Common event-based parser API

David Megginson (ak117@freenet.carleton.ca)
Tue, 16 Dec 1997 07:12:02 -0500

Tim and I have taken some of the gritty details of our discussion
offline, and we have not yet managed to agree on how to return
character data; however, I do agree that attributes should be returned
somehow in the startElement() event rather than passed as separate
events, so I'd like to propose this:

startElement(XmlParser p, String elname, java.util.Dictionary attributes)

Note the use of the Dictionary abstract base class here. Hashtable is
derived from Dictionary, as is my Trie class that I released a
couple of years ago. There are a couple of advantages to this
approach:

1) It can be implemented efficiently, without requiring allocation of
a hash table: you could return anything derived from
java.util.Dictionary, including a simple sequential lookup in an
array of attributes.

2) It makes the users' work much easier, since they can just use

/**
* Handle the start of an element.
*/
startElement (XmlParser p, String elname, Dictionary attributes)
{
String id = (String)attributes.get("id");
String role = (String)attributes.get("role");

[...]
}

(instead of)

/**
* Handle the start of an element.
*/
startElement (XmlParser p, String elname, Attribute attributes[])
{
String id = null;
String role = null;

for (int i = 0; i < attributes.length; i++) {
if (attributes[i].getName().equals("id")) {
id = attributes[i].getValue();
} else if (attributes[i].getName().equals("role")) {
role = attributes[i].getValue();
}
}

[...]
}

Comments?

All the best,

David

-- 
David Megginson                 ak117@freenet.carleton.ca
Microstar Software Ltd.         dmeggins@microstar.com
      http://home.sprynet.com/sprynet/dmeggins/


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