Programmation des Applications Internet Internet Application Programming JavaServer Pages These slid

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Programmation des Applications Internet Internet
Application Programming JavaServer PagesThese
slides and case studies can be downloaded from
www.PauWare.com/MTI
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What is JSP?

• A JSP page is a server-side Web page. Such a page
  is translated by a Web server into Web browser
  interpretable code (HTML)
• A JSP page is in fact translated into a servlet
  at deployment time
• A JSP page contains both common static data
  (HTML) and JSP-specific elements to create
  dynamic content
• Based on the Unified Expression Language (UEL),
  JSP is a more natural and efficient way for
  writing pages, compared to having Java code in
  pages, i.e., lt / Java statements here / gt
• Contrary to servlets, JSP avoids the mixing
  between control code and display code

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Common issues

• Common files extensions
• .jsp -gt standard JSP page
• .jspf -gt JSP page fragment
• .jspx -gt JSP XML-compliant page
• JSP promotes extensibility through tag libraries
  especially (.tld files), connectivity with Java
  code (beans)
• JSP shares most of the mechanisms associated with
  servelts configurations, filters, listeners
• Example of configuration
• ltservletgt
• ltservlet-namegtliste_detenuslt/servlet-namegt
• ltjsp-filegt/liste_detenus.jsplt/jsp-filegt
• lt/servletgt
• ltservlet-mappinggt
• ltservlet-namegtliste_detenuslt/servlet-namegt
• lturl-patterngt/Liste_detenuslt/url-patterngt
• lt/servlet-mappinggt

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JSP page contents

• JSP page header
• lt_at_page contentType"text/html"
  pageEncoding"UTF-8"gt
• Comment
• lt-- this is a comment --gt
• UEL expressions
• lth1gtCréation détenu, session id.
  pageContext.session.idlt/h1gt
• lt-- get_id getter is required --gt
• JSP elements
• ltjspsetProperty name"une_personne"
  property"initiales" value"FB"/gt /gt
• lt-- getInitiales getter is required --gt

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Dealing with simple objects (beans)

• ltjspuseBean id"date_incarceration"
  class"com.FranckBarbier.Java._Prison_de_Nantes._U
  tilities.Time_Date scope"session"/gt
• ltjspgetProperty name"date_incarceration"
  property"_value"/gt
• Java source code
• package com.FranckBarbier.Java._Prison_de_Nantes._
  Utilities
• public class Time_Date
• private java.sql.Timestamp _timestamp
• public Time_Date()
• _timestamp new java.sql.Timestamp(java.util.Cale
  ndar.getInstance().getTimeInMillis())
• public String get_value()
• return java.text.DateFormat.getDateInstance(java.t
  ext.DateFormat.FULL).format(_timestamp)
• public String toString()
• return get_value()

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Bean capabilities

• Possible scopes are application, session,
  request and page (default)
• Beans automatically benefit from being
  thread-safe
• Bean suppression
• session.removeAttribute("date_incarceration")
• Beans are accessible and usable in UEL expressions

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Unified Expression Language (UEL)

• The need for putting aside, as much as possible,
  Java code in pages has led to create and use UEL
• To be avoided
• lt any Java code here gt
• Examples of a UEL expression (one displays a list
  of items if and only if this list is not empty)
• ltcif test"not empty applicationScope.Prison_de
  _Nantes_Database._detenu_allInstances"gt
• lt/cifgt

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UEL, foundations

• Immediate evaluation -gt expression (see also
  JavaServer Faces)
• Deferred evaluation -gt expression
• Reserved keywords and or not eq ne lt gt le ge
  true false null instanceof empty div mod
• UEL inhibition (for compatibility)
• ltel_ignoredgt (web.xml)
• lt_at_page isELIgnored"true"gt
• Request parameters
• empty param -gt true if no parameters
• empty param.X -gt true if the X parameter does
  not exist
• param"X" -gt X parameter itself

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Predefined objects in JSP pages

• Scoped objects
• applicationScope
• sessionScope
• requestScope
• pageScope
• pageContext
• pageContext.serveltContext
• pageContext.sessionContext
• pageContext.request
• pageContext.response

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Accessing to request attributes

• Emitting servelt
• request.setAttribute("entete_detenu_cree", "Le
  détenu identifié par " detenu.get_n_ecrou() "
  existe déjà")
• Receiving JSP page
• lth3gtltcout value"requestScope.entete_detenu_cre
  e"/gtlt/h3gt

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initParam implicit variable

• Usage
• lth6gtParamètre ltigtAuteurlt/igt défini dans
  ltigtweb.xmllt/igt avec la balise ltigtltcontext-param
  gtlt/igt ltcout value"initParam.Auteur"/gt
• lt/h6gt
• Configuration (web.xml file)
• ltcontext-paramgt
• ltparam-namegtAuteurlt/param-namegt
• ltparam-valuegtFranck Barbierlt/param-valuegt
• lt/context-paramgt

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Getting data in pages

• Defining the destination of a forthcoming page
• ltform name"creation_incarceration"
  action"pageContext.request.contextPath/Incarce
  ration"gt
• Getting the value of the detenu_allInstances
  locally defined variable
• ltcset var"detenu_allInstances"
  value"applicationScope.Prison_de_Nantes_Databas
  e._affaire_allInstances"/gt
• ltcwhen test"not empty detenu_allInstances and
  not empty affaire_allInstances"gt
• Getting the value of a locally defined bean
• ltjspuseBean id"date_incarceration"
  class"com.FranckBarbier.Java._Prison_de_Nantes._U
  tilities.Time_Date" scope"session"/gt
• sessionScope.date_incarceration

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Using functions in EL expressions

• Functions are static methods
• Functions are statically identified and located
  as follows _at_taglib prefix"f" uri"/functions"
• Example
• _at_taglib prefix"Prison_de_Nantes"
  uri"/WEB-INF/Prison_de_Nantes_functions"
• Tag lib file
• lttaglib version"2.0" xmlns"http//java.sun.com/x
  ml/ns/j2ee" xmlnsxsi"http//www.w3.org/2001/XMLS
  chema-instance" xsischemaLocation"http//java.su
  n.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd"gt
• lttlib-versiongt1.0lt/tlib-versiongt
• ltshort-namegtPrison_de_Nanteslt/short-namegt
• lturigt/WEB-INF/Prison_de_Nantes_functionslt/urigt
• ltfunctiongt
• ltnamegtNombre_de_detenus_crees_dans_sessionlt/namegt
• ltfunction-classgtcom.FranckBarbier.Java._Prison_de_
  Nantes.Prison_de_Nanteslt/function-classgt
• ltfunction-signaturegtString Nombre_de_detenus_crees
  _dans_session()lt/function-signaturegt
• lt/functiongt

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Connectivity ot other pages

• Including pages
• ltjspinclude page"/Prison_de_Nantes_banniere"/gt
• Forwarding pages
• ltjspforward
• Dispatching statements may support UEL expressions

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JavaServer Pages Standard Tag Library (JSTL)

• JSTL is a predefined (optional) library of useful
  tags that is often used in JSP pages
• JSTL is implemented and embodied by Java
  third-party libraries (standard.jar and jstl.jar)
  -gt to be included in WEB-INF/lib
• Note GlassFish automatically makes JSTL
  available for every Web applications through the
  appserv-jstl.jar (proprietary) file

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JSTL elements

• Core
• lt_at_taglib uri"http//java.sun.com/jsp/jstl/core"
  prefix"c"gt
• Internationalization
• lt_at_taglib uri"http//java.sun.com/jsp/jstl/fmt"
  prefix"fmt"gt
• Database
• lt_at_taglib uri"http//java.sun.com/jsp/jstl/sql"
  prefix"sql"gt
• XML
• lt_at_taglib uri"http//java.sun.com/jsp/jstl/xml"
  prefix"x"gt
• Functions
• lt_at_taglib uri"http//java.sun.com/jsp/jstl/functi
  ons" prefixfn"gt

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JSTL core

• cif, cchoose, cwhen, cothewise, cforEach,
  cforTokens
• cset, cremove, cout, ccatch
• cimport, curl, credirect, cparam
• Example
• ltccatch var"e"gt
• ltcset var"detenu_allInstances"
  value"applicationScope.Prison_de_Nantes_Databas
  e._detenu_allInstances"/gt
• ltcset var"affaire_allInstances"
  value"applicationScope.Prison_de_Nantes_Databas
  e._affaire_allInstances"/gt
• lt/ccatchgt
• ltcif test"e ne null"gt
• lth2gtException e.messagelt/h2gt
• lt/cifgt

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Displaying a list of objects

• ltcif test"not empty applicationScope.Prison_de
  _Nantes_Database._detenu_allInstances"gt
• lttable border"2"gt
• lttheadgt
• lttrgt
• ltthgtDétenult/thgt
• lt/trgt
• lt/theadgt
• lttbodygt
• ltcforEach var"detenu" items"applicationScope.
  Prison_de_Nantes_Database._detenu_allInstances"gt
• lttrgt
• lttdgtltcout value"detenu"/gtlt/tdgt
• lt/trgt
• lt/cforEachgt
• lt/tbodygt
• lt/tablegt
• lt/cifgt

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JSTL control statements, samples

• ltcchoosegt
• ltcwhen test"not empty detenu_allInstances and
  not empty affaire_allInstances"gt
• ltselect name"choix_detenu" size"1"gt
• ltcforEach var"detenu" items"detenu_allInstanc
  es"gt
• ltoption value"detenu"gtdetenult/optiongt
• lt/cforEachgt
• lt/selectgt
• ltselect name"choix_affaire" size"1"gt
• ltcforEach var"affaire" items"affaire_allInsta
  nces"gt
• ltoption value"affaire"gtaffairelt/optiongt
• lt/cforEachgt
• lt/selectgt
• ltjspgetProperty name"date_incarceration"
  property"_value"/gt
• lt/cwhengt
• ltcotherwisegt
• lth2gtIl n'y a de données disponibles concernant
  les détenus et/ou les affaires pour procéder à
  une incarcérationlt/h2gt
• lt/cotherwisegt
• lt/cchoosegt

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JSTL internationalization

• Locale management fmtmessage, fmtsetLocale
• Formatting (relating to locales)
  fmtformatNumber, fmtformatDate
• Example
• ltjspuseBean id"date_incarceration"
  class"java.util.Date" scope"session"/gt
• ltfmtformatDate value"date_incarceration"
  type"date" dateStyle"full" var"date_incarcerati
  on_formatee"/gt
• ltcout value"date_incarceration_formatee"/gt

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Connecting to databases in pages

• Although the direct access to databases is
  possible in pages, such an approach may be
  considered as obsolete. Page setting up
• _at_taglib prefix"sql" uri"http//java.sun.com/jsp
  /jstl/sql"
• Database request example
• ltsqlquery var"detenus" dataSource"jdbc/Prison_d
  e_Nantes"gt
• select from DETENU
• lt/sqlquerygt

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Concurrent access

• lt_at_page isThreadSafe"false"gt lt-- default value
  is "true"--gt
• Compensations
• public class Counter
• private int _counter 0
• public synchronized int get_counter()
• return _counter
• public synchronized int set_counter(int counter)
  
• _counter counter
• return _counter
• public synchronized int increment()
• return _counter

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Custom tags

• A custom tag is a user-defined JSP new element
• Custom tags both accept incoming data from pages
  and may pass data back to pages
• Tags may have attributes or not attributes have
  the possible following types
• Simple
• Fragment
• Dynamic

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Tag file

• File location /WEB-INF/tags
• File name Prison_de_Nantes.tag (the file name is
  the name of the tag!)
• Content
• lt_at_tag description"Prison_de_Nantes.tag"
  pageEncoding"UTF-8"gt
• lt_at_tag body-content"empty"gt
• lt_at_attribute name"couleur" required"false"gt
• lt_at_attribute name"police" required"false"gt
• lt_at_attribute name"theme" required"false"gt
• lth1 style"colorcouleur font-stylepolice"
  gtCreacuteation themelt/h1gt
• Usage (tag declaration)
• lt_at_ taglib prefix"PN" tagdir"/WEB-INF/tags" gt
• ltPNPrison_de_Nantes couleur"red"
  police"italic" theme"deacutetenu"/gt

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More complex tag file (1/2)

• Usage
• lt_at_taglib prefix"PN" tagdir"/WEB-INF/tags" gt
• ltPNN_ecrou n_ecrou_max"2008" n_ecrou_aleatoire"
  x"/gt
• Saisir nécrou ltinput type"text"
  name"n_ecrou" value"x"/gt
• N_ecrou.tag file (v. 1)
• lt_at_tag body-content"empty" description"N_ecrou.t
  ag" example"ltPNN_ecrou n_ecrou_max\"2008\"
  n_ecrou_aleatoire\"x\"/gt"gt
• lt_at_attribute name"n_ecrou_max"
  type"java.lang.Integer"gt
• lt_at_attribute name"n_ecrou_aleatoire"
  required"true" rtexprvalue"false"gt
• lt_at_variable name-given"x" scope"AT_BEGIN"gt
• lt
• Integer max 0
• max (Integer) jspContext.getAttribute("n_ecrou_m
  ax")
• jspContext.setAttribute("x", com.FranckBarbier.Jav
  a._Prison_de_Nantes.Prison_de_Nantes.n_ecrou(max).
  toString())
• gt

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Called method in custom tag

• public class Prison_de_Nantes
• public static Integer n_ecrou(Integer max)
• if (max null)
• return new java.util.Random().nextInt(java.util.Ca
  lendar.getInstance().get(java.util.Calendar.YEAR))
  
• return new java.util.Random().nextInt(max)

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More complex tag file (2/2)

• Same usage
• lt_at_taglib prefix"PN" tagdir"/WEB-INF/tags" gt
• ltPNN_ecrou n_ecrou_max"2008" n_ecrou_aleatoire"
  x"/gt
• Saisir nécrou ltinput type"text"
  name"n_ecrou" value"x"/gt
• N_ecrou.tag file (v. 2)
• lt_at_tag body-content"empty" description"N_ecrou.t
  ag" example"ltPNN_ecrou n_ecrou_max\"2008\"
  n_ecrou_aleatoire\"x\"/gt"gt
• lt_at_attribute name"n_ecrou_max"
  type"java.lang.Integer"gt
• lt_at_attribute name"n_ecrou_aleatoire"
  required"true" rtexprvalue"false"gt
• lt_at_variable name-from-attribute"n_ecrou_aleatoire
  " alias"y" scope"AT_BEGIN"gt
• lt
• Integer max 0
• max (Integer) jspContext.getAttribute("n_ecrou_m
  ax")
• jspContext.setAttribute("y", com.FranckBarbier.Jav
  a._Prison_de_Nantes.Prison_de_Nantes.n_ecrou(max).
  toString())
• gt

Synchronized according to scope values NESTED
(default), AT_BEGIN and AT_END
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Tag files as library elements

• Prison_de_Nantes.tld file
• lttag-filegt
• ltnamegtN_ecroult/namegt
• ltpathgt/WEB-INF/tags/N_ecrou.taglt/pathgt
• lt/tag-filegt

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JavaServer Faces

• JavaServer Faces (JSF) is in fact an extended
  (normalized) use of custom tags within JSP
• JSF is based on an enhanced MVC framework like
  Struts for example
• JSF automates most of the recurrent tasks of Web
  appplications design (navigation, validations)
• Tag libraries
• lt_at_taglib uri"http//java.sun.com/jsf/core"
  prefix"f"gt
• lt_at_taglib uri"http//java.sun.com/jsf/html"
  prefix"h"gt
• Configuration faces-config.xml file

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JSF demo.

• See Prison_de_Nantes NetBeans Web application
  project