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From "Hibbs, David" <David.Hi...@ANICO.com>
Subject RE: application configuration
Date Thu, 08 Jul 2004 13:41:46 GMT
	I'll give you a good reason... file access inevitably risks
IOExceptions, and exceptions don't propogate well from a static block.

	That is to say, when the ClassLoader invokes the static block, it is
not invoked from within your code.  The exception gets thrown and propogates
through the *ClassLoader* stack rather than your application code, resulting
in an application that simply won't start for mysterious reasons, forcing a
long and drawn out investigation.

	The only reason I use static blocks any more is to initialize
constants that require more than 1 line to initialize correctly (such as
NumberFormats, where you may have additional methods to invoke once they are
corrected) or are order-dependent, so that if a field gets renamed and/or
the members are resorted the code doesn't blow up.
Even these examples are pretty scarce and serve very special purposes.

Best Practice: Don't do anything in a static block that can throw an
exception without good reason.  

	If you have something you'd like to initialize in a static way,
create a static synchronized accessor and allow the accessor to throw
exceptions as needed.  i.e.
a singleton-like implementation:

private static Config configInstance = null;
public static final synchronized getConfig()
{
	if(configInstance==null)
	{
		// create instance and read config;
		// this can throw any RuntimeExceptions
		// and still be compatible with the signature
	}
	return configInstance;
}

David Hibbs, ACS
Staff Programmer / Analyst
American National Insurance Company

> Id be wary about using static blocks for anything involving 
> file access. I
> cant give you a good reason for that, but it just seems like 
> a bad idea to
> me.

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