node.js 我无法读取未定义的属性“查询”
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i am getting cannot read property 'query' of undefined
提问by Amina Rahman
i have make a socket.io chatroom and i am using some database queries to insert and select data but unfortunately i am getting some error of query
我制作了一个 socket.io 聊天室，我正在使用一些数据库查询来插入和选择数据，但不幸的是我遇到了一些查询错误
The code of the file on which i am getting error is as follow
我收到错误的文件的代码如下
var rooms = [];
module.exports.getUserFeeds = function (chatpage, socket, io, pool,async)
{
socket.on('senddata', function (data)
{
socket.user_id = data.user_id;
socket.room_id=data.room_id;
socket.room = 'room' + data.room_id;
rooms['room' + data.room_id] = 'room' + data.room_id;
socket.join('room' + data.room_id);
pool.getConnection(function (err, connection)
{
async.parallel([
function(callback)
{
connection.query('SELECT user_id,username FROM chat_users where user_id=' + data.user_id + '', function (error1, userdata)
{
if (error1) return callback(error1);
callback(null, userdata);
});
},
function (callback)
{
if(data.user_id)
connection.query('SELECT user_id,username FROM chat_users', function (error3, memdata)
{
if (error3) return callback(error3);
callback(null, memdata);
});
else
callback(null,null);
},
function(callback)
{
if(data.user_id)
connection.query('SELECT comment_id,comment,chat_users.user_id,username,comments.added FROM comments INNER JOIN chat_users ON comments.user_id=chat_users.user_id',function(error4,converdata){
if (error4) return callback(error4);
callback(null, converdata);
});
else
callback(null,null);
}
], function (err, results)
{
if(err) throw err;
socket.emit('chatdata',
{
memdata:results[1],
converdata:results[2],
});
socket.broadcast.to('room'+ data.room_id +'').emit('newuser', {userdata:results[0]});
connection.release();
});
});
});
socket.on('sendcomment', function (data)
{
pool.getConnection(function (err, connection)
{
connection.query('INSERT INTO comments (user_id,comment,added) VALUES (' + data.user_id + ',"' + data.msg + '","' + data.datetime + '")', function (err, result)
{
if (err) throw err;
async.parallel([
function (callback)
{
connection.query('SELECT comments.*,username,comments.added from comments JOIN chat_users ON comments.user_id=chat_users.user_id WHERE comments.comment_id=' + result.insertId + '', function (err2, comments)
{
if (err2) return callback(err2);
callback(null, comments);
});
},
function (callback)
{
connection.query('SELECT count(comment_id) as tot_comment from comments', function (err3, comment_count)
{
if (err3) return callback(err3);
callback(null, comment_count);
});
},
], function (err, results)
{
if (err) throw err;
if (results[0])
{
chatpage. in('room'+ data.room_id +'').emit('showcomment',
{
room_comment: results[0],
comment_count: results[1]
});
}
connection.release();
});
});
});
});
socket.on('disconnect', function ()
{
console.log("user disconnected");
pool.getConnection(function (err, connection)
{
connection.query('DELETE from chat_users where user_id='+socket.user_id+'', function (err, removeuser)
{
if (err) throw err;
});
connection.query('DELETE from comments where user_id='+socket.user_id+'', function (err, removecomments)
{
if (err) throw err;
});
connection.release();
});
socket.broadcast.to('room'+ socket.room_id +'').emit('removeuser', {user_id:socket.user_id});
socket.leave(socket.room);
});
};
and the error i am getting because of this code is
我因为这段代码而得到的错误是
The image of the error i am getting
please can anyone help me regarding this issue
请任何人都可以帮助我解决这个问题
Thanks a lot Regards
非常感谢
回答by Adiii
It seems there is error in your mysql connection.try make proper connection first
您的 mysql 连接中似乎有错误。请先尝试进行正确的连接
Step 1: Create the pool (only do this once)
第 1 步：创建池（只做一次）
var mysql = require('mysql');
var pool = mysql.createPool({
host : 'hostname',
user : 'username',
password : 'password',
database : 'db_name',
connectionLimit : 10, // this is the max number of connections before your pool starts waiting for a release
multipleStatements : true // I like this because it helps prevent nested sql statements, it can be buggy though, so be careful
});
Step 2: Get a connection
第 2 步：获取连接
pool.getConnection(function (err, conn) {
if (err)
return res.send(400);
// if you got a connection...
conn.query('SELECT * FROM table WHERE id=? AND name=?', [id, name], function(err, rows) {
if(err) {
conn.release();
return res.send(400, 'Couldnt get a connection');
}
// for simplicity, just send the rows
res.send(rows);
// CLOSE THE CONNECTION
conn.release();
}
});
check this for more detail https://youtu.be/2CeAnrCsBQo
检查此以获取更多详细信息https://youtu.be/2CeAnrCsBQo
http://fearby.com/article/how-to-setup-pooled-mysql-connections-in-node-js-that-dont-disconnect/
http://fearby.com/article/how-to-setup-pooled-mysql-connections-in-node-js-that-dont-disconnect/
回答by Abhishek Goel
Adding the following 2 parameters solved my problem
添加以下2个参数解决了我的问题
queueLimit
connectionLimit
queueLimit
connectionLimit
exports.pool = mysqlCon.createPool({
host: host,
user: user,
port: 3306,
password: pass,
database: db,
queueLimit : 0, // unlimited queueing
connectionLimit : 0 // unlimited connections
});
Note : Be careful, this might break your database.
注意：小心，这可能会破坏您的数据库。
回答by mscdex
You need to handle errors, otherwise you can encounter issues like this. Specifically in this case, you aren't checking if erris set in your pool.getConnection()callback. It is most likely set and is why you don't have a valid connectionobject.
你需要处理错误，否则你会遇到这样的问题。特别是在这种情况下，您不会检查回调中err是否设置了pool.getConnection()。它很可能已设置，这就是您没有有效connection对象的原因。
