Chapter 2: JavaServer Pages (JSP) Basics 1

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Chapter 2JavaServer Pages (JSP)Basics 1
Reference Beginning JSP
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Objectives

• Review of JSP
• Quick Tour of JSP 2.0
• Anatomy of a JSP page
• JSP Directives, Actions
• JSTL 1.1
• JSP 2.0 EL
• Including JSP pages
• JSP Action and JavaBeans
• Passing parameters to a JSP page

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Java Server Pages - Review

• Web scripting technology
• Similar to Microsoft ASP and ASP.NET
• Creates dynamic content using static templates
• Java code enclosed in HTML
• Combines markup (e.g., HTML) with Java Code to
  produce a dynamic Web Page
• Java code runs on the server
• Full power of the Java language (JDBC, EJB, etc.)
• JSP tags allow non-Java developer to generate
  dynamic content

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How JSPs Work - Review
JSP Request
Server reads JSP File
FileChanged ?
Yes
Translate to a Servlet
No
Compile Servlet
Execute Servlet
HTML Returned
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Anatomy of a JSP page
Directive

• lt_at_ taglib prefix"tags" tagdir"/WEB-INF/tags"
  gt
• lt_at_ page language"java" import"" gt
• lthtmlgt
• ltheadgt
• lttitlegtJSP 2.0 Examples - Hello World Using a
  Tag Filelt/titlegt
• lt/headgt
• ltbodygt
• lth1gtJSP 2.0 Examples - Hello World Using a Tag
  Filelt/h1gt
• lthrgt
• ltpgt lttagshelloWorld/gt.lt/pgt
• ltH1gtWelcome back,
• lt
• String user (String) session.getAttribute("user
  ")
• out.println(user)
• gt
• lt/H1gt
• lt/bodygt
• lt/htmlgt

Template Data
Action
Scripting Elements
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JSP Directives

• Reference page 32
• Directives
• Gives special instructions to the JSP container
• Not used to generate output directly
• Allowable directives (more details in Chapter 7)
• page directive
• taglib directive
• include directive
• Syntax lt_at_ directive gt
• XML-compatible syntax (without using special
  characters)
• ltjspdirective.taglib /gt

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Template Data

• Reference page 33
• Template Data
• Static text
• Static HTML (.jsp file)
• Static XML (.jspx file)
• Generates the static portion of the page

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JSP Actions

• Reference page 34
• Action elements
• Directly involved in processing of request
• Access data and manipulate data when generating
  dynamic output
• Standard Action (more details in Chapter 8)
• Available in every JSP 2.0 container
• E.g., ltjspuseBeangt, ltjspgetPropertygt,
  ltjspsetPropertygt, ltjspincludegt
• Custom Action
• Actions created by developer

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Scripting Elements

• Reference page 35
• Scripting Elements (more details in Chapter 3)
• Embedded code, typically in Java
• Directives
• lt_at_ page language"java" import"" gt
• Declarations
• lt! java.text.SimpleDateFormat sdf new
  java.text.SimpleDateFormat("KKmm a' on 'MMMMM dd
  yyyy") gt
• Scriptlets
• lt String user (String) session.getAttribute("us
  er") gt
• Expressions
• lt sdf.format(new java.util.Date()) gt

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HTML Form Submission

• Reference
• Page 42, 37
• Using the GET method to submit a form
• ltform action"showportal.jsp" method"get"gt
• ltselect name"portchoice"gt
• lt/formgt

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GET vs. POST

• Reference Page 37
• GET
• Attach parameters with the URL request
• http//localhost8080/ch02/example1/showportal.jsp
  ?portchoicenews
• Limitations
• Length of parameter value cannot exceed max. URL
  length
• Special characters must be encoded
• POST
• Uses HTTP header to send parameter information
• Advantages
• Length of parameter not limited
• Less prone to tampering

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JSTL 1.1 Example

• Reference Page 42
• showportal.jsp
• lt_at_ taglib prefix"c" uri"http//java.sun.com/jsp
  /jstl/core" gt
• lthtmlgt
• ltcchoosegt
• ltcwhen test"param.portchoice 'news'"gt
• lt/cwhengt
• lt/cchoosegt
• lt/htmlgt

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Working with JSTL 1.1

• Reference Page 43
• JSP Standard Tag Library (JSTL) 1.1
• To perform common Web application programming
  tasks without using scripting elements
• Use the taglib directive to use JSTL 1.1 tags
• prefix prefix used for all tags in this library
• uri URI to uniquely identify this tag library
• JSP container finds the tag library (jstl.jar and
  standard.jar)
• Contains many constructs
• E.g., ltcchoosegt
• Tomcat 5.x designed to work with JSTL 1.1, JSP
  2.0, Servlets 2.4

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JSP 2.0 Expression Language

• Reference Page 44
• JSP 2.0 EL
• Always evaluated at runtime
• Always bracketed as
• EL expression
• Can be used
• Anywhere template data may be placed
• Within attributes of an action
• E.g., test attribute of ltwhengt action
• Can use EL implicit objects
• param.portchoice 'news'

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EL Implicit Objects

• Reference Page 45
• EL Implicit Objects (more details in Chapter 5)
• pageContext, pageScope, requestScope
• sessionScope, applicationScope
• param, paramValues
• header, headerValues
• cookie, initParam

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Including JSP pages

• Reference Page 46
• Individual portal pages reside in their own .jsp
  files.
• showportal.jsp dynamically selects one of the
  portals pages (weather.jsp, news.jsp, etc.)
• Use ltjspincludegt tag

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JSP Best Practice

• Reference Page 53
• Start with simplest HTML prototype
• Add style and layout later
• Separate JSP development from HTML layout and
  formatting, if possible
• Showportal.jsp (application logic) JSP developer
• ltcwhen test"param.portchoice 'news'"gt
• ltjspinclude page"news.jsp" /gt
• News.jsp (layout and formatting) graphic
  designer

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JSP Action and JavaBeans

• Reference Pages 55 - 58
• JavaBeans (more details in Chapter 9)
• Reusable software components that has properties,
  methods and events
• Can be used to generate dynamic content for the
  portal pages
• To create a JavaBean attached to the current
  request
• ltjspuseBean idnewsfeed" class"com.wrox.begjsp.
  ch2.NewsFeed
• scope"request"gtlt/jspuseBeangt
• To set the topic property to news
• ltjspsetProperty name"newsfeed"
  property"topic" value"news"/gt
• To get the value property
• ltjspgetProperty name"newsfeed"
  property"value"/gt

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Multi-valued JavaBeans

• Reference Pages 58 - 60
• Uses the JSTL 1.1 iteration tag to create a table
  with multiple values
• Instead of using ltjspgetPropertygt tag
• Weather.jsp example
• newsfeed.values returns a collection
• city and temp are properties of row variable
• lttablegt
• ltcforEach items"newsfeed.values" var"row"
  gt
• lttrgtlttd class"tableCell" width"200"gt
  row.city lt/tdgt
• lttdgt row.templt/tdgt
• lt/trgt
• lt/cforEachgt
• lt/tablegt

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Passing parameters to a JSP page

• Reference Page 67
• Add a username parameter within ltFORMgt tag of
  index.jsp
• In showportal.jsp, add a ltjspparamgt tag within a
  ltjspincludegt tag
• Update portal web page (e.g., news.jsp) to
  display username
• lttd class"boxTitle" gt
• Welcome to the News Portal, param.user!
• lt/tdgt

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Next Steps

• Try It Out sections of Textbook (Chapter 2)
• example1, example2, example3
• Assignment 1