (req.session.user) {
res.redirect("/profile");
}
res.render("register",{ user: req.session.user,online });
});
// Get
router.get("/",next) => {
// If there is a session named user that means the use is logged in. so we redirect him to home page by using /home route below
if (req.session.user) {
online = req.session.user.username;
res.redirect("/profile");
return;
}
// IF not we just send the index page.
res.render("index",online });
});
router.get("/error",next) => {
if (req.session.user) {
res.render("error",online });
}
res.render("error",online });
});
router.get("/profile",next) => {
if (req.session.user) {
online = req.session.user.username;
res.render("userprofile",online });
return res.status(400).json({
status: "error",error: "req body cannot be empty",});
}
res.redirect("/index");
return res.status(400).json({
status: "error",});
});
router.get("/logout",next) => {
// Check if the session is exist
if (req.session.user) {
// destroy the session and redirect the user to the index page.
req.session.destroy(function () {
res.redirect("/");
});
}
});
//Post
router.post("/login",next) => {
// The data sent from the user are stored in the req.body object.
// call our login function and it will return the result(the user data).
user.login(req.body.username,req.body.password,function (result) {
if (result) {
// Store the user data in a session.
req.session.user = result;
req.session.opp = 1;
online = req.session.user.username;
// redirect the user to the home page.
res.redirect("/profile");
} else {
// if the login function returns null send this error message back to the user.
res.send("Username/Password incorrect!");
}
});
});
router.post("/register",next) => {
let userInput = {
username: req.body.username,password: req.body.password,email: req.body.email,};
user.register(userInput,function (lastId) {
// if the creation of the user goes well we should get an integer (id of the inserted user)
if (lastId) {
// Get the user data by it's id. and store it in a session.
user.find(lastId,function (result) {
req.session.user = result;
req.session.opp = 0;
online = req.session.user;
res.redirect("/profile");
});
} else {
console.log("Error creating a new user ...");
}
});
});
module.exports = router;
用户注册/登录逻辑：
const pool = require("./mysql");
const bcrypt = require("bcrypt");
function User() {}
User.prototype = {
find: function(user = null,callback) {
if (user) {
var field = Number.isInteger(user) ? "id" : "username";
}
let sql = `SELECT * FROM users WHERE ${field} = ?`;
pool.query(sql,user,function(error,result) {
if (error) throw error;
if (result.length) {
callback(result[0]);
} else {
callback(null);
}
});
},login: function(username,password,callback) {
this.find(username,function(user){
if (user) {
if (bcrypt.compareSync(password,user.password)) {
callback(user);
return;
}
}
callback(null);
});
},register: function(body,callback) {
var username = body.username;
var email = body.email;
var password = bcrypt.hashSync(body.password,10);
let sql = `INSERT INTO users(username,email) VALUES ('${username}','${password}','${email}')`;
pool.query(sql,result){
if (error) throw error;
callback(result.insertId);
});
},}
module.exports = User;
用户个人资料（每次访问时，我都会在控制台中收到错误信息）
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<title><%= online %> | Profile</title>
<link href="css/userprofile.css" rel="stylesheet" type="text/css">
<%- include('index.ejs') -%>
</head>
<body>
<div class="container">
<div class="main-body">
<!-- Breadcrumb -->
<nav aria-label="breadcrumb" class="main-breadcrumb">
<ol class="breadcrumb">
<li class="breadcrumb-item active" aria-current="page">Welcome to <%= user.username %> profile!</li>
</ol>
</nav>
<!-- /Breadcrumb -->
<div class="row gutters-sm">
<div class="col-md-4 mb-3">
<div class="card">
<div class="card-body">
<div class="d-flex flex-column align-items-center text-center">
<img src='img/<%= user.avatar %>.png' class="rounded-circle" style="height:auto;" width="150" height="250">
<div class="mt-3">
<h5>
<b> <%= user.username %></b>
</h5>
<p class="text-secondary mb-1"> <img src='img/ig.png' class="rounded-circle" style="height:auto;" width="24" height="24"> <%= user.rank %></p>
<button class="btn btn-outline-primary">Editeaza</button>
</div>
</div>
</div>
</div>
<div class="card mt-3">
<ul class="list-group list-group-flush">
<li class="list-group-item d-flex justify-content-between align-items-center flex-wrap">
<h6 class="mb-0"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24"
viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"
stroke-linecap="round" stroke-linejoin="round"
class="feather feather-globe mr-2 icon-inline">
<circle cx="12" cy="12" r="10"></circle>
<line x1="2" y1="12" x2="22" y2="12"></line>
<path
d="M12 2a15.3 15.3 0 0 1 4 10 15.3 15.3 0 0 1-4 10 15.3 15.3 0 0 1-4-10 15.3 15.3 0 0 1 4-10z">
</path>
</svg>Personal Website</h6>
<span class="text-secondary"><%= user.nick %></span>
</li>
<li class="list-group-item d-flex justify-content-between align-items-center flex-wrap">
<h6 class="mb-0"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24"
viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"
stroke-linecap="round" stroke-linejoin="round"
class="feather feather-github mr-2 icon-inline">
<path
d="M9 19c-5 1.5-5-2.5-7-3m14 6v-3.87a3.37 3.37 0 0 0-.94-2.61c3.14-.35 6.44-1.54 6.44-7A5.44 5.44 0 0 0 20 4.77 5.07 5.07 0 0 0 19.91 1S18.73.65 16 2.48a13.38 13.38 0 0 0-7 0C6.27.65 5.09 1 5.09 1A5.07 5.07 0 0 0 5 4.77a5.44 5.44 0 0 0-1.5 3.78c0 5.42 3.3 6.61 6.44 7A3.37 3.37 0 0 0 9 18.13V22">
</path>
</svg>Github</h6>
<span class="text-secondary"><%= user.github %></span>
</li>
<li class="list-group-item d-flex justify-content-between align-items-center flex-wrap">
<h6 class="mb-0"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24"
viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"
stroke-linecap="round" stroke-linejoin="round"
class="feather feather-twitter mr-2 icon-inline text-info">
<path
d="M23 3a10.9 10.9 0 0 1-3.14 1.53 4.48 4.48 0 0 0-7.86 3v1A10.66 10.66 0 0 1 3 4s-4 9 5 13a11.64 11.64 0 0 1-7 2c9 5 20 0 20-11.5a4.5 4.5 0 0 0-.08-.83A7.72 7.72 0 0 0 23 3z">
</path>
</svg>Twitter</h6>
<span class="text-secondary"><%= user.twitter %></span>
</li>
<li class="list-group-item d-flex justify-content-between align-items-center flex-wrap">
<h6 class="mb-0"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24"
viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"
stroke-linecap="round" stroke-linejoin="round"
class="feather feather-instagram mr-2 icon-inline text-danger">
<rect x="2" y="2" width="20" height="20" rx="5" ry="5"></rect>
<path d="M16 11.37A4 4 0 1 1 12.63 8 4 4 0 0 1 16 11.37z"></path>
<line x1="17.5" y1="6.5" x2="17.51" y2="6.5"></line>
</svg>Instagram</h6>
<span class="text-secondary"><%= user.instagram %></span>
</li>
<li class="list-group-item d-flex justify-content-between align-items-center flex-wrap">
<h6 class="mb-0"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24"
viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"
stroke-linecap="round" stroke-linejoin="round"
class="feather feather-facebook mr-2 icon-inline text-primary">
<path d="M18 2h-3a5 5 0 0 0-5 5v3H7v4h3v8h4v-8h3l1-4h-4V7a1 1 0 0 1 1-1h3z">
</path>
</svg>Facebook</h6>
<span class="text-secondary"><%= user.facebook %></span>
</li>
</ul>
</div>
</div>
<div class="col-md-8">
<div class="card mb-3">
<div class="card-body">
<div class="row">
<div class="col-sm-3">
<h6 class="mb-0">Nume Complet</h6>
</div>
<div class="col-sm-9 text-secondary">
<%= user.nick %>
</div>
</div>
<hr>
<div class="row">
<div class="col-sm-3">
<h6 class="mb-0">Nivel</h6>
</div>
<div class="col-sm-9 text-secondary">
<%= user.rank %>
</div>
</div>
<hr>
<div class="row">
<div class="col-sm-3">
<h6 class="mb-0">Email</h6>
</div>
<div class="col-sm-9 text-secondary">
<%= user.email %>
</div>
</div>
<hr>
<div class="row">
<div class="col-sm-3">
<h6 class="mb-0">Data Inregistrarii: <h6>
</div>
<div class="col-sm-9 text-secondary">
<%= user.register_date %>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</body>
<footer>
</footer>
</html>
解决方法
问题出在快速路线上。 res.render 在 res.redirect 之后执行，代码部分类似于以下代码：
if (req.session.user) {
res.redirect("/profile");
}
res.render("register",{ user: req.session.user,online });
相反，使用 else 以便 res.render 仅在没有用户会话时执行：
if (req.session.user) {
res.redirect("/profile");
}
else {
res.render("register",online });
}
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