Input and Output

XSLT processors, like other XML tools, can read their input data from many different sources. In the most basic scenario, you will load a static stylesheet and XML document using the class. More commonly, the XSLT stylesheet will come from a file, but the XML data will be generated dynamically as the result of a database query. In this case, it does not make sense to write the database query results to an XML file and then parse it into the XSLT processor. Instead, it is desirable to pipe the XML data directly into the processor using SAX or DOM. In fact, we will even see how to read nonXML data and transform it using XSLT.

System Identifiers, Files, and URLs

The simple examples presented earlier in this chapter introduced the concept of a system identifier. As mentioned before, system identifiers are nothing more than URIs and are used frequently by XML tools. For example, javax.xml.transform.Source, one of the key interfaces in JAXP, has the following API:

public interface Source {
    String getSystemId(  );
    void setSystemId(String systemId);

The second method, setSystemId( ) , is crucial. By providing a URI to the Source, the XSLT processor can resolve URIs encountered in XSLT stylesheets. This allows XSLT code like this to work:

<xsl:import href="commonFooter.xslt"/>

When it comes to XSLT programming, you will use methods in and to convert platform-specific file names into system IDs. These can then be used as parameters ...

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