jython-users

[Jython-users] Import and NoClassDefFoundError

[Edward P. <epo...@te...>]

Hello All,

I've look in the archives, but only see questions, and no answers relating
to this.
I have a folder hierarchy impi/core/ and a .class file impi/core/Impi.class

when I 'from impi.core import *' from another module, I get
'java.lang.NoClassDefFoundError: java.lang.NoClassDefFoundError:
impi/core/impi (wrong name: impi/core/Impi)'

Is there a quick fix for this?

Thanks
-Ed

Re: [Jython-users] Import and NoClassDefFoundError

[Kevin B. <kb...@ca...>]

Hmm.

I'm not quite sure how you managed it, but I imagine at some point
you had Impi in a file named impi.java? You may also not be using Jython 
2.1?

Windows' case-insensitive filesystem is unfriendly to Java's 
case-sensitive class names & one-class-one-file philosophy.

I'd suggest doing a clean build of all your Java code related to Impi. 
This will probably identify some class that is using 'impi' instead of 
'Impi'.  'grep' may also do it.

kb

Edward Povazan wrote:

>Hello All,
>
>I've look in the archives, but only see questions, and no answers relating
>to this.
>I have a folder hierarchy impi/core/ and a .class file impi/core/Impi.class
>
>when I 'from impi.core import *' from another module, I get
>'java.lang.NoClassDefFoundError: java.lang.NoClassDefFoundError:
>impi/core/impi (wrong name: impi/core/Impi)'
>
>Is there a quick fix for this?
>
>Thanks
>-Ed
>
>
>_______________________________________________
>Jython-users mailing list
>Jyt...@li...
>https://lists.sourceforge.net/lists/listinfo/jython-users
>

Re: [Jython-users] Import and NoClassDefFoundError

[Edward P. <epo...@te...>]

> I'm not quite sure how you managed it, but I imagine at some point
> you had Impi in a file named impi.java? You may also not be using Jython
> 2.1?
That was my first thought ... I checked for rogue impi.java classes. Still
doesn't work. I did see similar questions in the archives, I think it is
something windows specific.

-Ed

Re: [Jython-users] Import and NoClassDefFoundError

[Samuele P. <pe...@in...>]

> Hello All,
> 
> I've look in the archives, but only see questions, and no answers relating
> to this.
> I have a folder hierarchy impi/core/ and a .class file impi/core/Impi.class
> 
> when I 'from impi.core import *' from another module, I get
> 'java.lang.NoClassDefFoundError: java.lang.NoClassDefFoundError:
> impi/core/impi (wrong name: impi/core/Impi)'
> 
> Is there a quick fix for this?
> 

Under which OS?
What does:

import impi.core
dir(impi.core)

display? Impli or impli

Samuele.
 

Re: [Jython-users] Import and NoClassDefFoundError

[Edward P. <epo...@te...>]

I am using Jython 2.1 under XP Pro.

> import impi.core
> dir(impi.core)
['__doc__', '__file__', '__name__', '__path__']

Hmm, this is strange, but I can acually:

import impi.core.Impi
dir(impi.core.Impi)

Which works as expected, showing all the static methods of the Impi class.
Impi is a class containing static methods only.

Do I have something set up wrong. My classpath is set to the root of my
project. Is there anything else?

Thanks
-Ed

R: [Jython-users] Import and NoClassDefFoundError

[Samuele P. <pe...@in...>]

From: Edward Povazan <epo...@te...>
> I am using Jython 2.1 under XP Pro.
> 
> > import impi.core
> > dir(impi.core)
> ['__doc__', '__file__', '__name__', '__path__']
> 
> Hmm, this is strange, but I can acually:

That means that impi.core is a Python package,
you have a __init__.py both in impi and impi/core?

That's OK.

But so your from impi.core import * will never
get you the Java class. Anyway why the error?

The thing you haven't said to us
is that you are doing the 
    from impi.core import *
from a module inside impi.core, is that true?

Samuele.

Re: [Jython-users] Import and NoClassDefFoundError

[Samuele P. <pe...@in...>]

From: Edward Povazan <epo...@te...>
> Ok,
> I have __init__.py in the proper places.
> I have this hierarchy
> /impi
> /impi/core
> /impi/core/Impi.class    # java class with static methods, ie "looks like a
> module"
> /impi/core/editors.py    # a bunch of basic gui's used by the app.
> 
> In a jython console, I can do this:
> from impi.core import *        # works ok

but does it get you Impi?
it shouldn't.

> from impi.core.editors import *    # I get the exception here
> 
> editors.py contains:
> from impi.core import *
> 
> > But so your from impi.core import * will never
> > get you the Java class. Anyway why the error?
> In the console
> from impi.core import * works fine, and I can call the static methods in
> class Impi. Just when import is from another file, I get the problem.
> 
> > The thing you haven't said to us
> > is that you are doing the
> >     from impi.core import *
> > from a module inside impi.core, is that true?
> Yes, from editors.py

A-ah,

you get the error because Python import 
are interpreted first as relative to the package
of the current module:

that means that  inside import.core.editors

from impi.core import *

tries from impi.core.impi.core import * 
before from impi.core import * # top-level impi

now the first should fallback to the second
because Impi.class is not impi something,

So it seems we have still a case-sensitivity problem
we shouldn't have anymore. That one is a bug :(!.

OTOH from py.pkg import * never
gets to the possible Java classes inside py.pkg,
the single import yes or if you have already imported
them otherwise.  from java.pkg import * works OTOH.

Now for a workaround, it really depends on what
 do you want to get with from impi.core import *?
 
regards.

PS: as a style note it is better to avoid import *
in production code.













 

Re: [Jython-users] Import and NoClassDefFoundError

[Edward P. <epo...@te...>]

> A-ah,
:) thanks for your trouble at least now it is not me. Looks like I need to
reread about python import.

> PS: as a style note it is better to avoid import *
> in production code.
Yes, I normally do, except that impi.core has most of the 'brains' of my
app, and it is used often.

I have tried to import the specific files I need. Seems that Impi.class
still causes problems. from impi.core import Whatever still causes problems.

I will write some test code separate from my app, and see if I can figure it
out.

Thanks
-Ed

[Jython-users] Re: Import and NoClassDefFoundError - recreated error

[Samuele P. <pe...@in...>]

From: Edward Povazan <epo...@te...>
> Ok, I have recreated the error in a separate test.
> Do you know where I can start looking in the source, where the import
> actually occurs.
> Or is there someone who 'maintains' the import code that would be interested
> to see this?

Maybe you refer to me <wink>. I'm guilty for much
of the import logic impl.

Sorry for the duplicated work but when I asked:
[me]
>The thing you haven't said to us
>is that you are doing the 
>    from impi.core import *
>from a module inside impi.core, is that true?

I had already code that duplicated the bug,
I was exploring whether my work hypothesis
matched your world(-view).

> 
> No matter if I use * or a specific method/object, the error still occurs.
> 
I never said the contrary, inside impi.core.editors
all

from impi.core import *
from impi.core import Impi
import impi.core
import impi

will fail.

The situation is more involved that it already seems <wink>.

[*] At some point we [the devels] decided that
NoClassDefFoundError should be treated
differently than ClassNotFoundException, and not
transformed in import errors, but just propagated
up to the user. Because it can contain
valuable debug info.

So the naive fix that we can apply - leaving [*] as it  is -
 would fix the problem as long as sys.path is
disjunct from classpath... So the point
is that maybe we should rethink about [*].

For your case, I don't know if this is acceptable for you,
but I would move the java classes in impi.core.jclasses,

jclasses being a java package (a dir without __init__.py),
and putting the right package statements in the java sources.

Then you can put a 
from jclasses import *
or from impi.core.import * inside impi.core.__init__

and murphy-willing things should work, unless
other subtlilities block this approach too.

regards.