Tag: mongoDB

Validating User Request: Node.js

Validating user requests is one of the key elements of a web application, and is critical for its performance.

validating-user-request

In this tutorial, we validate the user request against elements present inside an array. In real-time web applications, the request is validated against database values.

Validating User Request In Express: Node.js
app.js

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var names = [
 "Satish",
 "Kiran",
 "Sunitha",
 "Jyothi"
];
 
app.param('username', function(req, res, next, username){
var flag = parseInt(names.indexOf(username), 10);
 
if(flag >= 0)
 next();
else 
 res.end("No Such User!");
});
 
app.get('/user/:username', function(req, res){
res.send("Viewing user: "+req.params.username);
});

when the user requests for data via the route /user/someUsername we check if the user is actually present. If he is present, we’ll serve the data or else we’ll send No Such User! message to the browser.

To keep the routes clean, we shift the code to app.param First parameter indicates to which route the app.param is bound to. The callback method takes a couple of arguments – request, response, next and the username the user has requested.

we make use of indexOf() method to check if the requested username is actually present in our array. If the element is present in the array, indexOf() returns its position or else it returns -1.
If it returns 0 or any other positive value, then call next() to pass the control to the next layer of execution or else, display No Such User! and end the response.

Validating User Request: Node.js


[youtube https://www.youtube.com/watch?v=Bug_P3lxhfA]

YouTube Link: https://www.youtube.com/watch?v=Bug_P3lxhfA [Watch the Video In Full Screen.]



Note: Usually if you retrieve data out of a MongoDB server, the data will be present in the form of object( {key: value} pair ).

Validating User Request In Express: Node.js
app.js

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var names = [
 {
"id"        :  1,
"name"   :  "Apple",
"product": "iPhone"
},
 {
"id"        :  2,
"name"   :  "Google",
"product": "Nexus"
},
 {
"id"        :  3,
"name"   :  "Technotip",
"product": "Education"
},
 {
"id"        :  4,
"name"   :  "Microsoft",
"product":  "Nokia Lumia"
}
];
var flag = undefined;
app.param('id', function(req, res, next, id){
 
for(var i = 0; i < names.length; i++ )
 if(names[i].id == id)
   flag = "<b>Company: "+names[i].name+
            "<br /><b>Product: </b>"+names[i].product;
 
if(flag != undefined)
  next();
else
        res.end("No Such User!");
});
 
app.get('/user/:id', function(req, res){
res.send(flag);
});

Here we have an array of objects. Once the user requests company information using company id(/user/:id), we check through each object’s id and if it matches we call next() or else send No Such User! to the browser.

some output
/user/0
No Such User!

/user/1
Company: Apple
Product: iPhone

/user/2
Company: Google
Product: Nexus

/user/4
Company: Microsoft
Product: Nokia Lumia

Home Work Combine today’s learning with Error handling and write complete code for user request validation as well as error handling using Error object.

MongoDB Tutorial List

Follow the order in this post and make sure to practice all the tutorials and also share your knowledge with our awesome community on our official forum or in respective articles comment section.

logo-mongodb-tagline

If you got to learn anything from our website, then please do not forget to share this page with your friends on Facebook, Google Plus, LinkedIn, Twitter etc..

  1. MongoDB – Getting Started Guide
  2. Create and Insert Documents: MongoDB
  3. ObjectId ( _id ) as Primary Key: MongoDB
  4. Relationship Between Collections/Tables: MongoDB
  5. SELECT Columns/Fields: MongoDB
  6. Load Data From External JavaScript File: MongoDB
  7. Comparison Operators: MongoDB
  8. String Comparison: MongoDB
  9. $exists, $type, $regex operators: MongoDB
  10. $or (Union) Operator: MongoDB
  11. $and operator: MongoDB
  12. Dot Notation To Access Sub Document: MongoDB
  13. Cursor Object: MongoDB
  14. Count Method: MongoDB
  15. Update Method: MongoDB
  16. Update with SET Operator: MongoDB
  17. Update with UNSET Operator: MongoDB
  18. Increment($inc) operator: MongoDB
  19. Working With Arrays: MongoDB
  20. Update with upsert: MongoDB
  21. Multi-Update: MongoDB
  22. Removing Documents: MongoDB
  23. Multi-key Index: MongoDB
  24. index / key: MongoDB
  25. index creation: MongoDB
  26. Get Index and Delete Index: MongoDB
  27. Multi-key Indexes and Arrays: MongoDB
  28. Creating Unique Key/index: MongoDB
  29. Remove Duplicate Documents: MongoDB
  30. Sparse Index: MongoDB
  31. Index Creation for Production Server: MongoDB
  32. explain() method: MongoDB
  33. MongoDB Management Service To Rescue Your Application!

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Comparison Operators: MongoDB

In this video tutorial we shall illustrate the use of comparison operators in MongoDB.

Comparison Operators
$all
$in
$nin – not in
$ne – not equal to
$gt – greater than
$gte – greater than or equal to
$lt – less than
$lte – less than or equal to

red-apple-green-apple-comparison

JavaScript file
load.js – in path: C:/test/load.js

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db.person.insert({
name   : 'Satish',
age    : 25,
skills : ['nodejs', 'mongoDB', 'HTML5']
});
 
db.person.insert({
name   : 'Kiran',
age    : 27,
skills : ['PHP', 'mySQL', 'HTML5']
});
 
db.person.insert({
name   : 'Sunitha',
age    : 24,
skills : ['html', 'ASP']
});
 
db.person.insert({
name   : 'Jyothi',
age    : 23,
skills : ['html', 'ASP']
});
 
db.person.insert({
name   : 'Varsha',
age    : 30,
skills : ['.NET', 'Java']
});
 
db.person.insert({
name   : 'Amogh',
age    : 29,
skills : ['C#', 'ASP']
});

This JavaScript file contains some simple data, to be inserted into MongoDB server.
It contains, persons name, age and skills(in array form)
person is the collection name, we’re creating.

From our previous day video tutorial we already know, how to, Load Data From External JavaScript File: MongoDB.

load script to new database

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C:\mongodb>cd bin
 
C:\mongodb\bin>mongo 127.0.0.1/satish C:/temp/load.js
MongoDB shell version: 2.4.3
connecting to: 127.0.0.1/satish
 
C:\mongodb\bin>mongo
MongoDB shell version: 2.4.3
connecting to: test

Once these data/documents are loaded into new database, we start operating on this data using comparison operator.

Documents In person Collection

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> db.person.find().forEach(printjson)
{
        "_id" : ObjectId("518c76ba05ea2a1d2b3b33a0"),
        "name" : "Satish",
        "age" : 25,
        "skills" : [
                "nodejs",
                "mongoDB",
                "HTML5"
        ]
}
{
        "_id" : ObjectId("518c76ba05ea2a1d2b3b33a1"),
        "name" : "Kiran",
        "age" : 27,
        "skills" : [
                "PHP",
                "mySQL",
                "HTML5"
        ]
}
{
        "_id" : ObjectId("518c76ba05ea2a1d2b3b33a2"),
        "name" : "Sunitha",
        "age" : 24,
        "skills" : [
                "html",
                "ASP"
        ]
}
{
        "_id" : ObjectId("518c76ba05ea2a1d2b3b33a3"),
        "name" : "Jyothi",
        "age" : 23,
        "skills" : [
                "html",
                "ASP"
        ]
}
{
        "_id" : ObjectId("518c76ba05ea2a1d2b3b33a4"),
        "name" : "Varsha",
        "age" : 30,
        "skills" : [
                ".NET",
                "Java"
        ]
}
{
        "_id" : ObjectId("518c76ba05ea2a1d2b3b33a5"),
        "name" : "Amogh",
        "age" : 29,
        "skills" : [
                "C#",
                "ASP"
        ]
}

Comparison Operators: MongoDB


[youtube https://www.youtube.com/watch?v=937PSHo7F00]

YouTube Link: https://www.youtube.com/watch?v=937PSHo7F00 [Watch the Video In Full Screen.]



Switch to new database, ‘satish’

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> show dbs
admin   0.203125GB
company 0.203125GB
local   0.078125GB
satish  0.203125GB
> use satish
switched to db satish

$all operator

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> db.person.find({skills: { $all: ['html', 'css'] }}, {name: 1, _id: 0});
> db.person.find({skills: { $all: ['html', 'ASP'] }}, {name: 1, _id: 0});
{ "name" : "Sunitha" }
{ "name" : "Jyothi" }

Matches arrays that contain all elements specified in the query.

$in operator

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> db.person.find({skills: { $in: ['html', 'css'] }}, {name: 1, _id: 0});
{ "name" : "Sunitha" }
{ "name" : "Jyothi" }
> db.person.find({skills: { $in: ['java', 'css'] }}, {name: 1, _id: 0});
> db.person.find({skills: { $in: ['Java', 'css'] }}, {name: 1, _id: 0});
{ "name" : "Varsha" }

Matches any of the values that exist in an array specified in the query.

$nin operator: not in

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> db.person.find({skills: { $nin: ['Java', 'css'] }}, {name: 1, _id: 0});
{ "name" : "Satish" }
{ "name" : "Kiran" }
{ "name" : "Sunitha" }
{ "name" : "Jyothi" }
{ "name" : "Amogh" }
> db.person.find({skills: { $nin: ['Java', 'ASP'] }}, {name: 1, _id: 0});
{ "name" : "Satish" }
{ "name" : "Kiran" }

Matches values that do not exist in an array specified to the query.

$gt operator

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> db.person.find({age: { $gt: 25 }}, {name: 1, _id: 0});
{ "name" : "Kiran" }
{ "name" : "Varsha" }
{ "name" : "Amogh" }

Matches values that are greater than the value specified in the query.

$gte operator

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> db.person.find({age: { $gte: 25 }}, {name: 1, _id: 0});
{ "name" : "Satish" }
{ "name" : "Kiran" }
{ "name" : "Varsha" }
{ "name" : "Amogh" }

Matches values that are equal to or greater than the value specified in the query.

Combining multiple operators: $gt, $gte and $lt operator

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> db.person.find({age: { $gte: 25, $lt: 29 }}, {name: 1, _id: 0});
{ "name" : "Satish" }
{ "name" : "Kiran" }
> db.person.find({age: { $gt: 25, $lt: 29 }}, {name: 1, _id: 0});
{ "name" : "Kiran" }
> db.person.find({age: { $gt: 25, $lte: 29 }}, {name: 1, _id: 0});
{ "name" : "Kiran" }
{ "name" : "Amogh" }

$lt – less than – Matches vales that are less than the value specified in the query.
$lte – less than or equal to – Matches values that are less than or equal to the value specified in the query.

$ne operator

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> db.person.find({age: {$ne: 25}}, {name: 1, _id: 0});
{ "name" : "Kiran" }
{ "name" : "Sunitha" }
{ "name" : "Jyothi" }
{ "name" : "Varsha" }
{ "name" : "Amogh" }

Matches all values that are not equal to the value specified in the query.

Note:
Operators are useful when we do not know the exact value to be extracted or to fetch a range of values.
All mongoDB operators begin with $ sign.

Load Data From External JavaScript File: MongoDB

This video tutorial illustrates loading data to mongoDB server from an external JavaScript file ( Writing script for MongoDB shall )

Here, we write a simple JavaScript file and using command prompt we load the contents of JavaScript file into new Database.

import-data

JavaScript file
load.js – in path: C:/temp/load.js

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db.person.insert({
name:'Satish',
age:25,
skills:['nodejs', 'mongoDB', 'HTML5']
});
 
db.person.insert({
name:'Kiran',
age:27,
skills:['PHP', 'mySQL', 'HTML5']
});
 
db.person.insert({
name:'Sunitha',
age:24,
skills:['html', 'ASP']
});

Here we’re inserting some data/record/documents into the collection person.

Database’s Before running the script

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C:\>cd mongodb
 
C:\mongodb>cd bin
 
C:\mongodb\bin>mongo
MongoDB shell version: 2.4.3
connecting to: test
> show dbs
admin   0.203125GB
company 0.203125GB
local   0.078125GB
> exit
bye

Before running the script, we have only 3 databases.

Running the script

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C:\mongodb\bin>mongo 127.0.0.1/satish C:/temp/load.js
MongoDB shell version: 2.4.3
connecting to: 127.0.0.1/satish

Here, mongo is the JavaScript shall.
127.0.0.1 is nothing but our localhost.
satish is the new database we are creating.
C:/temp/load.js is the path of load.js file.
We’re loading the contents of load.js file into new database satish.

Database’s After running the script

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C:\mongodb\bin>mongo
MongoDB shell version: 2.4.3
connecting to: test
> show dbs
admin   0.203125GB
company 0.203125GB
local   0.078125GB
satish  0.203125GB
> use satish
switched to db satish
> show collections
person
system.indexes

New database satish has been added and it has person collection, which we loaded from the JavaScript file.

Documents/records In person collection

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> db.person.find().forEach(printjson)
{
        "_id" : ObjectId("518b62443cbad352108c321b"),
        "name" : "Satish",
        "age" : 25,
        "skills" : [
                "nodejs",
                "mongoDB",
                "HTML5"
        ]
}
{
        "_id" : ObjectId("518b62443cbad352108c321c"),
        "name" : "Kiran",
        "age" : 27,
        "skills" : [
                "PHP",
                "mySQL",
                "HTML5"
        ]
}
{
        "_id" : ObjectId("518b62443cbad352108c321d"),
        "name" : "Sunitha",
        "age" : 24,
        "skills" : [
                "html",
                "ASP"
        ]
}

Using find() method we display all its contents.

This way we could load application data from an external JavaScript file.

Writing script for MongoDB shall


[youtube https://www.youtube.com/watch?v=ygK2zE1-k0w]

YouTube Link: https://www.youtube.com/watch?v=ygK2zE1-k0w [Watch the Video In Full Screen.]



Note:
This method will be handy while migrating our application from one mongoDB server to another mongoDB server.
There is import/export options in mongoDB, but this method is also helpful if we have some custom data to be inserted. nontheless a useful tool to have.

SELECT Columns/Fields: MongoDB

In this video tutorial we shall see selecting of key: value in MongoDB.

In RDBMSs like MySQL, we do the same using SELECT statement.
In MongoDB, we use findOne() and find() methods.

key-value-pair-mongoDB

Documents in ‘info’ collection

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> db.info.find().forEach(printjson)
{
        "_id" : ObjectId("517e829d005b19f1f0d96b25"),
        "name" : "Apple",
        "product" : "iPhone5S",
        "emp_no" : "100"
}
{
        "_id" : ObjectId("517e8377005b19f1f0d96b26"),
        "name" : "Technotip",
        "product" : "Video Tutorials - Educational",
        "emp" : [
                "Satish",
                "Kiran"
        ],
        "videos" : {
                "mongo" : "MongoDB Videos",
                "php" : "PHP Video Tutorials"
        }
}

Learn Create and Insert Documents: MongoDB.

Note:
find() returns cursor objects.
findOne() returns single object.

We can use findOne() method to select and retrieve only one record at a time.

findOne() Method

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> db.info.findOne({name: 'Technotip'}).product
Video Tutorials - Educational
 
> db.info.findOne({name: 'Technotip'}).videos
{ "mongo" : "MongoDB Videos", "php" : "PHP Video Tutorials" }
 
> db.info.findOne({name: 'Technotip'}).emp;
[ "Satish", "Kiran" ]

Syntax for retrieving normal {key: value} pair, sub-object {key: value} pair and array {key: value} pair is same.

Limitation
Using findOne() method, we could select and return only 1 {key: value} pair.

To select and return more than 1 {key: value} pair, we can make use of find() method, with 2 parameters.

SELECT Columns or Fields ( { KEY: VALUE } ): MongoDB


[youtube https://www.youtube.com/watch?v=u0WGmvJFFy4]

YouTube Link: https://www.youtube.com/watch?v=u0WGmvJFFy4 [Watch the Video In Full Screen.]



find() Method, with two parameters

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> db.info.find({name: 'Apple'}, {product: 1}).forEach(printjson);
{ "_id" : ObjectId("517e829d005b19f1f0d96b25"), "product" : "iPhone5S" }

First parameter is the condition, second parameter specifies the {key: value} pairs.

We can pass more than 1 key in second parameter; that would returns multiple {key: value} pairs.

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> db.info.find({name: 'Apple'}, {product: 1, emp_no: 1}).forEach(printjson);
{
        "_id" : ObjectId("517e829d005b19f1f0d96b25"),
        "product" : "iPhone5S",
        "emp_no" : "100"
}

1 or true means, those {key: value} pairs need to be returned.
0 or false means, excluding those {key: value} pairs, all other {key: value} pairs(records) needs to be returned.

true(0)

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> db.info.find({name: 'Apple'}, {product: true}).forEach(printjson);
{ "_id" : ObjectId("517e829d005b19f1f0d96b25"), "product" : "iPhone5S" }
> db.info.find({name: 'Apple'}, {product: true, emp_no: true}).forEach(printjson);
{
        "_id" : ObjectId("517e829d005b19f1f0d96b25"),
        "product" : "iPhone5S",
        "emp_no" : "100"
}

False(0): Exclusion

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> db.info.find({name: 'Apple'}, {product: 0, emp_no: 0}).forEach(printjson);
{ "_id" : ObjectId("517e829d005b19f1f0d96b25"), "name" : "Apple" }

Note:
True and False combination doesn’t work

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> db.info.find({name: 'Apple'}, {product: true, emp_no: false}).forEach(printjson);
Wed May 08 12:11:30.184 JavaScript execution failed: error: {
        "$err" : "You cannot currently mix including and excluding fields. 
                  Contact us if this is an issue.",
        "code" : 10053
} at src/mongo/shell/query.js:L128
> db.info.find({name: 'Apple'}, {product: 0, emp_no: 1}).forEach(printjson);
Wed May 08 12:11:40.840 JavaScript execution failed: error: {
        "$err" : "You cannot currently mix including and excluding fields. 
                  Contact us if this is an issue.",
        "code" : 10053
} at src/mongo/shell/query.js:L128

We can not combine true(1) and false(0) together in the second parameter.

Special Provision!
But we can do it with _id(ObjectId)

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> db.info.find({name: 'Apple'}, 
               {product: 1, emp_no: 1, _id: 0}).forEach(printjson);
{ "product" : "iPhone5S", "emp_no" : "100" }

Operation of second document/record in ‘info’ collection.
This illustrates that the syntax for sub-objects, array and the normal key/value pair is same.

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> db.info.find({name: 'Technotip'}, {product: 1}).forEach(printjson);
{
        "_id" : ObjectId("517e8377005b19f1f0d96b26"),
        "product" : "Video Tutorials - Educational"
}
{ "_id" : ObjectId("518363e2d73694e289255486") }
> db.info.find({name: 'Technotip'}, {product: 1, videos: 1}).forEach(printjson);
 
{
        "_id" : ObjectId("517e8377005b19f1f0d96b26"),
        "product" : "Video Tutorials - Educational",
        "videos" : {
                "mongo" : "MongoDB Videos",
                "php" : "PHP Video Tutorials"
        }
}
 
> db.info.find({name: 'Technotip'}, 
               {product: 1, videos: 1, emp: 1}).forEach(printjson);
{
        "_id" : ObjectId("517e8377005b19f1f0d96b26"),
        "product" : "Video Tutorials - Educational",
        "emp" : [
                "Satish",
                "Kiran"
        ],
        "videos" : {
                "mongo" : "MongoDB Videos",
                "php" : "PHP Video Tutorials"
        }
}
 
> db.info.find({name: 'Technotip'}, 
               {product: 1, videos: 1, emp: 1, _id: 0}).forEach(printjson);
{
        "product" : "Video Tutorials - Educational",
        "emp" : [
                "Satish",
                "Kiran"
        ],
        "videos" : {
                "mongo" : "MongoDB Videos",
                "php" : "PHP Video Tutorials"
        }
}

Note:
Two documents with same name

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{
        "_id" : ObjectId("517e8377005b19f1f0d96b26"),
        "name" : "Technotip",
        "product" : "Video Tutorials - Educational",
        "emp" : [
                "Satish",
                "Kiran"
        ],
        "videos" : {
                "mongo" : "MongoDB Videos",
                "php" : "PHP Video Tutorials"
        }
}
{ "_id" : ObjectId("518363e2d73694e289255486"), "name" : "Technotip" }
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> db.info.findOne({name: 'Technotip'})._id;
ObjectId("517e8377005b19f1f0d96b26")

If we use findOne() method on this collection, and the condition being the name key, then the oldest document will be returned.
Only one key: value pair is returned, as findOne() returns only single object.