Andrew Zhang wrote:
Hi, all
Things are a little bit complex when I tried to implement this
workaround.
Consider availableCharsets() method from Charset.java, which loads
provider
classes from configuration file.
Please see my comments inline.
final ClassLoader cl = getContextClassLoader();
if (null != cl) { // what shall we do if context class loader is null?
try {
// context classloader is used to get resources.
Enumeration e = cl
.getResources(PROVIDER_CONFIGURATION_FILE_NAME);
// Examine each configuration file
while (e.hasMoreElements()) {
// here, context classloader is used to load class.
// If system classloader is used as backup when context classloader
fails to
load, it seems illogical, because it's context classloader who get
resources.
// It should be the same classloader who gets resources and loads
corresponding classes.
loadConfiguredCharsets((URL) e.nextElement(), cl, charsets);
}
} catch (IOException ex) {
// Unexpected ClassLoader exception, ignore
}
}
If we put another copy code after this section, using "system
classloader"
instead of "context classloader", it also seems illogical. What shall
we do
if context classloader fails to load a provider charset class? Should it
throw an error as spec requires or pass silently?
Hmm... I think more serious problem here is that the classloader is used
not only to load the CharsetProvider class, but also to load the
configuration files, so if we choose to try context classloader then
system classloader, they may load different config files! IMHO, the
behavior will be contradict with both RI and spec. I suggest we give up
the *third way* and choose one(RI or spec) to follow, from others'
comments, Sun has been aware of this for long time, so they must have
reason not to fix the codes, maybe just because this is a not trivial
difference(it may be significant for server application which has multi
classloaders and special charsets), so I suggest we follow RI.
To sum up, it's hard to follow RI, and comply with spec
simultaneously. We
have to choose one of them. Spec or RI?
I don't think RI would change its behaviour in later release. In fact,
the
"bug" still exists in SUN 6.0 rc version. Personally, +1 for following
RI.
Any comments or better suggestions?
Thanks!
--
Paulex Yang
China Software Development Lab
IBM
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