|Unless otherwise specified, the Xalan-Java extensions library discussed in this section refers to
the Xalan-Java Interpretive processor. See Extensions for XSLTC for
Extension elements and functions provide a powerful mechanism
for extending and simplifying what you can do with an XLST processor like
Xalan. With input and contributions from the XML open-source developer community, we are working on
placing the most useful extensions in an extensions library distributed with Xalan-Java. If you have
ideas and/or contributions you would like to make, please email us at
the Xalan Development Mailing List.
The Xalan extensions are implemented in one of the classes under org.apache.xalan.lib. The main
extension class is
org.apache.xalan.lib.Extensions. Some extension
functions (e.g. intersection, difference, etc.) used to be in this class are now moved to the
corresponding EXSLT modules. All Xalan extensions use namespace URIs
If you are calling Xalan-Java-supplied extensions, we recommend that you define the corresponding
namespace in your stylesheet, and call the extension using the namespace prefix that you have associated
with that namespace. That way, if we later reorganize how the Xalan-Java-supplied extensions are stored,
you won't have to modify your stylesheet.
For an example that uses this namespace, see Example with the nodeset
A standard XSL transformation involves an XSL stylesheet, an XML source tree, and the transformation
result tree. The transformation sends the entire result to a single
The namespace for the Redirect
It supplies three extension elements that you can use to redirect portions of your transformation
output to multiple files: <open>, <write>, and <close>. If you use the <write>
element alone, the extension opens a file, writes to it, and closes the file immediately. If you want
explicit control over the opening and closing of files, use <write> in conjunction with
the <open> and <close> elements.
The <open> and <write> elements include a file attribute and/or a select attribute to
designate the output file. The file attribute takes a string, so you can use it to directly specify
the output file name. The select attribute takes an XPath expression, so you can use it to dynamically
generate the output file name. If you include both attributes, the Redirect extension first evaluates
the select attribute, and falls back to the file attribute if the select attribute expression does
not return a valid file name.
The <open> and <write> elements also support an append attribute. If the append attribute
is set to true or yes, then the result is appended to the output file.
nodeset (result-tree-fragment) casts a result tree fragment into a node-set.
To use the nodeset extension, you can either use the
nodeset function in the
xmlns:xalan="http://xml.apache.org" or the EXSLT
node-set in the namespace
|When you bind a variable to a template, rather than to the value generated by a select
expression, the data type of the variable is result tree fragment. For more information,
see Result Tree
extension elements that you can use to get information about the location of nodes in the source
systemId() returns the system ID for the current node, and
systemId(node-set) returns the system ID of the first node in the node-set.
To be done. Implemented in
publicId() will return the public ID for the current node, and
publicId(node-set) will return the public ID of the first node in the node-set.
lineNumber() returns the line number in the source document for the current node, and
lineNumber(node-set) returns the line number in the source document for the first node
in the node-set.
|This function returns -1 if the line number is not known (for example, the source is a
columnNumber() returns the column number in the
source document for the current node, and
columnNumber(node-set) returns the column
number in the source document for the first node in the node-set.
|This function returns -1 if the column number is not known (for example, the source is a DOM
The namespace for the SQL extension is:
The SQL extension provides extension functions for connecting to a JDBC data source,
executing a query, and working incrementally through a "streamable" result set. Streaming
(reuse of a single row node to traverse the result set) is the default mode of operation.
if you want unlimited access to the entire result set, you can cache the query result set
(1 row node for each row in the result set).
If you use streaming mode (the default), you can only access row elements one at a time
moving forward through the result set. The use of XPath expressions in your stylesheet, for
example, that attempt to return nodes from the result set in any other manner may produce
|Many features of the SQL library, including support for connection pools, parameterized
queries, caching, and added support for extracting connection information and query parameters
from XML source documents exist thanks to John Gentilin (firstname.lastname@example.org), who has
also added a number of SQL library samples.
provides a number of extension functions that you can use in your stylesheet.
- new() -- Use one of the XConnection constructors to connect to a data source, and return an
XConnection object. You can use one of the constructors creates a connection pool from which
stylesheets can obtain connections to a datasource. To support connection pools, SQL library
includes a ConnectionPool interface and a implementation: DefaultConnectionPool. You can also
provide your own ConnectionPool implementation.
- query() -- Use the XConnection object query() method to return a "streamable" result set in
the form of a row-set node. Work your way through the row-set one row at a time. The same row
element is used over and over again, so you can begin "transforming" the row-set before the
entire result set has been returned.
- pquery(), addParameter(), addParameterFromElement(), clearParameters() --
Use the XConnection pquery() method in conjunction with these other methods to
set up and execute parameterized queries.
- Use enableStreamingMode() to use a single row node to "stream" through the result set, and
disableStreamingMode() to cache the query result set.
- close() -- Use the XConnection object close() method to terminate the connection.
The query() and pquery() extension functions return a Document node that contains (as needed)
an array of column-header elements, a single row element that is used repeatedly, and an array
of col elements. Each column-header element (one per column in the row-set) contains an attribute
(ColumnAttribute) for each of the column descriptors in the ResultSetMetaData object. Each col
element contains a text node with a textual representation of the value for that column in the
the pipeDocument extension element pipes an XML document through a series of one or more
transformations. The output of each transformation is piped to the next transformation. The
final transformation creates a target file.
The namespace for the pipeDocument extension is:
Suppose, for example,you have a stylesheet that is processing a "book" document with elements
designating the documents to be transformed. This primary stylesheet generates a table of
contents for the book. For each source document it uses a pipeDocument extension element to pipe
the document through a series of one or more transformations.
evaluate (xpath-expression) function returns the result of evaluating the xpath-expression
in the current XPath expression context (automatically passed in by the extension mechanism).
Use the evaluation extension function when the value of the expression is not known until run time.
|Although you can still use the evaluate extension function in the main Extensions class, the
preferred solution is to use the same function in the EXSLT dynamic package. This will make your
stylesheet more portable across XSLT processors that support EXSLT extensions.|
tokenize (tokenize-string, delimiters)
tokenize (tokenize-string) function returns a node-set containing one text node for each
token in the tokenize-string.
The delimiters determine which characters are used to divide the tokenize-string into individual
tokens. If you do not include the delimiters argument, the function uses tab (	), linefeed
), return (
), and space ( ) as delimiters. if tokenize-string is an empty
string or contains only delimiters, the result is an empty node-set.
|Although you can still use the tokenize extension function in the main Extensions class, the
preferred solution is to use the same function in the EXSLT strings package. This will make your
stylesheet more portable across XSLT processors that support EXSLT extensions.|