IBM Version 5 manual Xslt support packages in Jaxp

Studying Example 3-6, notice that JAXP can read directly from a File object, so three files objects are created for the source XML, the XSLT stylesheet, and the target HTML file. The Source interface is used to read both the XML file and the XSLT file. The Source interface can have many implementations. In this example, we are using StreamSource, which has the ability to read a File object, an InputStream, a Reader, or a system ID. Later we will examine additional Source implementations that use SAX and DOM as input. Just like Source, Result is an interface that can have several implementations. In this example, a StreamResult sends the output of the transformations to a target file.

Next an instance of TransformerFactory is created. The TransformerFactory is responsible for creating Transformer and Template objects. In our example, we create a Transformer object. Transformer objects are not thread-safe, although they can be used multiple times. For a simple example like this, we will not encounter any problems. In a threaded servlet environment, however, multiple users cannot concurrently access the same TransformerFactory instance. JAXP also provides a templates interface, which represents a stylesheet that can be accessed by many concurrent threads.

The transformer instance is then used to perform the actual transformation. It applies the XSLT stylesheet to the XML data, sending the result to the target file.

XSLT support packages in JAXP

JAXP support for XSLT is broken down into the packages listed below:

￿javax.xml.transform: defines a general purpose API for XML transformations without any dependencies on SAX or DOM. The Transformer class is obtained from the TransformerFactory class. The Transformer transforms from a source to a result.

￿javax.xml.transform.dom: defines how transformations can be performed using DOM. It also provides implementations of Source and Result:

DOMSource and DOMResult.

￿javax.xml.transform.sax: supports SAX2 transformations. It defines SAX

versions of Source and Result: SAXSource and SAXResult. It also defines a subclass of TransformerFactory that allows SAX2 events to be fed into an XSLT processor.

￿javax.xml.transform.stream: defines I/O stream implementations of Source

and Result: StreamSource and StreamResult.

The heart of JAXP XSLT support lies in the javax.xml.transform package, which lays out the mechanics and overall process for any transformation that is performed.

Chapter 3. Processing XML 67