XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (240 page)
Read XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition Online
Authors: Michael Kay
Another way of making the sort conditional is to use a conditional expression as the sort key. This is much easier in XSLT 2.0 with the introduction of conditional expressions in XPath:
else if ($sort-key = ‘author’) then author
else if ($sort-key = ‘isbn’) then isbn
else publisher”>
If the computation of the sort key is really complicated, you can do it in a sequence constructor rather than in the
select
attribute. This can even invoke templates or build temporary trees—there are no limits.
There are two other solutions to this problem that are worth mentioning, although both have their disadvantages:
- One is to generate or modify the stylesheet before compiling it, so that it includes the actual sort key required. This technique is popular when transformations are executed in the browser, typically under the control of JavaScript code in the HTML page. The stylesheet is then typically loaded from the server and parsed into a DOM document, which can be modified
in situ
before the transformation starts. The disadvantage is that this means recompiling the stylesheet each time it is run: this would probably be an unacceptable overhead if the transformation is running server-side within a Web server. - Another is to use an extension function that permits the evaluation of XPath expressions that have been constructed dynamically, as strings. Such a function,
dyn:evaluate()
, is defined in the third-party function library at
http://www.exslt.org/
, and is available in this or a similar form with a number of XSLT processors including Saxon and Xalan.
Examples
I'll start with a couple of simple examples and then show a full working example that you can download and try yourself.
- Example 1: Process all the
isbn
attribute:
- Example 2: Output the contents of all the
If
select=“.”
were omitted from the
Example: Sorting on the Result of a Calculation
This example outputs a list of products, sorted by the total sales of each product, in descending order.
Source
This is the file
products.xml
:
Stylesheet
products.xsl
is a complete stylesheet written using the simplified stylesheet syntax, in which the entire stylesheet module is written as a single literal result element. Simplified stylesheets are described in Chapter 3, on page 125.
The
sales
attribute over all their
sum()
function (described on page 889) and displayed using the
format-number()
function (page 788).
xmlns:xsl=“http://www.w3.org/1999/XSL/Transform”>
sales=“{format-number(sum(region/@sales), ‘$####0.00’)}”/>
For this to work correctly under XSLT 1.0, you need to add
data-type=“number”
to the
Output
I have added line breaks for readability:
See Also
xsl:strip-space
The
Changes in 2.0
The syntax of a
NameTest
has been extended to allow the format*:NCName, which matches all elements with a given local name, in any namespace.
Format
elements = tokens />
Position
Attributes
| Name | Value | Meaning |
| elements mandatory | Whitespace-separated list of NameTests | Defines elements in the source document whose whitespace-only text nodes are to be removed |
The construct
NameTest
is defined in XPath, and is described in Chapter 9, on page 614.
Content
None, the element is always empty.
Effect, Usage, and Examples
See
See Also
xsl:stylesheet
The
Changes in 2.0
A number of new attributes have been added:
xpath-default-namespace
,
default-collation
,
default-validation
,
input-type-annotation
, and
use-when
. Several of these attributes, although usually used on the
