WebLogics Streaming API

WebLogic s Streaming API

WebLogic's Streaming API offers a simple and intuitive way to parse and generate XML data. Compared to the SAX or DOM parsing models, it presents a fundamentally different viewpoint on an XML document. As the name suggests, parsing with the Streaming API is based around a stream. This stream is, in fact, a stream of XML events generated as the XML document is parsed. These events are similar to the events defined in the SAX API because they represent the same fundamental information about the XML data.

BEA is involved in the standardization of the Streaming API for XML (StAX), which has an API very similar to that described here. As a result, you can consider using BEA's implementation of StAX, available from the dev2dev web site.

When an XML document is parsed in SAX mode, the program registers a handler that can listen for SAX events as they occur. The SAX parser then automatically invokes the different callback methods of the event listener. In contrast, a program using the Streaming API pulls events off a stream, whereby each event represents some fundamental information about the XML being parsed. The Streaming API supports events that mark the occurrence of start and end tags, character data, whitespace characters, processing instructions, and several other document characteristics. These parser events enable you to step through the XML document, filter out certain event types, perhaps skip ahead in the document, and stop processing at any point. Parsing an XML document entails iterating over the stream of events and processing the XML data depending on the type of parse event. Thus, parsing with the Streaming API is demand-driven because you need to explicitly iterate over the stream and extract the events of interest. For this reason, it is often referred to as pull parsing.

Assume that xmlInput is a string variable holding the XML fragment shown in Example 18-5.

Example 18-5. Sample XML

Hello <inOne> <simple/>