XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (794 page)

Technically, this interface is rather poorly named. The Internet RFCs distinguish the process of
resolving
a relative URI against a base URI, which is essentially a syntactic operation on two character strings, from the process of
dereferencing
the resulting absolute URI, which typically sends a request over the wires to retrieve some resource. Although the
URIResolver
is passed the relative URI and base URI as separate arguments, it would be bad practice to resolve the relative URI in a nonstandard way. The real power of the
URIResolver
is its ability to control how the absolute URI is dereferenced.

The interface defines only one method:

Examples of JAXP Transformations

This section provides some simple examples of applications that use the JAXP API in different ways to control a transformation.

Example 1: Transformation Using Files

This example (
FileTransform.java
) performs a single transformation, reading the source document and stylesheet from files, and sending the XML output to another file.

This is a minimal JAXP application.

At one time I was reluctant to supply
File
objects to the JAXP
StreamSource
and
StreamResult
constructors, because the filename-to-URI conversion was buggy. In recent releases the problems seem to have been fixed.

Assuming you have installed the Sun Java JDK, you can compile this application by the command:

This assumes that the directory containing the Java source file is the current directory. Once you have compiled the code, you can run it from the command line, for example:

Of course, this is not a very professionally written application. It will fall over with a stack trace if incorrect arguments are supplied, if either of the input files doesn't exist, or if errors occur during the transformation; but it's a start. My aim in these examples is to show how the main JAXP classes work, not to teach you professional Java programming.

Because some people like to type examples exactly as they are written in the book, the folder containing the Java applications also contains specimen XML and XSL files called
source.xml
and
style.xsl
. So if you make this folder your current directory, you should be able to type the command line above exactly as shown. But, of course, the Java application will handle any source file and any stylesheet. The stylesheet
style.xsl
uses the construct shown at the start of this chapter to place in the output file a comment identifying which XSLT processor was used. So by experimenting with different classpath settings you should be able to satisfy yourself that this code works with multiple XSLT processors.

Example 2: Supplying Parameters and Output Properties

This example,
Parameters.java
, enhances the previous example:

• It allows a stylesheet parameter to be supplied from the command line.
  
• It modifies the output properties defined in the stylesheet.
  
• It directs the output to
  System.out
  instead of a file.
  

The
main()
method of the enhanced application looks like this:

This version of the program can be run using a command such as the following. The third argument on the command line (written in quotes because it contains spaces) is now a parameter value for the stylesheet, instead of the output filename.

Comparing the output with that of the previous example, note that the HTML is no longer indented, and that the contents of the