Archive for August 2009

What is IoC Container

August 28, 2009

The business logic layer can be developed without coupling it with any other layers by using IoC provided by the Spring Framework. The IoC container is the core component of the framework. IoC lets the developer implement the business logic as Plain Old Java Objects (POJO) and wire them up so that they can be injected or called at runtime. This approach lets you avoid specifying the business objects as dependencies at compile time.

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What is IoC

August 28, 2009

IoC stands for Inversion-of-Control. IoC is a concept,and an associated set of programming techniques, in which the control flow is inverted compared to the traditional approach. “In other words, the framework calls the procedures created by the programmer, rather than programmer calling the procedures or methods of the framework. IoC is based on the “Hollywood Principle.” The Hollywood Principle says “Don’t call me, I will call you.”

IoC is used to ‘inject’ dependencies at runtime. When one uses this pattern, the dependencies of a particular object are not satisfied at compile time. Instead, the framework provides the required dependencies to the object at runtime. Thus, this pattern releases the programmer from the chore of providing all the dependencies at compile time.

What is AOP

August 28, 2009

AOP stands for “aspect-oriented programming”. AOP is first introduced by Gregor Kickzales in the year 1996. AOP provides the ability to implement crosscutting logic- that is, logic that applies to many parts of your application in a single place and to have that logic applied across your application.

There are two kinds of AOP implementation. Static AOP, such as AspectJ provides a compile time solution for building AOP based logic and adding it to the application.

Dynamic AOP such as Spring, allows crosscutting logic to be applied arbitrary to any other code at runtime. it is basically used by Transaction Management.

What is Spring Framework

August 26, 2009

INTRODUCTION:
Spring is an open source framework created to address the complexity of enterprise application development. one of important advantage of spring framework is its layred architecture, which allows you select component you want while others are ignored. The spring framework is both comprehensive and modular. It is an ideal framework for test driven development.Spring’s main aim is to make J2EE easier to use and promote good programming practice. It does this by enabling a POJO-based programming model that is applicable in a wide range of environments.

HISTORY:
Spring was first released on February 2003, By Rod Johnson. Since January 2003, Spring has been hosted on SourceForge. There are now 20 developers, with the leading contributors devoted full-time to Spring development and support.

ARCHITECTURAL BENEFITS OF SPRING:
Spring can effectively organize your middle tier objects, whether or not you choose to use EJB. Spring takes care of plumbing that would be left up to you if you use only Struts or other frameworks geared to particular J2EE APIs. And while it is perhaps most valuable in the middle tier, Spring’s configuration management services can be used in any architectural layer, in whatever runtime environment. Spring can eliminate the proliferation of Singletons seen on many projects. In my experience, this is a major problem, reducing testability and object orientation. Spring can eliminate the need to use a variety of custom properties file formats, by handling configuration in a consistent way throughout applications and projects. Ever wondered what magic property keys or system properties a particular class looks for, and had to read the Javadoc or even source code? With Spring you simply look at the class’s JavaBean properties or constructor arguments. The use of Inversion of Control and Dependency Injection (discussed below) helps achieve this simplification.
Spring can facilitate good programming practice by reducing the cost of programming to interfaces, rather than classes, almost to zero. Spring is designed so that applications built with it depend on as few of its APIs as possible. Most business objects in Spring applications have no dependency on Spring. Applications built using Spring are very easy to unit test. Spring can make the use of EJB an implementation choice, rather than the determinant of application architecture. You can choose to implement business interfaces as POJOs or local EJBs without affecting calling code. Spring helps you solve many problems without using EJB. Spring can provide an alternative to EJB that’s appropriate for many applications. For example, Spring can use AOP to deliver declarative transaction management without using an EJB container; even without a JTA implementation, if you only need to work with a single database. Spring provides a consistent framework for data access, whether using JDBC or an O/R mapping product such as TopLink, Hibernate or a JDO implementation. Spring provides a consistent, simple programming model in many areas, making it an ideal architectural “glue.” You can see this consistency in the Spring approach to JDBC, JMS, JavaMail, JNDI and many other important APIs.

FEATURES OF SPRING FRAMEWORK:


  • Transaction Management: Spring framework provides a generic abstraction layer for transaction management. This allowing the developer to add the pluggable transaction managers, and making it easy to demarcate transactions without dealing with low-level issues. Spring’s transaction support is not tied to J2EE environments and it can be also used in container less environments.

  • JDBC Exception Handling: The JDBC abstraction layer of the Spring offers a meaningful exception hierarchy, which simplifies the error handling strategy.

  • Integration with Hibernate:

  • AOP Framework:

  • MVC Framework: Spring comes with MVC web application framework, built on core Spring functionality. This framework is highly configurable via strategy interfaces, and accommodates multiple view technologies like JSP, Velocity, Tiles, iText, and POI. But other frameworks can be easily used instead of Spring MVC Framework.

SPRING FRAMEWORK ARCHITECTURE:

Efficient use of add(0,object) method of java.util.List

August 22, 2009

If you want an efficient access of add(0,object) method of List interface, where quick and random access of the list is not a primary concern. You must use java.util.LinkedList instead of ArrayList,LinearList and Queue.

You can check the efficiency of LinkedList inplementation by the given example:

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class EfficientList
{

/**
* @author Prabir Karmakar
*/
public static void main(String[] args)
{
List list = new ArrayList();
System.out.println(“Using ArrayList..”);
System.out.println(“Before Manupulation:”
+System.currentTimeMillis());
for(int i=0;i<10000;i++)
{
list.add(0, “prabir”+i);
}
System.out.println(“After Manupulation:”
+System.currentTimeMillis());

List list1 = new LinkedList();
System.out.println(“Using LinkedList..”);
System.out.println(“Before Manupulation:”
+System.currentTimeMillis());
for(int i=0;i<10000;i++)
{
list1.add(0, “raj”+i);
}
System.out.println(“After Manupulation:”
+System.currentTimeMillis());
}
}

Program Output

Using ArrayList..
Before Manupulation:1250946828955 (current time Millis)
After Manupulation:1250946829024 (current time Millis)
Using LinkedList..
Before Manupulation:1250946829024 (current time Millis)
After Manupulation:1250946829034 (current time Millis)

Firebug for Internet Explorer6,7

August 16, 2009

You can debug HTML, CSS with Firebug in Internet Explorer.
Steps
1. You need to download the javascript file firebug.js
2. write the following lines in head section of HTML file:

Complete Example:

What is CDATA

August 10, 2009

CDATA stands for Character Data. CDATA section is a part of the XML document, which is not interpreted by XML processor. The text inside this section is directly passed to the application.

CDATA section is used to escape block of text containing markup characters such as >(greaterthan) , use > and

Syntax:

Printing from Java Program

August 8, 2009
import java.io.ByteArrayInputStream;
import java.io.FileInputStream;
import javax.print.Doc;
import javax.print.DocFlavor;
import javax.print.DocPrintJob;
import javax.print.PrintService;
import javax.print.PrintServiceLookup;
import javax.print.SimpleDoc;
import javax.print.attribute.HashPrintRequestAttributeSet;
import javax.print.attribute.PrintRequestAttributeSet;
public class TestPrinter
{
public static void main(String[] args)
{
DocFlavor flavor = DocFlavor.INPUT_STREAM.AUTOSENSE;
PrintRequestAttributeSet aset = new HashPrintRequestAttributeSet();
PrintService[] pservices = PrintServiceLookup.lookupPrintServices(flavor, aset);
int printnbr = 0;
DocPrintJob pj = pservices[printnbr].createPrintJob();
try
{
FileInputStream fis = new FileInputStream(“C:\\YServer.txt”);
Doc doc = new SimpleDoc(fis, flavor, null);
pj.print(doc, aset);
}
catch (Exception ex)
{
ex.printStackTrace();
}
}
}

Format Date/Time Using System package

August 3, 2009
You can easily format date/Time using System package in java.
public class PrintDateTime
{
public static void main(String [] arg)
{
//printf is not line feed and carriage return, so you have to put a line break.
System.out.printf(“Today is: %1$tm/%1$te/%1$tY”, Calendar.getInstance());
System.out.print(“\n”);
System.out.printf(“Time is: %tr”, Calendar.getInstance());
System.out.print(“\n”);
System.out.printf(“Time is: %tT”, Calendar.getInstance());
}
}
Here
  • t means, you want to deal with date/time.
  • m means, you want month from the date.
  • e means, you want day from the date.
  • Y means, you want Year from the date.
  • r means, you want time as 12-hour clock with AM/PM
  • T means, you want time as 24-hour clock.
Output:
Today is: 08/3/2009
Time is: 09:55:45 PM
Time is: 21:55:45

Formating String using String Class

August 3, 2009
public class FormatString
{
public static void main(String [] arg)
{
Object ob[] = {“prabir”,27};
st = String.format(“My name is %s, I am %d years old”, ob);
System.out.println(st);
st = String.format(“The value of PI is:%f”, Math.PI);
System.out.println(st);
//specify no. of decemals
st = String.format(“The value of PI is:%.2f”, Math.PI);
System.out.println(st);
}
}
Here
  • s expecting string value.
  • d expecting numeric value without decimal.
  • f expecting float value.
  • .2 specify no of decimal places.
Output:
The value of PI is: 3.141593
The value of PI is: 3.14