I'm wondering how to use the module node-mysql correctly in Node.js (using Express.js). I have a main router with this:
var Post = require('./models/post.js');
app.get('/archives', function (req, res) {
Post.findArchives(function(posts, err) {
if(err)
res.send('404 Not found', 404);
else
res.render('archives', { posts: posts});
});
});
And here's the content of the file post.js:
var mysql = require('mysql');
var dbURL = 'mysql://root#localhost/mydatabase';
exports.findArchives = function(callback) {
var connection = mysql.createConnection(dbURL);
connection.query('SELECT * FROM blog_posts_view WHERE status != 0 ORDER BY date DESC', function(err, rows) {
if(err) throw err
callback(rows, err);
connection.end();
});
};
How can I improve it? Improve the error handling? Also, there's the function handleDisconnect(connection); on their Github (https://github.com/felixge/node-mysql) that I'm not really sure how to integrate to make sure that the application will not crash when the database is not responding.
Thanks!
Take a look at the mysql-simple library. It combines node-mysql with a pooling library to create a connection pool, and also includes the code to handle the disconnects.
If you want to make it super easy, you could just use that module.
Related
So I've looked around all over the place for an answer for this but I cannot find one anywhere.
so I'm trying to setup a PostgreSQL database with nodeJS and I've installed pgadmin3 etc.
here is my code
const express = require("express");
const pg = require("pg");
const connect = "postgres://sean:sean#localhost/karls"
var pool = new pg.Pool(connect);
router.route("/").get((req, res) => {
pool.connect(function(err, client, done){
if(err) return console.error("the error ocurred on: " + err);
client.query("SELECT * FROM Recipe", function(err, result) {
if(err) console.error(error);
console.log(results)
done();
})
})
});
on my pgadmin3 I have a login role named sean as a super user so I don't know why it's not connecting I have the password correct but it keeps spitting out this error:
error: password authentication failed for user "sean";
I've been trying to fix this for ages if you need any more information let me know and ill update the question
I've solved this problem :)
I am currently using the python-shell module in a Node based web interface. The issue I am having is mostly syntactical. The code below shows the generation of a python script.
var PythonShell = require('python-shell');
PythonShell.run('my_script.py' function (err) {
if (err) throw err;
console.log('finished');
}):
This is just an example script from here. How do I relate this to node's
var procc = require('child_process'.spawn('mongod');
procc.kill('SIGINT');
The documentation states that PythonShell instances have the following properties:
childProcess: the process instance created via child_process.spawn
But how do I acutally use this? There seems to be a lack of examples when it comes to this specific module
For example -
var python_process;
router.get('/start_python', function(req, res) {
const {PythonShell} = require("python-shell");
var options = {
pythonPath:'local python path'
}
var pyshell = new PythonShell('general.py');
pyshell.end(function (err) {
if (err) {
console.log(err);
}
});
python_process = pyshell.childProcess;
res.send('Started.');
});
router.get('/stop_python', function(req, res) {
python_process.kill('SIGINT');
res.send('Stopped');
});
I'm having serious issues with an app I am building with Node.js, Express, MongoDB and Mongoose. Last night everything seemed to work when I used nodemon server.js to `run the server. On the command line everything seems to be working but on the browser (in particular Chrome) I get the following error: No data received ERR_EMPTY_RESPONSE. I've tried other Node projects on my machine and they too are struggling to work. I did a npm update last night in order to update my modules because of another error I was getting from MongoDB/Mongoose { [Error: Cannot find module '../build/Release/bson'] code: 'MODULE_NOT_FOUND'}. I used the solution in this answer to try and fix it and it didn't work and I still get that error. Now I don't get any files at all being served to my browser. My code is below. Please help:
//grab express and Mongoose
var express = require('express');
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
//create an express app
var app = express();
app.use(express.static('/public/css', {"root": __dirname}));
//create a database
mongoose.connect('mongodb://localhost/__dirname');
//connect to the data store on the set up the database
var db = mongoose.connection;
//Create a model which connects to the schema and entries collection in the __dirname database
var Entry = mongoose.model("Entry", new Schema({date: 'date', link: 'string'}), "entries");
mongoose.connection.on("open", function() {
console.log("mongodb is connected!");
});
//start the server on the port 8080
app.listen(8080);
//The routes
//The route for getting data for the database
app.get("/database", function(req, res) {
Entry.find({}, function(err, data) {console.log(err, data, data.length); });
});
//The route for posting data on the database
app.post("/database", function(req, res) {
//test new post
var newMonth = new Entry({date: '1997-10-30', link: 'https://wwww.youtube.com/'});
newMonth.save(function(err) {
if (err !== null) {
//object was not save
console.log(err);
} else {
console.log("it was saved!")
};
});
});
//create an express route for the home page at http://localhost:8080/
app.get('/', function(req, res) {
res.send('ok');
res.sendFile('/views/index.html', {"root": __dirname + ''});
});
//Send a message to the console
console.log('The server has started');
//The route for getting data for the database
app.get("/database", function(req, res) {
Entry.find({}, function(err, data) {console.log(err, data, data.length); });
});
//The route for posting data on the database
app.post("/database", function(req, res) {
//test new post
var newMonth = new Entry({date: '1997-10-30', link: 'https://wwww.youtube.com/'});
newMonth.save(function(err) {
if (err !== null) {
//object was not save
console.log(err);
} else {
console.log("it was saved!")
};
});
});
These routes don't send anything back to the client via res. The bson error isn't a big deal - it's just telling you it can't use the C++ bson parser and instead is using the native JS one.
A fix could be:
//The route for getting data for the database
app.get("/database", function(req, res) {
Entry.find({}, function(err, data) {
if (err) {
res.status(404).json({"error":"not found","err":err});
return;
}
res.json(data);
});
});
//The route for posting data on the database
app.post("/database", function(req, res) {
//test new post
var newMonth = new Entry({date: '1997-10-30', link: 'https://wwww.youtube.com/'});
newMonth.save(function(err) {
if (err !== null) {
res.status(500).json({ error: "save failed", err: err});
return;
} else {
res.status(201).json(newMonth);
};
});
});
updated june 2020
ERR_EMPTY_RESPONSE express js
package.json
"cors": "^2.8.4",
"csurf": "^1.9.0",
"express": "^4.15.4",
this error show when you try to access with the wrong HTTP request. check first your request was correct
maybe your cors parameter wrong
I am new to loopback and node.js.
I have created two models: Rating and RatingsAggregate
using the loopback explorer, I can query and post against the API just fine.
I am try to setup some basic business logic so I am editing the file Rating.js in common/models
Here is the content of it:
module.exports = function(Rating) {
Rating.afterRemote('**', function(ctx, inst, next) {
var loopback = require('loopback');
var app = loopback();
var ratingsaggregate = app.models.ratingsaggregate;
ratingsaggregate.post({"source":"foobar","restaurantID":"foobar","itemMenuName":"foobar","itemSectionName":"foobar","itemName":"foobar","nRatings1":123,"nRatings2":123,"nRatings3":123,"nRatings4":123,"nRatings5":123,"hasImage":true,"imageSize":123,"latestImageRatingID":"foobar","imageCount":123,"lastUpdated":"foobar"}, function(err, response) {
if (err) console.error(err);
next();
});
});
};
I can load my API, but whenever I run a get statement against it, I get this error:
TypeError: Cannot call method 'post' of undefined
My guess is that somehow ratingsaggregate never gets a value... but I don't know what I am doing wrong. Obviously this is not the end state of my business logic, but I am trying some basic CRUD right now between two models
And... here is the answer. There was a getModel function hidden in the documentation
module.exports = function(Rating) {
Rating.afterRemote('create', function(ctx, inst, next) {
var loopback = require('loopback');
var ratingsaggregate = loopback.getModel('ratingsaggregate');
ratingsaggregate.create({"source":"foobar","restaurantID":"foobar","itemMenuName":"foobar","itemSectionName":"foobar","itemName":"foobar","nRatings1":123,"nRatings2":123,"nRatings3":123,"nRatings4":123,"nRatings5":123,"hasImage":true,"imageSize":123,"latestImageRatingID":"foobar","imageCount":123,"lastUpdated":"foobar"}, function(err, response) {
if (err) console.error(err);
next();
});
});
};
Fixes everything and the behaviour is the expected one
I'm working with Node.js, express, mongodb, and got stuck on this data passing between frontend and backend.
Note: code below is middleware code for front- and backend communication
Here I successfully get the input value from the frontend by using req.body.nr
exports.find_user_post = function(req, res) {
member = new memberModel();
member.desc = req.body.nr;
console.log(req.body.nr);
member.save(function (err) {
res.render('user.jade', );
});
};
Here is the problem, I need to use the input value I got to find the correct data from my database(mongodb in the backend) and push out to the frontend.
My data structure {desc : ''}, the desc is correspond to the input value so it should look something like this {desc: req.body.nr} which is probably incorrect code here?
exports.user = function(req, res){
memberModel.find({desc: req.body.nr}, function(err, docs){
res.render('user.jade', { members: docs });
});
};
Would love to have some help.
Thanks, in advance!
Have a look at this great tutorial from howtonode.org.
Because as you can see he uses a prototype and a function callback:
in articleprovider-mongodb.js
ArticleProvider.prototype.findAll = function(callback) {
this.getCollection(function(error, article_collection) {
if( error ) callback(error)
else {
article_collection.find().toArray(function(error, results) {
if( error ) callback(error)
else callback(null, results)
});
}
});
};
exports.ArticleProvider = ArticleProvider;
in app.js
app.get('/', function(req, res){
articleProvider.findAll( function(error,docs){
res.render('index.jade', {
locals: {
title: 'Blog',
articles:docs
}
});
})
});
Also make sure you have some error checking from the user input as well as from the anybody sending data to the node.js server.
PS: note that the node, express and mongo driver used in the tutorial are a bit older.