Fwd: resource location problem in JDK 9 from build 148 onward

[Rick Hillegas]

Thanks, David and Alan. The suggested workaround works for me. I will 
mouse your response into the commentary on 
https://issues.apache.org/jira/browse/DERBY-6856, where I have been 
collecting all of the issues I've encountered when building and testing 
Apache Derby with JDK 9.

I strongly recommend a GA release note about this topic if the 
backward-incompatibility won't be ameliorated.

Thanks,
-Rick


On 1/16/17, 5:15 PM, David Holmes wrote:
> Hi Rick,
>
> <dropping derby-dev from cc list>
>
> On 17/01/2017 10:55 AM, Rick Hillegas wrote:
>> Resending since the moderator rejected my initial post for want of a
>> subscription to jigsaw-dev.
>>
>> -------- Original Message --------
>> Subject:     resource location problem in JDK 9 from build 148 onward
>> Date:     Mon, 16 Jan 2017 08:45:23 -0800
>> From:     Rick Hillegas <rick.hillegas at gmail.com>
>> To:     jigsaw-dev at openjdk.java.net, "derby-dev at db.apache.org"
>> <derby-dev at db.apache.org>
>>
>>
>>
>> Dalibor Topic suggested that I pose this question to the jigsaw-dev 
>> list:
>>
>> Starting (at least) with build 148, resource location has changed in a
>> way which is not backward compatible with JDK 8. The following
>> experiment shows the behavior change:
>>
>> 1) Compile the following class using JDK 8 and put it in a jar file
>> called z.jar:
>>
>> public class public class ResourceLocationProblem
>> {
>>   public static void main(String... args) throws Exception
>>   {
>>     String resourceName = "/META-INF/MANIFEST.MF";
>>     Class dummyClass = (new Object()).getClass();
>>     Object is = dummyClass.getResourceAsStream(resourceName);
>>
>>     if (is != null) { System.out.println("Resource found."); }
>>     else { System.out.println("Resource NOT found!"); }
>>   }
>> }
>>
>> 2) Then run the program thusly:
>>
>>   java -cp z.jar ResourceLocationProblem
>>
>> On JDK 8, the program produces this output...
>>
>> Resource found.
>>
>> ...while on JDK 9 build 151 the program produces this output...
>>
>> Resource NOT found!
>>
>> Dalibor pointed me to the following proposal, which indicates that some
>> significant changes have been made to resource location:
>> http://mail.openjdk.java.net/pipermail/jpms-spec-experts/2016-September/000392.html 
>>
>>
>> However, I am not trying to use any jigsaw features. This test program
>> suggests that JDK 9 will break many legacy applications.
>>
>> 1) Is the observed behavior change a bug?
>
> No. Modules enforce strong encapsulation of types and resources. As 
> per the link you were given:
>
>   - The `Class::getResource*` methods, when invoked upon a class defined
>     in a named module, only locate resources from within that module.
>     These methods are also caller-sensitive.
>
> So you are using Object.class is the named java.base module to try and 
> find local resources in the unnamed-module, that are in z.jar. That 
> won't work.
>
>> 2) What is the recommended workaround?
>
> Use a Class object from the "module" that contains the resource i.e. 
> ResourceAllocationProblem.class in your example.
>
> David
> -----
>
>> Thanks,
>> -Rick
>>
>