[semaj]

How to copy .VDI image

semaj — Thu, 22 Jul 2010 02:37:58 +0000

The following steps show you how to make a copy of virtual box hard disk:

Shut down the virtual machine you would like to copy.
From File -> Virtual Media Manager…, select the virtual machine you would like to copy and click “Release” from the Action toolbar.
It will ask you to confirm release. Click “Release” to release it.
In your command prompt, run the following command to set the new UUID for the newly created hard disk.C:\Users\Public\VirtualBox>”C:\Program Files\Oracle\VirtualBox\VBoxManage.exe” internalcommands sethduuid “Windows XP Professional – Clean.vdi”
Click the below image to see the screenshot:
In the File -> Virtual Media Manager…, add the new image you have created in step 4.
Press the New button to create a new virtual machine and link to the one created in step 4.

Concurrent Remote Users in Windows 7 Professional 64 bit

semaj — Wed, 21 Jul 2010 04:42:37 +0000

Download appropriate files from http://www.missingremote.com/images/stories/Win7RDP/Win7RDP.zip
Extract the files from the zip folder.
Back up your termsrv.dll under C:\Windows\System32.
Right click install.cmd and select “Run as Administrator” from the extracted folder.
Boom.. login to your computer locally using one user and remote desktop to same computer using another user.

Acknowledgement:
http://www.missingremote.com/index.php?option=com_content&task=view&id=3692&Itemid=232

The J2EE 1.4 Tutorial from Sun

semaj — Thu, 12 Oct 2006 17:51:45 +0000

Sun has a valuable J2EE 1.4 tutorial. This is really good for newbies who want to study J2EE Architecture. Click here to view the tutorial.

Enterprise JavaBeans

semaj — Sat, 07 Oct 2006 07:18:05 +0000

Difference between JavaBeans and Enterprise JavaBeans
* JavaBeans are components built in Java that can be used on any tier in an application. They often thought of in relationship to servlets, and as GUI components.
* Enterprise JavaBeans are specials, server-side components used for building the business logic and data access functionality of an application.

Why use EJBs?
Even though EJBs are difficult to understand for novice, it is a powerful technology. It is scalable and flexible. The EJBs share the following tasks:
* Client Communication
* Session State Management
* Transaction Management
* Database Connection Management
* User Authentication and Role-based Authorization
* Asynchronous Messaging
* Application Server Administration

Types of EJBs
1. Session Bean (Stateless and Stateful)
2. Entity Bean
3. Message-Driven Bean

Native JDBC Java Programming Steps

semaj — Sat, 07 Oct 2006 07:08:38 +0000

Class.forName(“com.mysql.jdbc.Driver”);
Connection con = DriverManager.getConnection( “jdbc:mysql://localhost/nepatalk”, “root”, “password”);
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(“SELECT …sql query”);
if (rs.next())
System.out.println(“ok”);
st.close();
con.close();

Singleton in Java

semaj — Sat, 07 Oct 2006 05:43:40 +0000

A singleton is a class that can be instantiated once and only once. But, why do you need them? If you are creating a class for a set up configuration and use the old fashioned class constrution, you may end up creating numerous configuration objects while you need only one copy. This singleton design pattern comes handy in this situation. You should also use Singleton when creating RMI lookup and creating JDBC connection.

How to create Singleton object?
1. Block off accessing to all constructors by making access modifier of default construtor as private.
2. Provide static method for getting an instance of the singleton.
3. Prevent cloning (usually developers forget to do; as every object inherits clone() method)

Implementation:
public class SingletonObject {

private static SingletonObject ref;

private SingletonObject() {
}

  public static SingletonObject getSingletonObject() {
    if (ref == null)
      ref = new SingletonObject();
    return ref;
  }

  public Object clone() throws CloneNotSupportedException {
    throw new CloneNotSupportedException();
  }

}

Reference: http://www.javacoffeebreak.com/articles/designpatterns/index.html