On Jul 15, 2016, at 10:28 PM, Ryan Schmidt wrote:
>
> On Jul 15, 2016, at 2:53 AM, paolodocet wrote:
>
>> I have an HTTP get request to extract from MySQL all records of a User
>> table.
>>
>> User table looks like as follow:
>>
>> + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + -
>> - ID + Username + Email + Password +
>> + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + -
>> - - - -
>> -
>> + 1 + a + a...@live.it + 123456789
>> +
>> - - - -
>> -
>> + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + -
>> - - - -
>> -
>> + 2 + b + b...@live.it + 123456789
>> +
>> - - - -
>> -
>> + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + -
>> - - - -
>> -
>> + 3 + c + c...@live.it + 123456789
>> +
>> - - - -
>> -
>> + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + -
>>
>> Then I create a javascript array where each element is a record of the
>> previous table and using stringify I convert the js array in a JSON. My get
>> response must reply with this JSON:
>>
>> app.get('/getUsers', function (req, res) {
>>
>> var users= [];
>> var userJSON="";
>>
>>
>> connection.query('SELECT * FROM USER ORDER BY ID', function (err, rows,
>> fields) {
>>
>> if (err) {
>> console.log('There was an error\n' + err);
>> }
>> else {
>> for (var i in rows) {
>> users.push({ID:rows[i].ID, Username:rows[i].Username,
>> Email:rows[i].email, Password: rows[i].Password});
>> }
>> userToJson = JSON.stringify(users);
>> console.log(userToJson);
>> }
>> });
>> res.setHeader('Content-Type','application/json');
>> res.json(userJSON);
>> res.end();
>>
>> });
>>
>> My res.json(userJSON) does not work and my response is empty. How can I send
>> to my client the JSON properly?
>
> You're calling res.setHeader, res.json and res.end *before* the userJSON
> variable has been filled with data. userJSON is not being filled with data
> until the anonymous function you give to connection.query runs, which won't
> be until the database has had time to process the query. You need to call
> your res functions in that anonymous function.
>
>
>
> app.get('/getUsers', function (req, res) {
>
> var users= [];
> var userJSON="";
>
>
> connection.query('SELECT * FROM USER ORDER BY ID', function (err, rows,
> fields) {
> res.setHeader('Content-Type','application/json');
> if (err) {
> console.log('There was an error\n' + err);
> res.json({error: err});
> }
> else {
> for (var i in rows) {
> users.push({ID:rows[i].ID, Username:rows[i].Username,
> Email:rows[i].email, Password: rows[i].Password});
> }
> userToJson = JSON.stringify(users);
> console.log(userToJson);
> res.json(userJSON);
> }
> res.end();
> });
>
> });
I was focused on the flow of your code and not on variable names. I realize now
that you also have variable name confusion: you have a variable userJSON which
you declare and initialize to the empty string and never modify, and then you
have a second variable userToJson which you fill with data but only use in your
console.log. Let's fix those issues by using only a single variable:
app.get('/getUsers', function (req, res) {
connection.query('SELECT * FROM USER ORDER BY ID', function (err, rows,
fields) {
res.setHeader('Content-Type','application/json');
if (err) {
console.log('There was an error\n' + err);
res.json({error: err});
}
else {
var users = [];
for (var i in rows) {
users.push({ID:rows[i].ID, Username:rows[i].Username,
Email:rows[i].email, Password: rows[i].Password});
}
var userJSON = JSON.stringify(users);
console.log(userJSON);
res.json(userJSON);
}
res.end();
});
});
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