Building Oracle XML Applications

Chapter 16. Extending XSQL and XSLT with Java

In this chapter, we examine how Java developers can extend the universe of built-in XSQL action handlers to provide custom actions and information sources and expand the universe of built-in functions in XSLT and XPath for use in stylesheets.

Developing Custom XSQL Actions

Oracle XSQL Pages is an extensible framework. With very straightforward Java code, you can introduce new kinds of actions to perform virtually any kind of custom processing required by your application and to easily incorporate XML information from custom sources. In this section, we’ll learn how to write custom XSQL action handlers.

How Action Handlers Work

As we highlighted in Chapter 15, the XSQL page processor processes an XSQL page by looking for action elements from the xsql namespace, and invoking an appropriate action element handler class to process each action. An action handler is a Java class that handles the runtime behavior of an action element in an XSQL page. Each action handler has full access to the objects it requires:

The DOM object representing the action element in the XSQL page

Allows the action handler to examine the attributes, nested elements, or text content of the action element to drive the behavior of the action

The XSQL page requesting the context object

Contains all the parameter values visible in the page, the current JDBC database connection (if any), and other resources available to the current page request

The XML result tree for ...