Stax
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Streaming API for XML (StAX) is an application programming interface (API) to read and write XML documents in the Java programming language.
Traditionally, XML APIs are either:
- tree based - the entire document is read into memory as a tree structure for random access by the calling application
- event based - the application registers to receive events as entities are encountered within the source document.
These two access metaphors can be thought of as polar opposites. A tree based API allows unlimited, random, access and manipulation, while an event based API is a 'one shot' pass through the source document.
StAX was designed as a median between these two opposites. In the StAX metaphor, the programmatic entry point is a cursor that represents a point within the document. The application moves the cursor forward - 'pulling' the information from the parser as it needs. This is different from an event based API - such as SAX - which 'pushes' data to the application - requiring the application to maintain state between events as necessary to keep track of location within the document.
Origins
StAX has its roots in a number of incompatible pull APIs for XML, most notably XMLPULL, the authors of which (Stefan Haustein and Aleksandr Slominski) collaborated with, amongst others BEA, Oracle, Sun, Breeze Factor and James Clark.Examples
From JSR-173 Specification• Final, V1.0 (used under fair use).
Quote:
- The following Java API shows the main methods for reading XML in the cursor approach.
// Java
public interface XMLStreamReader
- The writing side of the API has methods that correspond to the reading side for “StartElement” and “EndElement” event types.
// Java
public interface XMLStreamWriter
- 5.3.1 XMLStreamReader
- This example illustrates how to instantiate an input factory, create a reader and iterate over the elements of an XML document.
XMLInputFactory f = XMLInputFactory.newInstance();
XMLStreamReader r = f.createXMLStreamReader(... );
while (r.hasNext())
Implementations
- http://stax.codehaus.org/ Reference Implementation
- [Woodstox] Open source StAX implementation
See also
Competing and complementary ways to parse XML in Java:External links
- [Clark, James]
- [Introduction to StAX] XML.com, Harold, Elliotte Rusty
- [JSR (#173)]
- Download JSR specification document as a pdf here: [download now]
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