Sem v Unit III JSP Notes

8/8/2019 Sem v Unit III JSP Notes

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JavaServer Pages

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Introduction

JSP,like other JAVA APIs,is a specification provided by

sun for vendors to implement.

The JSP specification builds on the functionality providedby the servlet specification.

Then How JSP pages are different from servlets??

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Servlets are javas answer to CGI scripts.

They are more elegant and perform better than CGI

scripts.

They execute on the server and intercept browser

requests, acting as a sort of middle layer between clients

and lower level applications.

Servlets are well suited to deciding how to handle client

requests and invoking other server side objects.

But NOT well suited for generating content.

Servlets have to be written by developers familiar with

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JSP pages JSP pages,on the other hand, can be designed anddeveloped less like programs and more like web pages.

Ideal when we need to display markup with embedded

dynamic content.

But less suited to handling processing logic.

JSP pages can use JavaBeans with a specified scope or tag

extensions to achieve a clean separation of static content

and the java code that produces dynamic web applications.

This allows JSP pages to be created and maintained bydesigners with presentation skills ,they do not need to know

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Java Server PagesServlets are pure Java programs. They introduce dynamism intoweb pages by using programmatic content.

JSP technology is an extension/wrapper over the Java servlettechnology.

JSP are text based documents.

Two major components of JSP:

1. Static content: provided by HTML or XML

2. Dynamic content: generated by JSP tags and scripletswritten in Java language to encapsulate the application logic.

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What do you mean by Static & Dynamic Contents?

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JSP & Servlet asW

eb Components

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What is JSP Page?

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ASimple JSP Page

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Output

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ServletsServlets JSPJSP

HTML code in Java

Not easy to author

Java like code in HTML

Very easy to author

Code is compiled into

a servlet

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JSP Benefits

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JSP Benefits Over Competing Technologies

-Versus .NET & ASP

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JSP BenefitsO

ver Competing Technologies

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We have to find answers for :

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JSP Lifecycle

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JSP Page Lifecycle Phases -

Translation/Compilation

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Translation/Compilation (Contd.)

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JSP Page Lifecycle Phases -Execution

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API for the generated Servlet

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Initialization of a JSP Page

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Finalization of a JSP Page

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Examples

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General Rules of Syntax

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JSP Family.

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JSP syntactic elementsType of element Element content

Template content Everything in your JSP page's source file that is not a JSPelement.Includes all static content.

Directives Instructions you place in your JSP page to tell the JSPimplementation how to go about building your page, such as to

include another file.

Scripting elements Used to embed Java code into your JSP pages.

Actions Actions provide high-level functionality, in the form of custom XML-style tags, to a JSP page without exposing the scripting language.Standard actions include those to create, modify, and otherwise

use JavaBeans within your JSP page.

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JSP element syntaxElement

Hidden comments

Declarations

Java Languagedeclarations

Expressions

A Java expression

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JSP element syntax (Contd.)Element


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Template content

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Template content (Contd.)

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JSP elements - directives

Directive Purpose

page Controls properties of the JSP page.

include Includes the contents of a file into the JSP page at translationtime.

taglib Makes a custom tag library available within the including page.

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JSP Page- directives

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Page directive (Contd.)

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Page directive attributesAttribute Value Default

language java java

extends superclass Implementation-dependent. This tells theJSP container to use the specified classas the superclass for the generatedservlet

import java-import-list java.lang.*, javax.servlet.http.*,

javax.servlet.*, javax.servlet.jsp.*

session true | false true

buffer Kilobytes or none 8 KB or more

autoFlush true | false true

isThreadSafe true | false true

info text NoneerrorPage URL for errorPage None

contentType MIME type;encoding text/html

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Include directive

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Taglib directive attributes

Attribute Description

uri Either the absolute URI specification that uniquely identifies the TLD associatedwith this prefix.

tagdir Indicates this prefix is to be used to identify tag file extensions installed in the/WEB-INF/tags directory or a subdirectory,If a TLD is present in the specified

directory, its used.O

therwise, an implicit tag library is used.O

nly one of uri ortagdir may be specified. Otherwise a translation error will occur

prefix Defines a prefix string thats used to access tags (or actions) defined in the taglibrary. Empty prefixes are illegal.The following prefixes are reserved: jsp, jspx,java, javax, servlet, sun and sunw.

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Taglib directive - Examples

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JSP elements - declarations

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Declarations (Contd.)

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Declarations - Examples

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Implicit Objects

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Implicit Objects (Contd.)

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Scope Objects

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Scope Objects (Contd.)

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Scope Objects (Contd.)

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JSP elements - expressions

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Expressions - Examples

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Scriptlets - Examples

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Output

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Scriptlets vs Declarations

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JSP elements - actions

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JSP Standard ActionsJSP Standard Actions

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What are Java Beans ?

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Standard actions -

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Syntax

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Scope

Scope Duration

page The bean will be good only within the defining JSP page and will be re-createdfor each new request.

request The bean will be good throughout that request and is available to included orforwarded pages.

session The bean will be associated with the particular session responsible for itscreation and is good for the lifetime of the session.

application The bean is common to all sessions and is good until the Web application

terminates.

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Specification

Specification Meaning

class="className" class is the implementation class for the object.

type="typename"

class="className"

type is the type to be used for the bean within the page, andmust be compatible with the class. class is the implementationclass for the object.

type="typeName"

beanName="beanName"

type is the type to be used for the bean within the page.beanName is the name of an existing bean, and will be passedtojava.beans.Beans.instantiate(). The beanName may be a JSPexpression, whose value is computed at request time. Such anexpression must use the


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Standard actions -

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SpecificationPropertyDetails Meaning

property="*" All bean properties for which there is an HTTP requestparameter with the same name will be automatically set to thevalue of the request parameter. This is probably the single mostfrequently used form ofjsp:setProperty, typically used inconjunction with an HTTP form.

property="propertyName" Sets just that property to the corresponding request parameter.

property="propertyName"

param="parameterName"

Sets the specified property to the specified request parameter.

property="propertyName

value="propertyValue"

Sets the specified property to the specified string value, which

will be coerced to the property's type. The value may be a JSPexpression,whose value is computed at request time. Such anexpression must use the


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Standard actions -

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, and

Interaction

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Why use JavaBeans in JSP Page ?

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Why use JavaBeans in JSP Page ?(Contd.)

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Why use JavaBeans in JSP Page ? (Contd.)

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Standard actions -

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Standard actions -

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Include directive Vs include action

Include type Syntax Done when Includedcontent

Parsing

directive

Compilation time Static Parsed bycontainer

Action Requestprocessing time Static ordynamic Nor parsed butincluded inplace

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Example for include action & directive

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Output

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Example for include action & directive

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Output after changing the pages

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Standard actions -

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Standard actions -

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Sem v Unit III JSP Notes

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