import java.util.Random;

public class HeapSort {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		int[] input = new int[10];

		Random generator = new Random();
		for (int i = 0; i < input.length; i++) {
			input[i] = generator.nextInt(50);
		}

		System.out.println("Initial unsorted array");

		printArray(input);

		heapify(input);

		heapsort(input);

		System.out.println("");
		System.out.println("Sorted Array after the heap sort");

		printArray(input);

	}

	public static void heapify(int[] inputArray)
	{

		for(int i=1;i		{
			shiftUp(inputArray,i,((i+1)/2)-1);

		}
		System.out.println("");
		System.out.println("AFter first heapification");

		printArray(inputArray);
	}

	/**
	 * heap sort method which calls the swap function to adjust the aray after each swap of first
	 * and last element
	 * @param input
	 */
	public static void heapsort(int[] input)
	{

		for(int i=0;i end)
		{
			return;
		}

		else if((2*start)+1 == end)
		{

			if(input[start]			{
				int k = input[start];
				input[start]=input[(2*start)+1];
				input[(2*start)+1]=k;

			//	System.out.println("swappingmid: elemnt "+start +" end :"+end +"element: "+input[start]+" and "+input[(2*start)+1]);
				swapOn(input,(2*start)+1,end);
			}
			return;
		}

		else
		{
			if(input[start]			{
				if(input[(2*start)+1]=0 && parent >=0 &&array[child]>array[parent])
		{
			int k = array[child];
			array[child]=array[parent];
			array[parent]=k;
			int x=((parent+1)/2)-1;
			shiftUp(array, parent, x);
		}
		else
		{
			return;
		}

	}

	/**
	 * prints the array
	 * @param input
	 */

	public static void printArray(int[] input)
	{
		for(int i=0;i		{
			System.out.print(input[i]+",");
		}
	}

}

I have tested it few times , but yes if you find it not working well just let me know , may be I would fix it again.
Thanks
Gaurav

I looked into the workbench , into the import export options , found sql dump commands, to store into the csv u have to go and do it for every table or may be write a sql script which does that.What I was looking for was a single click to store the database dump in csv file.

Being a java programmer, I always tend to go for java coding rather than writing any sql script(it takes me far less time doing things in java than doing it in sql).So, the first step was google out some pre existing java class which does this kind of job.Was not convinced with what I got so decided to go with my own program.I use hibernate for interaction with database, but hql for my queries were not very clear to me so I had to write the platform specific(mysql in my case),learnt a bit of jdbc also. You may need to update those according to your database.So here is the working code, I have tried to comment logically so that it can be easily interpreted on reading.

package com.xbrl.dao;

import java.io.FileWriter;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

import jxl.write.Label;

import com.utility.HibernateUtil;

public class DB2CSV {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		 
		  //usual database connection part
		  Connection con = null;
		  String url = "jdbc:mysql://localhost:3306/";
		  String db = "db_name";
		  String driver = "com.mysql.jdbc.Driver";
		  String user = "username";
		  String pass = "password";
		  FileWriter fw ;
		  try{
		  Class.forName(driver);
		  con = DriverManager.getConnection(url+db, user, pass);
		  Statement st = con.createStatement();
		  
		  //this query gets all the tables in your database(put your db name in the query)
		  ResultSet res = st.executeQuery("SELECT table_name FROM INFORMATION_SCHEMA.TABLES WHERE table_schema = 'db_name' ");
		  
		  //Preparing List of table Names
		  List <String> tableNameList = new ArrayList<String>();
		  while(res.next())
		  {
			  tableNameList.add(res.getString(1));
		  }
		  
		  //path to the folder where you will save your csv files
		  String filename = "D:/db2csv/";
		  
		  //star iterating on each table to fetch its data and save in a .csv file
		  for(String tableName:tableNameList)
			{
				int k=0;
				
				int j=1;
				
				System.out.println(tableName);
				
				List<String> columnsNameList  = new ArrayList<String>();
				
				//select all data from table
				res = st.executeQuery("select * from xcms."+tableName);
				
				//colunm count is necessay as the tables are dynamic and we need to figure out the numbers of columns
				int colunmCount = getColumnCount(res);
				
				 try {
					fw = new FileWriter(filename+""+tableName+".csv");
					
					
					//this loop is used to add column names at the top of file , if you do not need it just comment this loop
					for(int i=1 ; i<= colunmCount ;i++)
					{
						fw.append(res.getMetaData().getColumnName(i));
						fw.append(",");
			
					}
					
					fw.append(System.getProperty("line.separator"));
					
					while(res.next())
					{
						for(int i=1;i<=colunmCount;i++)
						{
							
							//you can update it here by using the column type but i am fine with the data so just converting 
							//everything to string first and then saving
							if(res.getObject(i)!=null)
							{
							String data= res.getObject(i).toString();
							fw.append(data) ;
							fw.append(",");
							}
							else
							{
								String data= "null";
								fw.append(data) ;
								fw.append(",");
							}
							
						}
						//new line entered after each row
						fw.append(System.getProperty("line.separator"));
					}
					
					 fw.flush();
					  fw.close();
					
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
			}
				
		  con.close();
		  }
		  catch (ClassNotFoundException e){
		  System.err.println("Could not load JDBC driver");
		  e.printStackTrace();
		  }
		  catch(SQLException ex){
		  System.err.println("SQLException information");
		  }
 }
	
	//to get numbers of rows in a result set 
	public static int  getRowCount(ResultSet res) throws SQLException
	{
		  res.last();
		  int numberOfRows = res.getRow();
		  res.beforeFirst();
		  return numberOfRows;
	}

	//to get no of columns in result set
	
	public static int  getColumnCount(ResultSet res) throws SQLException
	{
		return res.getMetaData().getColumnCount();
	}
	

}

Hope this helps you!!

Thanks
Gaurav

Few days back I got the requirement to introduce captcha on my web registration page in my J2EE app. To be very frank I felt actually delighted to do this, as for a long time I was thinking  try my hands on captcha implementation.Two years back I  tried this but at that time I only got to know JCAPTCHA but it’s documentation was not thorough ,recaptcha was somewhat specific for php , so I  did not proceed at that time.

Now this time I started the search again and what I got to know was there is something called  SimpleCaptcha(http://simplecaptcha.sourceforge.net/) which I found to be sufficient and good enough. The advantage with simple Captcha was that implementation was damn easy,it was in java , it was totally on your server side which means that there is no need to connect to any third party on internet for captcha verification.  But I was not very sure about the strength of the algorithm which produces images and it required  httpsession which was creating some problem for me. Otherwise I found it to be good .

So I decided to go with reCaptcha (http://www.google.com/recaptcha/captcha)as I found its documentation to be very useful and implementation was also very straight forward. And I liked the recaptcha concept as well.The recaptcha comes with plugin for various languages like php, java etc.

So first thing one should do , if you wish to use recaptcha in your application, is to register your website name on http://www.google.com/recaptcha(max it will take 5 mins).  You would get a private key and a public key. Store it safely somewhere , we have to use it later.You can use this key for development on dev environment i.e localhost urls as well.

Now for the UI component I had to go from a static HTML page to a action class. So I was a bit worried about  how words in recaptcha divs would come for static HTML page.  But there is a solution to this. This thing can be done through Ajax based script which is very simple as written below:

<script type="text/javascript" src="/js/jquery-1.6.2.min.js">
<script type="text/javascript" src="http://www.google.com/recaptcha/api/js/recaptcha_ajax.js">

<script type="text/javascript">

Recaptcha.create("public key", 'div_name', {
theme: 'white'
});

</script>

Just make a div in your page namely ‘div_name’ , include this script in your page and you will be able to see the recaptcha images in your page. Simple Isn’t it. It will work for your jsps or any web page as well.You can use different themes as well. Don’t forget to use your public key here.You can also call few js functions like Recaptcha.reload() which generates a new image every time  it is called.

The div will be populated with captcha stuff and it will contain two fields namely recaptcha_challenge_field(the image part) and recaptcha_response_field(the user input part).Now fill the captcha user input filed and submit it like any normal form submission(get, post). If you do not want to  use ajax stuff , you can use sricplets in your jsp. You have to import a jar  from (http://code.google.com/p/recaptcha/downloads/list?q=label:java-Latest). This is all about the client side. So now we come to how handle and verify the submitted captcha value on  server side of our code.

To handle server side verification of captcha you have to connect to the recaptcha server through a http post method which you will make in your application and connect pro-grammatically using urls , open urls, making connection and  posting parameters . There is a very easy way to do this, Google gives a link to download jar which contains the  classes to do this stuff , so that we do need to take the pain to write this part.After downloading the jar you can write the code for captcha verification.Import the jars for recaptcha from (http://code.google.com/p/recaptcha/downloads/list?q=label:java-Latest)

The code is very simple and it looks like this

import net.tanesha.recaptcha.ReCaptchaImpl;
import net.tanesha.recaptcha.ReCaptchaResponse;

public static boolean isCaptchaValid(HttpServletRequest request)
{

boolean  valid=true;

String remoteAddr = request.getRemoteAddr();
ReCaptchaImpl reCaptcha = new ReCaptchaImpl();
reCaptcha.setPrivateKey(CaptchaPrivateKey);

String challenge = request.getParameter("recaptcha_challenge_field");
String uresponse = request.getParameter("recaptcha_response_field");
ReCaptchaResponse reCaptchaResponse = reCaptcha.checkAnswer(remoteAddr, challenge, uresponse);

if (reCaptchaResponse.isValid()) {
valid=true;
} else {
valid=false;
}

return valid;

}

You have to use your private key here which we generated earlier, get parameters value for response and challenge from request and then finally use this API call:

ReCaptchaResponse reCaptchaResponse = reCaptcha.checkAnswer(remoteAddr, challenge, uresponse);

When you look inside the source you will see its actually making a http post to http://api-verify.recaptcha.net/verify with your response and challenge words as parameters . So in order to save time I preferred using the provided API. If you want to do it yourself you can go ahead and do it yourself.Now it will return you the reCaptchaResponse object which will tell you whether response was right or wrong. If wrong it will return false and you can check the error message through getErrorMessage(). Do not forget to use correct private key otherwise it will always return false. Now you have got the response for captcha , its  up to your application logic what you want to do next.

Few things which I would say to be cautious of are :

1)You should always reload a new reCaptcha after a successful verification of captcha on captcha server . If you submit the form with same Captcha two times it will return false next time even the response is same as last one. (I was using ajax for form submission that’s why when another field was not validated , I was sent back to the input page  , was trying to submit the form with same Captcha value , you may use ReCaptcha.reload on any error )

2)If you are consistently getting false while verification of captcha , check your private key , the error message returned does not say clearly that key is not correct.

So that’s all about reCaptcha , I guess you will be able to implemement this after reading the blog.If you have any questions you can ask me and infact for Simple Captcha you can ask , I will try to your questions if possible.

Thanks

Gaurav

Now to configure SSL you do not need to do much if you are doing it on linux but on windows you have to do some extra stuff which may be a bit complicated.

First of all we need to prepare a test certificate which the user needs to accept .The certificate contains the web site authenticity and user needs to accept it for SSL handshake.

To prepare the certificate we require a library named openSSL which may come with your apache server distribution or it may not. Unfortunately I had to download the OpenSSL exe separately and then create certificate. Most of the places you will find the source to build it but there are some places where the binary file is kept and its better you download it from there if you are not very much aware of building these binaries from source code.

So let me provide you the link from where I downloaded this opnssl binary http://code.google.com/p/openssl-for-windows/downloads/list

Now copy libaay32.lib and ssleay32.lib in your windows/system32 folder .And there is a openssl conf file which is not here but you can download it by Google it  put it in same folder as openssl.exe

Now we are ready to create the certificate .

Issue this commands from  http://www.apache-ssl.org/#FAQ.

openssl req -config openssl.cnf -new -out my-server.csr
This creates a certificate signing request and a private key. When asked for "Common Name (eg, your websites domain name)", give the exact domain name of your web server (e.g. http://www.my-server.dom). The certificate belongs to this server name and browsers complain if the name doesn’t match.

openssl rsa -in privkey.pem -out my-server.key
This removes the passphrase from the private key. You MUST understand what this means; my-server.key should be only readable by the apache server and the administrator.
You should delete the .rnd file because it contains the entropy information for creating the key and could be used for cryptographic attacks against your private key.

openssl x509 -in my-server.csr -out my-server.cert -req -signkey my-server.key -days 365
This creates a self-signed certificate that you can use until you get a “real” one from a certificate authority. (Which is optional; if you know your users, you can tell them to install the certificate into their browsers.) Note that this certificate expires after one year, you can increase -days 365 if you don’t want this.

Now you have your certificate and the key file ready .

Create an Apache/conf/ssl directory and move my-server.key and my-server.cert into it.

Now include your conf/ssl.cof in httpd.conf

In ssl.conf give the path to the certificate and the key like this, these lines are already there ,you just require to uncomment and give the correct filenames :

SSLCertificateFile conf/extra/server.crt

SSLCertificateKeyFile conf/extra/server.key

Create a virtual host .

Do change for rewrite rules if you want specifics urls on https and if you need whole site to run o SSL you can do it like this

RewriteEngine On

RewriteCond %{SERVER_PORT} !^443$

RewriteRule ^/(.*) https://%{SERVER_NAME}/$1 [L,R]

Just do not forget to load the rewrite module in your conf file.

Basically this is all what we need to make our site run on SSL.

So in the first part we will deal with configuration for Apache+Jboss communication

1. Download and install Apache on your system.
2. Then you have to load the mod_jk module in your system. You need to download and copy mod_jk.so binary into your apache/modules folder. Then uncomment  load module mod_jk.so lines in httpd.conf file in conf folder.
3. Include a mod_jk.conf file in httpd.conf , the contents of mod_jk .conf should look like

# Load mod_jk module
# Specify the filename of the mod_jk lib
LoadModule jk_module modules/mod_jk.so
# Where to find workers.properties
JkWorkersFile conf/workers.properties
# Where to put jk logs
JkLogFile logs/mod_jk.log
# Set the jk log level [debug/error/info]
JkLogLevel info
# Select the log format
JkLogStampFormat “[%a %b %d %H:%M:%S %Y]“
# JkOptions indicates to send SSK KEY SIZE
# Notes:
# 1) Changed from +ForwardURICompat.
# 2) For mod_rewrite compatibility, use +ForwardURIProxy (default since 1.2.24)
# See http://tomcat.apache.org/security-jk.html
JkOptions +ForwardKeySize +ForwardURICompatUnparsed -ForwardDirectories
# JkRequestLogFormat
JkRequestLogFormat “%w %V %T”
# Mount your applications
JkMount /__application__/* node1
# Let Apache serve the images
#JkUnMount /__application__/images/* node1

# You can use external file for mount points.
# It will be checked for updates each 60 seconds.
# The format of the file is: /url=worker
# /examples/*=node1
JkMountFile conf/uriworkermap.properties

# Add shared memory.
# This directive is present with 1.2.10 and
# later versions of mod_jk, and is needed for
# for load balancing to work properly
# Note: Replaced JkShmFile logs/jk.shm due to SELinux issues. Refer to
# https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=225452
JkShmFile run/jk.shm
# Add jkstatus for managing runtime data

JkMount status
Order deny,allow
Deny from all
Allow from 127.0.0.1

Let me explain few key points in the above lines
You should define a workers .properties file in which you have to define the tomcat or jboss instance which will handle the request forwarded from apache .
So we define the port , server and type like this in workers file.
# Define list of workers that will be used
# for mapping requests
# The configuration directives are valid
# for the mod_jk version 1.2.18 and later
#
worker.list=node1,status

# Define Node1
# modify the host as your host IP or DNS name.
worker.node1.port=8009
worker.node1.host=localhost
worker.node1.type=ajp13
worker.node1.lbfactor=1
worker.node1.prepost_timeout=10000 #Not required if using ping_mode=A
worker.node1.connect_timeout=10000 #Not required if using ping_mode=A
worker.node1.ping_mode=A #As of mod_jk 1.2.27
# worker.node1.connection_pool_size=10 (1)

# Load-balancing behaviour
worker.loadbalancer.type=lb
worker.loadbalancer.balance_workers=node1

# Status worker for managing load balancer
worker.status.type=status

then you have to define the applications or the servlet contexts which you are going to access through the nodes which you have defined in worker file. So create a uriworkermap.properties file reference to which you have already given in your mod_jk .conf file.

Mount the Servlet context to the ajp13 worker
/jmx-console=node1
/jmx-console/*=node1
/web-console=node1
/web-console/*=node1
/ APP_Name /*=node1

Now we have to got to your jboss or tomcat instance and enable AJP port. You may comment your localhost:8080 settings if you do not want it to get accessed directly.
I am pasting the jboss snippet here although you may already know .

<Connector protocol=”AJP/1.3″ port=”8009″ address=”${jboss.bind.address}”

redirectPort=”8443″ />

<Engine name=”jboss.web” defaultHost=”localhost”  jvmRoute=”node1″>

That is all what is required to configure Apache+jboss to communicate .
You may hit http://localhost/<APP_Name > to check instead of 8080 port.

I hope you will be able to set up your server  with the configuration I have written above. Now in the next part I will let you know how to set up  SSL for this.

Now the second thing which I needed to do was to send the excel file as an attachment in a mail to the user. My existing code used to support the text mail sending part but now I have to attach the excel file to it. I had generated an array of bytes to dispaly in excel file and now I wanted to use this byte array to be sent as an excel attachment.
When I googled I found solutions majorly related to wiring the file on disk as temp.xls and then reading the file , attaching it and then deleting the temp file which was actually I what I was trying to  avoid as I have never done file handling and some how I am bit scared of file I/O APIs.

Since I was using spring framework , we were using mimeMessageHelper for mails. I looked into the API’s and found out that it also supports attachment with mails and that even without using file I/O  I was able to use my array of bytes.
But there were few problems at first due to InputStreamSource class as I never used it before. Moreover, I did not find a single article on internet which described the whole process with a complete working example. So, I had to hop from one place to another on web to finally get to the solution.

I guess its a very general problem which many people would encounter, so I am giving a sample code which I will explain a bit also.

*******************************************************************************

public void sendBulkAttachMentTextEmail(final Collection<String> to, final String from,
final String subject, final String emailText,final byte[] byteArray)
throws MailServiceException {
MimeMessagePreparator preparator = new MimeMessagePreparator() {
public void prepare(MimeMessage mimeMessage) throws Exception {

MimeMessageHelper message = new MimeMessageHelper(mimeMessage,true);

// Get the array to addresses.
Object[] toAddresses = to.toArray();
int noOfRecipients = toAddresses.length;
String[] addressTo = new String[noOfRecipients];
for (int i = 0; i < noOfRecipients; i++) {
addressTo[i] = (String) toAddresses[i];
}

//Set message To address list.
message.setTo(addressTo);
logger.info(“Recipient : ” + addressTo);
//Set email from address.
message.setFrom(from);
logger.info(“Sender : ” + from);
//Set email subject
message.setSubject(subject);
logger.info(“Subject : ” + subject);

//parse the template and replace the variable values.
freeMarkerConfig.clearTemplateCache();
/*Template mailTemplate = freeMarkerConfig.getTemplate(template);
String text = FreeMarkerTemplateUtils
.processTemplateIntoString(mailTemplate, params);*/

logger.info(“Email Content : “);
//Set the email text.
logger.info(emailText);
message.setText(emailText, true);

ByteArrayResource bar = new ByteArrayResource(byteArray);

message.addAttachment(“Report.xls”,bar,”application/vnd.ms-excel “);

}
};

}

**************************************************************************

You must set the boolean to true in MimemessageHelper constructor. It means that you are defining the mail to be multipart.

Now Spring provides different class implementing InputStreamSource . Since I had the array of bytes I created an instance of ByteArrayResource with the argument in constructor as my byte[]. Lastly you need to define the report name and its type while attaching the ByterArrayResource instance and then you can send the mail.

I guess this information may be useful for people looking for this kind of task and if you have any questions you can put in your comments over here and I would revert back.

Thanks

Gaurav Mutreja

I don’t know any design pattern yet I never faced any problems. Then why should I go through allthese design patterns?Yes , there is nothing that cannot be done without knowing design patterns.The answer to this question can be described as that knowledge of design patterns helps you in developing a design which can be altered at any time , that is not very tightly coupled and is quite flexible.Infact design patterns provide you
a base on which you can think , try out and find solution for your needs. When given a problem , if you just think of a solution then there are good chances that you may come out with a code that fits to your current needs but you may get stuck in future.
So when you try to solve these problem with some patterns in my mind you can see foresee those problems as to what is the thing which may create problem. So , you keep on thinking for the best solution.And its not necessary that you apply some design pattern in the end but you to an extent put a check on risk which may occur in future.

Now we can discuss these design patterns one by one in detail and here I would go with one of the most fundamental  design pattern
“Strategy pattern“

Strategy pattern by definition says:

“Define a family of algorithms, encapsulate each one, and make them interchangeable. [The] Strategy [pattern] lets the algorithm vary independently from clients that use it”.

That’s definition but how do we achieve this. Well to promote client to choose from different implements we need to use HAS A relationship over IS A relationship.
The HAS A relationship promotes loose coupling . Inheritance promotes code re-use but but it also sometimes makes your code very tightly coupled which in turn makes it difficult to change the code.It also makes it possible to make changes without affecting the existing code.

So, the strategy pattern says  that keep the IS A relationnship to only those part of the object which is not going to vary much in future.For those part where code may be varying you must use HAS A relationship so that depending on the varitaion you can inject the suitable implementation.

Let’s take an example .
Suppose I have an abstract class A . It has methods methodNotvaryMuch and methodVaryMuch.As the name suggest first method does not vary much while the second
varies a lot for differnt sub classes.Now I have say 20 subclasses of classes A which are using default implementation of two methods.One day I get a requirement that I need a different implementation for methodVaryMuch for 5 subclasses. So what I have to do is go to each of the five subclasses and override their methodVaryMuch , writing the same code in each class and edit my exisiting code.After few days I got to know have to add one more line to those code changes, again I have to edit those classes.

Now, Think we have that methodVaryMuch behaviour decalred in an interface and my base class has a reference to this object.
So in this case at start there would be one concrete class implementing interface which declares methodVaryMuch and base class has a referenceto it so do the sub classes.
Now for the changes described what we have to do is just create a new concrete class with new methodVaryMuch implementation and all the sub classes for which we need changes we need to change the reference to new interface implemention. It does not require chaning existing code.
This gives greater flexibility in design and is in harmony with the Open/closed principle (OCP) that states classes should be open for extension but closed for modification.

The Strategy pattern embodies two principles , encapsulate the concept that varies and program to an interface, not an implementation. Here in the example we have coded to interface which has enabled us to swap the implemention for change required class with different implemetnation.

So, I guess this is all about strategy pattern , and let me get into the next pattern Observer pattern for my next blog.

Gaurav Mutreja…..