Using Cookies and Sessions in Servlets

Using cookies and sessions from Nuha Noor

Handling Sessions in Servlets web technologies jntuh

 A web application takes a name as input and on submit it show a hello<name> page where <name> is taken from the request, it shows the start time and  a logout button on clicking this button it should show a logout page with thank you<name> and duration of usage(use session).

To implement the above program in servlets following folder structure is to be followed:

In the src folder all the required files for our application should be kept.

Below snapshots shows u detail of all the programs

home.html

index.html

op.html

res.html

FirstServlet.java

logout.java

After Compilation of your servlets keep the .class files in classes folder as shown below

Following are the images and css files:

The WEB-INF folder structure is as follows

The output of servlet is as follows:

wt calculator program using servlets

CALCULATOR PROGRAM

AIM: To implement calculator operations using servlets and access the results stored in database

The below image shows the directory structure to be followed in tomcat server

After compiling java programs place class files in classes folder

To use database we require mysqlconnector.jar file which should be placed in lib folder.

Below is the deployment descriptor which gives the details about servlet,servlet class,url-pattern 

All the source code file are kept in src folder.

This is the main page where we are creating frames and accessing servlets in it.

The File which gives the details about left frame.

Calculator html file.Notice the target attribute here.

The file for another frame where results are showed.

This is the calculator servlet.

Calculator HTML file.

Calculator results page.

Calculator db servlet.

Tomcat Manager page.U can see the deployed calc project.

Calculator index page running on tomcat server.

Calculator table in Database.

OBJECT ORIENTED PROGRAMMING

OBJECT ORIENTED PROGRAMMING

In this a main program is divided into small objects depending on the problem. Functions of object are linked with object using message passing. Data and functions of each individual object act like a single unit.

Data gets more importance than function in the program.

Each object controls its own data.

Data hiding is possible in OOP which prevents illegal access of function from outside of it.

More data and function can be added to program if required. It follows Bottom-up approach for program design. Popular Example: c++,java

 

From the above para we can infer that an object is an important part over here.So what an object is?

It has many definitions.Lets get to the basic one thatis  “it is a real world entity”.It could be a desk,T.V, bicycle etc.

These objects share two characteristic:

1.       State

2.       Behaviour

AN example would be :

A desktop lamp which has 2 states – (on and off) and 2 behavior (turn on && turn off).

An object stores its state in fields (variables) and exposes its behaviour through methods(functions).

Methods operate on an objects internal state and serve as the primary mechanism for object-object communication.

 

Features of OOP:

1.class

2.object

3.encapsulation

4.abstraction

5.inheritance

6.message passing

7.polymorphism.

Lets discuss each in detail.

1.       Class

Can be said as  a blueprint to create objects.This blueprint has attributes and methods that all created object share.

A class can be a person,place or thing.Fundamentally it encapsulates state andbehavior

Syntax of class:

         class  class_name{

                properties(variables);

                Action(methods);

}

 

Variables inside a class are called instance variables(Things that object knows about itself).

Variables inside a method are called method variables.

Methods are things an object can do.

When we create a class think about the objects that  will be created from that class type.

Example program for class explanation:

 

 

The below program describes the importance of objects .

 

This is the output:

First Java Program

Before initiating this let me make it very clear "Java is Case Sensitive Language".For  example if u have a method called forth() n if u have written Forth() while accessing this method than it is not correct as compiler might throw an error saying method not found.

To begin with we require following:

1.An IDE---  NetBeans 8.0 for windows 8.U can use different version compatible with your Operating System.

So Over here what u do is create a Java Application n start with your first program.

The First program is shown below:

You can view the output  as shown.



If you just want to opt for manual editor like notepad for executing java program then here are the screens which demonstrate the procedure.

You might be wondering why there is no import stmt just like how we include header files in C, because even if we don't mention the package gets imported by default over here.This package is java.lang.* package.