Re: [Jython-users] copy and deepcopy not copying Java class variables?

[Andy R. <bar...@gm...>]

Sorry for the late reply! It's been a busy week.

I'm still getting an error. I have a (serializable) Java class and a Python
class that extends it, and I've loaded the Python class (successfully) into
Java. After instantiating the Python class in Java, I'd like to make a copy
of it from Java.

So I've tried - with the new files you've sent me - creating a new function
in the superclass (that returned null) but I overrode it in the Python
class, having it return a copy.deepcopy(pythonClassName). That didn't work,
so what I then tried was using the copy method from DeepJavaCopier, and it's
giving me a ClassNotFound error when it tries to read the object back in
(obj = in.readObject();)

This is the first line of the error I'm getting:
java.lang.ClassNotFoundException:
org.python.proxies.MyTestClass$MyTestClass$0

So I'm not sure if I'm using it properly - my class is only serializable
(not cloneable), because I only want to make a deep copy of it.

Thanks again for all your help,
Andy

On Tue, Mar 9, 2010 at 2:54 AM, Josh Juneau <jun...@gm...> wrote:

> Andy-
>
> You are correct in that there were still issues with the version of copy.py
> which I previously sent to you.  I think that the issues you were seeing are
> twofold.  There are a couple of rules one must follow in order to create
> copies of Java objects.  First, in order to be deep copyable, a Java object
> must implement java.io.Serializable.  Ensure that your testClass is
> serializable.  Second, if you are trying to create a shallow copy of the
> object then it must implement the java.lang.Cloneable interface and override
> the clone() method.  I've attached one such Java object (Person.java) that
> should be both shallow and deep copyable via the new copy.py (which is also
> included).
>
> I found that in the previous version I sent to you , Java classes were not
> being deep copied correctly as the Python code was unable to actually create
> the copy.  In order to make it work, I've re-written the deep copy
> implementation in Java code and now the copy.py uses the new Java
> implementation each time a deep copy is necessary.  This seems to do the
> trick as I believe the Python deep copy implementation was encountering
> issues in translation and creating a proxy object rather than a straight
> copy.
>
> To use this new version, please place DeepJavaCopier.class, and copy.py in
> your Lib directory.  Then, ensure that your Java object adheres to the rules
> mentioned above.  The solution definitely could use some further testing, so
> any help would be appreciated!
>
> Thanks
>
>
> Josh Juneau
> jun...@gm...
> http://jj-blogger.blogspot.com
> http://www.jythonpodcast.com
> Twitter ID:  javajuneau
>
>
> On Mon, Mar 8, 2010 at 4:28 PM, Andy Rose <bar...@gm...> wrote:
>
>> Thanks very much to both of you for the help, but with the new copy.py I'm
>> getting an error:
>>
>> raise Error('un-deep-copyable object of type %s' % type(x))
>> copy.Error: un-deep-copyable object of type <class 'testClass.testClass'>
>>
>> testClass in this case is a very simple class containing only a single
>> integer. Any ideas why this might be happening? I can give my code if it
>> will help.
>>
>> Thanks again,
>> Barbalute
>>
>>
>> On Mon, Mar 8, 2010 at 4:08 PM, Josh Juneau <jun...@gm...> wrote:
>>
>>> Yes, there is an issue with the current version of copy.py that is being
>>> distributed with 2.5.1.  You can read more about the issue on the bug
>>> tracker at http://bugs.jython.org/issue1551...but it specifically
>>> addresses issues while making copies of Java objects using copy() and
>>> deepcopy().  I am going to be checking in the attached version of copy.py
>>> which has been corrected to address the issues related to the bug report.
>>>  There is also an effort taking place to convert the current version of
>>> copy.py into a Java implementation to help boost performance a bit.  Please
>>> stay tuned for that version sometime in the future.
>>>
>>> If you have a moment, please drop the attached version of copy.py into
>>> your jython Lib directory and give it a try.  Hopefully it will resolve your
>>> issues.  If it does not, please submit another bug or add onto issue 1551.
>>>
>>> Thanks
>>>
>>>
>>> Josh Juneau
>>> jun...@gm...
>>> http://jj-blogger.blogspot.com
>>> http://www.jythonpodcast.com
>>> Twitter ID:  javajuneau
>>>
>>>
>>>
>>> On Mon, Mar 8, 2010 at 1:49 PM, Barbalute <Bar...@gm...> wrote:
>>>
>>>>
>>>> As the name suggests, it seems that copy and deepcopy aren't copying the
>>>> variables in my Java class.
>>>>
>>>> I currently have a Python class extending an existing Java abstract
>>>> class.
>>>> For various reasons, I've overwritten clone() in the Python class so
>>>> that
>>>> when the Java class calls it, it returns a deepcopy() of itself.
>>>>
>>>> This seems to properly copy the methods from the class, but the
>>>> variables
>>>> from the abstract Java class are lost in the copy, and I have no idea
>>>> why.
>>>>
>>>> In the overwritten Python clone() method, I'm able to manually copy over
>>>> the
>>>> variables, doing for example:
>>>>
>>>> x = copy.deepcopy(self)
>>>> x.name = self.name
>>>> return x
>>>>
>>>> But this shouldn't be necessary and becomes increasingly unwieldy for
>>>> classes with lots of variables. If I don't do it, though, name is not
>>>> set in
>>>> x and will return null in Java. Am I doing something wrong, or is
>>>> something
>>>> broken with copy() and deepcopy()?
>>>>
>>>> Thanks for your time.
>>>> --
>>>> View this message in context:
>>>> http://old.nabble.com/copy-and-deepcopy-not-copying-Java-class-variables--tp27826254p27826254.html
>>>> Sent from the jython-users mailing list archive at Nabble.com.
>>>>
>>>>
>>>>
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>>>
>>>
>>
>