Tom Spencer | 13 Aug 19:16
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java.lang.TypeNotPresentException when using reflection

I have been attempting to use reflection, in particular to get the superclass of a particular class, but this seems to fail when using Classpath v0.97.2 with JamVM 1.5.0.

In a stripped down version of what I am trying to achieve, I am attempting to run the following code, which I have unceremoniously poached from http://developer.classpath.org/pipermail/classpath/2006-November/001605.html :

public class Main {

    static class A extends ArrayList<String> {};

    public static void main(String[] args)
    {
        A a = new A();
        Object x = a;
        ((Collection)x).add(new Byte((byte) 1));
        System.out.println(x.getClass().getGenericSuperclass());
        System.out.println("We have a list parametrized with: " +
                ((ParameterizedType)x.getClass().getGenericSuperclass()).getActualTypeArguments()[0]);
    }
}

This code is compiled using the Eclipse Compiler and run on a PowerPC implementation. Classpath was compiled using Sun's javac compiler, version 1.6. Running the code, however, yields the following stack trace:

# jamvm -Xbootclasspath:/share/jamvm/classes:/usr/local/classpath/share/classpath Main
java.lang.TypeNotPresentException: type "java$util$ArrayList" not found
at gnu.java.lang.reflect.ParameterizedTypeImpl.resolve(GenericSignatureParser.java:127)
at gnu.java.lang.reflect.TypeImpl.resolve(TypeImpl.java:59)
at gnu.java.lang.reflect.ClassSignatureParser.getSuperclassType(ClassSignatureParser.java:83)
at java.lang.Class.getGenericSuperclass(Class.java:1712)
at Main.main(Main.java:16)
Caused by: java.lang.ClassNotFoundException: java$util$ArrayList
at java.lang.VMClass.forName(Native Method)
at java.lang.Class.forName(Class.java:233)
at gnu.java.lang.reflect.ParameterizedTypeImpl.resolve(GenericSignatureParser.java:123)
...4 more


It seems to me that the refelction doesn't seem to be finding the type correctly. Does anybody have any insight as to why this might be?

I have found the following older forum posts, but neither have been that helpful in trying to diagnose the issue.

http://developer.classpath.org/pipermail/classpath/2006-November/001605.html
http://www.nabble.com/Error-in-resolving-java.util.Set-td9779444.html

Thanks!

Tom

Christian Thalinger | 15 Aug 12:40
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Re: java.lang.TypeNotPresentException when using reflection

On Wed, 2008-08-13 at 18:20 +0100, Tom Spencer wrote:
> This code is compiled using the Eclipse Compiler and run on a PowerPC
> implementation. Classpath was compiled using Sun's javac compiler,
> version 1.6. Running the code, however, yields the following stack
> trace:

When I run this code with current CVS of GNU Classpath I get:

$ cacao Main
java.util.ArrayList<java.lang.String>
We have a list parametrized with: class java.lang.String

Maybe try to update GNU Classpath?

- twisti

Robert Lougher | 16 Aug 01:18

Re: java.lang.TypeNotPresentException when using reflection

Hi,

On Wed, Aug 13, 2008 at 6:20 PM, Tom Spencer
<tom.spencer <at> iscanetworks.com> wrote:
> I have been attempting to use reflection, in particular to get the
> superclass of a particular class, but this seems to fail when using
> Classpath v0.97.2 with JamVM 1.5.0.
>

I've investigated this and there's a bug in JamVMs handling of generic
signatures (rather than returning the raw generic signature, slashes
are replaced by dots, as in other class names; the dots are then
converted to $).

This is fixed in CVS HEAD.  Instructions for checking it out can be found here:

http://developer.berlios.de/cvs/?group_id=6545

Alternatively, apply the attached patch to natives.c.  This has been
generated against JamVM 1.5.0.

> I have found the following older forum posts, but neither have been that
> helpful in trying to diagnose the issue.
>
> http://developer.classpath.org/pipermail/classpath/2006-November/001605.html
> http://www.nabble.com/Error-in-resolving-java.util.Set-td9779444.html
>

No idea how I missed these (especially the second post)!  Let me know
how you get on.

Thanks,
Rob.

> Thanks!
>
> Tom
>
>
Attachment (natives.c-patch): application/octet-stream, 1694 bytes
Tom Spencer | 16 Aug 16:17
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Re: java.lang.TypeNotPresentException when using reflection

Awesome, thanks a lot for this. I will give it a try when I get back
to a computer next week and let you know how I get on!

Tom

On 16/08/2008, Robert Lougher <rob.lougher <at> gmail.com> wrote:
> Hi,
>
> On Wed, Aug 13, 2008 at 6:20 PM, Tom Spencer
> <tom.spencer <at> iscanetworks.com> wrote:
>> I have been attempting to use reflection, in particular to get the
>> superclass of a particular class, but this seems to fail when using
>> Classpath v0.97.2 with JamVM 1.5.0.
>>
>
> I've investigated this and there's a bug in JamVMs handling of generic
> signatures (rather than returning the raw generic signature, slashes
> are replaced by dots, as in other class names; the dots are then
> converted to $).
>
> This is fixed in CVS HEAD.  Instructions for checking it out can be found
> here:
>
> http://developer.berlios.de/cvs/?group_id=6545
>
> Alternatively, apply the attached patch to natives.c.  This has been
> generated against JamVM 1.5.0.
>
>> I have found the following older forum posts, but neither have been that
>> helpful in trying to diagnose the issue.
>>
>> http://developer.classpath.org/pipermail/classpath/2006-November/001605.html
>> http://www.nabble.com/Error-in-resolving-java.util.Set-td9779444.html
>>
>
> No idea how I missed these (especially the second post)!  Let me know
> how you get on.
>
> Thanks,
> Rob.
>
>> Thanks!
>>
>> Tom
>>
>>
>

--

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Tom Spencer
Isca Networks Corporation Limited

Tel: +44 (0) 870 909 7813
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Gmane