Chapter 6: JSP Tag Libraries and JSTL

1
Chapter 6 JSP Tag Libraries and JSTL
Reference Beginning JSP
2
Objectives

• Role of JSP Tag Libraries
• Anatomy of a Tag Library
• JSP Standard Tag Library (JSTL)
• JSTL Tags
• Converting the Shopping Cart
• Declarations (including constants), iteration
• URL creation, control flow, method calls

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Role of JSP Tag Libraries

• Reference Page 180
• JSP Tag Library
• Collection of custom actions (tags) available for
  JSP pages
• Provide additional functionality beyond standard
  actions and implicit objects
• Portable between different JSP containers
• In general, HTML-like syntax easier to handle
  than embedded Java scriptlets

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Anatomy of a Tag Library

• Reference page 182
• JAR archive
• Tags (custom actions)
• May use Java code or JSP code (Chapter 11)
• TLD (Tag Library Descriptor)
• File in XML format
• Describes the tags
• E.g., declares the functions used in JSP pages
• Web.xml Deployment Descriptor
• Taglib map (TLD location URI)
• JSP page
• Tag directive lt_at_ taglib uri gt

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JSP Standard Tag Library (JSTL)

• Reference page 181
• Most popular tag library
• Latest version JSTL 1.1
• Covers the following
• set and remove scoped variables, display
  expressions and values, catch expressions
• Conditional flow control tags, Iteration tags
• URL tags, format numbers and dates tags
• Access to relational database (chapter 23)

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JSTL Tags

• Reference page 184-186, Appendix C
• Core Tags
• ltcifgt, ltcforEachgt, ltcchoosegt, ltcwhengt,
  ltcotherwisegt
• ltcsetgt, ltcremovegt
• ltcoutgt, ltcurlgt, ltccatchgt (Chapter 10)
• Formatting Tags
• ltfmtformatNumbergt, ltfmtformatDategt
• XML and SQL Tags
• ltcsqlgt (Chapter 23)

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Converting the Shopping Cart

• WARNING The ch06.war file does not have the Java
  sources
• IMPORTANT When creating a Web project using
  existing sources in NetBeans 4.1, do not delete
  the class files.

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Eliminate scripting declarations

• Replace Java code in jspInit()
• In new estore.jsp
• ltcif test"empty cats"gt
• ltcset var"cats" value"wxshopgetCats()"
  scope"application"/gt
• lt/cifgt
• Scoped variables
• Objects that are attached as named attributes to
  the scoping implicit objects.
• Scripting variables
• Actual Java source code variables

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Convert static method calls

• E.g., EShop.getCats() in jspInit()
• In web.xml
• lttaglibgt
• lttaglib-urigthttp//www.wrox.com/begjsp/eshop-
  functions-taglib
• lt/taglib-urigt
• lttaglib-locationgt/WEB-INF/jsp/eshop-taglib.tl
  d
• lt/taglib-locationgt
• lt/taglibgt
• Add getCats() method in the TLD
• ltfunctiongt
• ltdescriptiongtObtain the catalog
  categorieslt/descriptiongt
• ltnamegtgetCatslt/namegt
• ltfunction-classgtcom.wrox.begjsp.ch03.EShoplt/funct
  ion-classgt
• ltfunction-signaturegtjava.util.ArrayList
  getCats()lt/function-signaturegt
• lt/functiongt

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Use JSTL iteration tag

• In new estore.jsp
• ltcforEach var"curCat" items"cats"gt
• ltcurl value"/example1/estore.jsp"
  var"localURL"gt
• ltcparam name"catid" value"curCat.id"/gt
• lt/curlgt
• lta href"localURL" class"category"gtcurCat.n
  amelt/agt
• lt/brgt
• lt/cforEachgt
• URL Creation Tag
• ltcurlgt performs several tasks
• Appends required context path
• Encode URL parameters, etc.

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Declaring constants, Remove variable

• In new shopcart.jsp
• ltcset var"EXAMPLE" value"/example1"/gt
• ltcset var"SHOP_PAGE" value"/estore.jsp"/gt
• ltcset var"CART_PAGE" value"/shopcart.jsp"/gt
• Remove variable for reuse
• ltcremove var"tmpitem"/gt
• ltjspuseBean id"tmpitem" class"com.wrox.beg
  jsp.ch03.LineItem"gt
• ltjspsetProperty name"tmpitem"
  property"quantity" value"1"/gt
• lt/jspuseBeangt

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Format Number, Convert method call

• Format Number
• ltfmtformatNumber value"curItem.price / 100"
  type"currency"/gt
• No need to use dispPrice()
• Convert method call
• wxshopaddList(lineitems, tmpitem)
• Add ltfunctiongt tag in the TLD file
• ltfunctiongt
• ltdescriptiongtAdd an item to a
  listlt/descriptiongt
• ltnamegtaddListlt/namegt
• ltfunction-classgtcom.wrox.begjsp.ch03.EShoplt/funct
  ion-classgt
• ltfunction-signaturegtvoid addList(java.util.List,
  java.lang.Object)lt/function-signaturegt
• lt/functiongt

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Next Steps

• Try It Out sections of Textbook (Chapter 6)
• Example 1
• Exercise 2 (Chapter 6)
• Exercise 1 (optional)