Transcript Introduction to XSLT

Introduction to XSLT
What is XML?
Design Goals of XML
XML Format
XML Declaration
Elements
Attributes
Design Goals of XML
XML shall be straightforwardly usable over the Internet.
XML shall support a wide variety of applications.
XML shall be compatible with SGML.
It shall be easy to write programs which process XML documents.
The number of optional features in XML is to be kept to the absolute
minimum, ideally zero.
XML documents should be human-legible and reasonably clear.
The XML design should be prepared quickly.
The design of XML shall be formal and concise.
XML documents shall be easy to create.
Terseness in XML markup is of minimal importance.
XML Format
XML contains elements, attributes, and
data. An example XML entry would look
like:
<book isbn=” 102-0497449-4818519”>
<title>Tom Sawyer</title>
<author>Mark Twain</author>
</book>
XML Declaration
The XML Declaration should appear at the
top of each XML file and should specify
the XML version and the encoding used
within the XML. An example XML
declaration would look like:
<?xml version="1.0" encoding="ISO-88591"?>
Elements
XML Elements are contained within <>
symbols and must nest properly. Each
node that opens must have a
corresponding close node. Nodes can
contain attributes, data, and “child” nodes.
An example XML element (also called a
node) with a single piece of data would
look like:
<book>Tom Sawyer</book>
Attributes
An XML Attribute is a single piece of data
assigned to an XML Element. If data is
assigned as an attribute, the data can not be
split further into sub-elements. XML attributes
should only be used if the data will never need
additional elements created below. An example
XML element with an attribute and a single piece
of data would look like:
<book isbn=” 102-0497449-4818519”>Tom
Sawyer</book>
XSLT Basics
What is XSLT?
XML Declaration and XSLT Declaration
Connecting to an XML Data file
What is XSLT?
An XSLT stylesheet utilizes XPath in order
to transform the initial XML document into
another document. The original XML
document must be well formed. The
resultant document should also be well
formed, though in certain instances, this
can be overridden as necessary.
Declarations
<?xml version="1.0" encoding="ISO-8859-1"?>
In addition to the XML declaration, an XSLT
stylesheet must specify a style sheet
declaration. The style sheet declaration is what
enables the XSLT to utilize the binding features.
An example XML Style Sheet Declaration would
look like:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transfor
m">
Connecting to XML Data
In order to client-side bind the XML Data
with the XSLT Stylesheet, a single line
must be added within the XML Data. An
example binding line would look like:
<?xml-stylesheet type="text/xsl"
href="PageDesign.xsl"?>
This line should appear directly beneath
the XML Declaration in the XML Data file.
XSLT Tags
<xsl:template>
<xsl:template match=””>
<xsl:apply-templates>
<xsl:value-of>
<xsl:for-each >
<xsl:sort>
<xsl:if>
<xsl:choose>
position function
mod
<xsl:call-template>
<xsl:copy>
<xsl:copy-of>
<xsl:template>
The <xsl:template> element is used to
create individual templates within a single
stylesheet. These templates can be
accessed by simple matching or called
directly via the name attribute.
<xsl:template match=””>
When an XSLT style sheet comes across an
<xsl:template match=”/”> tag, the style sheet will
look for matching nodes. The matching node is
determined by the value located within the
match attribute. In this case a forward slash (/).
In XSLT, a forward slash represents the root
node of the XML data. In this case, the template
should be matched only a single time as only a
single root node can exist within an XML
document.
<xsl:apply-templates>
When an XSLT style sheet comes across
an <xsl:apply templates> tag, the style
sheet will compare current nodes with
available <xsl:template match=””> tags.
For each match it comes across (in the
current node set), the template will be
applied. The select statement can be
added to the tag in order to specify the
order in which the nodes are processed.
<xsl:value-of>
The <xsl:value-of> tag is used to take the
value (or attribute value) from an XML
element within the XML Data file and use it
within the output stream of the stylesheet.
The standard use is to write output to the
final output.
<xsl:for-each >
The <xsl:for-each> tag allows the XSLT to
loop through a set of nodes at which point
it can use data within each node for
output. The <xsl:for-each> is often used
to create lists or tables of repeating data.
XPath is used to determine which
selection will be looped and can include
select statements to filter the looped items.
<xsl:sort>
The <xsl:sort> tag can be used within
<xsl:for-each> lops in order to sort the
nodes before the final output has been
created. This is often useful for
alphabetizing items within a repeating list.
<xsl:if>
The <xsl:if > statement allows the XSLT to
perform a test on the current node set to
see if it meets conditions for continued
processing.
The <xsl:if> statement must contain the
entire section it will affect. <xsl:if>
statements are most often used within
<xsl:for-each> loops.
<xsl:choose>
The <xsl:choose> statement is used to
select a single instance of multiple
possibilities. The first condition that is met
will be used, if no condition are met, the
<xsl:choose> statement allows the use of
<xsl:otherwise> which will be the catch-all
condition.
position function
The position function is used to determine
the current position in the node set. This
tag will often be used within <xsl:for-each>
loops in order to number the output.
mod
Mod has many applications, but the most
common is alternating row colors within a
table. Because of the nature of mod, the
developer can determine how often a
pattern repeats (every other row, every
third row, etc.).
<xsl:call-template>
The <xsl:call-template> tag works very
much like <xsl:apply-templates> with the
exception that the developer is able to call
a chosen template regardless of the
current node in use. This adds the ability
to call template that have nested calls
whether or not the original template should
have been called in the first place.
<xsl:copy> and <xsl:copy-of>
The <xsl:copy> tag allows the XSLT to
create a copy of the currently selected
node.
The <xsl:copy-of> tag is very similar to the
<xsl:copy” tag but copies the children
nodes and data as well.
Old vs New
<img><xsl:attribute
name=“src”><xsl:value-of
select=“./source”
/></xsl:attribute><xsl:attribute
name=“alt”><xsl:value-of select=“./altTag”
/></xsl:attribute></img>
<img src=“{./source}” alt=“{./altTag}” />
Questions?