<i18n dev> RFR: JDK-8280902 ResourceBundle::getBundle may throw NPE when invoked by JNI code with no caller frame

[Mandy Chung]

On Wed, 2 Mar 2022 18:56:40 GMT, Tim Prinzing <duke at openjdk.java.net> wrote:

> The caller class returned by Reflection::getCallerClass was used to gain access to it's module in most cases and class loader in one case. I added a method to translate the caller class to caller module so that the decision of what module represents the caller with no stack frame is made in a single place. Calls made to caller.getModule() were replaced with getCallerModule(caller) which returns the system class loader unnamed module if the caller is null.
> 
> The one place a class loader was produced from the caller in getBundleImpl it was rewritten to route through the getCallerModule method:
> 
>         final ClassLoader loader = (caller != null) ?
>                 caller.getClassLoader() : getLoader(getCallerModule(caller));
> 
> A JNI test was added which calls getBundle to fetch a test bundle from a location added to the classpath, fetches a string out of the bundle and verifies it, and calls clearCache.
> 
> The javadoc was updated for the caller sensitive methods changed.

Instead of sprinkling the null caller text in the javadoc in each `getBundle` method, we can specify that that in the class specification, for example, after the "Resource bundles in other modules and class path" section.


In cases where the {@code getBundle} factory method is called from a context 
where there is no caller frame on the stack (e.g. when called directly from
a JNI attached thread), the caller module is default to the unnamed module for the
{@linkplain ClassLoader#getSystemClassLoader system class loader}.


What do you think?

src/java.base/share/classes/java/util/ResourceBundle.java line 1588:

> 1586:                                                 Control control) {
> 1587:         final ClassLoader loader = (caller != null) ?
> 1588:                 caller.getClassLoader() : getLoader(getCallerModule(caller));

Suggestion:

              ClassLoader loader = getLoader(getCallerModule(caller));


This can be simplified as above.  I would drop `final` too as it only adds noise to the code.

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PR: https://git.openjdk.java.net/jdk/pull/7663