CODEWITHSUNDEEP
node.jsexpressnode-mysql
Lloyd Banks
Lloyd Banks

Reputation: 36689

NodeJS / Express - Make Available MySQL Connection Object in Router File

I have the following in my app.js file: 

var mysql = require('mysql');
var connection = mysql.createConnection({
    host: 'localhost',
    port: 3306,
    user: 'user',
    password: 'password',
    database: 'mydatabase'
});
connection.connect();

In routes/index.js, I currently have only the boilerplate code: 

var express = require('express');
var router = express.Router();

module.exports = router;

How do I make available the connection object from the app.js file in routes/index.js?

Upvotes: 10

Views: 8724

Answers (4)

Robert Moskal
Robert Moskal

Reputation: 22553

My preference is to do some simple dependency injection and pass the required resource into the router by wrapping the module in a function:

var express = require('express');

module.exports = function (connection) {
    var router = express.Router();
    //do stuff with the connection
    return router;

}

Then you just instantiate the router module in app.js as a function with the database connection as an argument:

app.use('/where/ever', require('./module-b')(connection));

Usually I wrap up the dependencies in an object:

app.use('/where/ever', require('./module-b')({db:connection}));

This way you don't have to keep changing the function signature as dependencies are added. This gives you a super-lightweight inversion of control container for your express applications.

Upvotes: 11

Elad Nava
Elad Nava

Reputation: 7896

Check out express-myconnection, it lets you access the MySQL connection from within your routes.

Update: After using express-myconnection in production, I would not recommend it - it leaks connections, causing requests to hang (callback will never be called), and it is no longer actively maintained.

Upvotes: 0

maryum375
maryum375

Reputation: 727

I had the same problem, and Lloyds' suggestion was kind of a solution for me but I just didn't want to be stuck on a single type of db, I want to be able to move my app to another db with just a new implementation of a single class. So that worked for me:

function DataAccess(connectionData) {
    //Using the connectionData...
}

var _dataAccessInstance;

module.exports = function (connectionData) {
    if (!_dataAccessInstance) {
        _dataAccessInstance = new DataAccess(connectionData)
    }
    return _dataAccessInstance;
};

And then the usage will be just require the file:

//The object is the connection data to be sent to the module
var dataAccess = require('./data-access')({});

Sure, this has its own flaws like every module must know and send the connection data. But I assume the data is stored in the configuration and all hte modules can access it.

Upvotes: 0

Lloyd Banks
Lloyd Banks

Reputation: 36689

I ended up splitting the database connection logic from the app.js file. In a separate file called connection.js, I have the following: 

var mysql = require('mysql');

var connection = mysql.createConnection({
    host: 'localhost',
    port: 3306,
    user: 'user',
    password: 'password',
    database: 'mydatabase'
});

module.exports = connection;

Then in my route file, I add

var connection = require('../connection');

to the top of the file where all my other modules are brought in. In my instance, the connection.js file is one level higher than my route file, hence the ../ in the require() function parameter.

Upvotes: 15

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