setEntityResolver(null)

XOM user Nils Kilden-Pedersen has reported a bug that his parser is 
throwing a NullPointerException because XOM calls 
setEntityResolver(null) at one point inside the Builder class (which 
sits on top of a SAX parser). I'm still trying to determine exactly 
which SAX parser he's using (probably Xerces or Crimson), and I can 
probably work around this, but in the meantime he has raised an issue 
about the proper behavior of SAX.

It has previously been my understanding that you can remove an 
EntityResolver, and the various other listeners set on a XMLReader by 
passing null to the appropriate setter method such as 
setEntityResolver. The SAX API documentation does not justify this, 
but it doesn't say it's prohibited either. See

http://www.saxproject.org/apidoc/org/xml/sax/XMLReader.html#setEntityResolver(org.xml.sax.EntityResolver)

However, my user pointed out to me that the version of the SAX API 
documentation  included with J2EE does state that this method throws 
a NullPointerException. See

http://java.sun.com/j2ee/sdk_1.3/techdocs/api/org/xml/sax/XMLReader.html#setEntityResolver(org.xml.sax.EntityResolver)

I am requesting discussion and official resolution of whether or not 
its acceptable to pass null to setEntityResolver to remove any 
currently installed EntityResolver. Personally, since there's no 
other way to remove an EntityResolver without providing a new one, I 
think this is necessary. However, whatever the decision I would like 
to ask that the answer be explicitly placed in the official SAX docs.

I think we probably also need to ask and answer this question for the 
other setter methods: setContentHandler, setDTDHandler, etc. and 
perhaps also for the extensions such as LexicalHandler and 
DeclHandler that are set via properties.
-- 

+-----------------------+------------------------+-------------------+
| Elliotte Rusty Harold | [email protected] | Writer/Programmer |
+-----------------------+------------------------+-------------------+
|           Processing XML with Java (Addison-Wesley, 2002)          |
|              http://www.cafeconleche.org/books/xmljava             |
| http://www.amazon.com/exec/obidos/ISBN%3D0201771861/cafeaulaitA  |
+----------------------------------+---------------------------------+
|  Read Cafe au Lait for Java News:  http://www.cafeaulait.org/      |
|  Read Cafe con Leche for XML News: http://www.cafeconleche.org/    |
+----------------------------------+---------------------------------+


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