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8/4/2019 Wejp 2503 Unit III Jsp s5 Mca Students
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Java Server Pages
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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.
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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.
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JSP compilation into Servlets
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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.
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JSP & Servlet as Web Components
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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
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A Simple JSP Page
<html>
<body bgcolor="pink">
Hello World!
<br>
<centre><h2>Current time is <%= new java.util.Date()%>
</body></html>
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Output
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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
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JSP Benefits
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JSP BenefitsOver Competing Technologies -Versus
.NET & ASP
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JSP BenefitsOver Competing Technologies
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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.
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JSP Page Lifecycle Phases
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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
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.
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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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