Currently working on node rest api project where I want to fetch data for a list of data. for example : I have a list of post_id([1,2,3....]) for a particular tag(mobile) and for each post_id I want to retrieve post title and description from mysql database. But calling sql query is synchrounous.
How to control flow for each post id result to combine in one.
my db calling code is here :
var express = require('express');
var app = express();
var bodyParser = require('body-parser'); // call body-parser
var addData = require('./dbhandler/addData'); // call database handler to insertdata
var getData = require('./dbhandler/getData');
//route function to get feeds by tags
router.route('/postfeedsbytags/:tag')
// get all new article feeds filtered by tag
.get(function(req,res){
var success;
console.log(req.params.tag)
var json_results = [];
getData.getPostFeedsByTag(req.params.tag,function(error, results, fields){
if (!error){
for (var i = 0; i < results.length; i++) {
getData.getPostFeedsByPostId(results[0]['post_id'],function(error, results, fields){
if (!error){
success = 1;
json_results.push(results[0]);
res.json({"success" : success, "datasets" : json_results});
} else{
success = 0;
console.log('Error while performing Query.'+error);
res.json({"success" : success});
}
});
}
// res.json({"success" : success, "datasets" : results});
} else{
success = 0;
console.log('Error while performing Query.'+error);
res.json({"success" : success});
}
});
});
I think you can use the IN operator in the query to get all the posts in a single query and then iterate over it.
If you don't want to use IN operator then use async library for flow control. You can use the async.map function from it.
Related
I am new to nodejs and I was wondering if there is possibility to make pretty url in nodejs. I am trying to implement custom pagination on a table. I want the pagination page url should be like
http://localhost:3001/users/page/2
Instead of
http://localhost:3001/users?page=2
Here is my route code
const express = require('express');
const mysql = require('mysql');
const router = express.Router();
const authenticate = require('./middleware');
const connection = require('./lib/db');
// get all users listing
router.get('/users/:page', authenticate.login, function (req, res) {
console.log('request',req.params.page);
var cur = typeof req.params.page != "undefined" ? req.params.page : 1;
var limit = cur - 1;
limit = limit * 10;
connection.query('SELECT count(*) as total FROM lc_users', function(error, rws, flds) {
if(error) throw error
connection.query(mysql.format('SELECT * FROM lc_users ORDER BY uid DESC LIMIT ?,10',[limit]), function(err, rows, fields) {
if(err) throw err
res.render('Users/users',{
title: 'Users',
session: res.locals.session,
usersList: rows,
total: rws[0].total,
current: cur
});
});
});
});
Now when I try to open http://localhost:3001/users url I get error of no route found. I know the issue is with addition /page/ added in the url and that's why its not recognizing the correct route.
Can anyone suggest me what I am doing wrong?
Many Thank!
I need to catch some data by a mysql query, and use the result to build up and email message with its results with node.
I put the code inside a function, but the call to the query appear to still be async, as the result is never given back before the end of the function, and the returning variable is alwasy empty.
Tried different approach with async/await but still the execution seems async
In my following code is just get in the console log up to the step 3, the step 4 is mde no matter what I try to do at the end of the function call
async function querydb (utente){
console.log("sono in querydb");
var messageHTMLAllegati="";
var risultatoquery;
console.log("step 1");
var connection = mysql.createConnection({
host : process.env.IP_address,
user : process.env.nome_utente,
password : process.env.password,
port : process.env.port,
database : process.env.DB,
});
console.log("step 2");
const query = util.promisify(connection.query).bind(connection);
(async () => {
try {
console.log("step 3");
var result = await query('SELECT Link FROM Link_Foto where ID_Utente="' + utente + '"');
var i = result.length;
console.log("step 4");
var j ;
for (j=0; j < i; j++) {
messageHTMLAllegati +='Immagine ' + (j+1)+ '<BR>';
console.log("print the link found in the DB and added to the text to be printed"+result[j].Link);
}
} finally {
connection.end();
}
})()
return messageHTMLAllegati;
}
I do expect the final variable "messageHTMLAllegati" to contain some text plus the query fields needed, but it get always empty. In the log I see though that the variable is filled up, but only after that the function is returned, therefore the text used to put the email together is empty from the DB section
async/await method only works when await functions is a promise. functions like 'query' in mysql are using a callback function to get the result. So if you want to use it with async/await method you should use it in another function and get the result in its callback function as a promise like this:
function query_promise(q_string){
return new Promise((resolve, reject)=>{
query(q_string,(err, result)=>{
if(err) return reject(err);
resolve(result);
});
});
}
then in your code:
var result = await query_promise('SELECT Link FROM Link_Foto where ID_Utente="' + utente + '"');
Good Day how can i compute a public function to route and check it on Postman? here is my codes
router.post('/post_regular_hours/:employee_id/',function(request,response,next){
var id = request.params.employee_id;
var time_in = request.params.time_in;
var time_out = request.params.time_out;
// const timein = request.params.time_in;
// const timeout = request.params.time_out;
knexDb.select('*')
.from('employee_attendance')
.where('employee_id',id)
.then(function(result){
res.send(compute_normal_hours(response,result,diff))
})
});
function compute_normal_hours(res,result,diff){
let time_in = moment(time_in);
let time_out = moment(time_out);
let diff = time_out.diff(time_in, 'hours');
return diff;
}
I want the Diff to get posted on Postman as a result
Here is the App.js of my codes. How can i call the data from mysql query to the function and return the computed data on router post
or can you guys give the right terminologies for it.
var express = require('express');
var mysql= require('mysql');
var employee = require('./routes/employee');
var time_record = require('./routes/time_record');
var admin_employee = require('./routes/admin_employee');
var tar = require('./routes/tar');
var Joi = require('joi');
var app = express();
app.get('/hello',function(req,res){
var name = "World";
var schema = {
name: Joi.string().alphanum().min(3).max(30).required()
};
var result = Joi.validate({ name : req.query.name }, schema);
if(result.error === null)
{
if(req.query.name && req.query.name != '')
{
name = req.query.name;
}
res.json({
"message" : "Hello "+name + "!"
});
}
else
{
res.json({
"message" : "Error"
});
}
});
//Database connection
app.use(function(req, res, next){
global.connection = mysql.createConnection({
host : 'locahost',
user : 'dbm_project',
password : 'dbm1234',
database : 'dbm_db'
});
connection.connect();
next();
});
app.use('/', employee);
app.use('/employee', time_record);
app.use('/admin', admin_employee);
app.use('/tar', tar);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handler
app.use(function(err, req, res, next) {
// set locals, only providing error in development
res.locals.message = err.message;
res.locals.error = req.app.get('env') === 'development' ? err : {};
// render the error page
res.status(err.status || 500);
res.render('error');
});
app.listen(8000,function(){
console.log("App started on port 8000!");
});
module.exports = app;
Here is the App.js of my codes. How can i call the data from mysql query to the function and return the computed data on router po
There are a few problems with your code.
Please see explanations in the respective code chunks.
router.post('/post_regular_hours/:employee_id/',function(request,response,next){
// If you're receiving a post request
// you'll probably want to check the body for these parameters.
let id = request.params.employee_id; // make sure the param names are matching with what you post.
// This one is special because you are passing it through the url directly
let time_in = request.body.time_in;
let time_out = request.body.time_out;
knexDb.select('*')
.from('employee_attendance')
.where('employee_id',id)
.then(function(result){
// you are not sending time_in and time_out here - but difference. but difference is not calculated.
// changed the function signature a bit - you weren't using the result at all? leaving this callback here because I'm sure you want to map the used time to some user?
return response.send(compute_normal_hours(time_in, time_out))
});
});
// this function was (and still might be) incorrect.
// You were passing res and result which neither of them you were using.
// You also had time_in and time_out which were going to be undefined in the function scope. Now that we are passing them in it should be ok. Updated it so you don't have the params you don't need.
function compute_normal_hours(time_in, time_out){
// What was diff - if it's the time difference name things correctly
// You had a diff parameter passed in (which you didn't compute), a diff function called below and another variable declaration called diff.
// you were not passing time_in or time_out parameters.
// you have moment here - are you using a library?
let time_in = moment(time_in);
let time_out = moment(time_out);
let diff = time_out.diff(time_in, 'hours');
return `Computed result is: ${diff}`;
}
Important Edit
Please search for all occurences of res.render (response.render) and replace them with something like res.send - res.render is looking for the template engine
To set the scenario for the code, the database stores Documents, and each document has the potential to have Images associated with them.
I have been trying to write a route that queries the database for each Document that has Images related to them, storing this data in JSON which is returned to the ajax request when completed, so the data can be viewed on the page. The closest I have got so far is the below attempt (see code).
router.post('/advanced_image_search', userAuthenticated, function(req, res, next) {
async.waterfall([
// First function is to get each document which has an image related
function getDocuments(callback){
connection.query(`SELECT DISTINCT(Document.document_id), Document.doc_name, Document.doc_version_no, Document.doc_date_added
FROM Document WHERE doc_type = 'image'`, function(err, results) {
if (err) {
callback(err, null);
return;
}
// The Object containing the array where the data from the db needs to be stored
var documents = {
'docs': []
};
// foreach to iterate through each result found from the first db query (getDocuments)
results.forEach(function(result) {
// New object to store each document
var document = {};
document.entry = result;
// This is the array where each image assciated with a document will be stored
document.entry.images = [];
// Push each document to the array (above)
documents.docs.push(document);
var doc_id = result.document_id;
})
// Returning the results as 'documents' to the next function
callback(null, documents);
})
},
function getImages(documents, callback){
// Variable assignement to the array of documents
var doc_array = documents.docs;
// Foreach of the objects within document array
async.forEachOf(doc_array, function(doc, key, callback){
// Foreach object do the following series of functions
async.waterfall([
function handleImages(callback){
// The id of the document to get the images for
var doc_id = doc.entry.document_id;
connection.query(`SELECT * FROM Image, Document WHERE Image.document_id = '${doc_id}' AND Image.document_id = Document.document_id`, function(err, rows) {
if (err) {
callback(err, null);
return;
}
callback(null, rows);
})
},
// Function below to push each image to the document.entry.images array
//
function pushImages(rows, callback){
// If multiple images are found for that document, the loop iterates through each pushing to the images array
for (var j = 0; j < rows.length; j++) {
// Creating new object for each image found so the data can be stored within this object, then pushed into the images array
var image = {
'image_name': rows[j].image_name
};
doc.entry.images.push(image);
}
callback(null, doc_array);
}
], function(err, doc_array){
if (err) {
console.log('Error in second waterfall callback:')
callback(err);
return;
}
console.log(doc.entry);
// callback(null, doc_array);
})
}, function(err, doc_array){
if (err) {
callback(err);
return;
}
callback(null, doc_array);
});
callback(null, doc_array);
}
], function(err, doc_array) {
if (err){
console.log('Error is: '+err);
return;
}
// The response that should return each document with each related image in the JSON
res.send(doc_array);
})
});
At the moment the results returned are:
1:
{entry: {document_id: 1, doc_name: "DocumentNameHere", doc_version_no: 1,…}}
entry:
{document_id: 1, doc_name: "DocumentNameHere", doc_version_no: 1,…}
doc_date_added:"2016-10-24"
doc_name:"DocumentNameHere"
doc_version_no:1
document_id:1
images:[]
As can be seen above, the images array remains empty even though with testing, the images are being found (console.log).
I hope someone is able to assist with this, as I am struggling to find the problem with this complex one.
Thanks
There are several async operations going on here and each operation needs a callback. See revised code:
router.post('/advanced_image_search', userAuthenticated, function(req, res, next) {
var getDocuments = function(next) {
// Function for getting documents from DB
var query = `SELECT DISTINCT(Document.document_id), Document.doc_name, Document.doc_version_no, Document.doc_date_added FROM Document WHERE doc_type = 'image'`; // Set the query
connection.query(query, function(err, results) {
// Run the query async
if(err) {
// If err end execution
next(err, null);
return;
}
var documentList = []; // Array for holding docs
for(var i=0; i<results.length; i++) {
// Loop over results, construct the document and push to an array
var documentEntry = results[i];
var documentObject = {};
documentObject.entry = documentEntry;
documentObject.entry.images = [];
documentObject.id = documentEntry.document_id;
documentList.push(documentObject);
}
next(null, documents); // Pass to next async operation
});
};
var getImages = function(documents, next) {
// Function for getting images from documents
var finalDocs = []; // Blank arry for final documents with images
for (var i=0; i<documents.length; i++) {
// Loop over each document and construct the query
var id = documents[i].id;
var query = `SELECT * FROM Image, Document WHERE Image.document_id = '${doc_id}' AND Image.document_id = Document.document_id`;
connection.query(query, function(err, images) {
// Execute the query async
if(err) {
// Throw error to callback
next(err, null);
return;
}
var processedDoc = processImages(documents[i], images); // Call a helper function to process all images into the document object
finalDocs.push(processedDoc); // Push the processed doc
if(i === documents.length) {
// If there are no more documents move onto next async
next(null, finalDocs);
}
});
}
};
var processImages = function(doc, images) {
for (var i=0; i< images.length; i++) {
// Loop over each document image - construct object
var image = {
'image_name': rows[j].image_name
};
doc.entry.images.push(image); // Push image into document object
}
return doc; // Return processed doc
};
getDocuments(function(err, docs) {
if(err) {
// Your error handler
}
if(docs) {
getImages(docs, function(err, finalDocs) {
if(err) {
// Your error handler
}
if(finalDocs) {
console.log(finalDocs);
res.status(200).json(finalDocs); // Send response
}
});
}
});
});
First we create a function to get documents - This function accepts a callback as its parameter. We run our query and construct our doc list. Then we return the document list by executing our callback
Next we run a function to get our images for each document. This function accepts our document list and a callback as our parameters. It retrieves images for each document and calls a helper function (sync)
Our helper function processes the images into each document and returns the processed document.
We then finish our operations by returning an array of processed documents via the second callback.
Other notes
We could tide this up by structuring this procedural style code into a contained JSON object
The nesting of the function executions at the end of the document could be cleaned up further
I've avoided using the async libray as it helps better understanding of the callback model
Event emitters could be used to flatten the callbacks - see https://nodejs.org/dist/latest-v7.x/docs/api/events.html
Hope this helps
Dylan
I am using node, angular and mysql, the node routes would return a json that would be processed by angular, the json is returned by first querying the mysql DB using the node-mysql module,
In the below code I am unable to set the value of CreatedID, but the value gets logged properly in terminal. I was facing the same issue in the 1st query but then sorted it in the below code, now unable to access the nested query results.
var mysql = require('node-mysql/node_modules/mysql');
var connection = mysql.createConnection({
host : 'localhost',
user : "root",
password: "",
database:'designtaskmanager'
});
connection.connect();
var allDbCalls = function() {
var sendData = {};
var rowData = {};
var temp={};
var _this = this;
this.sendTask = function(callback) {
module.exports.taskData = rowData;
callback['success']();
};
this.getTask = function(callback) {
var strQuery = "select * from task";
connection.query( strQuery, function(err, rows){
if(err)
{
callback['failure']();
throw err;
}
else
{
//rowData = rows;
var tasks=[];
for (var i in rows)
{
var Title = rows[i].task_title;
var TaskDescription=rows[i].task_description;
var TaskCategory=rows[i].task_category;
var TaskID=rows[i].task_id;
var TaskStatus=rows[i].task_status;
var TaskStatusMessage
var CreatedBy;
var TaskCreationDate=rows[i].task_creation_date;
var _MS_PER_DAY = 1000 * 60 * 60 * 24;
var currentdate = new Date();
var ddd=dateDiffInDays(TaskCreationDate,currentdate);
function dateDiffInDays(a, b) {
// Discard the time and time-zone information.
var utc1 = Date.UTC(a.getFullYear(), a.getMonth(), a.getDate());
var utc2 = Date.UTC(b.getFullYear(), b.getMonth(), b.getDate());
return Math.floor((utc2 - utc1) / _MS_PER_DAY);
}
if(TaskStatus==0)
{
TaskStatus="label-info";
TaskStatusMessage="Ongoing since";
}
else if(TaskStatus==1)
{
TaskStatus="label-default";
TaskStatusMessage="Paused since"
}
else if(TaskStatus==2)
{
TaskStatus="label-success";
TaskStatusMessage="Completed in"
}
//USER DETAILS QUERY
var crid=rows[i].task_created_by;
var creatorQuery = "select user_email from users where user_id like ?";
connection.query( creatorQuery,[crid], function(err, createdbyrows){
if(err)
{
callback['failure']();
throw err;
}
else
{
for(var j=0; j< createdbyrows.length;j++)
{
CreatedBy=createdbyrows[0].user_email;
console.log(j);
}
console.log(CreatedBy);
}
});
var taskItem={"TaskID":TaskID,"TaskTitle":Title,"TaskDescription":TaskDescription,"TaskCategory":TaskCategory,"CreatedBy":CreatedBy,"TaskStatus":TaskStatus,"TaskStatusMessage":TaskStatusMessage,"DifferenceInDays":ddd};
tasks.push(taskItem);
}
rowData=tasks;
_this.sendTask(callback);
}
});
}
}
module.exports = function () {
var instance = new allDbCalls();
return instance;
};
The reason that you're seeing it on the console but not in the callback is due to a misunderstanding of asynchronous programming. When you:
for(var i in rows) {}
You are actually queuing up all of those queries at the same time, then, immediately after you try to set rowData to an empty array:
rowData=tasks; // remember, none of the queries have finished yet
_this.sendTask(callback);
So you pretty much call your callback when tasks is still an empty array. Remember, you can't call your final callback until ALL of your nested queries have finished!
To accomplish this, you may want to look at the async library: https://github.com/caolan/async#eachSeries
This will help you accomplish what you really want.
var async = require("async");
async.eachSeries(rows, function(row, cb) {
// Do each query here
// then call cb() when done, which tells the async library
// to "go to the next item in the array"
}, function(err) {
// This will get called when all of the single queries are finished
// Check err, then call your callback
_this.sendTask(callback);
});