RFR(M): 8165550: Add class loader names to ClassCastException message

[Rachel Protacio]

Ah yes, my apologies - I should have provided more context. This is the 
VM corollary of Mandy's change 
http://hg.openjdk.java.net/jdk9/dev/hotspot/rev/48fce55afe71 which 
implements the new classloader name scheme and uses it in Stack Traces. 
In the fullest instance, it could look like
     MyClassLoader/module1 at 9.0/package1.class1
The class loader is not listed if it is built-in, the module is not 
listed if it is unnamed, the version is not listed if it is a "non-jdk" 
module.

I appreciate your point about shortening this specific CCE message to 
not repeat information, but I think there's a stronger case for 
maintaining a VM-wide format for all ClassLoader-module-fqn strings. 
This format will be used for more messages as well, e.g. unified logging 
for class loading.  (The follow-up bug: 
https://bugs.openjdk.java.net/browse/JDK-8169559.) And most importantly, 
because there are the specific instances listed above for leaving out 
the CL or module, it could potentially be more confusing to use 
shorthand. Would the user know that the module isn't listed the second 
time because it's the same module or because it's the unnamed module?

Rachel

On 11/10/2016 5:02 PM, David Holmes wrote:
> Hi Rachel,
>
> Just wondering, in the most complex case, exactly what will this new 
> message look like? We seem to be including module names as well as 
> classloader names, and of course class names.
>
> Arguably we should only add the additional info when they differ 
> between the types ie if both in same classloader and same module then 
> only report class name; if same loader but different module report 
> module:class; if different loaders then report everything 
> loader:module:class. Also not sure module version is needed at all in 
> this message.
>
> Thanks,
> David
>
> On 11/11/2016 7:38 AM, Rachel Protacio wrote:
>> Hi,
>>
>> Please review this Jigsaw enhancement which adds the new format of class
>> loader names to VM ClassCastException messages. Includes an
>> updated/expanded jtreg test.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8165550
>> Open webrev: http://cr.openjdk.java.net/~rprotacio/8165550.00/
>>
>> Passes JPRT and jck vm and lang tests.
>>
>> Thanks!
>> Rachel