Tutorials : Deliver On-the-Fly Mapping Services to Your Rich Desktop Java Application, Part 2 :

XML Data Implementation

At the time of writing this article, the BuildURLFunction element in Listing 2 uses JavaScript which produces identical tile requests to that of the OpenStreetMap.org web site's JavaScript. Placing the logic for tile requests in JavaScript is easy and advantageous when the tile server's JavaScript is well known and understood.

Rather than providing a full example, which demonstrates all the additional metadata features, readers may refer to other XML examples here. The next section will show how to parse the XML.

Parsing Your XML with SAX

Parsing XML using SAX requires that you extend the appropriate handler class. You'll extend org.xml.sax.helpers.DefaultHandler in a private inner class of the parser class. The handler simply receives notification of what is happening as the XML is being parsed. The code shown in Listing 3 has been simplified to highlight the parsing process, but click here to view the entire code.

The steps of the parsing algorithm, shown below, are very simple and can be modified for parsing most XML data, granted that it is simple in nature.

1. The startDocument method performs initialization that is done once.
2. The startElement method checks for the FactoryInfo element and initializes for this element. This method also initializes the current string buffer.
3. The characters method captures the text for the current element being processed.
4. The endElement method copies the current string buffer into a data member of the enclosing parser class. This method also builds a new FactoryInfo structure when processing a FactoryInfo element end tag.

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