XOM API for Processing XML with Java

[John Cowan <jcowan AT reutershealth.com>]

Elliotte Rusty Harold scripsit:

> That's a new one to me. Where did you get that idea from?  

The 1.4.2 Javadoc for class Error says:

# An Error is a subclass of Throwable that indicates serious problems
# that a reasonable application should not try to catch.

Similarly, the JLS says in section 11.5.2:

# The class Error and its standard subclasses are exceptions from which
# ordinary programs are not ordinarily expected to recover.

JFBP is a component library I wrote where the user writes a small glue class 
to
connect the components; you can learn to write glue classes without really
knowing any Java, more or less analogous to shell programming.  If the 
components are unable to connect at run time,
the framework throws subclasses of Error to indicate what's wrong.

> unusualfor a Java program to throw an Error. Errors almost always 
> indicate a failure in the VM that can rarely be predicted or handled, 
> e.g. OutOfMemoryError or ClassFormatError. Very few user programs 
> should ever throw or even handle errors. The contract of error is not 
> that the programmer has blundered. It's that the VM has failed in 
> some way.

Not necessarily.  Loading the J2SE 1.4.2 class hierarchy at
http://java.sun.com/j2se/1.4.2/docs/api/overview-tree.html (takes a looong
time to load even over a fast wire), I see the following descendants of
java.lang.Error that don't have those semantics:

java.lang.AssertionError (this is all about programmer faults)
java.nio.charset.CoderMalfunctionError (this indicates an exception in a
  charset decoder or encoder, which is supposed to be "safe code")
javax.xml.parsers.FactoryConfigurationError (the parser factory given in the
  system properties doesn't exist or is broken)
javax.xml.transform.TransformerFactoryConfigurationError (same story, but for
  a transformation factory)

Indeed, it seems to me that the subclasses of nu.xom.XMLException are all
essentially very like assertion failures, which throw Errors as shown above.

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