Question

我想使用nodejs和mysql进行登录，但出现这样的错误：

undefined
undefined
SELECT * FROM user WHERE username = username AND password = password
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:455:11)

这是我的代码：

module.exports = (req, res) => {
    let login = "";
    res.send(htmlTemplate(login))

    var username = req.body.username;
    var password = req.body.password;
    var sql = `SELECT * FROM user WHERE username = username AND password = password`;

    console.log(username);
    console.log(password);
    console.log(sql);

    if(username && password) {
        connection.query('SELECT * FROM user WHERE username = username AND password = password', [username, password], function(error, results, fields){
        if(results.length > 0){
            req.session.loggedin = true;
            req.session.username = username;
            res.redirect('/dashboard');
        } else {
            res.send('Username and Password wrong!');
        }
        res.end();
        });
    } else {
        res.send('please enter Username and Password');
        res.end();
    }
}

您能帮我解决这个问题吗？

谢谢。

Answer 1

res.send和res.json结束了请求...因此您不必在之后添加请求。

if(username && password) {
    connection.query('SELECT * FROM user WHERE username = username AND password = password', [username, password], function(error, results, fields){
    if(results.length > 0){
        req.session.loggedin = true;
        req.session.username = username;
        res.redirect('/dashboard');
    } else {
        res.send('Username and Password wrong!');
    }
    });
} else {
    res.send('please enter Username and Password');
}

Answer 2

问题是您已经添加了res.send(htmlTemplate(login))，它结束了端点上收到的请求的响应。当此语句之后的方法流继续时，它会根据条件遇到res.redirect()或res.send()语句，并且该语句再次用于发送响应，但已经发送了响应，并引发错误。为了克服这个问题，请尝试分隔发送登录页面模板的路径，并分别处理登录用户背后的逻辑。

如何修复Node JS错误[ERR_HTTP_HEADERS_SENT]：将标头发送到客户端后无法设置标头

2 个答案: