Techno-Card

Eclipse/STS IDE shortcuts

2013-12-02T08:56:00.000+05:30

Hi Friends,

After a long gap i.e. near about a year, today I want to blog some of the useful shortcuts that will help us in coding any program using IDEs such as Eclipse and STS (Spring Source Tool Suite).

Its suggested that any java beginner programmer to use notepad/notepad++ as editor to start their coding. However IDEs like Eclipse and STS will increase speed of programming as they are built with lot of shortcuts. Today we are going to discuss some of the very useful shortcuts those will increase our speed of programming.

As STS is built up on Eclipse IDE, most of shortcuts that I explain in this blog are common for both editors.

File Navigation

CTRL + SHIFT + R - To open a resource (any file like .java, .jsp etc) in the projects present in current workspace of IDE.

CTRL + PAGE UP or PAGE DOWN - Nagivate to previous or next file from within the list of all open files.

CTRL + E - To display all open file list.

ALT LEFT ARROW (<-- alt="" arrow="" or="" right="">) - Navigate to previous or next edit positions from edit history.

Editing shortcuts

CTRL + SPACE - Type assist (For ex: if you type Str and then presse ctrl + space in some x.java file then it will show all available options like java.lang.String class etc. to complete your choice without typing full word)

CTRL + SHIFT + F - Will format the code according to the preferences set in IDE. You can change format preference by navigating to 'preferences' section of IDE.

CTRL + O - Will show list of methods (including inherited) of class (For ex: In X.java you have methods names x(), y(), z() and you pressed ctrl + o in that file then it will show all three methods)

CTRL + SHIFT + O - Will organize your class imports section. It will automatically remove/add any unused/required imports to fix import compile errors.

CTRL + SHIFT + C - Will comment selected lines (like // before starting of each line).

CTRL + SHIFT + / - Will comment selected lines as a block comment (like /* .. */).

CTRL + SHIFT + \ - Will uncomment selected commented block.

When you are free, don't hesitate to try these and post your feedback. Will discuss about some more useful shortcuts in next posts.

Fourteenth session of Some of basic UNIX commands that are useful very frequently

2012-11-27T11:26:00.000+05:30

In todays session, we will discuss about some more useful commands which are used frequently in UNIX/LINUX based Operating Systems.

df displays the amount of disk space available on the file system containing each file name argument. If no file name is given, the space available on all currently mounted file systems is shown. Disk space is shown in 1K blocks by default, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used.

As described in previous post, you can get the value of environment variable POSIXLY_CORRECT by echo command.

df filename.jpg

As depicted, above command will shows disk space available on the file system containing 'filename.jpg'. Below is output:

sanny@sanny-Inspiron-3420:~/Desktop$ df filename.jpg
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda6 171485500 3372236 159402232 3% /

There are some common features available which are used for I/O Redirection.

'<' Input Redirection. This allows one to take input from file rather than standard input (stdin) taken from console.

Ex: tr a x < filename

'>' Output Redirection. This allows one to take output to file rather than standard output (stdout) printed to console.

Ex: ls -a > filename

'|' Pipe This allows one to take one command's output to another commands input.

Ex: ls -a | more

When you are free, dont hesitate to try these and post your feedback. Will discuss about some more useful commands in next posts.

Thirteenth session of Some of basic UNIX commands that are useful very frequently

2012-10-18T12:51:00.000+05:30

Today we will discuss about some more commands that are used very frequently in UNIX/LINUX bases operating systems.

If one want to print value of 'PATH' system variable, then using below command we can achieve it.

echo $PATH$

Above command will displays the value of system variable 'PATH'. Its similar to the below command that we use in windows based operating systems.

echo %PATH%

Below is sample output:

$ echo $PATH$
/usr/local/bin:/usr/bin:/cygdrive/c/Program Files/Common Files/Microsoft Shared/Windows Live:/cygdrive/c/Program Files (x86)/Common Files/Microsoft Shared/Windows Live:/cygdrive/c/Program Files (x86)....

Like wise, if one want to display value of any system variable or user defined system variable like JAVA_HOME, CLASSPATH and CATALINA_HOME etc.., then he/she can achieve it as specified above.

To confirm what you are thinking in your mind to execute the same, below is one more similar example for displaying value of 'JAVA_HOME' ( one can also say that Java installed directory):

echo $JAVA_HOME$

Hmmmmmmmm...... yes, your thought is correct. Its similar to echo %JAVA_HOME% that we use in windows based operating systems to know Java installed directory.

If the variable that you want to know the value is not set in your system, then you will get result as an empty string ''. Below is sample illustration:

$ echo $JAVA_HOME$
$

Please feel free to try this. If you already got a chance to work with, then share your thoughts....

Can guess your next thought??????? to modify corresponding system variable (PATH, JAVA_HOME etc..).. how it can be achievable??? Don't worry, we can discuss about this in next post.. will keep posting...

Twelfth session of Some of basic UNIX commands that are useful very frequently

2012-10-17T00:16:00.000+05:30

Today we will discuss about some more commands that are used very frequently in UNIX/LINUX based systems.

echo is a command used to print any argument that we give. Basically this command is very useful when one want to write shell script(.sh) like batch script(.bat) that we used to write in Windows based systems.

echo argument

Above command will display 'argument' in the terminal. So, while writing shell script and want to debug/log user given argument then, we use this. Its similar to 'System.out.println' that we use in Java to print some thing.

file is a command used to determine type of file by examining its content.

file .bash_profile

Above command will display classification of file named '.bash_profile' present in home directory i.e. /home/ by examining its content. Below is its output:

$ file .bash_profile
.bash_profile: ASCII text

head is a command used to display first few lines of file specified as an argument.

head filename

Above command will display first few lines of a file named 'filename' present in current working directory. Below is output of head command executed on file named 'terimerilyrics':

$ head terimerisonglyrics
Aa......

Teri meri, meri teri prem kahani hai mushqil
Do lafzoon mein yeh bayaan na ho paaye
Ik ladka ik ladki ki yeh kahani hai nayi
Do lafzoon mein yeh bayaan na ho paaye

Teri meri, meri teri prem kahani hai mushqil
Do lafzon mein yeh bayaan na ho paaye
Ik dooje se huey juda Jab ik dooje ke liye bane

As conveyed in previous posts, don't hesitate to try these commands. We will discuss about some more useful commands in next posts.

Eleventh session of Some of basic UNIX commands that are useful very frequently

2012-10-16T01:01:00.000+05:30

Today we will discuss about some more useful commands that are frequently used in UNIX/LINUX based systems.

wc is a command by which one can know about no of lines, words and characters present in a file.

wc filename

Above command will gives number of lines, words and characters present in file named 'filename' present in current working directory. You can know current working directory by using pwd that we discussed in previous posts.

date is a command which displays current date and time.

diff is a command using which you can find differences between two files. It displays differences between two files by comparing each other.

diff filename1 filename2

Above command will show all differences between files named 'filename1 and filename2'present in current working directory.

du is a command by which one can know disk usage i.e. space used by directory and its contents.

Don't hesitate to try these when you are free. If you already got a chance to try these, feel free to give your valuable feedback/comments. We will discuss about some more useful commands in next posts.

Tenth session of Some of basic UNIX commands that are useful very frequently

2012-09-29T15:33:00.001+05:30

Today we will discuss about some more useful commands in UNIX/LINUX based operating systems.

Top is a command used to display and update information like PID, username, cpu, and time etc. about top CPU processes. By default, it displays about top 30 processes and periodically update information about them. Its some what like task manager in WINDOWS based systems where processes tab will dynamically update information about process like how much memory and cpu consumed... Below is sample snapshot of top command in UNIX.

As shown above it displays information and update it periodically of top running processes. If you want to kill any process, then you can simply press 'k' and then corresponding PID of the process. If you want to come back to your terminal, you can simply press 'q' to quit from top command i.e. displaying and updating information about top running processes. You can see the video which explains very clearly usage of this command.

One more important command that we are discussing today is su command which is very useful in executing any commands with respect to another user. It creates a shell(new terminal)with the user id of another user.

su root

Above command will opens a new shell(like new cmd prompt) with 'root' user which is real administrator in UNIX based systems. As UNIX is very secured, for some operations to execute, you need to be real administrator. In such cases this command will be very useful.

This command has many more uses that you can know by using 'man su' as we described in previous posts...

Will discuss about some more useful commands in UNIX/LINUX systems in next posts. Please feel free to post any suggestions/queries.

Ninth session of Some of basic UNIX commands that are useful very frequently

2012-09-26T00:53:00.000+05:30

Today we are going to discuss about one more important command in UNIX/LINUX based operating system that is used to kill processes that are running currently. It is some what like Task Manager in our windows based systems where task manager can be used to view/kill processes that are running currently instead this command is used only to kill processes.

kill -9 1234

Above command will kills process with process ID(PID) '1234'. You can get to know currently running process's PIDs by using 'ps' command that we discussed in our previous post. Below is sample output that a 'ps' command will show:

In above output, IDs that are present under heading 'PID' like '2660, 5796 and 4484'are PIDs similar to '1234' in out above kill example.

In our above example command '-9' that we used to kill process is signal that we are sending to kill process. There are several signals that we can send to kill process are below:

kill 4242

Above command will kill PID 4242 and exit gracefully.

kill -s SIGKILL 1414
kill -s KILL 1414
kill -s 9 1414
kill -SIGKILL 1414
kill -KILL 1414

All above commands are similar equal to above explained first example's -9 SIGKIL (i.e. forcefully kill 1414 process).

Please feel free to post your valuable comments. We will discuss about some more commands in our next posts.

Eighth session of Some of basic UNIX commands that are useful very frequently

2012-09-25T00:24:00.000+05:30

Today we will discuss about some more useful commands in UNIX/LINUX based operating system.

If you want to see quickly what is the content of a file, then you can use below command to see the content of file in the same terminal you are working currently.

cat filename

Above command will display content of file named 'filename' present in current working directory in the terminal.

cat filename > /x/y.txt

Above command will copies content of file named 'filename' present in current working directory into file named 'y.txt' present in path '/x'.

cat filename1 filename2 > /x/y.txt

Above command will concatenate content of files named 'filename1'and 'filename2' present in current working directory into file named 'y.txt' present in path '/x'.

cat filename1 filename2

Above command will concatenate content of files and displays in the terminal. It doesn't modify original files instead it display both files content into terminal by concatenating.

One more important command that we are going to discuss today is 'ps'.

ps

Above command will display current processes which are running. This command is some what like a 'Task Manager' in windows where as the difference is in task manager we can kill process which we don't want to run but, here we can know process IDs by which we can delete the process using 'kill' command that we can discuss in our next post. This command will display lot of information about processes that are currently running.

ps -u

Above command will display current processes that are running in current log-in.

Please feel free to post your comments/queries. We can discuss some more useful UNIX/LINUX commands in our next post.

Seventh session of Some of basic UNIX commands that are useful very frequently

2012-09-18T09:33:00.009+05:30

Today we are going to discuss about one more useful command which will be very important in security aspect i.e. When ever you have file/folder which is very important and you don't want others to read your content then this post is very very helpful in making your content private.

chmod is a command by which you can modify permission of a file/folder according to your wish.

chmod -R 777 /home/x/y.java

Above command will give permissions to read, write and execute for the file 'y.java' present in path '/home/x' so that 'y.java' can be accessed (read, write and execute) by anyone.

In the above command main important part is 3 '7's which decide up to what level one can access corresponding file.

First digit: First '7' is used to give permissions to corresponding user. And one can assign '0-7' We can discuss what is the meaning of each digit from '0-7'.

Second digit: Second '7'is used to give permissions to group to which corresponding user belongs too. And one can assign '0-7' for this digit too.

Third digit: Third '7'is used to give permissions to others. Similar to above 2 digits one can assign '0-7' for this digit too. And you can also refer previous post which contains same explanation.

Regarding assigning '0-7' to each user/group/others please read below table for clear explanation.

#	Permission	rwx
7	full	111
6	read and write	110
5	read and execute	101
4	read only	100
3	write and execute	011
2	write only	010
1	execute only	001
0	none	000

So, as per above table if you don't want to give neither of read,write and execute permission to user, group and others then you can use '000' to assign permissions to corresponding file.

chmod -R 700 /home/x/y.java

Yes, as per your guess, above command will give read,write and execute permission to user and gives no permission to group and others. So, that we can restrict 'y.java' file to corresponding user only.

Like this you can use different combinations in the above table to give/restrict permissions to corresponding user, group and others.

One more important point to remember to use this command is, file to which you are going to modify permissions should be closed and you should be owner of the file. You can also get more information about this command by hitting 'man chmod' in the terminal.

Please feel free to post any help/suggestion. Will discuss some more in next posts.....

Sixth session of Some of basic UNIX commands that are useful very frequently

2012-09-17T21:33:00.000+05:30

Today we will discuss about some more useful commands that are used very frequently when you work with UNIX/LINUX based Operating Systems.

mkdir is a command which created new directory in your file system.

mkdir NewDirectory

Above command will create new folder named 'NewDirectory' in present working directory. You can fetch your present working directory by hitting 'pwd' in your terminal. For suppose you are in directory '/home/x/y' then new directory named 'NewDirectory' will be created in ' /home/x/y'.

mkdir /x/y/z NewDirecotory

Above command will create new folder named 'NewDirecotry' in the path '/x/y/z'.

Similarly you can remove a folder and its contents by using command rmdir.

rmdir NewDirectory

Above command will deletes/removes a folder named 'NewDirectory' from current working directory. If that directory contains any sub folders/files then will confirm from user before deleting each file/folder with 'Y/N ?'. So, you can remove/delete each file/folder by pressing 'y'.

rmdir -f NewDirectory

Above command will deletes/removes 'NewDirectory' and its contents without asking confirmation to delete.

rmdir -f /home/x/y/*

Above command will deletes/removes content (files/sub folders) in the path '/home/x/y' without asking confirmation to delete. Like '*', we can use patterns to delete files. Below is small example:

rmdir -f /home/x/y/a*.java

Above command will deletes/removes files whose names starts with 'a' and extension '.java' in the path '/home/x/y/'.

Don't hesitate to try these when you are free.. If you already had a chance to try these, then don't hesitate to write your valuable comments. Will discuss some more in next post....

Fifth session of Some of basic UNIX commands that are useful very frequently

2012-09-11T10:20:00.001+05:30

Today we will discuss about some more useful commands that are used frequently when you use UNIX/LINUX based system.

Whenever you are running your application in UNIX/LINUX based server, then you may get to view log files for debugging purpose. In that case below command will be useful.

more filename

Above command will display content in the file named 'filename' that fits according to screen. If you want next content in that file to display, then you can simply press 'space' to scroll file content. If you want to quit to view the file then you can simply press 'q' to quit that view. In the displayed content of file if you want to search for some string, then you can use '/pattern' for searching that string.

For example, above file name displayed below content:

Hi My Name is John.

And in that if you want to search for 'John' then you can simply press '/John' and enter will highlight the word 'John'. If there are more 'John's in the displayed content then all will be highlighted. You can traverse one by one.

There is one more way to view file content but not whole content instead just last few lines in that file, then you can use below command.

tail -f filename

Above command will display last few lines of file according to screen fit. If that file is getting modified then it will display accordingly.

For example you are viewing 'catalina.log' file in the tomcat server, then it will be modified frequently based up on the hits to your application. In that case this command will display last few lines accordingly.

If you want to rename one file to another, then you can use below command.

mv filename1 filename2

Above command renames 'filename1' to 'filename2' . I.e. moves content from 'filename1' to 'filename2'. If you want to move 'filename1' to different directory then also you can use same command but in different manner.

mv filename1 dir2

Above command will move 'filename1'from current directory to 'dir2'. If your file is not present in current directory, then you need to give 'filename1'with full path.

As specified in my previous post, you can get more uses of this command by hitting 'man mv' in your terminal.

Like 'mv' command that we use for renaming or moving files, there is one more command that you may used very frequently in windows if you are get familiar with command prompt. i.e. copy command. Below is its usage:

cp filename1 filename2

Above command will copy 'filename1'into 'filename2'. As specified above with 'mv' command, you can use all similar patterns with this command.

To delete a file you can use below command.

rm filename

Above command will removes file named 'filename' from the system. You can use option ' -i ' for asking confirmation to delete.

For all these three commands, you can use patterns for handling set of files. Below is one small example.

mv /dir1/* /dir2

Above command will moves all files present in '/dir1' to '/dir2'. Here '*' is one patten that we discussed in our previous post.

Will discuss some more useful commands in next post...

Fourth session of Some of basic UNIX commands that are useful very frequently

2012-09-10T12:38:00.000+05:30

Today we are going to have some useful information on very useful command 'find' in UNIX systems. find is a command used to search any set of directories that you specified for searching files that matched your search criteria. It is useful to locate the path of files on a UNIX/LINUX system. Below is sample syntax:

find where-to-look criteria

find . -name "*.java"

Above command will display all the files that have file name extension as '.java'in the current directory.

find . -mtime 1

Above command will display all the files that are modified exactly one day in the current directory.

find .. -mtime -1

Above command will display all the files that are modified less than one day in the parent directory i.e. suppose if you are in directory '/x/y' then above command will display all files that are modified less than one day in 'x' directory. It will also include 'y' directory in searching.

find . -perm 444 'perm'

sub-option is used to search files based up on permissions. I.e. Above command will display all the files that have permission to read for owner,group and others in the current directory. Here in '444', first '4'indicates read permission to current user. Second '4'indicates read permission to current group that current user belongs to. Third '4'indicates read permission to other users that are in current system.

find . -iname "string"

If you want to search with case insensitive then you can use option '-i' preceding 'name'. I.e. Above command will display all files that have word 'string' irrespective of case.

As specified in my previous post, you can also get more information about this command by hitting 'man find' in your terminal.

Third session of Some of basic UNIX commands that are useful very frequently

2012-09-09T23:17:00.000+05:30

Hey Folks,

Am back for continuing on posting some more of UNIX commands that are useful whenever you are using any UNIX based operating System.

Grep is a command which is useful for searching any word/name of file/partial name of file in a working directory or any path mentioned. This will display with both case sensitive and case-insensitive results based on the command specified..

grep -i "searchword" FILE

Above command will search for 'searchword' in file named 'FILE' and display matching lines in that file as a result.

We can also use regular expressions to search as per our requirements.

grep "string.*string1" file

Above command will display any line that has 'string' starting with and 'string1'ending with and anything in between... in the file named 'file'.

A regular expression may be followed with one of the following operators.

? The preceding item is matched with at most one time.
* The preceding item is matched with zero or more times.
+ The preceding item is matched with one or more times.
{n,m} The preceding item is matched with minimum 'n' times and maximum 'm' times.

Like this you can use of regular expression for searching your patterns.

In this way 'grep' is useful for searching purpose. There are many more uses of this command that you can know by hitting command 'man grep' in your unix/linux based operating system's terminal(you can call it as cmd prmpt in terms of windows).

shutdown is a command in unix that is useful for letting your system down. You can shutdown your machine immediately or after a specified time..

shutdown -t 2

Above command will shutdown the system securely after 2 seconds.

shutdown -r

Above command will reboot your machine securely..

shutdown -c

Above command will cancel shutdown job that is already running..

As specified above there are many more uses of this command that u can get to know by hitting 'man shutdown' in your terminal..

Will specify some more in next post...

Second session of Some of basic UNIX commands that are useful very frequently

2011-12-23T10:10:00.052+05:30

Hi Folks,

In this i want to share some other UNIX/LINUX command which is useful for us very frequently.

To display list of files,directories that are available in current directly please run below command.

'ls'

If you want to see more options that are available for this command then you can run below command

ls -a - This option is used to display hidden files along with normal files.

ls -l - This option displays full details of all files and folders present in current directory. For example see below sample output of this command.

drwxr-xr-x 2 user group 4096 2011-01-06 12:06 Public
In this output, highlighted part consists total 10 fields which includes of below information:
d - means its a directory.(If it is file then this will be blank).
r - read permission for user,group,others.
w - write permission for user,group,others.
x - execute permission for user,group,others.
So, first 'rwx' means this file has all permissions for user. Next 'r-x' means this file has only read and execute permissions for group. Next 'r-x' means this file has only read and execute permissions for others.

ls -d */ - This option shows only folders present in current directory.

ls -s - This option shows files and folders present in current directory along with their sizes in blocks.

ls -lt - This option shows files in the order of their last modified time.

pwd - This option shows present working directory.

Please try these when you are free. In our next session we can discuss some other commands.

First session of Some of basic UNIX commands that are useful very frequently

2011-12-22T21:00:00.004+05:30

Hi Folks,

In this blog i want to discuss some of basic unix/linux commands that are useful very frequently.

If you want to display total,used and free RAM of your machine in size of MB then run below command.

free -m

If you want to see more options that are available for this command then you can run below command

man free

Some of useful options in free command:

free -t - This option will also displays data containing the totals for physical memory and swap space along with RAM.

free -ms 5 - This option i.e. '-s' followed by an integer will display commands output i.e. total,used and free RAM in MB available in your machine for every 5 seconds.

watch free - Usage of this command is same as above but in an interval of 2 seconds. When you time this command and then press enter then a new screen will be opened and automatically refresh total,used and free available of RAM in KBs. If you press 'CTRL + C' then newly opened screen will be closed and you will be returned to your command ran screen.

watch -n 1 -d free - This is can be taken as advanced version of above command. Here '-d' option is for highlighting the changes in memory usage and '-n' is for interval. For example in this command '1' is followed by '-n' so, for every one second its going to display RAM usage in KB as we didn't mention '-m' option.

Please try these when you are free. In our next session we can discuss some other commands.

Some Of Basic FAQ about Core JAVA

2011-12-03T19:17:00.001+05:30

Hi Friends,

In this blog i want to share some of basic FAQ about Core JAVA that may help you have some basic information.

Can multiple inheritance be achieved in Java. If yes, how?
Answer – Yes, through implementing interfaces as we can implemente multile interfaces in a single class.
What is the basic difference between String and StringBuffer object?
Answer - String is an immutable object. StringBuffer is a mutable object.
What is the base class for Error and Exception?
Answer – Throwable is base class for Exception.
What is a static block?
Answer – this is the block executed before the class initialization.
Can static methods call directly non static methods of the same class?
Answer – No. They cannot directly call. If they need, they will have to create object.
From an overridden method of the sub class, how can you call the overridden base class method ?
Answer – call the method by using 'super' keyword.
Can protected methods be accessed by classes in different package.
Answer – Yes, provided they are subclasses. Otherwise no.
Can a subclass reference hold a superclass object.
Eg: Class A, Class B.
If B extends A. Can we say B b = new A()
Answer – No. Viceversa is true (if A a = new B() is fine).
If a super class method is throwing an IOException, what should the overriding sub class method throw?
Answer – It should either
Throw the same IOException
Throw a sub class of IOException.
Throw nothing
What are the two ways of making a class non-extensible?
Make the class Final
Make the constructor private

Brief uses and advantages of java.util.Arrays

2011-06-04T19:40:00.001+05:30

Hi Folks,

In this post i want to introduce you guys about one common utility class that is very helpful in sorting and searching of values in an array of any type like int,long,String etc. Simply we can state it as java.util.Arrays which is very useful in manipulating arrays such as searching,sorting and viewing all values as a list at a time without any iteration etc.

This class contains various methods to manipulate arrays of any type. For example, you have an array of string values like below

String s[] = {"hi", "ramu", "cris"};

and you want to sort these values then you don't need to write/implement any sorting algorithm instead you can simply use statement

Arrays.sort(s[]);

to sort those values. This java.util.Arrays.sort(Object[] a) method is useful to sort array of objects. Here our s[] is String type of object so we can simply use this method to sort our array.

If you want to print all the values using at a time then also you don'e need to iterate instead you can use

System.out.println(Arrays.asList(s[]);

This method java.util.Arrays.asList(T... a) is used to back the values to a List.

Like these there are many more methods by which you can easily manipulate arrays.

Hibernate With Examples: Hibernate Hello World Program

2011-05-19T17:28:00.001+05:30

In this post i want to give some reference which is intuitive for beginners.

Hibernate With Examples: Hibernate Hello World Program

Brief About InvalidClassException in Java

2010-03-19T00:54:00.004+05:30

Hi Folks,

How are you all? Today i have a got an error below which stop me to work for a couple of hours

Unable to de-serialize job. Blah.... local class incompatible: stream classdesc serialVersionUID = -9148880418277643823, local class serialVersionUID = 2323422343
java.io.InvalidClassException: ClassName local class incompatible: stream classdesc serialVersionUID = -9148880418277643823, local class serialVersionUID = 2323422343

I thought most of the folks facing this error some time and start searching google for solution. Then i also thought i share a light of my work around here.

Generally InvalidClassException comes when your class implements Serializable interface and you didn't mention serialVersionUID field in your class. If your class doen't contain this field when ever your class compiles, compiler generates a unique id like roll no which causes conflicts with old one results exception.

To avoid this problem, solution is very simple. You need to enter below field in your class when it extends Serializable interface.

public static final long serialVersionUID = 34354354435l;

This small filed eliminates problem causing InvalidClassException

When you are programming your java code in Eclipse then you get a warning like "The serializable class FlattenAllWorkingSetsJob does not declare a static final serialVersionUID field
of type long" this. If you try to eliminate that warning that automatically resolves problem of causing InvalidClassException

Important Links For Technical

2008-12-27T11:10:00.004+05:30

You can just know brief explanation about lisp language by the below link:

http://girnartech.blogspot.com/2008/12/lisp-tutorial-1.html

You can just know how to format pen drive in ubuntu using the below link:

http://girnartech.blogspot.com/2008/12/how-format-pen-drive-in-ubuntu.html

You can know how to install ftp server in ubuntu which will be useful for every one to connect to your system and make your system as server using the below link

http://girnartech.blogspot.com/2008/12/installing-ftp-server-in-ubuntu.html

Part2-MVC Layer

2008-11-08T12:56:00.006+05:30

Business Logic:

Business logic mainly describes actual logic of your software going to impliment. It means for example if you want to design a desktop search software using java then for it business logic is as follows:

First you need to manipulate the incoming data from the database ,in that you need to develop some logic .
To make another developer's way to read your logic very easily business logic helps very most.

There is also some other point which describes the business logic perfectly i.e. In sigle tier architecture if you want to write your software of desktop search then all your software code comes in single file which makes another developer difficult to modify your code because everything comes in single file i.e GUI ,Business Logic and retrieving from database etc. When you see multi-tier architecture in which every thing is divided into separa module so,anyone can understand it very clearly and modify it where ever they want.

MVC model for doing software projects

2008-08-05T16:30:00.005+05:30

MVC MODEL

In general any software Industry want to do projects in mvc architecture.But what it actually
is Model View Controller architecture.In this you find three new words,here below i am explaining clearly about those terms.

Model means Buisyness Logic .It includes actual logic in working project. This adds meaning to raw
data.(Ex: calculating whether today is the user's birthday, or the totals, taxes, and shipping charges for shopping cart items).
View means GUI(Graphical User Interface) in your project i.e. what you are giving user to interact with your project.(Ex: yahoo login page in yahoo website,searching text field in google website etc.)These includes JSP(java server pages),HTML pages,etc.
Controller means Action Servelets for controlling your whole project from one part to another part.Using this controller anyone's project will run from initial user interaction to storing details into database(if needs).(Ex: In yahoo site user enters his details ,this controller will take that details and forward to action,from action to form,from form to service,from service to DAO(Data Access Object) etc.) You will clearly know about these highlited terms below.

Buisyness Logic means actual logic in the software or project which you are trying to build i.e. if you want to write login action,in that you need to check the user entered data is valid or not? So,for that you need to write logic,that logic is called as buisyness logic.It acts as an interface between Data Access Layer and Action Class.

Data Access Layer means it is the layer which contains methods to access data from DataBase. It has the direct access to database(i.e. inserting data into database,updating data in the database,retrieving data from database etc.).For this generally we use "Beans" which contain the required feilds,their Getters and Setters. SPRINGS is one of the technologies used to write logic of Data Access Layer.

GUI means graphical user interface which containls the actual LOOK and FEEL of your project.It contains the UI screens with which user can avail the services of your project.For example you want to search for some article in google then you need some interface to enter your idea to be searched that is what ,which attracts people to click Your site after that only. you need is it working perfectly or not? So GUI is very important for any project.There are several technologies to write the logic of GUI.In that some of them are JSP,HTML etc.

Controller is the one which controlls all actions ,works of your project.It manages the whole layers of your project.From the starting i.e. accessing the details entered by user to accessing the database(i.e. inserting ,deleting,updating,retrieving etc.)In contrller Action Servelet is one which intializes the running of your project.

The following diagram gives you some description about this model.