Lap trinh web [Slide jsp]
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This document provides an overview of Java Server Pages (JSP) technology. It discusses JSP architecture and components like expressions, scriptlets, declarations, comments, directives, standard actions, implicit objects, and JavaBeans. Expression Language (EL) is also introduced, which allows accessing Java objects in JSP using a simpler syntax. Key elements like scopes, operators, and implicit objects available in EL are explained.
![21/07/2009
8
EL Implicit Objects
43Implicit Objects
pageContext
cookie
initParamparamValues
param
header
headerValuesapplicationservletContext
request
session
response
Request Headers and Parameters
44
param: return a value that maps a request parameter name to a single string valueex: "${param.Name}“
paramValues: return an array of values is mapped to the request parameters from clientex: “${paramValues.Name[0]}”
header: return a request header name and maps the value to single string value. ex: ${header[“host”]}
headerValues: return an array of values is mapped to the request headerex: ${headerValues.Name}
cookie: returns the cookies name mapped to the single cookie objectex: ${cookie.name.value}
initParam: returns a context initialization parameter name, which is mapped to a single value.
Scope variables (1)
45
Variables are used to store and access values in JSPprogram
Variable refers as a attributes that are stored in standard scope such as page, request, session and application
Dot operator . or square brackets [ ] can be used to access value of variable
Example
${pageScope.color}
${pageScope[“color”]}
Scope Variables (2)
46
EL Operators
47
*
/ or div
+
-
% or mod
< or lt
> or gt
< = or le
> = or ge
= = or eq
!= or ne
&& or and
|| or or
! or not
empty
Operators
Empty
LogicalRelational
Arithmetic
Example
48](https://image.slidesharecdn.com/slidejsp-141104093528-conversion-gate01/85/Lap-trinh-web-Slide-jsp-8-320.jpg)
Lap trinh web [Slide jsp]
- 1. 21/07/2009 1 Java Server Pages http://www.vovanhai.wordpress.com 1 JSPBasics 2 JSP JavaServerPage(JSP)isaserversidescriptlanguage Savedwith.jspextension Asimple,yetpowerfulJavatechnologyforcreatingandmaintainingdynamic-contentwebspages JSPpageareconvertedbythewebcontainerintoaServletinstance Itfocusonthepresentationlogicofthewebapplication 3 Architecture of JSP 4 JSPExpression Includes expression in a scripting language page 5 Scriptlet Refers to code blocks executed for every request. 6
- 2. 21/07/2009 2 Declarations Defines the variables and methods for a JSPpage 7 Comments Explains the functioning of the code Comments are ignored by the servletduring compilation Syntax ... <!–-HTML comments --> ... ... <%--JSPcomments --%> ... ... <% /*Scripting languages comments*/ %> ... 8 Directives ControlsthestructureoftheservletbysendingmessagesfromtheJSPpagetotheJSPcontainer. Specifythescriptinglanguagetoused. DenotetheuseofcustomtaglibraryinaJSPpage. BeusedtoincludethecontentofanotherJSPpage. … Syntax ... <%directivenameattribute = “value”%> ... Specifies the JSPdirective Refers to the directive attribute 9 Directives –Contd… The types of JSPdirectives are: page-Associates the attributes that affect the entire JSPpage include-Sends message to the JSPcontainer to include the contents of one file into another taglib-Enables the use of custom tags in the JSPpage 10 pageDirective 11 includeDirective12
- 3. 21/07/2009 3 taglibDirective 13 Standard Actions Tags affecting the behavior of JSPat runtime and the response sent back to web browser Syntax: ... <jsp: standard action> ... Standard Action Description <jsp: useBean> Accesses the functions of custom tags <jsp: param> Provides name and value to the parameters used by the JSP page <jsp: include> Includes the output from one file into the other files <jsp: forward> Transfers control from a JSPpage to another <jsp: plugin> Uses a pluginto execute an applet or bean 14 JSPImplicit Object 15 Implicit Objects Are loaded by the Web Container automatically and maintains them in a JSPpage The names of the implicit objects are reserved words of JSP Access dynamic content using JavaBeans Types of implicit objects 16 Implicit Objects (cont) Object Class / Interface page javax.servlet.jsp.HttpJspPage config javax.servlet.ServletConfig request javax.servlet.http.HttpServletRequest response javax.servlet.http.HttpServletResponse out javax.servlet.jsp.JspWriter session javax.servlet.http.HttpSession application javax.servlet.ServletContext pageContext javax.servlet.jsp.PageContext exception java.lang.Throwable 17 The requestObject 18 RepresentstherequestfromtheclientforaWebpage Controlsinformationassociatedwitharequestfromclient Includesthesource,URL,headers,cookiesandparameters
- 4. 21/07/2009 4 The responseObject 19 Manages the response generated by JSPcontainer and sends response to the client Is passed as a parameter to JSP_jspService() method The outObject 20 Represents the output stream, then it will be sent to the client as a response for the request Is has page scope The sessionObject 21Provides all the objects available in the JSPpages within the session The applicationObject 22 Is used to share the data between all application pages Can be accessed by any JSPpresent in the application The pageContextObbject(1) 23 Provides methods to access all attributes defined by implicit objects in the page. Provides methods to transfer control from one web page to another osetAttribute() ogetAttribute() ogetAttributeNamesInScope() oremoveAttribute() The pageContextObbject(2) 24 Find the scope or specify the scope
- 5. 21/07/2009 5 ServletObject (1) 25 The pageobject: is an instance of the servletprocessing the current request in a JSPpage. ServletObject (2) 26The “config” Object: oStores the information of the servlet oRepresents the configuration of the servletdata where a JSPpage is compiled oIt has page scope The exceptionObject 27 Is used to handle errors in a JSPpage Is used to trace the exception thrown during the execution It has page scope Error handling <%@page errorpage=“error.jsp”%> < --some of code,…--> index.jsp error.jsp <%@page isErrorPage=“true”%> <% if(exception!=null){ out.println(exception.getMessage()); } %> 28 Standard Actions 29 Standard Actions 30 AreXMLliketagswhichtaketheformofanXMLtagwithanameprefixedjsp Areusedfor Forwardingrequestsandperformingincludesinpage EmbeddingtheappropriateHTMLonpages InteractingbetweenpagesandJavaBeans Providingadditionalfunctionalitytotaglibraries Syntax: <jsp:actionNameattribute=“value”>...</jsp:actionName> Someproperties Using<jsp>prefix Theattributesarecasesensitive Valueintheattributesmustbeenclosedindoublequotes Standardactionscanbeeitheranemptyoracontainertag 30
- 6. 21/07/2009 6 <jsp:include> 31 Include either static or dynamic file in jspfile at the time of page request. Static case: The content is included in the calling jspfile. Dynamic case: it acts on the request and send back a result that is include in the JSPpage. Syntax: <jsp:include: page=“webURL”|<%=exp%> flush=“true”/> <jsp:forward> 32 It’s used to forward the request and response to another jsppage or servlet Syntax: <jsp:forwardpage=“{webURL|<%=exp%>}”> <jsp:paramname=“{paramName|<%=exp%>”}/> <jsp:forward> Allow to pass one or more name/value pairs as parameters to an included or forwarded resource like a jsppage. Syntax: <jsp:paramname=“thename” value=“{thevalue|<%=exp%>}” <jsp:param> <jsp:plugin> 33 Used in the execution of an applet or bean. Syntax: <jsp:plugintype=“bean|applet” code=“ClassFileName” codebase=“classFileDirectoryName” <jsp:params> <jsp:paramname=“thename” value=“thevalue”> </jsp:params> [<jsp:fallback> display message to user</jsp:fallback> </jsp:plugin> <jsp:fallback> 34 Display a text message to user if the plug- in could not start. Syntax: <jsp:fallback> html message</jsp:fallback> JavaBeans 35 Concept 36 JavaBeans are reusable components that can be deployed in java. Define the interactivity of Java object Allow creation of graphical components that can be reused in GUI application. Can be embedded in multiple applications, servletand jsp. Requirements: oBe a public class oHave a public constructor with no arguments oHave get/set methods to read/write bean properties Components of JavaBeans: ◦Properties Getters and setters ◦Methods ◦Events
- 7. 21/07/2009 7 <jsp:useBean> Is used to create a reference and include an existing bean component in JSP The <jsp:useBean> follows to locate or instantiate the Bean Attempsto locate a Bean within the scope Defines an object reference variable with the name Stores a reference to it in the variable, if it retrieves the Bean Instantiates it from the specified class, it is cannot retrieve the Bean Syntax: <jsp:useBeanid=“name” class=“class” scope=“page/session/request/application” /> 37 <jsp:getProperty> 38 Using for retrieve properties value of the Bean. RetrievesabeanpropertyvalueusingthegettermethodsanddisplaystheoutputinaJSPpage The<jsp:getProperty>andexpressionconvertthevalueintoastringandinsertitintoanimplicitoutobject Somedrawbacks Failstoretrievethevaluesofindexesproperty Failstodirectlyaccessenterprisebeancomponents Syntax: <jsp:getPropertyname=“Bean_Alias” property=“PropertyName”/> <jsp:setProperty> 39 Retrieves a bean property value using the getter methods and displays the output in a JSPpage The <jsp:getProperty> and expression convert the value into a string and insert it into an implicit out object Some drawbacks: ◦Fails to retrieve the values of indexes property ◦Fails to directly access enterprise bean components Syntax: <jsp:setPropertyname=“Bean_Alias” property=“Property_Name” value=“TheValue” param=“Parameter”/> JavaBeans & Scriptlets 40 JavaBeanscanbeaccessedfromscriptingelementindifferentways.DoitlikesinJ2SE. TheJSPcontainerconvertsthestringvaluesintononstringvaluesbytheattributevaluesthatevaluatethecorrectdatatypetosetthepropertyvalue Expression Language 41 Expression Language (EL) 42 New feature of JSP2.0 Allows JSPdevelopers to access java objects via a compact, easy-to-use shorthand style (similar to JavaScript) It can handle both expressions and literals Developed by two groups JSPStandard Tag Library expert group JSP2.0 expert group Syntax: ${EL Expression}
- 8. 21/07/2009 8 EL Implicit Objects 43Implicit Objects pageContext cookie initParamparamValues param header headerValuesapplicationservletContext request session response Request Headers and Parameters 44 param: return a value that maps a request parameter name to a single string valueex: "${param.Name}“ paramValues: return an array of values is mapped to the request parameters from clientex: “${paramValues.Name[0]}” header: return a request header name and maps the value to single string value. ex: ${header[“host”]} headerValues: return an array of values is mapped to the request headerex: ${headerValues.Name} cookie: returns the cookies name mapped to the single cookie objectex: ${cookie.name.value} initParam: returns a context initialization parameter name, which is mapped to a single value. Scope variables (1) 45 Variables are used to store and access values in JSPprogram Variable refers as a attributes that are stored in standard scope such as page, request, session and application Dot operator . or square brackets [ ] can be used to access value of variable Example ${pageScope.color} ${pageScope[“color”]} Scope Variables (2) 46 EL Operators 47 * / or div + - % or mod < or lt > or gt < = or le > = or ge = = or eq != or ne && or and || or or ! or not empty Operators Empty LogicalRelational Arithmetic Example 48
- 9. 21/07/2009 9 JSPStandard Tag Library (JSTL) 49 Concept JSTLprovides a set of reusable standard tag that work for create jsppages. JSTLallows programming using tags rather than scriptletcode. JSTLhas tags, such as: ◦Iteratorsand conditional tags ◦Internationalization tags ◦SQL tags 50 Types Of Tags Libraries 51 JSP Standard Tag Library (JSTL) Core Tag Library I18N & Formatting Tag Library SQL Tag Library XML Tag Library Core Tag Library 52 General Purpose Tags Decision Making Tags Iteration Tags set removeout forEachforTokens if choose Core Tag Library General Purpose Tags 53 <c:set>: assigns a value to a variable in scope <c:remove>: remove a scope variable <c:out>: evaluate an expression and store a result in the current JspWriterobject. <c:catch>: provides an exception handling functionality, such as try-catch inside jsppages without using scriptlet Syntax: <c:setvar=“varName” value=“value” scope=“page|request|session|application” /> <c:removevar=“varName” scope=“page|request|session|application” /> <c:outvalue=“value|expression” escapeXml=“true|false” default=“defaultValue” /> <c:catch/> Example 54
- 10. 21/07/2009 10 Decision-Making Tags 55 <c:if>: used for conditional execution of the code <c:choose>: similar switch statement in java Iteration Tags 56 <c:forEach>: used to repatethe body content over a collection of objects. <c:forTokens>: used to iterate over a collection of tokens separated by user-specified delimiters. SQL Tag Library 57 SQL Tag Library setDataSourcequery update param transaction The sql:setDataSourceTag 58 The sql:queryTag The sql:updateTag 59 The sql:paramTag 60
- 11. 21/07/2009 11 The sql:transactionTag 61 62 Internationalization(I18N) 63 I18NBasics(1) 64 Internationalization Themethodofdesigninganapplicationthatcanbeadaptedtoaregionoralanguagewithoutmuchchangeinthetechnology HelpsincreatinginternationalizedWebapplicationthatstandardizeformattednumericanddate-timeoutput(supportingmultiplelanguages) Localization Isaprocessofmakingofproductorservicelanguage,culturalandlocal“lookandfeel”specific ALocaleisasimpleobjectidentifyingaspecificlanguageandgeographicregion(java.lang.Locale) Isdenotedbyxx_YY(languagecode_lettercountry) UnicodeinJava,isa16bitcharacterencoding ResourceBundlescontainlocale-specificobjects Internationalizing (1) 65 ResourceBundles IsasetofrelatedclassesthatinheritfromResourceBundle Theseveralmethods publicstaticfinalResourceBundlegetBundle(StringbaseName, Localelocale) publicabstractEnumerationgetKeys() publicLocalegetLocale() publicfinalObjectgetObject(Stringkey) publicfinalStringgetString(Stringkey) FormattingDatesinServlets UsingpredefinedFormats:SHORT,MEDIUM,LONG,FULL CreateaformatterwiththegetDateInstance()methodofDateFormatclass Invokingtheformat()method CustomisingFormats:UsingtheSimpleDateFormatclass Internationalizing (2) 66 FormattingCurrencies Currency:thisclassrepresentscurrencybyISO4217currencycodes publicStringgetCurrencyNode() publicStringgetSymbol() publicstaticCurrencygetInstance(Localelocale) NumberFormat:thisisanabstractbaseclassforallnumberformats publicfinalStringformat(doublenumber) publicCurrencygetCurrency() publicstaticfinalNumberFormatgetInstance() publicNumberparse(Stringstr)throwsParseException publicvoidsetCurrency(Currencycurrency) FormattingPercentages publicstaticfinalNumberFormatgetPercentInstance() publicstaticNumberFormatgetPercentInstance(LocaleinLocale)
- 12. 21/07/2009 12 Internationalizing (3) 67 FormattingMessages UsingtheMessageFormatObjects ThearrayofobjectsusingtheformatspecifiersembeddedinthepatternformatetedbytheMessageFormat.format() Theclassesforformattingmessages MessageFormat MessageFormat.Field