Category Archives: DEVELOPMENT

Building a Web Application Using EJB, JPA, and JavaServer Faces – Annotations

Any symbol in Java code beginning with @ is known as an annotation.  

The use of annotations allows you to add metadata to your objects. Examples of annotations follow:

Annotation Description
@Entity Identifies the file as an EJB 3.0 entity
@NamedQuery A query that can be used at run time to retrieve data
@Table Specifies the primary table for the entity
@Id Can define which property is the identifier for the entity
@Column Specifies a mapped column for a persistent property or field
@ManyToOne Specifies a type of foreign key relationship between tables
@JoinColumn Specifies the join column and referenced column for a foreign key relationship

Python – Coding with fun

How to reverse a string?

s = 'abcdef'

s = s[::-1]

print s

Explanation: “::” is known as stride notation

s[::2]
s[::-2]

Returns “ace” and “fdb” respectively.

How to read from console in Python?

name = raw_input()

Want to read an integer?

num = raw_input()
num = int(num) # raw_input returns string, so convert it to integer

Swap values in python:

a, b = b, a

My motivation to learn python is: life is short – you need Python

Installing Apache Maven-Java tool

Download maven.

Windows OS:

  1. Unzip the distribution archive, i.e. apache-maven-3.0.4-bin.zip to the directory you wish to install Maven 3.0.4. These instructions assume you chose C:\Program Files\Apache Software Foundation. The subdirectory apache-maven-3.0.4 will be created from the archive.
  2. Add the M2_HOME environment variable. [almost similar as this]: adding the M2_HOME variable in the user variables with the value C:\Program Files\Apache Software Foundation\apache-maven-3.0.4. Be sure to omit any quotation marks around the path even if it contains spaces.
  3. In the same dialog, add the M2 environment variable in the user variables with the value %M2_HOME%\bin.
  4. In the same dialog, update/create the Path environment variable in the user variables and prepend the value %M2% to add Maven available in the command line.
  5. In the same dialog, make sure that JAVA_HOME exists in your user variables or in the system variables and it is set to the location of your JDK, e.g.C:\Program Files\Java\jdk1.5.0_02 and that %JAVA_HOME%\bin is in your Path environment variable.
  6. Open a new command prompt and run mvn –version to verify that it is correctly installed.

Linux based/Ubuntu Operating Systems:

  1. Extract the distribution archive, to the directory you wish to install Maven 3.0.4. These instructions assume you chose /home/username/java/tools/maven.
  2. Open terminal and type:  gedit ~/.bashrc
  3. Set environment variable by adding the following lines at the bottom of .bashrc :
    •  export M2_HOME=/home/username/java/tools/maven
    • export M2=$M2_HOME/bin
    • export PATH=$M2:$PATH
    • export JAVA_HOME=/usr/lib/jvm/jdk-default #if JAVA_HOME not exist.
  4. Run mvn –version to verify that it is correctly installed.

Send and receive SMS using GSM modem or phone on Ubuntu | TechyTalk.info

Send and receive SMS using GSM modem or phone on Ubuntu | TechyTalk.info.

#go to terminal and give the msg as below
#sudo python sms.py 'CellNumber Msg you want to send'
import gammu
import sys
def main():
	words = sys.argv[1].split(None, 1)
	dest = words[0]
	msg = words[1]
	print msg + "-----" + dest
	#return
	sms = gammu.StateMachine()
	sms.ReadConfig()
	sms.Init()
	message = {
	    'Text': msg,
	    'SMSC': {'Location': 1},
	    'Number': destinationNumber,
	}
	print sms.SendSMS(message)

if  __name__ =='__main__':
	main()

How to create non-editable JTable:

Override the method “isCellEditable” and implement as needed, such as:

//instance table model
DefaultTableModel tableModel = new DefaultTableModel(){
   @Override
   public boolean isCellEditable(int row, int column) {
      return false;
   }
};
//...others
table.setModel(tableModel);

System.getProperty(key) key list for java:

 







java.version
Java Runtime Environment version




java.vendor
Java Runtime Environment vendor




java.vendor.url
Java vendor URL




java.home
Java installation directory




java.vm.specification.version
Java Virtual Machine specification version




java.vm.specification.vendor
Java Virtual Machine specification vendor




java.vm.specification.name
Java Virtual Machine specification name




java.vm.version
Java Virtual Machine implementation version




java.vm.vendor
Java Virtual Machine implementation vendor




java.vm.name
Java Virtual Machine implementation name




java.specification.version
Java Runtime Environment specification version




java.specification.vendor
Java Runtime Environment specification vendor




java.specification.name
Java Runtime Environment specification name




java.class.version
Java class format version number




java.class.path
Java class path




java.library.path
List of paths to search when loading libraries




java.io.tmpdir
Default temp file path




java.compiler
Name of JIT compiler to use




java.ext.dirs
Path of extension directory or directories




os.name
Operating system name




os.arch
Operating system architecture




os.version
Operating system version




file.separator
File separator (“/” on UNIX)




path.separator
Path separator (“:” on UNIX)




line.separator
Line separator (“\n” on UNIX)




user.name
User’s account name




user.home
User’s home directory




user.dir
User’s current working directory








 

					

	
	


				
					


	

		
Installing Oracle-JDK in Ubuntu
	


	

		

				
Download JDK from ORacle. Run Terminal:


chmod u+x jdk-6u31-linux-i586.bin
./jdk-6u31-linux-i586.bin
sudo mv jdk1.6.0_31 /usr/lib/jvm/




#Next line will add java to symlink


sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.6.0_31/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.6.0_31/bin/javac" 1



Or, you can set environment variable by adding the following lines at the bottom of .bashrc by “gedit ~/.bashrc”:


export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_03
export PATH=$PATH:$JAVA_HOME/bin



You can now check if the java is installed properly in terminal:


java -version
javac -version



These will return the version of java and javac.

					

	
	


				
					


	

		
Generics are not supported in -source 1.3 error in Maven Project
	


	

		

				
When compiling via maven project, you may have encountered following error:


generics are not supported in -source 1.3 error in Maven Project. use -source 5 or higher to enable generics.


Annotation is not allowed in -source 1.3 use -source 5 or higher to enable annotation.


To solve this you must add the below lines at your pom.xml :


<build>
 <plugins>
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-compiler-plugin</artifactId>
   <configuration>
    <source>1.5</source>
    <target>1.5</target>
   </configuration>
  </plugin>
 </plugins>
</build>


					

	
	


				
					


	

		
C++ : keywords
	


	

		

				
32 keywords defined by standard C.







auto
double
int
struct




break
else
long
switch




case
enum
register
typedef




char
extern
return
union




const
float
short
unsigned




continue
for
signed
void




default
goto
sizeof
volatile




do
if
static
while






A list of some commonly used extended keywords:







asm
 _cs
 _ds
 _es




_ss
 cdecl
 far
 huge




interrupt
 near
 pascal
 






All C (and C++) keywords are lowercase. Also, uppercase and lowercase are

different: else is a keyword; ELSE is not.