Connection pooling means that connections are reused rather 
than created each time a connection is requested. To 
facilitate connection reuse, a memory cache of database 
connections, called a connection pool, is maintained by a 
connection pooling module as a layer on top of any standard 
JDBC driver product.

A custom tag is a user-defined JSP language element. When a 
JSP page containing a custom tag is translated into a 
servlet, the tag is converted to operations on an object 
called a tag handler

ex-bodyless tag 2 tags with body
1<tagName attributeName="value" 
anotherAttributeName="anotherValue"/>

2.<tagName attributeName="value" 
anotherAttributeName="anotherValue">
...tag body...
</tagName>

1.servletconfig is nothing but per one servlet and servlet 
context is nothing but per entier web Application.

Servlet Config: Servlet config is Unique for every Servlet.

Servlet Context: Servlet Context is same for all the Servlet.

Enumaration is an intetrface.It enumarates the elements 
from top to bottom

Java Abstract classes are used to declare common 
characteristics of subclasses. An abstract class cannot be 
instantiated. It can only be used as a superclass for other 
classes that extend the abstract class. Abstract classes 
are declared with the abstract keyword. Abstract classes 
are used to provide a template or design for concrete 
subclasses down the inheritance tree

Abstract class should must used for only implemented the 
body in its Subclass and also implemented the astract 
methods in ts subclasses.

elimination of pointer avoids programsto gain access to 
memory location without proper authorization..

Inheritance:Your are in a situation where you have to the
properties of a whole class repeatedly then you can go for
inheritance.
Note:Final class can't be inherited.

Polymorphism:When you are in a situation where you need to
use a method repeatedly then you can go for polymorphism.
Eg:
  consider this method
    add(int i,int j) and add(String s1,String s2)
the former will add two integers and later will concatenate
two strings but both using the same method name.

You can say so many diff b/w welogic and websphere

In websphere u can add standalone server as a maneged 
server in Domain

Where as in weblogic u can't add WLS server as member to 
the another domain.

In websphere u can add webserver as a unmanaged node where 
as u cannnt do that in weblogic.

process of creating , invoking , destroying the servlet is
known as "life cycle of struts". here three methods are
involved 

1.init() :

Total intialization part of servlet ll be there in this .

2.service() :

Actual Bussiness code ll be there  in this method

3.destroy() :

just destroying the servlet  .

In life cycle of struts there r several part are there 

ActionServlet
Struts-config.xml
RequestProceser
formBean
Action class

There are many steps, 

1. After getting the request from the client, the 
ActionServlet invokes the goGet() or doPost() method, in 
which there is a invokation of process() method.This method 
desides the module.

2. Action servlet dispatches the request to RequestProcesor 
class which does some core works of ActionServlet.Then 
invokes the appropriate Action class.

3. Action class does main business logic and data accessing 
(communicating with Moedl) thru execute() method and which 
returns the ActionForward object.

4. In b/w the form field validations happens in form bean.

5. Depends upon the value of ActionForward object the view 
is decided to display.(output)


4. Form bean is invoked for form field validation,

The request is given to Action Servlet i.e; doGet or 
doPost.
ActionServlet with the help of request uri locates one of 
the RequestProcessor and dispatch the request to 
RequestProcessor i.e; process method on RequestProcessor is 
called InRequestProcessor.

It processes content type.
processes Locale.
processes actionPath.
processes actionMapping.
processes formBean.
processes action.
Error handling.

After processing action(i.e; execute method) depending on 
the results locate the path to view(with the help of 
ActionMapping) and dispatch the request to the located 
path.

When the Framework is loaded, it first loaded the Web.xml 
file. Then from the Servlet tag of Web.xml, it identifies 
the ActionServlet(or the Struts-Cofig.xml). Then from 
welcome-file tag of Struts-Cofig.xml, it identifies the 
first JSP page and runs it. Then when the request comes 
through that jsp, from acion-mappings tag of Struts-
Cofig.xml it identifies the request, through path tag
(request name) and input tag (jsp name), through name tag 
it identifies which bean is needed to access the data and 
through type tag it identifies which Action should be 
invoked. Then through the forward tag it identifies to 
which jsp it has to forward the response.

Sorry in the previous answer I made one mistake, welcome-
file-list is located in web.xml not in Struts-cofig.xml

A class that implements javax.servlet interface is cslled a
sevlet.It alloes is to develop a web application.

servlet is the controller of the mvc pattern it is an java 
class that extends  javax.servlet .through which the user 
should be taken to a new page .

Servlet:
simply say,Servlet is a serverside java code ... it is 
mainly used  to write business logic 
there are two types of servlet


1.Generic Servlet
2.HttpServlet

Servlet is a java program which is running in web server.

A class that implements javax.servlet interface is cslled a
sevlet.It alloes is to develop a web application.

Servlet is server side web application component written in
java which is used to handle client side request.

there are two type of servlet 

1. Generic Servlet : extends javax.servlet. 
2. HttpServlet : extends javax.Servlet.HttpServlet.

servlets r used to design the server side applications that 
work on clint server architecture 

there are two type of servlet 

1. Generic Servlet : extends javax.servlet.*
2. HttpServlet : extends javax.Servlet.HttpServlet.*

we should import these two packages

using the same method for different ways

In object-oriented programming, polymorphism (from the 
Greek meaning "having multiple forms") is the 
characteristic of being able to assign a different meaning 
or usage to something in different contexts - specifically, 
to allow an entity such as a variable, a function, or an 
object to have more than one form.

grouping of data in a class.such methods varibles etc

Encapsulation means binding the data and code into a single 
entity.

In runtime polymorphism ... the code is called at run time 
according to need or given conditions.

suppose there r two methods namely Add() one in super class 
and other is in sub class.both have the same name and same 
parameters.

so we have to choose that which method from them shld 
called at run time i.e. of super class or of sub class.by 
polymorphism we do that.

ex:-

 class A

{

int add(){//code of the method}

//some other code

}

class B extends A

{

int add(){//code of the method}

//some other code

}

class AB

{

public static void main(String s[])

{

A ob1;

ob1=new A();

int i=ob1.add();//will call the method of super class.

ob1=new B();// sub class's reference can be assigned to 
super class address but not vice versa.to do that we have 
to type cast the reference of the sub class in reference of 
the super class.

int j=ob1.add();//will call the method of sub class

}

}

In C++ ; 
if i have 2 clases  
class A {

 int x();
}
class B : public A {

int x(); 
}
void main(){

A* a = new B() ;
a.x(); // it will call the method of  the super class A
// not B  but in java it will call the method in the
// child B  why ?? 

}

In Java Method overriding is the runtime or late binding
polymorphism.

class object is determine which class method is invoked.

ex:

class A {
  protected void display(){  }

}

class B extends A {

protected void display(){  }

}

class MainClass {
  public static void main(String arg[]){

   A objA=null;
   objA=new B();
  objA.display(); // it invoke the Class B's display()

   objA=new A();
  objA.display(); // it invoke the Class A's display()

}

}

Note: the class's object only determine which method to call.

say string s1="1234567";
for(int i=s1.length()-1;i<=0;i--)
{
System.out.Println(CharAt[i].toString());
}

public static void main (String args[])
    {	   	String s1="1234567";
  	
    	for(int i=s1.length()-1;i>=0;i--)
    	{
    	System.out.print(s1.charAt(i));
    	}
    }

public class reverse {
     public static void main(String args[]){
    	 
    	 String s="malayalam";
    	 StringBuffer sb=new StringBuffer();
    	 int k=s.length();
    	 for (int i = k-1; i >-1; i--) {
    		 sb.append(s.charAt(i));
    
		}
    	 System.out.println(sb);
         }

}

public class StringReverseExample {
	
	    public static void main(String[] args)
	    {
	    String string=args[0];
	    String reverse = new StringBuffer
(string).reverse().toString();
	    System.out.println("\nString before 
reverse:"+string);
	    System.out.println("String after 
reverse:"+reverse);
	  }     
	  

}