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From "Benjamin Bentmann (JIRA)" <j...@codehaus.org>
Subject [jira] Created: (DOXIA-226) Make XML based parsers better handle whitespace
Date Fri, 22 Feb 2008 23:37:28 GMT
Make XML based parsers better handle whitespace
-----------------------------------------------

                 Key: DOXIA-226
                 URL: http://jira.codehaus.org/browse/DOXIA-226
             Project: Maven Doxia
          Issue Type: Improvement
            Reporter: Benjamin Bentmann


Regarding whitespace in XML documents, one needs to consider the following aspects:
- ignorable whitespace, i.e. view "{{<tr> <td/> </tr>}}" and "{{<tr><td/></tr>}}"
as equivalent
- collapsible whitespace, i.e. view "{{Text &nbsp; Text}}" and "{{Text Text}}" as equivalent
- trimmable whitespace, i.e. view "{{<p>  Text  </p>}}" and "{{<p>Text</p>}}"
as equivalent

Those distinctions require a DTD/XSD in combination with a validating parser and/or application-specific
knowledge. For robustness, doxia parsers for XML-based formats should not depend on the existence
of a schema definition such that they reliably deliver events into the sinks. Hence I suggest
to hard-code the required logic for proper whitespace handling into each parser.

Currently, whitespace handling is rather static, e.g. {{XhtmlBaseParser}} pushes all input
whitespace into the sink. This might cause troubles with sinks that are not expected to receive
ignorable whitespace. To address this issue, it seems helpful if {{AbstractXmlParser}} provided
a default implementation of {{handleText()}} that subclasses can simply control via state
flags instead of implementing {{handleText()}} from scratch in each parser. Copy&Paste
- which caused DOXIA-225 - needs to be avoided.

More precisely, I image the following changes:
- Have {{AbstractXmlParser}} maintain a stack of tuples (ignorable, collapsible, trimmable)
where each tuple describes the whitespace handling for the currently parsed element
- Have {{AbstractXmlParser}} push/pop a tuple from this stack before/after calling {{handleStartTag()}}/{{handleEndTag()}}
- Have {{AbstractXmlParser}} provide setters to allow subclasses to control the desired whitespace
handling in their {{handleStartTag()}} implementation
- Have {{AbstractXmlParser}} implement {{handleText()}} where it evalutes the top-most tuple
from the stack


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