ERR_HTTP_HEADERS_SENT - Express：标头在发送到客户端后无法设置，我该如何解决这个错误？

Posted 2023-03-08

【中文标题】ERR_HTTP_HEADERS_SENT - Express：标头在发送到客户端后无法设置，我该如何解决这个错误？

【英文标题】：ERR_HTTP_HEADERS_SENT - Express: headers cannot be set after they are sent to the client, how can i solve this error?

【发布时间】：2020-05-15 05:39:45

【问题描述】：

我已经在 *** 上尝试了很多不同的解决方案，但是。但他们没有工作。

它引发了这个错误：

错误 [ERR_HTTP_HEADERS_SENT]：在将标头发送到客户端后无法设置标头 在 ServerResponse.setHeader (_http_outgoing.js:485:11) 在 ServerResponse.location (/mnt/c/Users/Lucas-PC/) 的 ServerResponse.header (/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/response.js:771:10) Desktop/OnlineChat/node_modules/express/lib/response.js:888:15) 在 ServerResponse.redirect (/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/response.js:926: 18) 在声明中。 (/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/app.js:135:28) --> 在 Database#each("SELECT * FROM users WHERE email='yyyy@yyyy'", [Function]) 在 /mnt/c/Users/Lucas-PC/Desktop/OnlineChat/app.js:133:16 在 Layer.handle [as handle_request] (/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/router/layer.js:95:5) 在下一个（/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/router/route.js:137:13） 在 Route.dispatch (/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/router/route.js:112:3) 在 Layer.handle [as handle_request] (/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/router/layer.js:95:5) 在 /mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/router/index.js:281:22 在 Function.process_params (/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/router/index.js:335:12) 在下一个（/mnt/c/Users/Lucas-PC/Desktop/OnlineChat/node_modules/express/lib/router/index.js:275:10） 在 /mnt/c/Users/Lucas-PC/Desktop/OnlineChat/app.js:70:5 代码：'ERR_HTTP_HEADERS_SENT'， __augmented：是的

这是我的代码：

const redirectLogin = (req, res, next) => 
    if (!req.session.userId)
        res.redirect('/login');
    else 
        next();
    


const redirectHome = (req, res, next) => 
    if (req.session.userId)
        res.redirect('/dashboard');
    else 
        next();
    


app.post('/login', redirectHome, (req, res) => 
    reloadUsers(users);
    const  email, password  = req.body;
    if (email && password) 
        const user = users.find(user => user.email === email && user.password === password) // TODO: hash password
        if (user)
            console.log(user.id);
            req.session.userId = user.id;
            res.redirect('/dashboard');
            return;
        
    
    res.redirect('/')
)


app.post('/register', redirectHome, (req, res) => 
    const  name, job, email, password  = req.body;

    if (name && job && email && password) // TODO: validation more complex
        const exists = users.some(user => user.name === name && user.email === email);

        if(!exists)
            let infos = [name, email, job, password];
            let placeholders = infos.map((info) => '?').join(',');
            let sql = 'INSERT INTO users(name, email, job, password) VALUES('+ placeholders +')';
            db.run(sql, infos);
            console.log('email: '+req.body.email);
            db.each("SELECT * FROM users WHERE email='"+req.body.email+"'", (err, row) => 
                req.session.userId = row.id;
            )
            return res.redirect('/dashboard');
        
    

    res.redirect('/');
)

app.post('/logout', redirectLogin, (req, res) => 
    reloadUsers(users);
    req.session.destroy(err => 
        if (err)
            return res.redirect('/dashboard');
        
        res.clearCookie(SESS_NAME);
        res.redirect('/login');
    );
)

我认为错误来自res.redirect('/dashboard') 上的app.post('/login') 和app.post('/register')

【参考方案1】：

在您的/register 路由器下，您尝试在发送响应后设置请求。

db.each("SELECT * FROM users WHERE email='"+req.body.email+"'", (err, row) => 
    req.session.userId = row.id;
)
return res.redirect('/dashboard');

db.each() 是一个异步函数，因此您必须在函数内处理响应。

db.each("SELECT * FROM users WHERE email='"+req.body.email+"'", (err, row) => 
    req.session.userId = row.id;
    return res.redirect('/dashboard');
)

一些提示：在构造 SQL 语句时，还要尝试转义字符串以避免 SQL 注入。