i-Lab Guide To : JSP

Key Acronyms

JSP  = JavaServer Pages
JSTL = JSP Standard Tag Library
TLD  = Tag Library Descriptor
WAR  = Web-application ARchive
EL = Expression Language

Page Lifecycle

1. Page Translation
2. Page Compilation
3. Load Class
4. Create Object
5. Call jspInit()
6. Call _jspService()
7. Call jspDestroy()

BASIC SYNTAX

Directive Elements (translation phase)

<%@ page ... %>                                      - <jsp:directive.page .. /> in XML
<%@ include file="filename" %>                       - <jsp:directive.include .. /> in XML
<%@ taglib prefix="shortName" uri="tldUniqueName" %> - xmlns:prefix="tldUniqueName" in XML

Scripting Elements

<%  ...; %> - script-let   - <jsp:scriptlet> in XML
<%= ...  %> - expression   - <jsp:expression> in XML
<%! ...; %> - declaration  - <jsp:declaration> in XML
<%-- ... --%> - comment    - <!-- ... --> in XML
${ <EL expression> }       - JSTL 1.0/JSP2.0

Implicit objects (note not available in declarations)

application  - ServletContext
config       - ServletConfig
exception    - Throwable (only for pages with page directive isErrorPage="true")
request      - HttpServletRequest
response     - HttpServletResponse
out          - JSPWriter
page         - Object
pageContext  - PageContext
session      - HttpSession (only for pages with page directive session="true")

Page Directive Attributes

autoFlush    - Boolean indicating whether buffer should flush when full (true)
buffer       - buffer size in kilobytes, e.g. "32kb"
contentType  - MIME type and character encoding of output (text/html;ISO-8859-1)
errorPage    - URL of a JSP page capable of handling errors for this page (null)
extends      - sub-class of javax.servlet.jsp.JspPage to use
import       - comma-separated list of packages/classes (java.lang.*, etc..)
isErrorPage  - boolean indicating page can accept errors (false)
isThreadSafe - Boolean indicating whether page is thread-safe (true)
language     - scripting language (java)
pageEncoding - character encoding of output (ISO-8859-1)
session      - boolean indicating whether takes part in a session (true)

Action Elements/Tags (request processing phase)

<jsp:useBean id="beanName" class="com.classes.BeanClass" [scope="page"]/>
<jsp:useBean id="beanName" class="com.classes.BeanClass" type="com.classes.BeanSuperClass"/>
<jsp:useBean id="beanName" beanName="serializedName" type="com.classes.BeanSuperClass"/>
<jsp:getProperty name="beanName" property="propertyName"/>
<jsp:setProperty name=“beanName" property="propertyName" value="propertyValue"/>
<jsp:setProperty name=“beanName" property="propertyName" [param="requestParamName"]/>
<jsp:include page="relativeURL"/>
<jsp:forward page="relativeURL"/>
<jsp:param name="paramName" value="paramValue"/>
<jsp:plugin/>

JSTL libraries

http://java.sun.com/jsp/jstl/core (c)
http://java.sun.com/jsp/jstl/xml (x)
http://java.sun.com/jsp/jstl/fmt (fmt)
http://java.sun.com/jsp/jstl/sql (sql)
http://java.sun.com/jsp/jstl/fn (fn)

JSTL functions (JSTL 1.1)

c:out(value)
c:param(name, value)
c:forEach(var, items, varStatus)
c:forToken
c:url
c:import(url)

fmt:formatNumber(value, pattern)
fmt:parseNumber
fmt:formatDate
fmt:parseDate
fmt:timeZone
fmt:setTimeZone
fmt:setLocale(value)
fmt:bundle(basename)

fn:contains(string, substring)
fn:containsIgnoreCase(string, substring)
fn:endsWith(string, suffix)
fn:escaleXml(string)
fn:indexOf(string, substring)
fn:join(array, separator)
fn:length(item)
fn:replace(string, before, after)
fn:split(string, separator)
fn:startsWith(string, prefix)
fn:substring(string, begin, end)
fn:substringAfter(string, substring)
fn:substringBefore(string, substring)
fn:toLowerCase(string)
fn:toUpperCase(string)
fn:trim(string)

sql:setDataSource(var,driver,url)
sql:query(var,datasource)
sql:update
sql:transaction(dataSource)

x:parse(source, var)
x:out(select)
x:transform(source, xslt)

PageContext methods

setAttribute(name, valueObject)
getAttribute(name)
setAttribute(name, valueObject, scope)
getAttribute(name, scope)
getAttributeNamesInScope(scope)
removeAttribute(name, scope)
getServletContext()
getSession()
getResponse()
getRequest()

Variable scopes

jsp:usebean  Servlet
===========  =======
page         PageContext.PAGE_SCOPE
request      PageContext.REQUEST_SCOPE
session      PageContext.SESSION_SCOPE
application  PageContext.APPLICATION_SCOPE

Custom tag interfaces

Tag          - base class for simple tags
IterationTag - adds doAfterBody() for iteration processing     (default implementation -> TagSupport)
BodyTag      - adds doInitBody() for handling tags with bodies (default implementation -> BodyTagSupport)

Tag methods (in order of execution)

setPageContext() - called by the container
setParent()      - called by the container
setXXXXXX()      - called for each attribute
doStartTag()     - returns either EVAL_BODY_INCLUDE or SKIP_BODY (or EVAL_BODY_BUFFERED for BodyTag)
setBodyContent() - called by the container (BodyTag only if EVAL_BODY_BUFFERED)
doInitBody()     - return void             (BodyTag only if EVAL_BODY_BUFFERED)
doAfterBody()    - returns either EVAL_BODY_AGAIN or SKIP_BODY (IterationTag and BodyTag)
doEndTag()       - returns either EVAL_PAGE or SKIP_PAGE
release()        - called when tag handler no longer required

 
doStart
doAfterBody
doEndTag
EVAL_BODY_INCLUDE
All
    
EVAL_BODY_BUFFERED
BodyTag
    
EVAL_BODY_AGAIN  
Iteration
  
SKIP_BODY
All
Iteration
  
EVAL_PAGE    
All
SKIP_PAGE    
All

Expression Language - Literals

true, false, 5, -5, 5.5, 5.5E5, "string", 'string', null

Expression Language - Operators

+,-,*,/,%,==,!,!=,<,>,<=,>=,&&,||,(,)
condition ? ifTrue : ifFalse
empty set

Expression Language - Equivalent JSP expressions

{$list[1]}               == <%= list.elementAt(1) %>
{$map.name}              == <%= map.get("name") %>
{$map['name']}           == <%= map.get("name") %>
{$map[name]}             == <%= map.get(pageContext.findAttribute("name")) %>
{$bean.property}         == <%= bean.getProperty() %>

{$pageContext.response}  == <%= pageContext.getResponse() %>
{$pageContext.session}   == <%= pageContext.getSession() %>
{$pageContext.context}   == <%= pageContext.getServletContext() %>
{$pageContext.request.requestURI} == <%= pageContext.getRequest().getRequestURI() %>

{$param.name}            == <%= request.getParameter("name") %>
{$paramValues.name}      == <%= request.getParameterValues("name") %>
{$header.name}           == <%= request.getHeader("name") %>
{$headerValues.name}     == <%= request.getHeaderValues("name") %>

{$pageScope.cart.count}  == <%= pageContext.getAttribute("cart", PageContext.PAGE_SCOPE).getCount() %>
{$requestScope.cart}     == <%= pageContext.getAttribute("cart", PageContext.REQUEST_SCOPE) %>
{$sessionScope.cart}     == <%= pageContext.getAttribute("cart", PageContext.SESSION_SCOPE) %>
{$applicationScope.cart} == <%= pageContext.getAttribute("cart", PageContext.APPLICATION_SCOPE) %>

{$mytl:myfn()}           - calls the myfn() function of the mytl tag library

EL functions are code as public static methods and identified using the function element of the TLD.

Tag Library Descriptor (META-INF/taglib.tld)

  • taglib
    • short-name
    • [display-name]
    • [description]
    • [uri] - if implicit taglib URI indirection is used
    • tlib-version
    • jsp-version
    • tag*
      • name
      • [display-name]
      • [description]
      • tag-class   - implementation of Tag
      • [tei-class] - implementation of TagExtraInfo
      • [body-content] - { empty | JSP | tagdependent }
      • [variable]*
      • [attribute]*
        • name
        • [description]
        • [required]    - { yes | no | true | false }
        • [rtexprvalue] - { yes | no | true | false } request time expressions
        • [type]        - request time expression type (default java.lang.String)
      • [example]
    • [function]*
      • name
      • [display-name]
      • [description]
      • function-class
      • function-signature
    • [listener]

WAR structure

/WEB-INF/web.xml
/WEB-INF/classes/
/WEB-INF/lib/
See also our guide to servlets

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