Chapter 4 XML Processing

173

By definition, XSLT supports not only processing XML input documents but

it also can output XML documents. (Other output methods include text, HTML,

and so forth.) Note that although the DOM version level 2 API does not support

serialization that is, transformation of a DOM tree to an XML document the

JAXP implementation of XSLT addresses the serialization of a DOM tree using

an identity transformer. An identity transformer copies a source tree to a result

tree and applies the specified output method, thus solving the serialization

problem in an easy, implementation independent manner. For example, to output

in XML, the output method is set to 

xml

. XSLT can also be used to serialize to

XML from DOM trees, SAX events, and so forth.

Consider using XSLT when any of the following circumstances apply:

E

You want to change the structure, insert, remove, rename, or filter content of 

an XML document.

E

You potentially have more than one transformation for the same document. Al 

though one transformation can be hand coded using another API, multiple 

transformations, because of the scripting nature of style sheets, are better done 

using XSLT transformations.

E

You have to perform complex transformations. Because of XSLT's functional 

declarative model, it is easier to design complex transformations by coding in 

dividual rules or templates than by hard coding procedures.

E

You want the ability to be flexible and leave room for future changes in the 

schemas of documents you are processing.

E

You want to process documents that contain a significant amount of data to 

minimize performance overhead.

E

You need to transform a document for non interactive presentation or in batch 

mode. The performance overhead of transformation is usually less of an issue 

with non interactive presentations. Such a document might be a purchase order 

or an invoice, for example.

E

You must support multiple external schemas but you want to internally pro 

gram only against a generic schema (schema adapter).