Preview: JDK-8055854 Examine overhead in java.net.URLClassLoader (stack-less exceptions)

[Peter Levart]

Hi,

As for usage of SharedSecrets, they are not needed to access CNFE 
package-private constructor from java.lang.ClassLoader, since they are 
in the same package, and from java.net.URLClassLoader, the call to 
super.findClass(name) does the job. So here's an updated webrev that 
also includes more descriptive message:

http://cr.openjdk.java.net/~plevart/jdk9-dev/ClassLoader.CNFE/webrev.02/


Regards, Peter

On 10/16/2014 09:35 AM, Peter Levart wrote:
> On 10/16/2014 01:49 AM, Stanimir Simeonoff wrote:
>> First, really nice tests.
>>
>> As for hiding: missing the real classloader impl. might be quite a 
>> bumper
>> for some middleware implementations. That would make pretty hard to 
>> trace
>> dependency issues without explicit logging, the latter is usually 
>> available
>> but still. Also it'd depend if the classloaders actually use
>> super.findClass() or not.
>> IMO, the option should be switchable via some system property.
>
> With a little tweak, the message of the stack-less exception thrown 
> from findClass() methods can be extended to include the classloader's 
> runtime class name and this message can be inherited by a replacement 
> stack-full exception. So the stack-trace would look like:
>
> Exception in thread "main" java.lang.ClassNotFoundException: XXX 
> (thrown by: sun.misc.Launcher$AppClassLoader)
>     at java.lang.ClassLoader.loadClass(ClassLoader.java:366)
>     at java.lang.Class.forName0(Native Method)
>     at java.lang.Class.forName(Class.java:265)
>     at Test.doIt(Test.java:7)
>     at Test.main(Test.java:11)
>
> Instead of what we have now:
>
> Exception in thread "main" java.lang.ClassNotFoundException: XXX
>     at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
>     at java.lang.ClassLoader.loadClass(ClassLoader.java:426)
>     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:317)
>     at java.lang.ClassLoader.loadClass(ClassLoader.java:359)
>     at java.lang.Class.forName0(Native Method)
>     at java.lang.Class.forName(Class.java:265)
>     at Test.doIt(Test.java:7)
>     at Test.main(Test.java:11)
>
>
> Would this be enough to cover your concern?
>
> Regards, Peter
>
>>
>> I am not sure about the need to hide the stackless c-tor as the 
>> effect can
>> be achieved by overriding fillInStackTrace(); w/o the extra baggage of
>> JavaLangAccess.
>>
>> Overall very decent improvement.
>>
>> Cheers
>> Stanimir
>>
>>