Sample Saxon Applications

Several sample applications are included in the Saxon distribution.

Note: the example commands here are for the Windows platform, using the SUN Java Virtual Machine. UNIX users will have little difficulty in adapting the commands; the only real change is to use "/" instead of "\" in path names (this affects the command line only: the Java code itself should work on any platform). Running Java applications on a Macintosh is a little more complicated, because of the absence of a conventional command line.

Knight's Tour

This is a stylesheet whose output is a knight's tour of the chessboard (the knight can start on any square, and has to visit each square exactly once). This was published as an example stylesheet in my book XSLT Programmers Reference (Wrox Press) but has been completely reworked so it now makes extensive use of XSLT 2.0 and XPath 2.0 features. It is worth studying this stylesheet as an introduction to the use of XSLT 2.0 functions, and XPath 2.0 for and if expressions.

The stylesheet can be found in the file samples\tour.xsl. It takes no input from the source document, so you can supply any XML document as input, for example the stylesheet itself. You can run this example with a command of the form:

java -jar saxon7.jar -a samples\styles\tour.xsl start=e5 >tour.html


When you display the resulting HTML file in your browser it should look like this:

JAXP 1.1 examples

Saxon supports the Java JAXP 1.1 API, also known as TrAX (package javax.xml.transform) for invoking the stylesheet processor. This API is useful when you want to write your own Java applications that invoke Saxon.

A sample program that illustrates many features of the TrAX interface is included in the distribution as TraxExamples.java. Source XML and XSLT files for use with this program are included in the trax directory. To run the program, use the command:

cd $saxonhome/samples/trax java TraxExamples


You can supply an argument to indicate which of the examples you want to run; see the source code for details. By default, they are all executed in turn.

One of the examples shows how to use TrAX to process input from a third-party (non-Saxon) DOM document, and how to send output to a third-party DOM document. This example tests to see if either Crimson or Xerces is present on the classpath; if not, it should fail cleanly. You will need to change the source code and recompile if you want to use it with a different DOM implementation.

SaxonServlet

This is a general-purpose servlet that takes the name of a source document and stylesheet as URL parameters, and processes the stylesheet to create a result document which is sent back to the browser for display. The result document may have any media type, though HTML and XML are the most likely.

The servlet maintains a cache of prepared stylesheets; if the same stylesheet is used repeatedly, it is only parsed and validated once, which will often greatly improve performance. Prepared style sheets are thread-safe so they can be used to serve documents to several users concurrently.

The URLs for the source document and the stylesheet document are supplied in the URL, which will typically take the form:

http://server.com/servlets/SaxonServlet?source=doc.xml&style=sheet.xsl

Note: Internet Explorer assumes that if the URL ends with ".xml" or ".xsl", as in the above example, then the returned file will be XML - even if the media type in the HTTP header is set to "text/html". You can prevent this behaviour by adding an extra dummy parameter, for example "&x=y".

The source and style parameters identify the source document and stylesheet by URL. These are interpreted relative to the servlet context. This means that specifying say "style=/styles/styleone.xsl" in the URL will locate the stylesheet in this file relative to the root directory for the web server.

The stylesheet is prepared the first time it is used, and held in memory in a cache. The cache may be cleared (for example, if a stylesheet has been changed) using a URL such as:

http://server.com/servlets/SaxonServlet?clear-stylesheet-cache=yes

This code is provided purely as a sample, in the expectation that you will customise it to your particular site requirements.

The Book List Stylesheet

An SQL style sheet

Saxon implements the element extensibility feature of the XSLT standard, allowing you to extend the XSLT language by implementing your own stylesheet elements. A specimen extension has been written to illustrate this feature: it allows you to create stylesheets to load data into a relational database.

To use the SQL extension elements in a stylesheet, you need to define a namespace prefix (for example "sql") in the extension-element-prefixes attribute of the xsl:stylesheet element, and to map this prefix to namespace URI that ends in "/net.sf.saxon.sql.SQLElementFactory".

This extension defines five new stylesheet elements: sql:connect, sql:query, sql:insert, sql:column, and sql:close:

• sql:connect creates a database connection. It has attributes "driver", "database", "user", and "password", all of which are attribute value templates (so the values can be passed in as parameters). the driver attribute names the JDBC driver class to be used. The database name must be name that JDBC can associate with an actual database, and in the sample stylesheet this database must contain a a table "Book" with three character columns, "Title", "Author", and "Category".

• sql:query performs a query. The attributes are as follows:

  table	The table to be queried (the contents of the FROM clause of the select statement). This is mandatory, the value is an attribute value template.
  column	The columns to be retrieved (the contents of the SELECT clause of the select statement). May be "*" to retrieve all columns. This is mandatory, the value is an attribute value template.
  where	The conditions to be applied (the contents of the WHERE clause of the select statement). This is optional, if present the value is an attribute value template.
  row-tag	The element name to be used to contain each row. Must be a simple name (no colon allowed). Default is "row".
  column-tag	The element name to be used to contain each column. Must be a simple name (no colon allowed). Default is "col".

• sql:insert performs an SQL INSERT statement. This causes a row to be added to the table identified by the "table" attribute.

• sql:column is used as a child element of sql:insert, and identifies the name and value of a column to be included in the INSERT statement. The name of the column is identified by the "name" attribute, the value may be indicated either by evaluating the expression contained in the "select" attribute, or as the expanded contents of the sql:column element. The value is always interpreted as a String. (Remember this is purely a demonstration of extensibility, in a real system there would be a need to cater for SQL columns of other data types).

• sql:close closes the database connection.

A specimen stylesheet that uses these XSL extension is books-sql.xsl. This loads the contents of the books.xml file into a database table.

To run this stylesheet you will need to do the following:

• Create a database (e.g. Microsoft Access) containing a table "Book" with three character columns, "Title", "Author", and "Category".
• Register this database as a JDBC data source. (If you use Microsoft Access, register it as an ODBC data source called, say, Books, and then it will automatically be available under JDBC as "jdbc:odbc:Books".
• Modify the <sql:connect> element in the stylesheet to specify the correct JDBC connection name for the database, and if necessary to supply a username and password. Alternatively you can supply the driver class, database name, username, and password as parameters on the command line.
• Execute the stylesheet from the command line, as follows:

java net.sf.saxon.Transform data\books.xml books-sql.xsl


The database will be populated with data from the books.xml document.

Shakespeare Example

This example works on an input file containing a Shakespeare play. You can use any of the Shakespeare plays in Jon Bosak's distribution at http://metalab.unc.edu/bosak/xml/eg/shaks200.zip, but for convenience one of them, Othello, is included in the Saxon distribution (in the samples\data directory).

Shakespeare stylesheet

There is an XSL stylesheet, play.xsl, which processes an input play in XML and generates a set of linked HTML files (one for the play and one for each scene) in an output directory. To run this, create a directory (say playhtml) and execute the following from the command line:

cd samples
java net.sf.saxon.Transform data\othello.xml styles\play.xsl dir=playhtml

The last parameter sets the value of the constant dir to the value playhtml; this constant is referenced from the style sheet when creating output files.

As well as showing how to produce multiple output files using the new XSLT 2.0 xsl:result-document element, this example stylesheet shows how to use saxon:preview to reduce the memory requirements when processing the source document sequentially.

The Bible

The stylesheet bible.xsl takes as input an XML file containing the text of the Old or New Testament. These files are not included in the Saxon distribution for space reasons, but can be downloaded from http://metalab.unc.edu/bosak/xml/eg/rel200.zip or from various mirror sites. They were prepared by Jon Bosak.

The output of the stylesheet is a set of 292 HTML files in a single directory, which together provide a frames-oriented rendition of the text. You can see the result (for the New Testament) at http://www.wokchorsoc.freeserve.co.uk/bible-nt/index.html. The application also works with the Old Testament text, but not with the other religious texts included in Jon Bosak's distribution.

To run the stylesheet first create an output directory (say htmldir), then execute the following from the command line:

java  net.sf.saxon.Transform   data\nt.xml  styles\bible.xsl  dir=htmldir

The final parameter sets the value of the XSLT parameter "dir" to the value "htmldir", which is referenced within the stylesheet to select a directory for output files.

Applet Examples

The directory samples/applet contains two demonstrations showing how to use Saxon from an applet embedded in an HTML page. Note that because this release of Saxon requires JDK 1.2 or later, you cannot run these applets with the default Microsoft JVM used by Internet Explorer. Instead, you will have to download and install the Sun Java plugin, obtainable from http://java.sun.com/getjava.

The subdirectory /demo contains a demonstration taken straight from the Xalan sample application, showing a window with three frames, containing the source document, stylesheet, and result. Click on "index.html" to open this in the browser, then click on the "Transform" button to run a transformation. Note that the HTML page is written in such a way that expects the saxon7.jar file to be located in the same directory as the HTML files; you will need to change the HTML to reflect its actual location. The SUN Java VM uses a security architecture that is fussy about where the file is located, even when you are running everything on your local machine: I found I had to move saxon7.jar into the data directory to make it work.

The subdirectory /family-tree contains a demonstration showing some members of the Kennedy family; open the HTML file to view the data. This demonstration is adapted from the one in my book XSLT Programmer's Reference. It illustrates how repeated transformations using the same source document and the same stylesheet can be used to browse around a data-set, without making repeated visits to the server.

JDOM Example

Saxon includes an adapter that allows the source tree to be a JDOM document.

To use this facility:

• The JAR file saxon-jdom.jar must be on the classpath
• JDOM version 0.7 must be installed and on the classpath
• You must be using JDK 1.2 or later.

The sample application JDOMExample.java illustrates how a JDOM tree can be used with Saxon. It combines two scenarios: running XPath expressions directly against a JDOM tree, from the Java application; and invoking a transformation with the JDOM document supplied as the Source object.

The application is designed to take two arguments, the books.xml file in the samples/data directory, and the total.xsl file in the samples/styles directory. The application builds a JDOM tree, modifies it in situ to add extra attributes, and then references these attributes from the stylesheet.

Michael H. Kay
20 December 2001