CODEWITHSUNDEEP
javascriptnode.jsexpress
정성진
정성진

Reputation: 79

"Can't set header after they are sent" Node.js

C:\Users\jsj10\node_modules\mysql\lib\protocol\Parser.js:80
    throw err; // Rethrow non-MySQL errors
    ^

Error: Can't set headers after they are sent.
at validateHeader (_http_outgoing.js:491:11)
at ServerResponse.setHeader (_http_outgoing.js:498:3)
at ServerResponse.header (C:\Users\jsj10\node_modules\express\lib\response.js:767:10)
at ServerResponse.append (C:\Users\jsj10\node_modules\express\lib\response.js:728:15)
at ServerResponse.res.cookie (C:\Users\jsj10\node_modules\express\lib\response.js:853:8)
at ServerResponse.clearCookie (C:\Users\jsj10\node_modules\express\lib\response.js:800:15)
at Query.<anonymous> (C:\Users\jsj10\Desktop\TravelA\server.js:177:18)
at Query.<anonymous> (C:\Users\jsj10\node_modules\mysql\lib\Connection.js:502:10)
at Query._callback (C:\Users\jsj10\node_modules\mysql\lib\Connection.js:468:16)
at Query.Sequence.end (C:\Users\jsj10\node_modules\mysql\lib\protocol\sequences\Sequence.js:83:24)
Program node server.js exited with code 1

This is my error. I can't find what's problem although I looked so many questions. Please help me what's the problem. I think all of my code isn't wrong at all. Tell me where should I fix. Down is my code.

app.post('/writing_server',function(req,res){
var title = req.body.writing_title;
var author = req.body.author;
var contents = req.body.contents;
var user_id = req.body.user_id;
var sql = "insert into "+before_page+"(title,author,content,user_id) values(?,?,?,?)";
if(user_info.id != 'admin' && author.toLowerCase() === 'admin'){
    write_message = "You can't use admin NickName!";
    res.redirect('/write?before='+before_page);
} 
else {
    conn.query(sql,[title,author,contents,user_info.id],function(err,rows,fields){
        if(err) console.log(err);
        else {
            res.redirect('/menu/'+before_page);
            res.clearCookie('before_page'); 
        }
    });
}
})

Upvotes: 1

Views: 487

Answers (2)

Adam
Adam

Reputation: 3965

In Express, the response (or res) parameter of the callback of a routing method (app.get(), app.post(), etc.) has methods that send data back to the client (such as res.redirect()) and methods that set header data before a method like res.redirect() is called.

In your code, you are trying to do this:

res.redirect('/menu/'+before_page);
res.clearCookie('before_page');

But it should be the other way around:

res.clearCookie('before_page');
res.redirect('/menu/'+before_page);

The res.clearCookie() method sets header data for res.redirect() to make use of, so these methods have to be called in this order.

Upvotes: 1

mpm
mpm

Reputation: 20155

Put these two lines in the following order

 res.clearCookie('before_page'); 
 res.redirect('/menu/'+before_page);

You can check whether an operation sends headers to the client or not with 

console.log(res.headersSent)

https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies https://developer.mozilla.org/en-US/docs/Web/HTTP/Redirections

Upvotes: 0

Related Questions