Using XSLT and XPath to Enhance HTML Documents

Using XSLT and XPath to Enhance HTML Documents
Roger L. Costello XML Technologies

Acknowledgement I wish to thank David Jacobs for showing me a new way of looking at HTML and XSLT/XPath Many of the examples that I use in this tutorial come straight from David's excellent paper, Rescuing XSLT from Niche Status (see

History XSL XSLT XSL XPath XSLT (low-precision graphics, e.g.,HTML,
text, XML) XQuery (high-precision graphics, e.g., PDF) XLink/ XPointer XSLT XSL XML Schemas XPath XSLT

Note For brevity, instead of using the term XSLT/XPath, I will simply call it XSL.

Multiple Output Formats
XSL may be used to generate either HTML, XML, or text XSL XML XSL Processor HTML (or XML or text)

xalan/xt/saxon XML XSL HTML (or XML or text)
xalan: A free XSL processor, implemented in Java, from Apache ( xt: A free XSL processor, implemented in Java, from James Clark ( saxon: A free XSL processor, implemented in Java, from Michael Kay ( XML XSL xalan/xt/saxon HTML (or XML or text) Invoking from a DOS command line: run-xalan FitnessCenter.xml FitnessCenter.xsl FitnessCenter.html run-xt FitnessCenter.xml FitnessCenter.xsl FitnessCenter.html run-saxon FitnessCenter.xml FitnessCenter.xsl FitnessCenter.html

Styling XML Documents using IE6 or Netscape7
Put a stylesheet PI at the top of your XML document. Now you can simply drop the XML document into the browser and the XML will be automatically styled using the stylesheet referenced in the stylesheet PI. <?xml version="1.0"?> <?xml-stylesheet type="text/xsl" href="FitnessCenter.xsl"?> <FitnessCenter> <Member level="platinum"> <Name>Jeff</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightgrey</FavoriteColor> </Member> </FitnessCenter> Add this stylesheet PI to the top of your XML document

HTML Generation We will first use XSL to generate HTML documents
When generating HTML, XSL should be viewed as a tool to enhance HTML documents. That is, the HTML documents may be enhanced by extracting data out of XML documents XSL provides elements (tags) for extracting the XML data, thus allowing us to enhance HTML documents with data from an XML document

Enhancing HTML Documents with XML Data
(with embedded XSL elements) XSL Processor XSL element XML data XML data

Enhancing HTML Documents with the Following XML Data
<?xml version="1.0"?> <?xml-stylesheet type="text/xsl" href="FitnessCenter.xsl"?> <FitnessCenter> <Member level="platinum"> <Name>Jeff</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightgrey</FavoriteColor> </Member> </FitnessCenter> FitnessCenter.xml

Embed HTML Document in an XSL Template
<?xml version="1.0"?> <xsl:stylesheet xmlns:xsl=" version="1.0"> <xsl:output method="html"/> <xsl:template match="/"> <HTML> <HEAD> <TITLE>Welcome</TITLE> </HEAD> <BODY> Welcome! </BODY> </HTML> </xsl:template> </xsl:stylesheet> Note how we have the HTML document embedded within an XSL template FitnessCenter.xsl (see html-example01)

Note The HTML is embedded within an XSL template, which is an XML document Consequently, the HTML must be well formed, i.e., every start tag must have an end tag Because the HTML is embedded within an XSL template, we are able to add XSL elements to the HTML, allowing us to extract data out of XML documents Let's customize the HTML welcome page by putting in the member's name. This is achieved by extracting the name from the XML document. We use an XSL element to do this.

Extracting the Member Name
<?xml version="1.0"?> <xsl:stylesheet xmlns:xsl=" version="1.0"> <xsl:output method="html"/> <xsl:template match="/"> <HTML> <HEAD> <TITLE>Welcome</TITLE> </HEAD> <BODY> Welcome <xsl:value-of select="/FitnessCenter/Member/Name"/>! </BODY> </HTML> </xsl:template> </xsl:stylesheet> (see html-example02)

Note Notice how we have enhanced the HTML document by using data from the XML document!

Extracting a Value from an XML Document, Navigating the XML Document
Extracting values: use the <xsl:value-of select="…"/> XSL element Navigating: The slash ("/") indicates parent/child relationship A slash at the beginning of the path indicates that it is an absolute path, starting from the top of the XML document /FitnessCenter/Member/Name "Start from the top of the XML document, go to the FitnessCenter element, from there go to the Member element, and from there go to the Name element."

<?xml version=“1.0”?>
Document / PI <?xml version=“1.0”?> Element FitnessCenter Element Member Element Name Element Phone Element Phone Element FavoriteColor Text Jeff Text Text Text lightgrey

Extract the FavoriteColor and use it as the bgcolor
<?xml version="1.0"?> <xsl:stylesheet xmlns:xsl=" version="1.0"> <xsl:output method="html"/> <xsl:template match="/"> <HTML> <HEAD> <TITLE>Welcome</TITLE> </HEAD> <BODY bgcolor="{/FitnessCenter/Member/FavoriteColor}"> Welcome <xsl:value-of select="/FitnessCenter/Member/Name"/>! </BODY> </HTML> </xsl:template> </xsl:stylesheet> (see html-example03)

Note Attribute values cannot contain "<" nor ">"
- Consequently, the following is NOT valid: <Body bgcolor="<xsl:value-of select='/FitnessCenter/Member/FavoriteColor'/>"> To extract the value of an XML element and use it as an attribute value you must use curly braces: <Body bgcolor="{/FitnessCenter/Member/FavoriteColor}"> Evaluate the expression within the curly braces. Assign the value to the attribute.

Extract the Home Phone Number
<?xml version="1.0"?> <xsl:stylesheet xmlns:xsl=" version="1.0"> <xsl:output method="html"/> <xsl:template match="/"> <HTML> <HEAD> <TITLE>Welcome</TITLE> </HEAD> <BODY bgcolor="{/FitnessCenter/Member/FavoriteColor}"> Welcome <xsl:value-of select="/FitnessCenter/Member/Name"/>! <BR/> Your home phone number is: <xsl:value-of </BODY> </HTML> </xsl:template> </xsl:stylesheet> (see html-example04)

Note In this example we want "the Phone element where the value
of its type attribute equals 'home' ": <xsl:value-of The expression within […] is called a "predicate". Its purpose is to filter. Note the use of the single quotes within the double quotes. select=" … ' …' …"

Review - HTML Table <table border=“1” width=“100%”> <th>
<tr> </tr> <td> </td> <td> </td> <td> </td> <tr> </tr> <td> </td> <td> </td> <td> </td> <tr> </tr> </table> This will create a table with 3 rows - the first row contains a header for each column. The next two rows contains the table data.

Fruit Color Papaya Red Banana Yellow
<table border=“1” width=“75%”> <tr> <th>Fruit</th> <th>Color</th> </tr> <td>Papaya</td> <td>Red</td> <td>Banana</td> <td>Yellow</td> </table> Fruit Color Papaya Red Banana Yellow

Create a Table of Phone Numbers
Suppose that a Member has an arbitrary number of phone numbers (home, work, cell, etc). Create an HTML table comprised of the phone numbers. On each row of the table put the type (home, work, cell, etc) in one column and the actual phone number in the next column.

(see html-example05) <?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl=" version="1.0"> <xsl:output method="html"/> <xsl:template match="/"> <HTML> <HEAD> <TITLE>Welcome</TITLE> </HEAD> <BODY bgcolor="{/FitnessCenter/Member/FavoriteColor}"> Welcome <xsl:value-of select="/FitnessCenter/Member/Name"/>! <BR/> Your phone numbers are: <TABLE border="1" width="25%"> <TR><TH>Type</TH><TH>Number</TH></TR> <xsl:for-each select="/FitnessCenter/Member/Phone"> <TR> <TD><xsl:value-of <TD><xsl:value-of select="."/></TD> </TR> </xsl:for-each> </TABLE> </BODY> </HTML> </xsl:template> </xsl:stylesheet> (see html-example05)

Iterating through XML Elements
<xsl:for-each select="/FitnessCenter/Member/Phone"> <!- - Within here we are at one of the Phone elements. Thus, in <xsl:value-of select="path", the value for path is relative to where we are in the XML document. The "." refers to the Phone element that we are currently positioned at. - -> </xsl:for-each>

Absolute Path versus Relative Path
<xsl:value-of This is an absolute xPath expression (we start from the top of the XML tree and navigate down the tree) <xsl:value-of This is a relative xPath expression (relative to where we currently are located, give me the value of the type attribute) Do Lab1, Parts 1-3

Special Offer to Platinum Members
Let's further enhance our example to provide a special offer to "platinum" members. We need to check to see if the "level" attribute on the Member element equals "platinum".

(see html-example06) <HTML> <HEAD>
<TITLE>Welcome</TITLE> </HEAD> <BODY bgcolor="{/FitnessCenter/Member/FavoriteColor}"> Welcome <xsl:value-of select="/FitnessCenter/Member/Name"/>! <BR/> <xsl:if Our special offer to platinum members today is ... </xsl:if> Your phone numbers are: <TABLE border="1" width="25%"> <TR><TH>Type</TH><TH>Number</TH></TR> <xsl:for-each select="/FitnessCenter/Member/Phone"> <TR> <TD><xsl:value-of <TD><xsl:value-of select="."/></TD> </TR> </xsl:for-each> </TABLE> </BODY> </HTML> (see html-example06)

Conditional Processing
Use the <xsl:if test="…"/> element to perform conditional processing. Do Lab1, Part 4

Accessing Multiple Parts of the XML Document
Let's enhance the table to contain three columns - the name of the Member, the type of the phone (home, work, cell, etc), and the actual phone number.

<HTML> (see html-example07) <HEAD>
<TITLE>Welcome</TITLE> </HEAD> <BODY bgcolor="{/FitnessCenter/Member/FavoriteColor}"> Welcome <xsl:value-of select="/FitnessCenter/Member/Name"/>! <BR/> <xsl:if Our special offer to platinum members today is ... </xsl:if> Your phone numbers are: <TABLE border="1" width="25%"> <TR><TH>Name</TH><TH>Type</TH><TH>Number</TH></TR> <xsl:for-each select="/FitnessCenter/Member/Phone"> <TR> <TD><xsl:value-of select="../Name"/></TD> <TD><xsl:value-of <TD><xsl:value-of select="."/></TD> </TR> </xsl:for-each> </TABLE> </BODY> </HTML> (see html-example07)

Getting the Name when accessing the Phone
Member Notice how when in the for-each loop we need to access the Name which is "up and over" with respect to the Phone element Name Jeff Phone Phone Bottom line: we can access elements in other parts of the XML tree via the “../” operator.

Other ways to Access the XML Data
Note: Assume that there are multiple Members <xsl:value-of select="/FitnessCenter/Member[1]/Name"/> "Select the Name of the first Member" <xsl:value-of select="/FitnessCenter/Member[position()=1]/Name"/> <xsl:value-of select="/FitnessCenter/Member[last()]/Name"/> "Select the Name of the last Member" <xsl:for-each select="/FitnessCenter/Member[not(position()=last())]"> <!- - Process all Members but the last - -> </xsl:for-each>

Other ways to Access the XML Data (cont.)
<xsl:for-each select="/FitnessCenter/Member[position() != last())]"> <!- - Process all Members but the last - -> </xsl:for-each> <xsl:for-each select="/FitnessCenter/Member[position() >1]"> <!- - Process all Members but the first - -> <xsl:for-each select="/FitnessCenter//Name"> <!- - Process all Name elements which have FitnessCenter as an ancestor - ->

Other ways to Access the XML Data (cont.)
<!- - Iterate through a list of Member nodes - -> <xsl:for-each select="/FitnessCenter/Member"> <!- - Output the Name of the "current" Member - -> <xsl:value-of select="./Name"/> </xsl:for-each> <!- - Since a specific Member is not specified, all Member nodes - -> <!- - all selected. That is, the Name node within each Member > <!-- node is selected > <xsl:for-each select="/FitnessCenter/Member/Name"> <xsl:value-of select="."/>

Nodelist This xPath expression: /FitnessCenter/Member
selects a list of nodes (a list of Member nodes). This list of nodes is called a "nodelist".

Enhanced XML Document Note that each Member now has a unique id
<?xml version="1.0"?> <FitnessCenter> <Member id="1" level="platinum"> <Name>Jeff</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightgrey</FavoriteColor> </Member> <Member id="2" level="gold"> <Name>David</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightblue</FavoriteColor> <Member id="3" level="platinum"> <Name>Roger</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightyellow</FavoriteColor> </FitnessCenter> Note that each Member now has a unique id (the id attribute)

Review - HTML Hyperlinking
<A name="AnnaAndTheKing"></A> … <A href="#AnnaAndTheKing">Click Here</A> ... This creates an internal hyperlink (the source "anchor" links to the target anchor).

Hyperlink Name to Home Phone
Problem: create an HTML document that has two tables - a Member Name table, and a Member home Phone number table. Hyperlink the Member's Name to his/her Phone.

<TABLE border="1" width="25%">
<TR><TH>Name</TH></TR> <xsl:for-each select="/FitnessCenter/Member"> <TR> <TD> <A <xsl:value-of select="Name"/> </A> </TD> </TR> </xsl:for-each> </TABLE> <BR/><BR/><BR/><BR/><BR/> <TR><TH>Home Phone Number</TH></TR> <A <xsl:value-of (see html-example08) Do Lab1, Parts 5-6

Numbering There is an XSL element that returns a number corresponding to the element's position in the set of selected nodes <xsl:for-each select="/FitnessCenter/Member"> <xsl:number value="position()" format="1"/> <xsl:text>. </xsl:text> <xsl:value-of select="Name"/> <BR/> </xsl:for-each> Output: 1. Jeff 2. David 3. Roger (see html-example09)

Start Numbering from 0 How would you start the numbering from zero, rather than one? <xsl:number value="position() - 1" format="1">

format attribute of xsl:number
In the previous example we saw how to generate numbers, and we saw that the generated numbers were 1, 2, 3, etc. With the format attribute we can specify the format of the generated number, i.e., 1, 2, 3 or I, II, III, or A, B, C, or … format=“1” generates the sequence: 1, 2, 3, … format=“01” generates: 01, 02, 03, … format=“A” generates: A, B, C, … format=“a” generates: a, b, c, … format=“I” generates: I, II, III, … format=“i” generates: i, ii, iii, ...

format attribute of xsl:number
<xsl:for-each select="/FitnessCenter/Member"> <xsl:number value="position()" format="A"/> <xsl:text>. </xsl:text> <xsl:value-of select="Name"/> <BR/> </xsl:for-each> Output: A. Jeff B. David C. Roger

Sorting There is an XSL element that sorts the elements that you extract from the XML document <xsl:for-each select="/FitnessCenter/Member"> <xsl:sort select="Name" order="ascending"/> <xsl:value-of select="Name"/> <BR/> </xsl:for-each> Output: David Jeff Roger (see html-example10) "For each Member, sort the Name elements"

Sorting The set of Member elements selected by xsl:for-each is
<xsl:for-each select="/FitnessCenter/Member"> <xsl:sort select="Name" order="ascending"/> <xsl:value-of select="Name"/> <BR/> </xsl:for-each> The set of Member elements selected by xsl:for-each is sorted using the Name child element. This occurs prior to the first iteration of the loop. After the set of Member elements are sorted then the looping begins.

concat() function concat(destination string, string to add)
Note: if you want to concatenate more than one string to the destination string then simply add more arguments

<xsl:for-each select="/FitnessCenter/Member">
<xsl:value-of select="concat('Welcome ', Name, '!')"/> <BR/> </xsl:for-each> Output: Welcome Jeff! Welcome David! Welcome Roger!

xsl:variable This XSL element allows you to create a variable to hold a value (which could be a string or a subtree of the XML document). The variable is referenced by $variable-name <xsl:variable name=“hello” select=“'Hello World'”/> This creates a variable called hello, that has a value which is the literal string, ‘Hello World’. We could use this variable as follows: Value = <xsl:value-of select=“$hello”/> This will output: Value = Hello World hello Hello World

(see html-example12) Member's Phone Numbers:
<TABLE border="1" width="25%"> <TR><TH>Name</TH><TH>Type</TH><TH>Number</TH></TR> <xsl:for-each select="/FitnessCenter/Member"> <xsl:variable name="name" select="Name"/> <xsl:for-each select="Phone"> <TR> <TD><xsl:value-of select="$name"/></TD> <TD><xsl:value-of <TD><xsl:value-of select="."/></TD> </TR> </xsl:for-each> </TABLE> (see html-example12)

xsl:variable <xsl:variable name=“member” select=“Member[1]”/>
This creates a variable called member, that has a value which is a subtree. We could use this variable as follows: Name = <xsl:value-of select=“$member/Name”/> Home Phone = <xsl:value-of This will result in generating: Name = Jeff Home Phone = Member Name Phone Phone ... Jeff

xsl:variable A variable is “write once, read many”.
That is, you can assign a variable a value only once, but then you can retrieve the value of the variable many times. A variable has a scope limited to the XSL element that it is nested within. Its scope starts where it is defined and extends to the end of the XSL element that it is nested within.

The name variable's life ends here
Member's Phone Numbers: <TABLE border="1" width="25%"> <TR><TD>Name</TD><TD>Type</TD><TD>Number</TD></TR> <xsl:for-each select="/FitnessCenter/Member"> <xsl:variable name="name" select="Name"/> <xsl:for-each select="Phone"> <TR> <TD><xsl:value-of select="$name"/></TD> <TD><xsl:value-of <TD><xsl:value-of select="."/></TD> </TR> </xsl:for-each> </TABLE> The name variable's life ends here Do Lab2, Part 1

Global Variables <HEAD>
You can create a variable outside of <xsl:template match="/">. Then, the variable is global. <?xml version="1.0"?> <xsl:stylesheet xmlns:xsl=" version="1.0"> <xsl:output method="html"/> <xsl:variable name="pi" select="' '"/> <xsl:template match="/" > <HTML> <HEAD> <TITLE>Value of Pi</TITLE> </HEAD> <BODY> The value of pi = <xsl:value-of select="$pi"/> </BODY> </HTML> </xsl:template>

Problem (see html-example13)
Suppose that we want to create a variable, names, and we want this variable to contain a list of the Member Names, with each name separated by a slash. How would you create such a variable? Here’s what you might attempt to do: Member's Names: <xsl:variable name="names" select="/FitnessCenter/Member[1]/Name"/> <xsl:for-each select="/FitnessCenter/Member[position() > 1]"> <xsl:variable name="names" select="concat($names, '/')"/> <xsl:variable name="names" select="concat($names, Name)"/> </xsl:for-each> <xsl:value-of select="$names"/> (see html-example13) Output: Jeff

Let’s add some statements to trace this example
<xsl:variable name="names" select="/FitnessCenter/Member[1]/Name"/> <xsl:value-of select="$names"/> <BR/> <xsl:for-each select="/FitnessCenter/Member[position() > 1]"> <xsl:variable name="names" select="concat($names, '/')"/> <xsl:variable name="names" select="concat($names, Name)"/> </xsl:for-each> (see html-example14) Output: Jeff Jeff/ Jeff/David Jeff/ <--- Why did we loose the previous Name? That name went out of scope. Jeff/Roger Obviously, this approach doesn’t work. So how do we do it?

Here’s what we would like to do
names Open up the names box Jeff … / … David … / … Roger <xsl:for-each select="/FitnessCenter/Member"> Add this iteration’s Name and a slash to the open names box </xsl:for-each> Iterate through each name, adding into the open box names Jeff/David/Roger Close the box

Problem - Solution <xsl:variable name=“names”>
In all previous examples of creating a variable we declared the name of the variable and then had a select attribute which gave the variable its value. We can omit the select attribute: <xsl:variable name=“names”> - Do stuff in here. All output will go into the names “box”. </xsl:variable>

Problem - Solution (see html-example15) Output:
Member's Names: <xsl:variable name="names"> <xsl:value-of select="/FitnessCenter/Member[1]/Name"/> <xsl:for-each select="/FitnessCenter/Member[position() > 1]"> <xsl:text>/</xsl:text> <xsl:value-of select="Name"/> </xsl:for-each> </xsl:variable> <xsl:value-of select="$names"/> (see html-example15) Output: Member's Names: Jeff/David/Roger

contains() function contains(string to be tested, test string) returns true if string to be tested contains test string <xsl:if test=“contains($greeting, ‘welcome’)”> $greeting contains ‘welcome’ </xsl:if> Do Lab2, Part 2

xsl:choose xsl:choose allows you to elegantly express multiple conditional tests. Here’s the structure: <xsl:choose> <xsl:when test='something> [action] </xsl:when> <xsl:when test='something'> <xsl:otherwise> </xsl:otherwise> </xsl:choose> The first xsl:when statement that evaluates to true is executed. If none evaluates to true then the xsl:otherwise statement is executed.

Implementing an if-then-else
There is no if-then-else element in XSL. However, there is an elegant way to do it: <xsl:choose> <xsl:when test="contains($member-list, 'Jeff')"> <xsl:text>Jeff is a member</xsl:text> </xsl:when> <xsl:otherwise> <xsl:text>No member by the name Jeff</xsl:text> </xsl:otherwise> </xsl:choose>

substring-before() String Function
Here’s the form of this string function: substring-before(string, pattern) Example: <xsl:variable name="phone" select="Phone"/> <xsl:value-of select="substring-before($phone, '-')"/> “Get the contents of Phone and put it into the variable called ‘phone’. Then extract from the content of ‘phone’ the string before the '-' (i.e., the telephone exchange)”. phone substring-before($phone, ‘-’) 555

substring-after() String Function
Here’s the form of this string function: substring-after(string, pattern) Example: <xsl:variable name="phone" select="Phone"/> <xsl:value-of select="substring-after($phone, '-')"/> “Get the contents of Phone and put it into the variable called ‘phone’. Then extract from the content of ‘phone’ the string after the '-'”. phone substring-after($phone, ‘-’) 1234

starts-with() String Function
Here’s the form of this string function: starts-with(string, pattern) Example: <xsl:if test="starts-with(Phone, '555')"> [action] </xsl:if> “If the Phone starts with the string, ‘555’ then do [action]”.

substring() function substring(string, i, len?) returns the substring of string that starts at the ith position and has length, len. The length argument (len) is optional. If not present then this function returns the substring starting at the ith position all the way to the end of the string. Note: the first character is at position 1 (not 0 as with some languages) substring(‘ ’, 2, 5) returns ‘23456’

string-length() function
string-length(string) returns the length of the string string-length(‘ ’) returns 10

translate() function translate(string, from-pattern, to-pattern)
Example. translate(“Hello”, “ABCDEFGHIJKLMNOPQRSTUVWXYZ”, “abcdefghijklmnopqrstuvwxyz”); this will convert Hello to hello (i.e., convert to lower case) A better approach to the above problem is: <xsl:variable name="upperCaseChars" select=" 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' "/> <xsl:variable name="lowerCaseChars" select=" 'abcdefghijklmnopqrstuvwxyz' "/> translate(“Hello”, $upperCaseChars, $lowerCaseChars) Note: need to put the string within (single) quotes, otherwise the XSL Processor will try to interpret it as an XML element. Do Lab2, Part 3

Boolean and Relational Operators
Boolean operators: not, and, or Relational operators: <, >, =, <=, >=, != The less than and greater than signs are reserved symbols, so they need to be escaped when you use them. Thus, the relational operators will appear in your XSL code like this: Want this: Use this: < > = <= >= != < > = <= >= !=

Arithmetic The arithmetic operators available: +, -, *, div, mod (remainder from doing a division) Note: recall that an XML element can have a dash in the name. So, if you want to indicate subtraction, be sure to surround “-” with blank spaces.

Arithmetic functions sum(node set) this function sums up all the values in the set of nodes floor(number) returns the largest integer that is not greater than number Example. floor(2.5) returns 2 ceiling(number) returns the smallest integer that is not less than number Example. Ceiling(2.5) returns 3 round(number) returns the integer closest to number Example. round(2.3) returns 2

Enhanced XML Document Note that each Member now has MembershipFee
<?xml version="1.0"?> <FitnessCenter> <Member id="1" level="platinum"> <Name>Jeff</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightgrey</FavoriteColor> <MembershipFee>340</MembershipFee> </Member> <Member id="2" level="gold"> <Name>David</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightblue</FavoriteColor> <MembershipFee>500</MembershipFee> <Member id="3" level="platinum"> <Name>Roger</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightyellow</FavoriteColor> </FitnessCenter> Note that each Member now has MembershipFee element

Compute Membership Revenue
Membership Fee Revenue: <xsl:value-of select="sum(//MembershipFee)"/> (see html-example16)

xsl:attribute This XSL element is used by nesting it within an output element. It enables you to create an attribute for the output element

Coloring alternate rows
Member Names: <TABLE border="1" width="25%"> <xsl:for-each select="/FitnessCenter/Member"> <TR> <xsl:if test="position() mod 2 = 0"> <xsl:attribute name="bgcolor">yellow</xsl:attribute> </xsl:if> <TD><xsl:value-of select="Name"/></TD> </TR> </xsl:for-each> </TABLE> (see html-example17) For each even row of the table, the TR value will be: <TR bgcolor="yellow">

count() function count(set of node) returns an integer representing the number of nodes (i.e., XML elements) in the set. Example. Number of members = <xsl:value-of select="count(//Member)"/> Output: Number of members = 5 Do Lab2, Part 4

Selecting all Elements/Attributes
<xsl:for-each select="/FitnessCenter/Member"> <xsl:for-each ... </xsl:for-each> <xsl:for-each select="*"> For each attribute do ... For each child element do ...

Getting the Name of the Element/Attribute using the name() Function
<xsl:for-each select="/FitnessCenter/Member"> <xsl:for-each Attribute = <xsl:value-of select="name(.)"/> </xsl:for-each> <xsl:for-each select="*"> Element = <xsl:value-of select="name(.)"/> (see html-example19) name(node) returns the name of "node"

When to use Curly Braces?
“When I assign an attribute a value, when do I use curly braces and when do I not use them?” Use curly braces for these attributes: - the attribute of a literal result element (where you literally type what should be output) Example: <a - the name attribute of xsl:attribute Example: <xsl:attribute name - the name attribute of xsl:pi Example: <xsl:pi name - the name attribute of xsl:element Example: <xsl:element name - the optional attributes of xsl:sort: Example: <xsl:sort order lang data-type case-order

document( ) Function This function enables you to access other XML documents (besides the XML document that you specify when you invoke the XSL Processor). The format for using the document() function is: document(url), where url is a URL to another XML document

Fitness Centers Merger
Another fitness center has just merged with us. They have an xml document (FitnessCenter2.xml) containing their Members. You are to create an XSL-enhanced HTML document that creates a single table comprised of all the Members from both fitness clubs.

(see html-example20) <TABLE border="1" width="75%">
<TR><TH>Name</TH><TH>Phone(home)</TH>...</TR> <xsl:for-each select="/FitnessCenter/Member"> <TR> <TD><xsl:value-of select="Name"/></TD> <TD><xsl:value-of <TD><xsl:value-of <TD><xsl:value-of select="FavoriteColor"/></TD> </TR> </xsl:for-each> <xsl:variable name="fitnessCenter2" select="document('file://localhost/xml-course/.../FitnessCenter2.xml')"/> <xsl:for-each select="$fitnessCenter2/FitnessCenter/Member"> </TABLE> Do Lab3, Part 1 (see html-example20)

Parameterized Processing
You can create a subroutine (called a named template), and you can pass to it parameters.

<xsl:template match="/">
<HTML> <HEAD> <TITLE>Fitness Center</TITLE> </HEAD> <BODY> <xsl:call-template name="displayNameWithFont"> <xsl:with-param name="fontFace" select="'Impact'"/> <xsl:with-param name="name" select="/FitnessCenter/Member[1]/Name"/> </xsl:call-template> <BR/> ... </BODY> </HTML> </xsl:template> <xsl:template name="displayNameWithFont"> <xsl:param name="fontFace" select="'Braggadocio'"/>  <xsl:param name="name"/> <FONT face="{$fontFace}"> <xsl:value-of select="$name"/> </FONT> (see html-example21)

Call by Reference How do we create a named template that returns a value? Example: create a named template which, when passed a number, it returns the number div 2.

<xsl:template match="/">
<HTML> <HEAD> <TITLE>Fitness Center</TITLE> </HEAD> <BODY> 16 / 2 = <xsl:variable name="result"> <xsl:call-template name="NumDiv2"> <xsl:with-param name="N" select="16"/> </xsl:call-template> </xsl:variable> <xsl:value-of select="$result"/> </BODY> </HTML> </xsl:template> <xsl:template name="NumDiv2"> <xsl:param name="N"/> <xsl:value-of select="$N div 2"/> (see html-example22)

Problem: Determine if all <Number> values are <= 100
<?xml version="1.0"?> <NumberList> <Number>23</Number> <Number>41</Number> <Number>70</Number> <Number>103</Number> <Number>99</Number> <Number>6</Number> </NumberList> (see html-example22-1)

This is a recursive routine
<xsl:template match="/"> <xsl:text>All numbers in the list are less than or equal to 100: </xsl:text> <xsl:variable name="result"> <xsl:call-template name="AllLessThan100"> <xsl:with-param name="numberList" select="NumberList/Number"/> </xsl:call-template> </xsl:variable> <xsl:value-of select="$result"/> </xsl:template> <xsl:template name="AllLessThan100"> <xsl:param name="numberList"/> <xsl:choose> <xsl:when test="not($numberList)"> <xsl:text>true</xsl:text> </xsl:when> <xsl:otherwise> <xsl:when test="$numberList[1] > 100"> <xsl:text>false</xsl:text> <xsl:with-param name="numberList" select="$numberList[position() > 1]"/> </xsl:otherwise> </xsl:choose> Pass to the named template a list of <Number> nodes, i.e., a nodelist. This is a recursive routine If the nodelist is empty then return true Check the first node on the list. If it's greater than 100, then return false (and we're done). Otherwise, recurse over the remaining nodes. Do Lab3, Part 2

generate-id() Use this function to generate a unique string for a node
Example. generate-id(/FitnessCenter/Member[1]) will return a unique id for the first Member

Using generate-id() to Uniquely Identify Elements
In html-example08 we created two tables - a table containing the Members Names, and a separate table containing home Phone numbers. Each Name was hyperlinked to his/her home Phone. We used the id attribute on each Member element to link the two tables together. Suppose there is no id attribute. We can use generate-id() to create a unique identifier.

<TABLE border="1" width="25%">
<TR><TH>Name</TH></TR> <xsl:for-each select="/FitnessCenter/Member"> <TR> <TD> <A href="#{generate-id(.)}"> <xsl:value-of select="Name"/> </A> </TD> </TR> </xsl:for-each> </TABLE> <BR/><BR/><BR/><BR/><BR/> <TR><TH>Home Phone Number</TH></TR> <A name="{generate-id(.)}"> <xsl:value-of (see html-example23)

Same (XML) Data, Multiple Views
In html-example24 I show how to create an HTML document that allows a client to view an XML document in different forms. Look at html-example24. With the buttons on the left side of the screen we can select which view is desired.

Multiple Stylesheets to provide the different views
FitnessCenter.xml ShowMembers.xsl ShowPlatinumMembers.xsl ShowGoldMembers.xsl ShowAll.xsl

FitnessCenter.html - comprised of two frames
ShowMembers ShowPlatinumMembers ShowGoldMembers ShowAll RawXML Controls.html Body.html FitnessCenter.html

FitnessCenter.html FitnessCenter.html
<HEAD> <TITLE>Welcome</TITLE> </HEAD> <FRAMESET cols="20%,80%"> <FRAME src="controls.html" name="controlsFrame"> <FRAME src="body.html" name="bodyFrame"> </FRAMESET> </HTML> Two columns. The first column is 20% of the width of the screen. The second column is 80% of the width of the screen. FitnessCenter.html NOTE: do NOT have a <BODY> element (it won't work if you do)

Body.html <HTML> <HEAD>
<TITLE>Fitness Center</TITLE> </HEAD> <BODY> </BODY> </HTML> Body.html This document is very simple - it's empty! The body will be filled in with the HTML that is generated by styling the XML document

Controls.html (tracing through the actions that occur when a user selects "ShowGoldMembers")
Press Show Gold Members button Invoke the Javascript function, ShowGoldMembers() Load ShowGoldMembers.xsl Transform (the previously loaded) FitnessCenter.xml using ShowGoldMembers.xsl Set the body of Body.html to the generated html

Controls.html (code to ShowGoldMembers)
<FORM name="controlForm"> <INPUT type="button" value="Show Gold Members" onclick="ShowGoldMembers </FORM> <SCRIPT language="JScript" defer="true"> var xml = new ActiveXObject("Msxml2.DOMDocument.3.0"); xml.async = false; xml.load("FitnessCenter.xml"); function ShowGoldMembers() { var xsl = new ActiveXObject("Msxml2.DOMDocument.3.0"); xsl.async = false; xsl.load("ShowGoldMembers.xsl"); parent.bodyFrame.document.body.innerHTML = xml.transformNode(xsl); } </SCRIPT> This is preloading the XML document Load the XSL document Transform the XML document using the stylesheet, and assign the body of Body.html to the generated html.

Using SAXON in a Browser (rather the XSL Processor built into IE)
The last example utilized the XSL Processor built into IE (msxml) to do the transformations. Suppose the you would like to use a different XSL Processor, e.g., SAXON? Why would you want to do this? Answer: SAXON has several capabilities that msxml does not have. SAXON comes with a Java applet that you can use to do XSL processing within a browser. See html-example-24-a for details on how to use SAXON's Java applet to implement the multi-button example. See html-example-24-b for an example of how to use SAXON as the XSL Processor within a browser.

Inserting spaces into HTML output
<xsl:text disable-output-escaping="yes"><![CDATA[ ]]></xsl:text> Put one character references for each space required

Debugging your Stylesheets using xsl:message
xsl:message is used to display a message, and (optionally) terminate execution of the stylesheet. The message is sent to the screen, not to the output file. This provides a very nice way to monitor the flow of your stylesheet, without impacting the output file.

Example using xsl:message
<?xml version="1.0"?> <xsl:stylesheet xmlns:xsl=" version="1.0"> <xsl:output method="html"/> <xsl:template match="/"> <HTML> <BODY> <xsl:for-each select="FitnessCenter/Member"> <xsl:if test="MembershipFee < 0"> <xsl:message terminate="yes"> <xsl:text>Invalid MembershipFee</xsl:text> </xsl:message> </xsl:if> </xsl:for-each> <xsl:text>All the MembershipFee elements are valid</xsl:text> </BODY> </HTML> </xsl:template> </xsl:stylesheet> See html-example26 Two possible values for terminate - yes, or no. terminate="yes" means that you want the message output to the screen and then the program stopped. terminate="no" means that you screen and the program to continue executing.

system-property() function
The system-property(property name) function enables you to obtain information about the XSL Processor that you are using: xsl:vendor - if you specify this as the value for property name then it will return the name of the XSL Processor vendor xsl:vendor - this provides the URL to the vendor's web site xsl:version - this indicates what version of the XSL spec is implemented.

Recommended Practice It is very good practice to add this to the
<?xml version="1.0"?> <xsl:stylesheet xmlns:xsl=" version="1.0"> <xsl:output method="html"/> <xsl:template match="/"> <xsl:message> XSLT Processor: <xsl:value-of select="system-property('xsl:vendor')"/> </xsl:message> <HTML> <HEAD> <TITLE>Welcome</TITLE> </HEAD> <BODY> Welcome! </BODY> </HTML> </xsl:template> </xsl:stylesheet> It is very good practice to add this to the start of every stylesheet. This will give you a message indicating which XSL Processor you are using. When might you be uncertain which XSL Processor is being used? Java comes bundled with xalan. Suppose that you want to write a Java program which uses Saxon instead. You will definitely want to use the above to ensure that you are invoking Saxon and not the built-in xalan. (I know. I have made the mistake of thinking that I was using Saxon when in fact I was using xalan.) See html-example27

Embedded Stylesheets You can embed a stylesheet within an XML document. <?xml version="1.0"?> <!DOCTYPE FitnessCenter [ <!ATTLIST xsl:stylesheet id ID #REQUIRED> ]> <?xml-stylesheet type="text/xml" href="#embed"?> <FitnessCenter> <Member level="platinum"> <Name>Jeff</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightgrey</FavoriteColor> </Member> ... <xsl:stylesheet id="embed" xmlns:xsl=" version="1.0"> </xsl:stylesheet> </FitnessCenter> Stylesheet embedded within the XML document

Embedded Stylesheets <?xml version="1.0"?>
<!DOCTYPE FitnessCenter [ <!ATTLIST xsl:stylesheet id ID #REQUIRED> ]> <?xml-stylesheet type="text/xml" href="#embed"?> <FitnessCenter> <Member level="platinum"> <Name>Jeff</Name> <Phone type="home"> </Phone> <Phone type="work"> </Phone> <FavoriteColor>lightgrey</FavoriteColor> </Member> ... <xsl:stylesheet id="embed" xmlns:xsl=" version="1.0"> </xsl:stylesheet> </FitnessCenter> You must indicate that the id attribute is of type ID. The stylesheet PI references the embeded stylesheet (as indicated by the"#" sign) Add an id attribute to the xsl:stylesheet element. See html-example28 (Note: not all XSL Processors support embedded stylesheets)

Using XSLT and XPath to Enhance HTML Documents

Similar presentations

Presentation on theme: "Using XSLT and XPath to Enhance HTML Documents"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Using XSLT and XPath to Enhance HTML Documents

Similar presentations

Presentation on theme: "Using XSLT and XPath to Enhance HTML Documents"— Presentation transcript:

Similar presentations

About project

Feedback