JSTL, XML and XSLT An introduction to JSP Standard Tag
Download
Report
Transcript JSTL, XML and XSLT An introduction to JSP Standard Tag
JSTL, XML and XSLT
An introduction to JSP Standard Tag
Library and XML/XSLT transformation
for Web layout
JSP Standard Tag Library (JSTL)
JSTL is a standardized set of Custom Tags
with several implementations
http://jakarta.apache.org/taglibs/doc/standard
-doc/intro.html
JSTL is one Tag Library, but it’s functionally is
divided into four parts with its own TLD
Core
XML Processing
I18N
Database Access (SQL)
JSTL - Prerequisites
In all examples a couple of objects are supposed to be available
customers - A collection of Customer objects
intArray - An array of int's
stringArra - An array of Strings
The Customer Object
int key
String lastName
String firstName
Date birthDate
Address address
The Address Object
String line1
String line2
String city
String state
String country
JSTL Core
The Core part of JSTL contain tags the core
of JSTL such as iteration, conditional
processing and expression language support
< %@ taglib prefix="c"
uri="http://java.sun.com/jstl/ea/core" %> at
the top of your JSPs
JSTL Core – General tags
<c:set …> is used to declare variables and
assign values to them
<c:set var=“name”
scope=“application|request|session” value=“val” />
<c:set var=“name”
scope=“application|request|session”/>
<bookshop:shoppingCart />
</c:set>
JSTL Core – General tags
<c:out …> is used to print values
<c:out value="${customer.lastName}"/>
<c:out value="${customer.lastName}“
scope=”session” />
<c:out value="${customer.phoneHome}"
default="no home phone specified"/>
JSTL Core – Conditional tags
Conditional tags are used for execution control
<c:if />
<c:if test="${customer.address.country == 'USA'}"> <c:out
value="${customer}"/><br> </c:if
<c:chose /> and <c:when /> - a switch/case
structure
<c:choose>
<c:when test="${customer.address.country == 'USA'}"> <font
color="blue"> </c:when>
<c:when test="${customer.address.country == 'Canada'}">
<font color="red"> </c:when>
<c:otherwise> <font color="green"> </c:otherwise>
</c:choose>
JSTL Core – iteration tags
Iteration tags are used to loop over some
data structure, often a Collection
<c:forEach var=“current” items=“Collection ”
begin=“start” end=“10” />
<c:forEach var="customer" items="${customers}">
</c:forEach>
<c:forEach var="i" begin="1" end="10">
<c:out value="${customer}"/><br>
<c:out value="${i}"/> •
</c:forEach>
JSTL Core – iteration tags
<c:forTokens var=“token” items=“a,b,c” delims=“,”>
<c:forTokens var="token"
items="bleu,blanc,rouge|vert,jaune|blanc,rouge"
delims="|">
</c:forTokens>
<c:forTokens var="token"
items="bleu,blanc,rouge|vert,jaune|blanc,rouge"
delims="|,">
<c:out value="${token}"/> •
<c:out value="${token}"/> •
</c:forTokens>
JSTL Core – Import tags
There are several tags for importing
information from http and ftp (and more)
<c:import url=“url” var=“resultVar”/>
<c:import url=“http://developer.mimer.com” />
Relative path is ok
Will get the content of the URL and print it
<c:import url="LocalSample.jsp"/>
<c:import url=“ftp://ftp.mimer.se/readme_v.txt/”
var=“result”/>
Will get the content and store it in the variable resultVar
JSTL Core – Import tags
The <c:param name=“name” value=“value” />
can be combined with <c:import /> to import
content from dynamic sites
<c:import
url=http://developer.mimer.se/support/support_faq
.tml>
<c:param name=“category” value=“3” />
</c:import>
JSTL Core – Working with URLs
The <c:url /> and <c:param /> is used
together to construct URLs with proper
escaping and rewriting
<c:url value=“base.jsp” />
<c:param name=“name" value=“Fredrik Alund"/>
</c:url>
Gives base.jsp?name=Fredrik%20Alund
Possibly with jsessionid appended
JSTL XML
JSTL contains several tags for working with
XML and XSLT
But first an introduction to XML and XSLT
XML
XML is an abbreviation for EXtensible
Markup Language
A markup language like HTML
Not used to generate layouts but to describe
data
No tags are defined in XML, just syntax rules
for tags
XML uses a DTD (Document Type Definition)
to formally describe the data
XML
XML tags are case sensitive
All XML elements must have a closing tag
All XML elements must be properly nested
<a></a> or <a />
<a><b><c></b></c></a> is not valid
All XML documents must have a root/start tag
<a></a><b></b> is not valid, but
<root><a></a><b></b></root> is
XML
A XML document is well formed if it conforms
to the XML syntax rules
A XML document is valid if it is well formed
and conform to the rules of a DTD
XML Example 1
<?xml version="1.0“ encoding=“UTF-8” ?>
<person>
<name>Fredrik</name>
<surname>Ålund</name>
<age>32</age>
</person>
The first line tells what version of XML is
used and what encoding to use
XML bigger example
<family>
<person>
<name>Fredrik</name>
<surname>Ålund</name>
<age>32</age>
</person>
<person>
<name>Annika</name>
<surname>Ålund</name>
<age>28</age>
</person>
<person>
<name>Viktor</name>
<surname>Ålund</name>
<age>0,5</age>
</person>
</family>
XML attributes
XML elements can have attributes
<employees>
<employee empid=“1”>
<name>Fredrik Ålund</name>
<department depid=“3”>Services</department>
</employee>
<employee empid=“2”>
<name>Helena Larsson</name>
<department depid=“3”> Services </department>
</employee>
</employees>
XML CDATA
If the value of an element contain binary data
or some other illegal characters, CDATA can
be used
<element><!CDATA[anytext]]></element>
Why XML?
Describe your data
Give you a structure of your data
Easier integration of systems
The same XML document can be
transformed to HTML, WML or VoiceXML to
support different clients
XSL and XSLT
XSL is an abbreviation of eXtensible
Stylesheet Language
XSLT means XSL Transformation
XSL consists of two parts
A method for transforming XML documents
A method for formatting XML documents
A XML document can be transformed into a HTML
document
Elements can be sorted and formatted in different ways
XSL files are valid XML documents
A XSL example
A XSL to transform our employee list to html might look like
<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="/">
<html> <body>
<table border="2" bgcolor="yellow">
<tr>
<th>Name</th>
<th>Department</th>
</tr>
<xsl:for-each select=“employees/employee">
<tr>
<td><xsl:value-of select=“name"/></td>
<td><xsl:value-of select=“department"/></td>
</tr> </xsl:for-each>
</table>
</body> </html>
</xsl:template>
</xsl:stylesheet>
XSL templates
Stylesheets starts with <xsl:stylesheet
xmlns:xsl="http://www.w3.org/TR/WD-xsl">
A template matches a part of a XML
document and is evaluted
<xsl:template match="/"> - matches the root
<xsl:template match=“employees"> - matches
employees
XSL <xsl:for-each/>
<xsl:for-each select=“employees/employee">
loops over all employees
<xsl:for-each select=" employees/employee "
order-by="+ name"> will order the elements
on the name element (+ ascending, descending)
XSL <xsl:for-each/> and filters
Filters can be applied to filter out elements
<xsl:for-each
select=“employees/employee[department/@depid =
‘3’“ >
<xsl:for-each
select=“employees/employee[department =
‘Services’“ >
Valid filter operations are
= (equal)
=! (not equal)
<& (less than)
>& (greater than)
XSL <xsl:value-of/>
<xsl:value-of ..> returns the value of an
element or attribute
<xsl:value-of select=“name"/> return the
value of the name element for the current
employee
<xsl:value-of select=“@empid"/> returns the
empid attribute of the employee element
XSL IF
The conditional statement if is available in
XSL
<xsl:if match=".[@empid=‘1']">
</xsl:if>
XSL chose
<xsl:choose>
<xsl:when match=".[@empid=‘3']">
... some code ...
</xsl:when>
<xsl:otherwise>
... some code ....
</xsl:otherwise>
</xsl:choose>
XSL Text
<xsl:text disable-output-escaping=“true/false”
/>
Used to output text. Useful if the text is not valid
XML since it can be combined with
<![CDATA[xxx]]>
<xsl:text disable-output-escaping="yes">
<![CDATA[shop?action=detail&bookid=]]>
</xsl:text>
<xsl:apply-template />
Instead of using for-each, we can use
<xsl:apply-templates match=“element”/>
Make <xsl:template match=“xxx” /> for each
element
Put <xsl:apply-template where you want the
output of the other template
<xsl:element />
In XSL you have to follow XML syntax rules. This
makes it hard to construct HTML form elements and
HREFs. <xsl:element > can be used to ease this
A HREF link in XSL
<xsl:element name="input">
<xsl:attribute name="href">
<xsl:text disable-output-escaping="yes">
<![CDATA[ shop?action=detail&bookid= ]]>
</xsl:text>
<xsl:value-of select="id" />
</xsl:attribute>
<xsl:text>Detail</xsl:text>
</xsl:element>
<xsl:element>
A HTML Form text input field
<xsl:element name="input">
<xsl:attribute name="size">2</xsl:attribute>
<xsl:attribute name="type">text</xsl:attribute>
<xsl:attribute name="value">1</xsl:attribute>
<xsl:attribute name="name">
quantity
</xsl:attribute>
</xsl:element>
The same XSL with apply-template
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="employees">
<html> <body>
<table border="2" bgcolor="yellow">
<tr> <th>Id</th><th>Name</th> <th>Department</th> </tr>
<xsl:apply-templates />
</table>
</body> </html>
</xsl:template>
<xsl:template match="employee">
<tr>
<td><xsl:value-of select="@empid"/></td>
<td><xsl:value-of select="name"/></td>
<td><xsl:value-of select="department"/></td>
</tr>
</xsl:template>
</xsl:stylesheet>
JSTL and XML, resumed
JSTL has support for navigating XML with
XPath and to do XSLT processing
<%@ taglib prefix="x"
uri="http://java.sun.com/jstl/xml" %> is used
to specify that the XML part is to be used
JSTL XML - parsing
A XML structure can be parsed into a XML
document that can be navigated
<x:parse var="a"> <a> <b> <c> foo </c> </b>
<d> bar </d> </a> </x:parse>
<x:out select="$a/a/d"/>
The XML is parsed into variable a
The value of the element d is selected
JSTL XSL Transformation
<c:set var="xml">
<a><b>header!</b></a>
</c:set>
<c:set var="xsl">
<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:template match="text()"> <h1>
<xsl:value-of select="."/></h1>
</xsl:template>
</xsl:stylesheet>
</c:set>
<x:transform xml="${xml}" xslt="${xsl}"/>
JSTL XSL Transformation combined with
JSTL Core and Custom Tags
Combine the Core import with XSLT to read
the XSL file from disk
Get XML output from a Custom tag (or Java
Bean)
Do XSL Transformation
JSTL XSL Transformation combined with
JSTL Core and Custom Tags
<c:set var="booklist_xslt">
<c:import url="booklist_xslt.xsl"/>
</c:set>
<x:transform xslt="${booklist_xslt}">
<jsp:getProperty name="bookList"
property="xml"/>
</x:transform>