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Xparse-J aspires to be the smallest Java XML parser on the planet.
Xparse-J favors compactness over conformance, so it is mainly useful for being embedded in Java applets for simple XML processing tasks, such as parsing RSS as demonstrated in RSSApplet.
Xparse-J is a literal translation of Xparse, an XML parser in 5k of JavaScript, into Java. I added a helper class JSArray to mimic the Javascript array built-in data structure.
Xparse-J reads XML documents from a given string and presents the resulting
document as a tree structure comprised of com.exploringxml.xml.Node
and com.exploringxml.xml.JSArray. Both Node
and JSArray have basic functionality for navigating the document
tree and accessing its data. All character encodings that are supported by
Java can be processed.
Xparse-J does not conform to any standard XML API such as SAX or DOM. Most of their functionality is not needed for simple XML processing tasks, and would substantially increase the size of the parser. If you favor conformance over compactness, have a look at Aelfred and TinyXML, among others. The parser does not read DTDs and the error handling is minimal, so presenting it with documents that have been checked before, e.g. on the server side, is recommended.
Incorporating Xparse-J into your own project is fairly simple:
Xparse-J consists of only three classes:
Xparse
Node
JSArray
The most important function for reading a document is
Xparse.parse(). It takes the string containing the XML document
as the sole argument and returns the root node of the parsed XML document.
A node can be navigated using Node.find(path, occurrance),
which finds the n-th occurrance of a child node matching the supplied path
expression. The path syntax mirrors XPath abbreviated syntax, looking like
directory arguments, e.g. "/rss/item/title" specifying the title element of an
RSS item.
Every node contains a java.util.Hashtable of attributes, which
can be queried and
enumerated in the standard Java way. The JSArray member named contents
contains the set of child nodes.
JSArray is using a java.util.Vector and offers
the typical getter and setter functions JSArray.getElementAt(index)
and JSArray.selElementAt(index, object).
Sure. RSSApplet is a small, configurable applet for displaying news in the RSS format, which is derived from XML. The code for loading the document is:
// read XML document from URL into a string
URL u = new URL("http://my.machine.com/my/URL");
InputStreamReader r = new InputStreamReader(u.openStream());
StringBuffer sb = new StringBuffer();
int c;
while ((c = r.read()) != -1) {
sb.append((char)c);
}
// parse string and build document tree
root = new Xparse().parse(sb.toString());
To find the root node of the RSS document, which could either be rss
or RDF, one would say:
int occur[] = {1};
Node doc = root.find("RDF", occur);
if (doc == null) doc = root.find("rss", occur);
if (doc == null) throw new Exception("<RDF> or <rss> missing, is this an RSS file?");
Extracting the title of the RSS channel would work like this:
int occur[] = {1, 1};
Node n = doc.find("channel/title", occur);
if (n == null) throw new Exception("<channel><title> missing.");
String channelTitle = n.getCharacters();
System.out.println("Channel: " + channelTitle);
Right here.
Xparse-J is published under the GNU Public License. Feel free to use it in your projects.
When you are using Xparse-J, I'd like to hear from you. Just send me feedback.
Congratulations, you've come to the right place ;-)
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Produced by Michael Claßen
All Rights Reserved. Legal Notices.
URL: http://www.webreference.com/xml/tools/xparse-j.html
Created: Jan 16, 2001
Revised: Aug 01, 2001
