Wejp 2503 Unit III Jsp s5 Mca Students

8/4/2019 Wejp 2503 Unit III Jsp s5 Mca Students

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Java Server Pages



JAVA SERVER PAGES

Servlets are pure Java programs. They introducedynamism into web pages by using programmatic content.

JSP technology is an extension/wrapper over the Javaservlet technology.

JSP are text based documents.

We will focus only on JSP since it subsumes the servlettechnology.

Two major components of JSP:

1. Static content: provided by HTML or XML

2. Dynamic content: generated by JSP tags andscriplets written in Java language to encapsulate the

application logic.



What do you mean by Static & Dynamic

Contents?

Static contents

Typically static HTML page

Same display for everyone

Dynamic contents Contents is dynamically generated based on conditions.

Conditions could be

User identity.

Time of the day. User entered values through forms and selections.



JSP compilation into Servlets



More on JSP syntax and contents

HTML code for user interface lay outJSP tags:

Declarations ± Java declarations

Actions

Directives-page/include/taglib

Expressions- Java Expressions

Scriplets-Java Statements

JSP implicit objects: a request object, response object,session object, config object

Javabeans: for logic that can be taken care of at theJSP level.



JSP & Servlet as Web Components



What is JSP Page?

A text-based document capable of returning both static anddynamic content to a client browser.

Static content and dynamic content can be intermixed.

Static content

HTML, XML, Text

Dynamic content

Java code Displaying properties of JavaBeans

Invoking business logic defined in Custom tags



A Simple JSP Page

<html>

<body bgcolor="pink">

Hello World!

<br>

<centre><h2>Current time is <%= new java.util.Date()%>

</body></html>



Output



Servlets vs. JSP

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



JSP Benefits



JSP BenefitsOver Competing Technologies -Versus

.NET & ASP



JSP BenefitsOver Competing Technologies



JSP Lifecycle

When a HTTP request is mapped to a JSP page, it is handled by a special built-inservlet (that is provided by a container) that first checks whether the JSP

page's servlet is older than the JSP page. If it is, the container translates the JSP

page into a servlet Java code and compiles the servlet code into servlet class.

And this is done automatically by the container. This is one of the advantages

of using JSP over servlet from developer standpoint.



JSP Page Lifecycle Phases



JSP Page Lifecycle Phases -Translation/Compilation



Translation/Compilation (Contd.)



JSP Page Lifecycle Phases -Execution

Once the page has been translated and compiled, the JSP page's servlet for the most part

follows the servlet life cycle as following:

1. If an instance of the JSP page's servlet does not exist, the container Loads the JSP page'sservlet class

2. Container then creates an instance of the servlet class

3. Container then initializes the servlet instance by calling the jspInit method

4. Container invokes the _jspService() method, passing a request and response object.

If the container needs to remove the JSP page's servlet, it calls the jspDestroy() method.



API for the generated Servlet



Initialization of a JSP Page



Finalization of a JSP Page



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Wejp 2503 Unit III Jsp s5 Mca Students