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Extending the Oracle XML Platform
We conclude this chapter with a discussion of the ways in which you can extend the Oracle XML platform. Extensibility and interoperability are such important XML characteristics that they are required to be carried through to the application level. This section addresses two types of extension: functional extension and code extension.Oracle Database 10g and Oracle XDK 10g provide many ways in which you can extend the built-in XML functionality. With Oracle Database 10g, when you are using PL/SQL, you can create Java stored procedures to invoke Oracle’s or your own Java code from the Oracle JVM. A great example of this is using the XDK’s Java SAX parser to provide SAX parsing support to PL/SQL, as documented in an excellent code sample that is available on OTN. As long as you are not making continuous, fine-grained calls to Java—as you would when accessing the DOM—this method works extremely well. Moving to the midtier, you can extend XSLT stylesheets by means of extension elements that can invoke Java, which allows you to execute Java methods from an XSLT process. You can create custom XML Pipeline modules (as shown in Chapter 17) to extend the functionality of the Oracle XML Pipeline Processor. Finally, you can create custom action handlers to use with the XSQL Servlet to perform special server-side XML processing.Code extension or reusability is a key design goal for cost-efficient, maintainable, and reliable applications. By including data and its metadata in a single document, XML offers the capability to build generic functionality that derives its processing from the metadata. Examples include applications that key off of a doctype or schema declaration to determine the type of processing required, such as XPaths to search or a stylesheet to apply, applications whose GUI or controls are configured by XML files, and applications that automatically configure themselves for the client devices they are communicating with. The first five years in the life of XML technology has broadened and matured the infrastructure that is necessary for serious enterprise-level XML-enabled application development. We predict that the next five years will see XML power applications as support is built into hardware, bringing XML processing anywhere…and fast everywhere.
