Introduction to jsp

Introduction to JSP

JSP and Servlets / Session 5 / 2 of 24

Objectives

Explain JSP

Identify the advantages of using JSP

Describe various elements of JSP

Describe the JSP Life Cycle

Develop JSP using Java Studio Enterprise 8


Introduction to JSP

Java Server Pages (JSP) are saved with the extension .jsp.

Efficiently controls dynamic content generation.Uses Java programming language and class

libraries.Uses HTML for presentation of pages and Java

code to access dynamic content.

JSP page

JAVA

Server

JSP uses JAVA to access

dynamic content


Benefits of JSP 3-1

Separates content from presentation

Request

Response

JSP page

Static Content

DynamicContent

Server

Client

Web Designer JSP Programmer


Benefits of JSP 3-2

Emphasizes reusable components

JSP page 1

Static Content

DynamicContent

JSP page 2

Static Content

DynamicContent

JSP page 3

Static Content

DynamicContent

JavaBean

Multiple JSP pages use the

same JavaBean


Benefits of JSP 3-3

Simplified page development - Web designer and Web programmer use Web development tools to develop a JSP page.

JSP page

Static Content

DynamicContent

Web Designer JSP Programmer

Web Development Tools

Macromedia Dreamweaver

Java Studio Enterprise 8

.....


Elements of JSP 2-1

Elements of a JSP page

Static Content

Directives

Expressions

Scriptlets

JSP PageTaglib: <%@ taglib uri= "tagLibraryURI" prefix= "tagPrefix" %>

<%valid Java code block%>

<%= Java Expression %>

Page : <%@ page ATTRIBUTES %>

Include:<%@ include file = " Filename" %>

Declarations

Actions

<%! declaration(s) %>

Forward

Include

Plug-ins

Bean tags


Elements of JSP 2-2

<%@ page language="java" %> <html>…… <h1>Elements of JSP</h1> <p>Today is </p> <page id="clock" class= "calendar.jspCalendar" /> <ul> <li>Day: <%=clock.getDayOfMonth() %> <li>Year: <%=clock.getYear() %> </ul>

Page Directive

JSP ExpressionStatic Content

<% if (Calendar.getInstance().get(Calendar.AM_PM) == Calendar.AM) { %> Good Morning <% } else { %> Good Afternoon <% } %> <%@ include file="copyrightfile.html" %> ……</html>

JSP Scriptlet

Include Directive


Static Content

Static content is the text written on a Web page.Any text-based format can be used to write static

content.A page directive is used to specify the format of

content.

<html> <%@ page contentType = "text/html" %> <head> <title>Example for static content</title> </head> … //Contains text in specified content type. … </body></html>

HTML tags contain static content


JSP Directives

JSP container uses directives for processing of JSP page.

Controls the structure of the Servlet Provides global information about a JSP page Scope of directives is the entire JSP file

<html>... <%@ page language="Java" import= “java.rmi.*, java.util.*" session="true" buffer="12kb" autoFlush="true" info="PageDirective" errorPage="error.jsp" isErrorPage="false" isThreadSafe="true" %> <head> <title>Testing Page Directive</title> </head> <body> <h1>Testing Page Directive</h1> This page is testing Page Directive. </body >……</html>

page Directive

Demonstration: Example 1

<html> <head> <title>Testing include directive</title> </head> <body> <h1> Example of directives</h1> <%@ include file ="testFile.html" %> </body></html>

include Directive// testFile.html<html><body>The JSP <b>"include"</b> directive example.</body></html>



JSP Expression

Contains a Java statementValue of Java Statement will be evaluated and

inserted into generated Web page. Displays individual variables, or the result of

some calculation.

<html> <head> <title>Testing Expression directive</title> </head> <body> <h1> Testing Expression directive </h1> <% int i = 2, j=3;%> <% i++;%> <% j=j+i; %> … </body></html>

JSP Expression


JSP Scriptlet

Block of Java code that performs functions which are not supported by tags.

Executed during run time

<html> <head> <title>Scriptlet of a JSP </title> </head> <body> <h1>Scriptlet of a JSP</h1> <% int k=0; for(int i=0;i<5;i++) { k=k+i; System.out.println(k); } %> ... </body></html>

JSP Scriptlet


JSP Declaration

Used to define variables and methods in a JSP page.

Declared variables and methods can then be referenced by other scripting elements on the same page.

Used to define single or multiple variables

<%! int x = 0, y = 0; private String units = "ft"; %>

Declares x and y as integer variables

Declares units as a String variable

<%! public long fact (long x) {if (x == 0) return 1;else return x * fact(x-1);} %>

Declares fact method


JSP Actions

Allows the transfer of control between pagesAllows JSP pages to access JavaBeans

component objects stored on the server.

JSP Actions

Forward Include Plug-ins Bean tags


Forward Action

Permanently transfers control from a JSP page to another location.

JSP Page 1

Forward Action

JSP Page 2Transfers control to another page


Include Action 2-1

Inserts the content generated by remote resource in the output of the current JSP page.

Temporarily transfers the control to a new page

JSP Page 1

Include Action

JSP Page 2Transfers control to another page

Transfers control back to the original

page


Include Action 2-2

<%@page contentType="text/html"%><%@page pageEncoding="UTF-8"%><html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>jspactionexample</title> </head> <body bgcolor="#ffffff"> <h1>Jsp actions and declarations</h1> <jsp:include flush="true" page="JspExample.jsp"> <jsp:param name="stringeg" value="String passed using forward directive"/> </jsp:include> </body></html>

Include Action


<%@page contentType="text/html"%><%@page pageEncoding="UTF-8"%><%@page language="java" %><html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Declaration, Expression and Actions</title> <%=request.getParameter("stringeg")%> <%! static private char[] vowels ={ 'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'}; String word; public boolean startsWithVowel(String word) { this.word=word; char first = word.charAt(0); for (int i = 0; i < vowels.length; ++i) { if (first == vowels[i]) return true; } return false; }

JSP Declarations

static private String[] articles = { "a ", "an " }; public String withArticle(String noun) { if (startsWithVowel(noun)) return articles[1] + noun; else return articles[0] + noun; } %> </head> <body bgcolor="#ffffff"> <br /> <b>Starts with a vowel: </b> <%=startsWithVowel("I am a very good Programmer")%> <br/> <b>String entered is: </b> <%=word%> <br /> <b>Article:</b> <%=withArticle("apple")%> <br /> </body></html>

JSP Declarations



JSP Plug-ins and Bean Tags

JSP Plug-ins - Used to generate browser-specific HTML.

JSP Bean Tags – Used to interact with JavaBeans stored on the server.


JSP Life Cycle 3-1

Client

JSP page

3 Execution

2

Translation

Compilation

1

Servlet

Request

Server

Request

ResponseResponse

JSP Life Cycle


JSP Life Cycle 3-2

Translation and Compilation

Translation

Compilation

Servlet

JSP

Determines Errors in JSP

Extracts data from JSP element

Generates a Servlet for JSP


JSP Life Cycle 3-3

Execution – Actions performed during execution are:

<%@ page buffer = "none|20kb" %>

<%@ page errorPage = "errorJSP.html" %>

Handling ErrorsSets buffer size

Specifies error page

Buffering Output



<%@page contentType="text/html"%><%@page pageEncoding="UTF-8"%> <%! double radius=6.0; private double getRadius(){ return radius; } private double getDiameter(){ return (radius * 2); } private double getArea(){ return (3.1415 * radius); } private double getCircumference(){ return(3.1415 *(radius * 2)); }%>

JSP declarations

JSP Application in Java Studio Enterprise 8

<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Declaration Tag - Methods</title> </head> <h3>Calculating area and circumference of a Circle</h3> <hr/> <b>Radius of circle:</b> <%=radius%> cm<br/> <b>Diameter:</b> <%=getDiameter()%> cm<br/> <b>Area of Circle is:</b> <%=getArea()%> cm<sup>2</sup><br/> <b>Circumference of a circle is:</b> <%=getCircumference()%><br/> <hr/> <body></body></html>

JSP scriptlets


Summary

JSP uses Java programming language and class libraries.

JSP page uses HTML to display static text and Java code to generate dynamic content.

Elements of JSP page are static content, JSP directives, JSP expressions, and JSP scriptlets.

A JSP page can be created using standard development tools.

JSP uses reusable and cross-platform components, such as JavaBeans.

JSP allows the creation of user-defined tags and makes the JSP development process easy.

Different phases in JSP life cycle are translation, compilation, and execution.

Introduction to jsp

Technology

Transcript of Introduction to jsp