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Introduction - Java Server Programming (JSP)
1. Overview of JSP Technology
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.
2. 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.
3. Architecture of JSP Page
⚫ The web server needs a JSP engine, i.e, a container to process JSP pages.
⚫ The JSP container is responsible for intercepting requests for JSP pages.
⚫ A JSP container works with the Web server to provide the runtime
environment and other services a JSP needs.
⚫ Following diagram shows the position of JSP container and JSP files in a
Web application.
5. Understanding the JSP Page Lifecycle
⚫The JSP pages follow these phases:
● Compilation
● Initialization
● Execution
● Cleanup
⚫ jspInit(), _jspService() and jspDestroy() are the life cycle
methods of JSP.
6. Compilation
⚫ The compilation process involves three steps −
● Parsing the JSP.
● Turning the JSP into a servlet.
● Compiling the servlet.
Initialization
public void jspInit(){
// Initialization code...
}
Execution
void _jspService(HttpServletRequest request,
HttpServletResponse response)
{ // Service handling code...}
Cleanup
public void jspDestroy()
{ // Your cleanup code goes here.}
7. ⚫ <%-- JSP comment --%>
⚫ <HTML> <HEAD>
⚫ <TITLE>MESSAGE</TITLE>
⚫ </HEAD> <BODY>
⚫ <%out.print("Hello, Sample JSP code");%>
⚫ </BODY>
⚫ </HTML>
The above JSP generates the following output:
Hello, Sample JSP code.
⚫ Explanation of above code
1) The line <%–JSP Comment–%> represents the JSP element called JSP Comment, While adding
comments to a JSP page you can use this tag, we will discuss this in detail in coming posts.
Note: JSP Comments must starts with a tag <%– and ends with –%>
⚫ 2) Head, Title and Body tags are HTML tags – They are HTML tags, frequently used for static
web pages. Whatever content they have is delivered to client(Web browser) as such.
⚫ 3) <%out.print(“ Hello, Sample JSP code ”);%> is a JSP element, which is known as Scriptlet.
Scriptlets can contain Java codes. syntax of scriptlet is: <%Executable java code%>. As the
code in Scriptlets is java statement, they must end with a semicolon(;). out.print(“ Hello, Sample
JSP code ”) is a java statement, which prints“ Hello, Sample JSP code”.
⚫ JSP is used for creating dynamic webpages. Dynamic webpages are usually a mix of static &
dynamic content.
⚫ The static content can have text-based formats such as HTML, XML etc and the dynamic
content is generated by JSP tags using java code inside HTML .
8. Elements of JSP
The JSP elements are used to create JSP page. They are divides
into three categories:
JSP Scripting Elements
JSP Directive Elements
JSP Standard Action Elements
9. Scripting Elements of JSP
JSP Scripting Elements are used for writing the Java Code inside the JSP page. There
are different types of scripting elements these elements are used for various
purposes.
The scripting elements of JSP are:
The Scriptlet
⚫ A scriptlet can contain any number of JAVA language statements, variable or
method declarations, or expressions that are valid in the page scripting language.
⚫ syntax of Scriptlet −
<% code fragment %>
⚫ You can write the XML equivalent of the above syntax as follows −
<jsp:scriptlet> code fragment </jsp:scriptlet>
<html> <head><title>Hello World</title></head>
<body> Hello World!
<br/>
<%
out.println("Your IP address is " + request.getRemoteAddr());
%>
</body> </html>
10. JSP Declarations
⚫ A declaration declares one or more variables or methods
that you can use in Java code later in the JSP file.
⚫ You must declare the variable or method before you use it in
the JSP file.
⚫ syntax for JSP Declarations −
<%! declaration; [ declaration; ]+ ... %>
You can write the XML equivalent of the above syntax as
follows −
<jsp:declaration> code fragment </jsp:declaration>
example for JSP Declarations −
⚫ <%! int i = 0; %>
⚫ <%! int a, b, c; %>
⚫ <%! Circle a = new Circle(2.0); %>
11. JSP Expression
A JSP expression element contains a scripting language expression that is
evaluated, converted to a String, and inserted where the expression appears
in the JSP file.
⚫ The expression element can contain any expression that is valid according to
the Java Language Specification but you cannot use a semicolon to end an
expression.
syntax of JSP Expression −
<%= expression %>
You can write the XML equivalent of the above syntax as follows −
<jsp:expression> expression </jsp:expression>
JSP Expression −
<html> <head><title>A Comment Test</title></head>
<body>
<p>Today's date: <%= (new java.util.Date()).toLocaleString()%></p>
</body> </html>
The above code will generate the following result −
Today's date: 11-Sep-2010 21:24:25
12. JSP Comments
⚫ JSP comment marks text or statements that the JSP container
should ignore. A JSP comment is useful when you want to hide
or "comment out", a part of your JSP page.
syntax of the JSP comments −
<%-- This is JSP comment --%>
example of the JSP Comments −
<html> <head><title>A Comment Test</title></head> <body>
<h2>A Test of Comments</h2>
<%-- This comment will not be visible in the page source --%>
</body> </html>
The above code will generate the following result −
A Test of Comments
14. JSP directives
⚫ JSP directives are the messages to JSP container. They
provide global information about an entire JSP page.
⚫ JSP directives are used to give special instruction to a
container for translation of JSP to servlet code.
⚫ In JSP, directive is described in <%@ %> tags.
Syntax of Directive:
<%@ directive attribute=“value" %>
There are three types of directives:
⚫ Page directive
⚫ Include directive
⚫ Taglib directive
15. JSP Page directive
Syntax of Page directive:
<%@ page attribute="value" %>
⚫ It provides attributes that get applied to entire JSP
page.
⚫ JSP page directive is used to define the properties
applying the JSP page, such as the size of the allocated
buffer, imported packages and classes/interfaces,
defining what type of page it is etc.
⚫ It is used to provide instructions to a container that
pertains to current JSP page.
17. Import Attribute
This tells the container what packages/classes are needed to be imported into
the program.
Syntax:
<%@page import = "value"%>
Example :
<%-- JSP code to demonstrate how to use page directive to import a package
--%>
<%@page import = "java.util.Date"%>
<%Date d = new Date();%>
<%=d%>
18. contentType Attribute
This defines the format of data that is being exchanged between the client and
the server. It does the same thing as the setContentType method in servlet
used to.
Syntax:
<%@page contentType="value“ %>
<%-- JSP code to demonstrate how to use page directive to set the type of
content --%>
<%@page contentType = "text/html" %>
<% = "This is sparta" %>
19. buffer Attribute
⚫ The buffer attribute of page directive is used to specify
behavior of JSP container with respect to sending the output
to an intermediate buffer, before it is sent to Http response.
⚫ The default size of buffer is 8KB. This means that the JSP
container will send the HTTP response in chunks of 8 KBytes.
⚫ The feature can be disabled by setting the buffer attribute to
none. In this case, JSP container does not perform any
buffering, and sends contents to the client as they are
generated.
<%@page buffer=”none”%>
The buffer attribute of page directive may also be used to
change the buffer size.
The example below sets the buffer size to 4 KBytes.
<%@page buffer=”4kb”%>
20. language Attribute
⚫The language attribute indicates the
programming language used in scripting the JSP
page.
⚫For example, because you usually use Java as the
scripting language, your language option looks
like this
<%@ page language = "java" %>
21. errorPage and isErrorPage Attribute
errorPage Attribute
In JSP, the errorPage attribute of page directive is used to specify a web page which will be
displayed as an error page for the current JSP page i.e. if there is an error while executing the
current page).
Syntax
<%@ page errorPage= "path-to-another-jsp-page" %>
isErrorPage Attribute
In JSP, the isErrorPage attribute of page directive is used to specify whether the current page
could be displayed as an error page for another JSP page. We could set the value of isErrorPage
to either true or false.
Syntax
<%@ page isErrorPage= "true|false" %>
isErrorPage = "true“
⚫ When isErrorPage is set to true, the current page is displayed in case an error appears in
another JSP page.
<%@ page isErrorPage= "true" %>
isErrorPage = "false“
⚫ By default, the isErrorPage attribute value is false, hence we don't have to
set isErrorPage to false, in case if we don't want the current page to be displayed as an error
appears for any JSP page.
22. Include Directive
⚫ The include directive is used to include a file during the
translation phase.
⚫ This directive tells the container to merge the content of other
external files with the current JSP during the translation phase.
⚫ You may code include directives anywhere in your JSP page.
⚫ The include directive is used to include the contents of any
resource it may be jsp file, html file or text file.
⚫ The include directive includes the original content of the included
resource at page translation time (the jsp page is translated only
once so it will be better to include static resource).
⚫ Advantage of Include directive
Code Reusability
Syntax of include directive
<%@ include file="resourceName" %>
23. Include Directive Example
index.jsp
<html> <head> <title>Main JSP Page</title> </head>
<body>
<%@ include file="file1.jsp" %>
Main JSP Page: Content between two include directives.
<%@ include file="file2.jsp" %>
</body> </html>
file1.jsp
<p align="center">
This is my File1.jsp and I will include it in index.jsp using include directive
</p>
file2.jsp
<p align="center"> This is File2.jsp </p>
25. Taglib Directive
⚫ The taglib directive is used to define tag library that the current JSP
page uses.
⚫ A JSP page might include several tag library.
⚫ JavaServer Pages Standard Tag Library (JSTL), is a collection of useful
JSP tags, which provides many commonly used core functionalities.
⚫ It has support for many general, structural tasks such as iteration
and conditionals, readymade tags for manipulating XML
documents, internationalization tags, and for performing SQL
operations.
Syntax of taglib directive is:
<%@ taglib prefix="prefixOfTag" uri="uriOfTagLibrary" %>
The prefix is used to distinguish the custom tag from other libary
custom tag. Prefix is prepended to the custom tag name. Every
custom tag must have a prefix.
⚫ The URI is the unique name for Tag Library.
27. JSP Actions
⚫JSP actions use the construct in XML syntax
to control the behavior of the servlet engine.
⚫We can dynamically insert a file, reuse the
beans components, forward user to another
page, etc. through JSP Actions like include
and forward.
⚫Unlike directives, actions are re-evaluated
each time the page is accessed.
Syntax:
<jsp:action_name attribute="value" />
29. jsp:include
⚫ It also used to insert a jsp file into another file, just like include
directive.
⚫ It is added during request processing phase
Syntax of jsp:include
<jsp:include page="page URL" flush="true/false">
<%@ page language="java" contentType="text/html"%>
<html>
<head>
<title>Date JSP</title>
</head>
<body>
<jsp:include page="date.jsp" flush="true" />
</body>
</html>
31. jsp:forward:
⚫ It is used to forward the request to another jsp or any static page.
⚫ Here the request can be forwarded with no parameters or with
parameters.
Syntax:
<jsp:forward page="value">
Here value represents where the request has to be forwarded.
Action.jsp
<%@ page language="java" contentType="text/html"%>
<html>
<head>
<title>Guru Action JSP1</title>
</head>
<body>
<jsp:forward page="jsp_action.jsp" />
</body>
</html>
![JSP Declarations
⚫ A declaration declares one or more variables or methods
that you can use in Java code later in the JSP file.
⚫ You must declare the variable or method before you use it in
the JSP file.
⚫ syntax for JSP Declarations −
<%! declaration; [ declaration; ]+ ... %>
You can write the XML equivalent of the above syntax as
follows −
<jsp:declaration> code fragment </jsp:declaration>
example for JSP Declarations −
⚫ <%! int i = 0; %>
⚫ <%! int a, b, c; %>
⚫ <%! Circle a = new Circle(2.0); %>](https://image.slidesharecdn.com/jsp-250613152008-47c9bae3/85/Introduction-Java-Server-Programming-JSP-10-320.jpg)
