Introduction to JSP - GeeksforGeeks

Introduction

It stands for Java Server Pages.
It is a server side technology.
It is used for creating web application.
It is used to create dynamic web content.
In this JSP tags are used to insert JAVA code into HTML pages.
It is an advanced version of Servlet Technology.
It is a Web based technology helps us to create dynamic and platform independent web pages.
In this, Java code can be inserted in HTML/ XML pages or both.
JSP is first converted into servlet by JSP container before processing the client’s request.

JSP pages are more advantageous than Servlet:

They are easy to maintain.
No recompilation or redeployment is required.
JSP has access to entire API of JAVA .
JSP are extended version of Servlet.

Features of JSP

Coding in JSP is easy :- As it is just adding JAVA code to HTML/XML.
Reduction in the length of Code :- In JSP we use action tags, custom tags etc.
Connection to Database is easier :-It is easier to connect website to database and allows to read or write data easily to the database.
Make Interactive websites :- In this we can create dynamic web pages which helps user to interact in real time environment.
Portable, Powerful, flexible and easy to maintain :- as these are browser and server independent.
No Redeployment and No Re-Compilation :- It is dynamic, secure and platform independent so no need to re-compilation.
Extension to Servlet :- as it has all features of servlets, implicit objects and custom tags

JSP syntax

Declaration Tag :-It is used to declare variables.

Syntax:- 
<%!  Dec var  %>
Example:-
<%! int var=10; %>

Java Scriplets :- It allows us to add any number of JAVA code, variables and expressions.

 Syntax:- 
<% java code %>

JSP Expression :- It evaluates and convert the expression to a string.

 Syntax:- 
<%= expression %> 
 Example:- 
<% num1 = num1+num2 %>

JAVA Comments :- It contains the text that is added for information which has to be ignored.

 Syntax:- 
<% -- JSP Comments %>

Process of Execution

Create html page from where request will be sent to server eg try.html.
To handle to request of user next is to create .jsp file Eg. new.jsp
Create project folder structure.
Create XML file eg my.xml.
Create WAR file.
Start Tomcat
Run Application

Example of Hello World
We will make one .html file and .jsp file

demo.jsp
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Hello World - JSP tutorial</title>
</head>
<body>
    <%= "Hello World!" %>
</body>
</html>

Advantages of using JSP

It does not require advanced knowledge of JAVA
It is capable of handling exceptions
Easy to use and learn
It can tags which are easy to use and understand
Implicit objects are there which reduces the length of code
It is suitable for both JAVA and non JAVA programmer

Disadvantages of using JSP

Difficult to debug for errors.
First time access leads to wastage of time
It’s output is HTML which lacks features.

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