nodejs connect mysql error

Question

I use mysql and express to write a easy login system.

database.js:

var mysql = require('mysql');
var config = require('../config/config');

var pool = mysql.createPool(config.mysql_dev);

var query=function(sql,callback){  
    pool.getConnection(function(err,conn){  
        if(err) console.log("POOL ==> " + err);
        else{  
            conn.query(sql,function(qerr,vals,fields){  
                //release connection  
                conn.release();
                callback(qerr,vals,fields);  

            });  
        }  
    });  
};  

module.exports=query;

index.js:

router.post('/login',function(req,res){ 
    var query = require('../modules/database');
    query("select * from managers where ManagerID =10001",function(err,vals,fields){  
        var temp=JSON.stringify(vals);

        var manager = JSON.parse(temp)[0];

        if(req.body.password===manager.password){
           req.session.manager = manager;
           res.redirect('/home');
        }
        res.send('ID or password wrong!');
    });
});

However, everytime when i get this error:

/opt/workspace/project/nodejs-demo/node_modules/mysql/lib/protocol/Parser.js:77
        throw err; // Rethrow non-MySQL errors
        ^

Error: Can't set headers after they are sent.
    at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11)
    at ServerResponse.header (/opt/workspace/project/nodejs-demo/node_modules/express/lib/response.js:718:10)
    at ServerResponse.send (/opt/workspace/project/nodejs-demo/node_modules/express/lib/response.js:163:12)
    at /opt/workspace/project/nodejs-demo/routes/index.js:40:7
    at Query._callback (/opt/workspace/project/nodejs-demo/modules/database.js:16:17)
    at Query.Sequence.end (/opt/workspace/project/nodejs-demo/node_modules/mysql/lib/protocol/sequences/Sequence.js:96:24)
    at Query._handleFinalResultPacket (/opt/workspace/project/nodejs-demo/node_modules/mysql/lib/protocol/sequences/Query.js:144:8)
    at Query.EofPacket (/opt/workspace/project/nodejs-demo/node_modules/mysql/lib/protocol/sequences/Query.js:128:8)
    at Protocol._parsePacket (/opt/workspace/project/nodejs-demo/node_modules/mysql/lib/protocol/Protocol.js:280:23)
    at Parser.write (/opt/workspace/project/nodejs-demo/node_modules/mysql/lib/protocol/Parser.js:73:12)

How to solve it? I do not know how to solve it and search for a long time. If i describe it not clearly, just comment and i will add anything i know.

I think your problem is not with mysql but it's that you are trying to change response object after sending it to user. (see stack trace) — Mohammad Rahchamani
– Mohammad Rahchamani, Commented May 14, 2016 at 8:28

Ozgur · Accepted Answer · 2016-05-14 11:30:38Z

1

I explained your problem in comments in code.

router.post('/login',function(req,res){ 
    var query = require('../modules/database');
    query("select * from managers where ManagerID =10001",function(err,vals,fields){  
        var temp=JSON.stringify(vals);

        var manager = JSON.parse(temp)[0];

        if(req.body.password===manager.password){
           req.session.manager = manager;


           //You are redirecting user to home
           res.redirect('/home');

           //You should add 'return'
           return;
        }

        //This will only accessible if password is not match
        res.send('ID or password wrong!');
    });
});

answered May 14, 2016 at 11:30

Ozgur

3,76620 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Mukesh Sharma · Accepted Answer · 2016-05-14 08:39:53Z

0

You have issues in the following snippet.

if(req.body.password===manager.password){
   req.session.manager = manager;
   res.redirect('/home');
}
res.send('ID or password wrong!');

It is clear from error stack trace that you are trying to set headers after it is being sent. It means that if statement executes first and if it true, it redirect to /home, after that it exits the if clause and tries to send message to user.

Possible Solution

if(req.body.password===manager.password){
   req.session.manager = manager;
   res.redirect('/home');
} else {
   res.send('ID or password wrong!');
}

Check it, if it helps you.

answered May 14, 2016 at 8:39

Mukesh Sharma

9,0428 gold badges40 silver badges56 bronze badges

Comments

Gandalf the White · Accepted Answer · 2016-10-31 10:59:18Z

0

I should return in the if:

if(req.body.password===manager.password)       
 {
    req.session.manager = manager;
    res.redirect('/home');
    return;
  }

edited Oct 31, 2016 at 10:59

Gandalf the White

2,4752 gold badges21 silver badges39 bronze badges

answered May 14, 2016 at 8:39

ZMath_lin

5533 gold badges6 silver badges15 bronze badges

Collectives™ on Stack Overflow

nodejs connect mysql error

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related