Write a method get sum of two element which closest to Zero

Here is the code in Javascript:

/*
 * Please implement this method to return the sum of the two elements closest to zere. If there are two elements equally close to zero like -2 and 2.
 * consider the positive element to be "closer" to zero than the negative one.
 * 
 *
 */

function sumOfTwoElementsClosestToZero(arr) {
    var length = arr.length;
    var first = arr[0];
    var second = arr[0];

    for (var i = 0; i < length; i++) {
        if (arr[i] == 0) {
            continue;
        }
        if (abs(first) > abs(arr[i]) || (abs(first) == abs(arr[i]) && arr[i] > 0)) {
            first = arr[i];
        }
    }

    for (var i = 0; i < length; i++) {
        if (arr[i] == 0) {
            continue;
        }
        if (abs(arr[i]) > abs(first) && (abs(second) > abs(arr[i]) || abs(second) == abs(arr[i]) && arr[i] > 0)) {
            second = arr[i];
        }
    }

    return (second + first);
}

function abs(num) {
    return num < 0 ? -num : num;
}


console.log("test 1 : " + (sumOfTwoElementsClosestToZero([7, 8, 3, 4, 2, 8, -3, 4, -2, -100]) == 5));
console.log("test 2 : " + (sumOfTwoElementsClosestToZero([7, 8, -3, 4, 2, 8, -3, 4, -2, -100]) == -1));
console.log("test 3 : " + (sumOfTwoElementsClosestToZero([7, 8, 3, 4, -1, 8, -3, 4, -2, -100]) == -3));
console.log("test 4 : " + (sumOfTwoElementsClosestToZero([7, 8, 3, 4, 2, 8, -3, 4, -2, -100]) == 5));
console.log("test 5 : " + (sumOfTwoElementsClosestToZero([-3, -2, -1, 1, 0, 2]) == 3));

How to start using DerbyDB with Netbean?

Why we need to use DerbyDB, fisrt of all , it is shipped a long with Java JDK,

If you first learn Java and want to learn How Java work with Database,

We can use DerbyDB, Because we dont need to install a new DB that reason.

Another reason, I am wonder, how to use all tools shipped by Java JDK,

First Open Netbean,

Check Derby database configuration

Check configuration of JavaDB Choose location of JavaDB installed on your machine, normally the

DerbyDB was shipped along with JDK

 Right click on JavaDB --> Choose create new DB

After create DB success, a new database connection automatically created by Netbean,

Click on connect to

Netbean will automatically startup DerbyDB and Connect to that data.

 Now database is ready for futher more steps.

Serialization and Deserialization JSON in JAVA with GSON

Hello,

Today I will give an example of using GSON to Serialization and Deserialization JSON in JAVA

When we work with JSON, there are some tasks we usually do,

1. Parse Object to JSON and vice versa
2. Parse Collection to JSON and vice versa
3. And sometime we need to create an JSON object with dynamic field, In my example I used Map to do it.We also need to Deserialization and JSON object with dynamic field to Java Object

Here is some code example:

package com.blogspot.ducnguyen.dev.json.example;

import com.google.gson.Gson;
import java.awt.Point;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 *
 * @author ducnguyen
 */
public class Main {

    private static Gson gson = new Gson();

    public static void main(String[] args) {
        System.out.println("Serialization and Deserialization an OBJECT");
        Point p1 = new Point(2, 1);
        String json1 = gson.toJson(p1);
        System.out.println("p1 -> json1 : " + json1);
        Point p2 = gson.fromJson(json1, Point.class);
        System.out.println("json1 -> p2 : " + p2.toString());

        System.out.println("Serialization and Deserialization a LIST");
        List l1 = Arrays.asList(new Point(2, 1), new Point(3, 4));
        String json2 = gson.toJson(l1);
        System.out.println("l1 -> json2 : " + json1);
        List l2 = gson.fromJson(json2, List.class);
        System.out.println("json2 -> l2 : " + l2.toString());

        System.out.println("Create object fields with MAP");
        Map jsonObject = new HashMap<>();
        jsonObject.put("integer", 100);
        jsonObject.put("string", "hello world");
        jsonObject.put("boolean", Boolean.TRUE);
        String json3 = gson.toJson(jsonObject);
        System.out.println("jsonObject -> json3 : " + json3);
        System.out.println("Deserialization MAP");
        Map jsonObject2 = gson.fromJson(json3, Map.class);
        System.out.println("json3 -> jsonObject2 : "+ jsonObject2.toString());

    }

}

Here is output of the code:

Serialization and Deserialization an OBJECT
p1 -> json1 : {"x":2,"y":1}
json1 -> p2 : java.awt.Point[x=2,y=1]
Serialization and Deserialization a LIST
l1 -> json2 : {"x":2,"y":1}
json2 -> l2 : [{x=2.0, y=1.0}, {x=3.0, y=4.0}]
Create object fields with MAP
jsonObject -> json3 : {"integer":100,"string":"hello world","boolean":true}
Deserialization MAP
json3 -> jsonObject2 : {integer=100.0, string=hello world, boolean=true}

You can download source code here

AngularJS - formatter and parser example

When I work with an old project built use AxonIvy ,

I got an issue with date format

In that project, If I want to send a date from Web application using AngularJS to Server Side.

I need to send a date with format

For example:

{
 day: 31,
 month: 12,
 year:2016
}

Also the Server will return the same format for date fields.

For the client side, I use an AngluarJs UI Angular-Strap ,
Which provided very nice widgets.

Unfortunately, bsDate picker only work with common dateformat like ISO , UTC or Timestamp
which look likes:

"2016-10-16T04:06:15.481Z"

or 

1476590721627

In order to make Ivy Date work, I create a new directive :

app.directive('ivyDate', function() {
  return {
    require: 'ngModel',
    priority: 1,
    link: function(scope, elem, attrs, ngModelCtrl) {
      // formats text going to user (from model to view)
      ngModelCtrl.$formatters.push(function(value) {
        var modelValue = scope[attrs['ngModel']];
        return new Date(Date.UTC(modelValue.year, modelValue.month - 1, modelValue.day));
      });

      // formats text from the user (from view to model)
      ngModelCtrl.$parsers.push(function(value) {
        var date = new Date(value);
        return {
          day: date.getUTCDate(),
          year: date.getFullYear(),
          month: date.getMonth() + 1
        };
      });
    }
  };
})

So this directive with get date object from Server and display it as normal date to View

And everytime the View change, it will return a date with Server format to Model

One of the most important thing in my code is priority,

I set priority to 1 to ensure my $formatter function with run before the $formatter of bsDatePicks, After take my time to investigate that my formatter always run after the formatter of bsDatePicker, and bsDatePicker can only work with date in common format.

Here is remainng code:

Controller:

var app = angular.module('mgcrea.ngStrapDocs', ['ngAnimate', 'ngSanitize', 'mgcrea.ngStrap']);
app.controller('MainCtrl', function($scope, $timeout) {
  $scope.simpleDate= new Date();
  $scope.ivyDate= {
    day: 30,
    month: 11,
    year: 2016
  };
  $scope.setDate = function() {
    $scope.ivyDate= {
      day: 30,
      month: 11,
      year: 2015
    };
  }

HTML - View:

 <body ng-controller="MainCtrl">  
  <form name="datepickerForm" class="form-inline" role="form">  
   <div class="form-group" ng-class="{'has-error': datepickerForm.date2.$invalid}">  
    <label class="control-label"><i class="fa fa-calendar"></i> Normal Date <small></small></label>  
    <input type="text" class="form-control" ng-model="simpleDate" data-date-format="yyyy-MM-dd" data-date-type="number" data-min-date="02/10/86" data-autoclose="1" name="date2" bs-datepicker >  
   </div>  
   <hr />  
   <br />  
   <!-- Custom example -->  
   <div class="form-group" ng-class="{'has-error': datepickerForm.date2.$invalid}">  
    <label class="control-label"><i class="fa fa-calendar"></i> Ivy Date <small></small></label>  
    <input type="text" class="form-control" ng-model="ivyDate" data-date-format="yyyy-MM-dd" data-date-type="number" data-min-date="02/10/86" data-autoclose="1" name="date2" ivy-date bs-datepicker >  
   </div>  
   <br />  
   <br />  
   <button class="btn btn-primary" ng-click="setDate($event)"> setDate </button>  
   <textarea cols="14" rows="7">  
   {{ivyDate|json}}  
    </textarea>  
   <hr>  
  </form>  
 </body>  

Here is live demo on Plunker

Java8 - Working with Base64

In JDK8, It is supported Base64 decode/encoding,

Here is an example of using Base64

package my.example.java.base64;

import java.util.Base64;
import org.junit.Assert;
import org.junit.Test;

/**
 *
 * @author nvduc
 */
public class Base64Test {

    public Base64Test() {
    }

    @Test
    public void test() {
        String origin = "Hello World";
        String base64 = new String(Base64.getEncoder().encode(origin.getBytes()));
        String fromBase64 = new String(Base64.getDecoder().decode(base64));
        System.out.println("text Encoded : " + base64);
        System.out.println("text Decoded : " + fromBase64);
        Assert.assertEquals(origin, fromBase64);
    }
}

You can find this example code on Github

CSS - Centering element

Hello,

Here is CSS using for centering element

 <html>  
 <head>  
 <style>  
   /*display table cell*/  
  .container1{  
  width: 200px;  
  height: 200px;  
  border : 1px solid red;  
  display : table-cell;  
  vertical-align: middle;  
  }  
  .content1{  
  border:1px solid blue;  
  }  
  /*CSS3 with transform*/  
  .container2{  
  margin-top:50px;  
  width: 200px;  
  height: 200px;  
  border : 1px solid red;  
  position:relative;  
  }  
  .content2{  
  border:1px solid blue;  
  position: absolute;  
  top: 50%;  
  transform: translate(0, -50%);  
  }  
  /*CSS3 with transform*/  
  .container3{  
  margin-top:50px;  
  width: 200px;  
  height: 200px;  
  border : 1px solid red;  
  display: flex;  
  align-items: center;  
  }  
  .content3{  
  border:1px solid blue;  
  }  
 </style>  
 </head>  
 <body>  
  <h2>  
 Centering vertical with table style:</h2>  
 <div class="container1">  
  <div class="content1">  
   1. This small paragraph is vertically centered.<br />  
  </div>  
 </div>  
 <h2>  
 Centering vertical CSS3 :</h2>  
 <div class="container2">  
  <div class="content2">  
   2. This small paragraph is vertically centered.<br />  
  </div>  
 </div>  
 <h2>  
 Centering vertical using Flex :</h2>  
 <div class="container3">  
  <div class="content3">  
   3. This small paragraph is vertically centered.<br />  
  </div>  
 </div>  
 </body>  
 </html>  

You can find the live demo here Plunker

Java - Create image inside a rectangle

Here is an example put image into a rectangle, with calculation to keep full width of image:

package my.example.image;

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Point;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.nio.file.Paths;

import javax.imageio.ImageIO;

public class ImageInRectange {

    public static void main(String[] args) throws IOException {
        createImageInRectagle(512, 1024, new File("./src/main/resources/chelsea.png"));
    }

    public static File createImageInRectagle(int width, int height, File image) throws IOException {
        Image originImage = ImageIO.read(image);
        int oImgWidth = originImage.getWidth(null);
        int oImgHeight = originImage.getHeight(null);
        float imageRatio = (float) oImgHeight / oImgWidth;
        float rectangleRatio = (float) width / height;

        BufferedImage combined = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        BufferedImage bufferedImage = ImageIO.read(image);
        Graphics g2 = combined.getGraphics();
        Point p = new Point(0, 0);
        if (Math.abs(imageRatio - rectangleRatio) < 0.05) {
            bufferedImage = scale(bufferedImage, width, height);
            p.x = 0;
            p.y = 0;
        } else {
            int minEdge = width < height ? width : height;
            if (oImgHeight > oImgWidth) {
                float diff = (float) oImgHeight / minEdge;
                int newWidth = Math.round(oImgWidth / diff);
                bufferedImage = scale(bufferedImage, newWidth, minEdge);
                if (minEdge == height) {
                    p.x = Math.abs((width - newWidth) / 2);
                    p.y = 0;
                } else {
                    p.x = 0;
                    p.y = Math.abs((height - minEdge) / 2);
                }
            } else {
                float diff = (float) oImgWidth / minEdge;
                int newHeight = Math.round(oImgHeight / diff);
                bufferedImage = scale(bufferedImage, minEdge, newHeight);
                if (minEdge == height) {
                    p.x = Math.abs((width - minEdge) / 2);
                    p.y = 0;
                } else {
                    p.x = 0;
                    p.y = Math.abs((height - newHeight) / 2);
                }
            }
        }
        g2.drawImage(bufferedImage, p.x, p.y, null);
        g2.dispose();
        File tempImage = Paths.get("target", "ok.png").toFile();
        ImageIO.write(combined, "png", tempImage);
        return tempImage;
    }

    public static BufferedImage scale(BufferedImage imgb, int newWidth, int newHeight) {
        Image image;
        image = imgb.getScaledInstance(newWidth, newHeight, Image.SCALE_SMOOTH);
        return toBufferedImage(image);
    }

    public static BufferedImage toBufferedImage(Image img) {
        if (img instanceof BufferedImage) {
            return (BufferedImage) img;
        }
        BufferedImage bimage = new BufferedImage(img.getWidth(null), img.getHeight(null), BufferedImage.TYPE_INT_ARGB);
        Graphics2D bGr = bimage.createGraphics();
        bGr.drawImage(img, 0, 0, null);
        bGr.dispose();
        return bimage;
    }
}

You can find source code on Github

APACHE PDFBOX EXAMPLE WITH MAVEN

Here is an example of create a Maven project using Netbean.

In this example, I used Apache PDFBox as an example of using maven for managing Java library

1. We create a new project using Netbean:

New Maven project with Netbean

Input the artifactId and package name

2. Add code

Declare maven dependenies

    4.0.0
    com.blogspot.ducnguyen.dev
    pdfbox-example
    1.0-SNAPSHOT
    jar
    
        UTF-8
        1.7
        1.7
    
    
        
        
            org.apache.pdfbox
            pdfbox
            2.0.0
        
    

Add Java Code:

package com.blogspot.ducnguyen.dev.pdfbox.example;

import java.io.IOException;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.apache.pdfbox.pdmodel.font.PDType1Font;

/**
 *
 * @author nvduc
 */
public class Main {
    public static void main(String[] args) throws IOException
    {
        long timestamp = System.currentTimeMillis();
        String filename = "test-"+timestamp+".pdf";
        String message = "Hello World at : "+ timestamp;
        
        PDDocument doc = new PDDocument();
        try
        {
            PDPage page = new PDPage();
            doc.addPage(page);
            
            PDFont font = PDType1Font.HELVETICA_BOLD;

            PDPageContentStream contents = new PDPageContentStream(doc, page);
            contents.beginText();
            contents.setFont(font, 12);
            contents.newLineAtOffset(100, 700);
            contents.showText(message);
            contents.endText();
            contents.close();
            
            doc.save(filename);
        }
        finally
        {
            doc.close();
        }
    }
}

3. Running

Before running, we must build project, When we build, maven will get pdfbox library from maven repository

Build project in NetBean

Right click on Main.java file, Choose Run File

We can check the result in Files view

Result after choose Run File

You can check the source code on Github

Chaining multiple promises

Sometimes we need to perform several asynchronous operations, no matter the order, and to be notified when they all done.
$q.all(promisesArr) can help us with that.
Assume we have N methods that return promises: async1(), ..., asyncN().
The following code will log done only when all operations are resolved successfully.

function readOneFileAsDataURL (file, scope) {
    var deferred = $q.defer();
    var reader = getReader(deferred, scope);         
    reader.readAsDataURL(file);
    return deferred.promise;
};
function readManyFileAsDataURL (files, scope){
    var promises=[];
    for(var i = 0 ; i < files.length; i ++){
        promises.push(readOneFileAsDataURL(files[i], scope));
    }
    return $q.all(promises);
};
/*
*Usage 
*/
readManyFileAsDataURL(files, scope).then(function(allImages){
    console.log(allImages.length);
});

Result:

/*
*Some log for more clear
"begin read image : 0"
"begin read image : 1"
"begin read image : 2"
"end read image : 2"
"end read image : 0"
"end read image : 1"
*
/

MONGODB BASIC CONFIGURATION

1. Mongodb without authentication

Mongodb folder structure

 C:\\mongodb\\bin
 C:\\mongodb\\data

Start mongoDB without authentication

C:\mongodb\bin\mongod.exe --dbpath "C:\mongodb\data"

or

C:\mongodb\bin\mongod.exe --dbpath="C:\mongodb\data"

Default port is 27017

2. Enable authentication

First we need to start mongoDB without authentication

C:\mongodb\bin\mongod.exe --dbpath "C:\mongodb\data"

After that run following commands :

1. Run  mongo client with : mongo.exe

2. Use data base with : use admin

3. Add user and role : db.createUser({"user":"root","pwd":"123456","roles":[{"role":"readWriteAnyDatabase","db":"admin"},{"role":"userAdminAnyDatabase","db":"admin"},{"role":"dbAdminAnyDatabase","db":"admin"}]})

The object of root user(for easy to read)

db.createUser({
 "user":"root",
 "pwd":"123456",
 "roles":[
  {
   "role":"readWriteAnyDatabase",
   "db":"admin"
  },
  {
   "role":"userAdminAnyDatabase",
   "db":"admin"
  },
  {
   "role":"dbAdminAnyDatabase",
   "db":"admin"
  }
 ]
});

And start with authentication mode:

 #mongod.exe --dbpath="C:\mongodb\data" --auth

3. Creating window service with configuration file

mongo.cfg placed in c:\mongodb\etc\

systemLog:
   destination: file
   path: c:\\mongodb\\etc\\mongodb.log
   logAppend: true
storage:
   dbPath: c:\\mongodb\\data
   journal: 
      enabled: true
processManagement: 
   windowsService: 
      serviceName: t2i-mongodb-server
      displayName: T2i mongoDb server display name.
      description: The service for MongoDatabase
security: 
   authorization: enabled
net:
   bindIp: 127.0.0.1
   port: 27017

Command to start as service

"C:\mongodb\bin\mongod.exe" --config "C:\mongodb\etc\mongo.cfg" --install

LINUX BASIC COMMON COMMANDS

Filter result:

grep

ex: filter all processes and ports of java

ps -e | grep java
netstat -tunap | grep java

Process and infomation :

Information about process

$ls -l /proc/$PID/exe
OR
$ps -p PID -o comm=
OR
$cat /proc/PID/cmdline

Kill process

sudo kill -9 PID

User and Group:

Login

#su - {user-name}

Login as root

#su -

check username

#whoami

logout

#logout

Extract & Compress file:

Extract

#tar -zxvf {file.tar.gz}
#tar -xf {file.tar.gz} -C /target/directory
#tar -xzf backup.tar.gz -C /target/directory
#unzip file.zip -d destination_folder

Download

#wget http://ftp.gnu.org/gnu/wget/wget-1.5.3.tar.gz  -P /target/directory

Restating the network service:

To restart the network service under RHEL / CentOS based systems, enter:

service network restart

OR

/etc/init.d/network restart

Check linux kernel version number :

Open a shell prompt (or a terminal) and type the following command to see your current Linux kernel version:

uname -r

Or type the following command

uname -mrs

To print all information, enter

uname -a

Type the following command to see Linux version info

cat /proc/version

Find Distribution Version :

Type the following command

cat /etc/*release

OR

lsb_release -a

Port & Firewall :

Port and process command

netstat -tunap

If you want to open a single port

open iptables file

vi /etc/sysconfig/iptables

Add below line to open port.

-A INPUT -m state --state NEW -m tcp -p tcp --dport 143 -j ACCEPT

For multiple, you can use the following instead (or repeat the above line multiple times):

-A INPUT -m state --state NEW -m tcp -p tcp -m multiport --dports 22,80,143 -j ACCEPT

service iptables save

Disable / Turn off Linux Firewall (Red hat/CentOS/Fedora Core)

Type the following two commands (you must login as the root user)

/etc/init.d/iptables save

/etc/init.d/iptables stop

Turn off firewall on boot

chkconfig iptables off

Enable / Turn on Linux Firewall (Red hat/CentOS/Fedora Core)

Type the following command to turn on iptables firewall

/etc/init.d/iptables start 

Turn on firewall on boot

chkconfig iptables on 

Linux / Unix - Checking Free Disk Space:

df command examples - to check free disk space

Type df -h or df -k to list free disk space

df -h

OR

df -k

Find Files and Folders in Linux :

find / -name "java" 

/: meaning is the root folder. hold systems
-name "java": all files have name is java.

NODEJS - RUNNING A NODEJS SERVER AS A SERVICE ON LINUX

1. Download the project for testing:

The user logged in was: root

Download the demo server here

[root@homepc opt]# wget https://github.com/vanduc1102/nodejs-example/archive/daemon-bauth.tar.gz

[root@homepc opt]# tar -zxvf daemon-bauth.tar.gz

[root@homepc opt]# cd nodejs-example-daemon-bauth/

[root@homepc nodejs-example-daemon-bauth]# npm install

[root@hompec nodejs-example-daemon-bauth]# node index.js

You can open browser and test the application at localhost:3000

We had nodejs-example folder placed in /opt/nodejs-example-daemon-bauth

2. Create a service file in systemd:

Create file below in folder : /etc/systemd/system/
nodejs-example-service.service

[Unit]
Description=The nodejs-example server start

[Service]
WorkingDirectory=/opt/nodejs-example-daemon-bauth
ExecStart=/usr/bin/node index.js
Restart=always
StandardOutput=syslog
StandardError=syslog
SyslogIdentifier=nodejs-example-nodejs-server
User=root
Group=root

[Install]
WantedBy=multi-user.target

Load the service at first time:

#systemctl enable nodejs-example-service

Start service:

#systemctl start nodejs-example-service

View status of the service:

#systemctl status nodejs-example-service

Stop the service:

#systemctl stop nodejs-example-service

3. Testing the service:

[root@homepc system]# systemctl start  nodejs-example-service.service
[root@homepc system]# systemctl status  nodejs-example-service.service
nodejs-example-service.service - The nodejs-example server start
          Loaded: loaded (/etc/systemd/system/nodejs-example-service.service; enabled)
          Active: active (running) since jeu 2014-11-06 19:18:02 ICT; 8s ago
        Main PID: 3967 (node)
          CGroup: name=systemd:/system/nodejs-example-service.service
                  └─3967 /usr/bin/node index.js
[root@homepc system]# ps -e | grep "node"
 3967 ?        00:00:00 node
[root@homepc system]# kill 3967
[root@homepc system]# ps -e | grep "node"
 4038 ?        00:00:00 node
[root@homepc system]# systemctl status nodejs-example-service.service
nodejs-example-service.service - The nodejs-example server start
Loaded: loaded (/etc/systemd/system/nodejs-example-service.service; enabled)
          Active: active (running) since jeu 2014-11-06 19:18:02 ICT; 8s ago
        Main PID: 4038 (node)
          CGroup: name=systemd:/system/nodejs-example-service.service
                  └─4038 /usr/bin/node index.js
[root@homepc system]#

As you can see, After we kill the process, It will automatically create new one.

nodejs - secured server with https connections

Previous post

Checkout

Checkout the code at github

If you can use command below for checkout and run the app.

vanduc@VGN-FZ290E:~/test2$ git clone --depth=10 https://github.com/vanduc1102/nodejs-example.git
vanduc@VGN-FZ290E:~/test2$ cd nodejs-example/
vanduc@VGN-FZ290E:~/test2/nodejs-example$ git checkout -f 4-https
vanduc@VGN-FZ290E:~/test2/nodejs-example$ npm install
vanduc@VGN-FZ290E:~/test2/nodejs-example$ node index.js

HTTPS configuration 

For configuration HTTPS connection we need a key and self signed certification to make the SSL work.

Creating key/certificate pair very easy with only one line, if you already installed OpenSSL

openssl req -subj '/CN=localhost/O=mycompany/C=VN' -new -newkey rsa:2048 -days 365 -nodes -x509 -keyout server.key -out server.crt

Code for HTTPS connection:

var options = {
  key: fs.readFileSync('./ssl/server.key'),
  cert: fs.readFileSync('./ssl/server.crt')
};
var server = https.createServer(options,app).listen(serverConfigure.sslPort, function () {
 var address,
        host = serverConfigure.host ? serverConfigure.host : 'localhost',
        port = serverConfigure.sslPort;
    address = host + ':' + port;
    console.log('HTTPS server is listenning on localhost:3443');
});

We will create HTTPS server by add option, the option is about the path of key and certificate,
the server will create with the option for SSL connection , express server by app variable.

HTTPS auto redirection

In order to protect our server (users still can access our server by HTTP connection). We need to redirect the user request to HTTPS connection.

There is some ways to make HTTP auto redirection

1. inside nodejs code.
2. configure firewall to auto forward.

We can simply configure inside nodejs code

function requireHTTPS(req, res, next) {
    if (!req.secure) {
        var addressSSL,
            host = serverConfigure.host ? serverConfigure.host : 'localhost',
            port = serverConfigure.sslPort;
        addressSSL = host + ':' + port;
        return res.redirect('https://' + addressSSL + req.url);
    }
    next();
}
if (serverConfigure.httpsAutoRedirection) {
    app.use(requireHTTPS);
}

If the option httpsAutoRedirection in serverConfigure file is true,  we will check every request to the server and redirect the request to HTTPS port.

NODEJS - Basic Access Authentication

Previous Post

This article is about how to do basic authentication with NodeJS.

Checkout my project on GitHub. For one who never checkout my project before.

vanduc@VGN-FZ290E:~/test2$ git clone --depth=10 https://github.com/vanduc1102/nodejs-example.git
vanduc@VGN-FZ290E:~/test2$ cd nodejs-example/
vanduc@VGN-FZ290E:~/test2/nodejs-example$ git checkout -f 3-basic-auth
vanduc@VGN-FZ290E:~/test2/nodejs-example$ npm install
vanduc@VGN-FZ290E:~/test2/nodejs-example$ node index.js

For one who already checked out my project.

vanduc@VGN-FZ290E:~/test2/nodejs-example$ git pull
vanduc@VGN-FZ290E:~/test2/nodejs-example$ git checkout -f 3-basic-auth
vanduc@VGN-FZ290E:~/test2/nodejs-example$ npm install
vanduc@VGN-FZ290E:~/test2/nodejs-example$ node index.js

You can login with username and password is  admin:123456

The code require authentication on server side:

var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var session = require('express-session');
var app = express();
app.use(bodyParser.json());
app.use(cookieParser());
app.use(session({
 secret: '1234567890QWERTY',
    saveUninitialized: true,
    resave: true}));
var realm = 'localhost';
function unauthorized(res, realm) {
    res.statusCode = 401;
    res.setHeader('WWW-Authenticate', 'Basic realm="' + realm + '"');
    res.setHeader('Content-Type', 'text/html');
    res.end("This request requires HTTP authentication");
}
function checkLogin(username, password, callback){
 if(username =='admin' && password =='123456')
 {
  callback(null,username);
 }
 else
 {
  callback('worng user name',username);
 }
};
app.use(function (req, res, next) {
    var authorization = req.headers.authorization;
    var session = req.session;
    if (req.user) {
        console.log('User already stored in request : ' + req.user);
        return next();
    }

    if (!authorization) {
        return unauthorized(res, realm);
    }
    var parts = authorization.split(' ');
    if (parts.length !== 2) return next(error(400));
    var scheme = parts[0]
        , credentials = new Buffer(parts[1], 'base64').toString()
        , index = credentials.indexOf(':');
    if ('Basic' != scheme || index < 0)
    {
     return next(error(400));
    }
    var user = credentials.slice(0, index)
        , pass = credentials.slice(index + 1);
 if(session.user_id != ''&&session.user_id == user){
        return next();
    }
    //async check authentication
    checkLogin(user, pass, function (err, username) {
        if (err != null) {
            session.destroy();
            req.user = req.remoteUser = null;
            return unauthorized(res, realm);
        }
        req.user = req.remoteUser = user;
        session.user_id = user;
        next();
    })
});

Then we use the tricky code for doing the logout basic authentication:

$(document).ready(function(){
      $('span.logout').on('click',function(e){
           e.preventDefault();
                var xmlHttp;
                if (window.XMLHttpRequest) {
                    xmlHttp = new XMLHttpRequest();
                }
                // code for IE
                else if (window.ActiveXObject) {
                    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
                }
                if (window.ActiveXObject) {
                    // IE clear HTTP Authentication
                    document.execCommand("ClearAuthenticationCache");
                    window.location.reload();
                } else {
                    xmlHttp.open("GET", window.location, true, "logout", "logout");
                    xmlHttp.send("");
                    xmlHttp.onreadystatechange = function () {
                        if (xmlHttp.readyState == 4) {
                            window.location.reload();
                        }
                    }
                }
                return false;
      });
    });

In order to secured your site with basic access authentication, You must provide SSL connection.
Otherwise it is not good solution.
Some disvantages of basic-auth is you cant modify the login pop-up, It depends on the browser provider.
The user credentials will store on browers cache .... :( very bad

Next Post

Restore grub2 after install windows

The problem is after you install linux and then you install a windows 

For example after install Ubuntu 9.10 and then I install Windows operating system along with Ubuntu. The windows will override Master Boot Record on Hard driver , so from now when your computer boot up, you only can see Windows.

To solve the problem:

We need to have a CD version of Ubuntu 9.10. Boot our PC with live mode of Ubuntu 9.10
.Open Terminal ( Applications  > Accessories > Terminal)

(We suppose that the Ubuntu already installed on  partition sda3 of sda)

sudo -i (change user to  root user).

mount /dev/sda3 /mnt

grub-install --root-directory=/mnt/ /dev/sda

mount --bind /proc /mnt/proc

mount --bind /dev /mnt/dev

mount --bind /sys /mnt/sys

chroot /mnt update-grub

umount /mnt/sys

umount /mnt/dev

umount /mnt/proc

exit

Reboot your computer and enjoy !

Setting Global Environment Variables in LINUX

The easiest way to set an environment variable in CentOS is to use export as in :

vanduc@VGN-FZ290E:~/Downloads$export JAVA_HOME=/usr/lib/java/jdk1.7.0_71

vanduc@VGN-FZ290E:~/Downloads$export PATH=$PATH:$JAVA_HOME

However, variables set in such a manner are transient i.e. they will disappear the moment you exit the shell. Obviously this is not helpful when setting environment variables that need to persist even when the system reboots.

In such cases, you need to set the variables within the system wide profile. 

In CentOS (I’m using v5.2), the folder /etc/profile.d/ is the recommended place to add customizations to the system profile.

For example, when installing the Sun JDK, you might need to set the JAVA_HOME and JRE_HOME environment variables. In this case:
Create a new file called java.sh

vanduc@VGN-FZ290E:~/Downloads$ sudo vi /etc/profile.d/java.sh

Within this file, initialize the necessary environment variables

export JAVA_HOME=/usr/lib/java/jdk1.7.0_71

export JRE_HOME=$JAVA_HOME/jre

export PATH=$PATH:$JRE_HOME/bin

export PATH=$PATH:$JAVA_HOME/bin

Now when you restart your machine, the environment variables within java.sh will be automatically initialized (checkout /etc/profile if you are curious how the files in /etc/profile.d/ are loaded) .

If you want to load the environment variables within java.sh without having to restart the machine, you can use the source command as in:

vanduc@VGN-FZ290E:~/Downloads$ source /etc/profile.d/java.sh

Test command:

vanduc@VGN-FZ290E:~/Downloads$ java -version

java version "1.7.0_71"

Java(TM) SE Runtime Environment (build 1.7.0_71-b14)

Java HotSpot(TM) Server VM (build 24.71-b01, mixed mode)

vanduc@VGN-FZ290E:~/Downloads$

P/S : some common commands use to setup java environment

vanduc@VGN-FZ290E:~/Downloads$ cd Downloads/
vanduc@VGN-FZ290E:~/Downloads$ ls
google-chrome-stable_current_i386.deb  jdk-7u71-linux-i586.tar.gz  sublime-text_build-3065_i386.deb
vanduc@VGN-FZ290E:~/Downloads$ tar -zxvf jdk-7u71-linux-i586.tar.gz 
vanduc@VGN-FZ290E:~/Downloads$ sudo mkdir /usr/lib/java
vanduc@VGN-FZ290E:~/Downloads$ mv jdk1.7.0_71/ /usr/lib/java/

NODEJS - CREATE STATIC SERVER WITH EXPRESS MIDDLEWARE

About NodJs

One of the great things about Node.js is that it has a built in HTTP server. This means you don't need Apache or nginx. This means serving a static site can be done in few lines of code. This article goes into how this can be achieved.

Express Static Middleware

Express has become the defacto Node.js web framework and it has great built in capabilities to serve static content. The nice thing is that not only can you serve static content you can also gzip compress it and cache it. But let's just start with the required package.json and a basic static server.

Let's start

1. Set up package.json file

Use command $npm init for creating package.json file

D:\static>npm init
This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sane defaults.

See `npm help json` for definitive documentation on these fields
and exactly what they do.

Use `npm install  --save` afterwards to install a package and
save it as a dependency in the package.json file.

Press ^C at any time to quit.
name: (static) static-server
version: (0.0.0) 0.0.1
description: this is an example how to create static server with nodejs
entry point: (index.js)
test command:
git repository:
keywords:
author: ducnguyen
license: (ISC)
About to write to D:\static\package.json:

{
  "name": "static-server",
  "version": "0.0.1",
  "description": "this is an example how to create static server with nodejs",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "ducnguyen",
  "license": "ISC"
}


Is this ok? (yes) yes

D:\static>

After init we will have the contain of package.json file

{
  "name": "static-server",
  "version": "0.0.1",
  "description": "this is an example how to create static server with nodejs",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "ducnguyen",
  "license": "ISC"
}

2. Install express module

Using command $npm install expess

Add contains for index.js file:

var express = require('express');
var app = express();
var http = require('http');
app.use(express.static(__dirname + '/public'));
var server = http.createServer(app).listen(3000, function () {
 console.log('server is listenning on localhost:3000');
});

The above code is very simple, it creates an Express server, adds the static middleware and finally starts listening on port 3000 .

The static middleware handles serving up the content from a directory. In this case the 'public' directory is served up and any content (HTML, CSS, JavaScript) will be available. This means if the public directory looks like:
index.html
js/boostrap.min.js
css/boostrap.min.css

Then you can request the root route '/' and you'll get index.html file and the index.html also load the css and js file of boostrap. This is all expected from a static server.
Now just start the server by type command in command line promt $node index.js, and go to bowser hit http://localhost:3000/

We can also specify the url of static server:

app.use('/static',express.static(__dirname + '/public'));

Now  instead of type http://localhost:3000/ we will have our static page at http://localhost:3000/static/

Command for checkout :

vanduc@VGN-FZ290E:~/test2$ git clone --depth=10 https://github.com/vanduc1102/nodejs-example.git
vanduc@VGN-FZ290E:~/test2$ cd nodejs-example/
vanduc@VGN-FZ290E:~/test2/nodejs-example$ git checkout -f 1-static
vanduc@VGN-FZ290E:~/test2/nodejs-example$ npm install
vanduc@VGN-FZ290E:~/test2/nodejs-example$ node index.js

1. You will clone my repository at depth=10 means you will get last 10 commits
2. Change your directory working directory nodejs-example
3. Change the checkout to the 1-static, this was the tags with for static version.
4. Installing nodejs module need to run my application.
5. Start the application and enjoy.

Next Post

Common SQL Commands

Delete all except:

DELETE FROM edu_subscription WHERE id NOT IN ( 
   SELECT id FROM edu_subscription  
   WHERE status_value_code = 'YES' 
  UNION
   SELECT id FROM edu_subscription 
   WHERE status_value_code = 'NO' 
)  

Horizontal list Sencha Tounch 2.1.1

Views:

Tile-View

Ext.define('MyApp.view.TileView', {
    extend: 'Ext.dataview.DataView',
    alias: 'widget.mydataview',

    config: {
        baseCls: 'tile-data-view',
        height: '100%',
        id: 'tile-view',
        width: '100%',
        itemCls: 'tile',
        store: 'ThemeStore',
        scrollable: {
            directionLock: true,
            direction: 'horizontal',
            momentumEasing: {
                momentum: {
                    acceleration: 30,
                    friction: 0.5
                },
                bounce: {
                    acceleration: 0.0001,
                    springTension: 0.9999,
                    
                },
                minVelocity: 3
            },
            outOfBoundRestrictFactor: 0
        },
        inline: {
            wrap: false
        },
        itemTpl: [
            '

',
            '    


{name}
',
            '    


{numOfCourses} courses
',
            '
'
        ]
    },

    initialize: function() {
        this.callParent();
        var me = this.container;
        //me.setWidth(2080);
        var el1 = Ext.get('MainContainer');
        var parent = this.getParent();
        //CSBfleXcroll.defer(1, window, [this.body.dom]);
        //var scroller = me.getScrollable();
        //console.info('My parent is : '+parent);
        //console.info('Main container : '+el1.getHeight());
        //console.info('scroller : '+ scroller);
    }

});

My-Panel

Ext.define('MyApp.view.MyPanel', {
    extend: 'Ext.Panel',

    requires: [
        'MyApp.view.TileView'
    ],

    config: {
        layout: {
            type: 'vbox'
        },
        scrollable: false,
        items: [
            {
                xtype: 'titlebar',
                docked: 'top',
                itemId: 'top-bread-crumb',
                items: [
                    {
                        xtype: 'button',
                        itemId: 'increase',
                        text: 'Increase'
                    },
                    {
                        xtype: 'button',
                        itemId: 'decrease',
                        text: 'Decrease'
                    }
                ]
            },
            {
                xtype: 'mydataview',
                itemId: 'tileview1',
                flex: 1
            }
        ],
        listeners: [
            {
                fn: 'onIncreaseTap',
                event: 'tap',
                delegate: '#increase'
            },
            {
                fn: 'onDecreaseTap',
                event: 'tap',
                delegate: '#decrease'
            },
            {
                fn: 'onPanelPainted',
                event: 'painted'
            }
        ]
    },

    onIncreaseTap: function(button, e, eOpts) {
        var tileView = this.down('#tile-view').container;
        var h = tileView.getHeight();
        var w = tileView.getWidth();
        console.log('this get width : '+ this.getWidth());
        console.log('height : '+ h + ' width : '+w);
        tileView.setWidth(w+300);
    },

    onDecreaseTap: function(button, e, eOpts) {
        var tileView = this.down('#tile-view').container;
        var h = tileView.getHeight();
        var w = tileView.getWidth();
        console.log('this get width : '+ this.getWidth());
        console.log('height : '+ h + ' width : '+w);
        tileView.setWidth(w-300);
    },

    onPanelPainted: function(element, eOpts) {
        console.log('on panel painted function');
        this.containerHeight= this.element.getHeight();
        this.containerWidth = this.element.getWidth();
        console.log('h = '+ this.containerHeight +' w = '+ this.containerWidth);
        var breadcrumb = this.down('#top-bread-crumb');
        var h = breadcrumb.element.getHeight();
        var w = breadcrumb.element.getWidth();
        console.log('height = '+h +' widht = '+ w);
        //this.setTileViewSize(h,w);
    },

    initialize: function() {
        this.callParent();
        var container = this.element;
        this.containerHeight=0;
        this.containerWidth=0;
        console.log('container : '+container);
        console.log('container width : '+ container.getWidth() + ' height : '+ container.getHeight());
        var tileView = this.down('#tile-view').container;
        tileView.setWidth(2080);
    }

});

Store:

Ext.define('MyApp.store.ThemeStore', {
    extend: 'Ext.data.Store',

    requires: [
        'MyApp.model.ThemeModel'
    ],

    config: {
        autoLoad: true,
        model: 'MyApp.model.ThemeModel',
        storeId: 'ThemeStore',
        proxy: {
            type: 'ajax',
            url: 'data/test.json',
            reader: {
                type: 'json'
            }
        }
    }
});

Model

Ext.define('MyApp.model.ThemeModel', {
    extend: 'Ext.data.Model',

    config: {
        fields: [
            {
                name: 'code'
            },
            {
                name: 'name'
            },
            {
                name: 'numOfCourses'
            }
        ]
    }
});

Data

[
    {
        "code": "TH10",
        "name": "Computer",
        "numOfCourses": 5
    },
    {
        "code": "TH11",
        "name": "Midwifery",
        "numOfCourses": 3
    },
    {
        "code": "TH12",
        "name": "Professional",
        "numOfCourses": 7
    },
    {
        "code": "TH13",
        "name": "Sport and Exercise Science",
        "numOfCourses": 4
    },
    {
        "code": "TH14",
        "name": "International Business",
        "numOfCourses": 5
    },
    {
        "code": "TH15",
        "name": "Design Engineering",
        "numOfCourses": 6
    },
    {
        "code": "TH16",
        "name": "Work Based Learning Studies",
        "numOfCourses": 4
    },
    {
        "code": "TH17",
        "name": "Business Management",
        "numOfCourses": 18
    },
    {
        "code": "TH18",
        "name": "Biology",
        "numOfCourses": 4
    },
    {
        "code": "TH2",
        "name": "Languages",
        "numOfCourses": 5
    },
    {
        "code": "TH3",
        "name": "Miscellaneous",
        "numOfCourses": 36
    },
    {
        "code": "TH5",
        "name": "Financial",
        "numOfCourses": 1
    },
    {
        "code": "TH6",
        "name": "Psychology",
        "numOfCourses": 7
    },
    {
        "code": "TH7",
        "name": "Healthcare Science",
        "numOfCourses": 5
    },
    {
        "code": "TH8",
        "name": "Criminology",
        "numOfCourses": 6
    },
    {
        "code": "TH9",
        "name": "Other Course",
        "numOfCourses": 6
    }
]

Google Map API in Sencha Touch

View:

Ext.define('MyApp.view.MyPanel', {
    extend: 'Ext.Panel',

    config: {
        layout: {
            type: 'hbox'
        },
        items: [
            {
                xtype: 'list',
                itemId: 'list',
                width: '200px',
                itemTpl: [
                    '

{name}
'
                ],
                store: 'MyJsonStore'
            },
            {
                xtype: 'map',
                flex: 1,
                itemId: 'googleMap',
                width: 300,
                mapOptions: {
                    disableDefaultUI: true,
                    zoom: 17,
                    mapTypeId: google.maps.MapTypeId.ROADMAP
                }
            }
        ],
        listeners: [
            {
                fn: 'onListSelect',
                event: 'select',
                delegate: '#list'
            }
        ]
    },

    onListSelect: function(dataview, record, eOpts) {
        var me = this;
        var googleMap = me.down('#googleMap');
        console.log('name  = '+ record.get('name')+' ; address = '+ record.get('address'));
        if (record){
            var address = record.get('address');
            // Geodecode
            var geocoder = new window.google.maps.Geocoder();
            var map = googleMap;
            geocoder.geocode({ 'address': address }, function (results, status) {
            if (status == window.google.maps.GeocoderStatus.OK) {
                setTimeout(function () {
                    map.getMap().setCenter(new google.maps.LatLng(results[0].geometry.location.lat(), results[0].geometry.location.lng()));
                    var marker = new google.maps.Marker({
                        map: map.getMap(),
                        position: results[0].geometry.location
                    });
                    //map.markersArray.push(marker);
                    var infowindow = new google.maps.InfoWindow({
                        content: address,
                        maxWidth: 120
                    });
                    infowindow.open(map.getMap(), marker);
                }, 500);
            } else {
                console.log('Geocode was not successful for the following reason: ' + status);
            }
        });

    }

    }

});

Store

Ext.define('MyApp.store.UniversityStore', {
    extend: 'Ext.data.Store',

    requires: [
        'MyApp.model.University'
    ],

    config: {
        autoLoad: true,
        autoSync: true,
        model: 'MyApp.model.University',
        storeId: 'MyJsonStore',
        proxy: {
            type: 'ajax',
            url: 'university.json',
            reader: {
                type: 'json'
            }
        }
    }
});

Model:

Ext.define('MyApp.model.University', {
    extend: 'Ext.data.Model',

    config: {
        fields: [
            {
                name: 'name'
            },
            {
                name: 'address'
            }
        ]
    }
});

Data:

[
 {
 "name":"New York University",
 "address":"70 Washington Square S New York, NY 10012"
 }
 ,
 {
 "name":"University of Zurich",
 "address":"Rämistrasse 71 8006 Zürich Switzerland"
 },
 {
 "name":"Yale University",
 "address":"New Haven, CT 06520"
 },
 {
 "name":"Hanoi University of Science and Technology",
 "address":"Số 1 Đại Cồ Việt Bách Khoa, Hai Bà Trưng Hà Nội, Vietnam"
 },
 {
 "name":"Trường Đại Học Bách Khoa Đà Nẵng",
 "address":"54 Nguyễn Lương Bằng Hòa Khánh Bắc, Liên Chiểu Đà Nẵng, Vietnam"
 },
 {
 "name":"Trường Đại học Bách khoa tp Hồ Chí Minh",
 "address":"268 Lý Thường Kiệt phường 14, Quận 10 Hồ Chí Minh, Vietnam"
 }
]

Add listener when click

var me = this;
var googleMap = me.down('#googleMap');
console.log('name  = '+ record.get('name')+' ; address = '+ record.get('address'));
if (record){
    var address = record.get('address');
    // Geodecode
    var geocoder = new window.google.maps.Geocoder();
    var map = googleMap;
    geocoder.geocode({ 'address': address }, function (results, status) {
        if (status == window.google.maps.GeocoderStatus.OK) {
            setTimeout(function () {
                map.getMap().setCenter(new google.maps.LatLng(results[0].geometry.location.lat(), results[0].geometry.location.lng()));
                var marker = new google.maps.Marker({
                    map: map.getMap(),
                    position: results[0].geometry.location
                });
                //map.markersArray.push(marker);
                
                var infowindow = new google.maps.InfoWindow({
                    content: address,
                    maxWidth: 120
                });
                google.maps.event.addListener(marker, 'click', (function(marker) {
                    return function() {                                        
                        infowindow.open(map.getMap(), marker);
                    }
                })(marker));
                
            }, 500);
        } else {
            console.log('Geocode was not successful for the following reason: ' + status);
        }
    });
    
}