Andrus Adamchik wrote:
> Looks like CGLib itself depends on ASM (although I may be completely
> wrong) -
>
> http://ibiblio.org/maven2/cglib/cglib-asm/
>
Yes...CGLib is a higher level front end to ASM. I guess a good analogy
for CGLib/ASM is C and assembler. With assembler, you need to have a
good understanding of the processor and opcodes. C is a much higher
level abstraction and relieves the need to know op codes. CGLib is
essentially the same concept. Its a higher level abstraction for ASM,
relieving the need to know byte code and JVM inner workings.
Jeff
> Andrus
>
>
> On Mar 27, 2006, at 10:45 PM, Bill Dudney wrote:
>
>> Hi All,
>>
>> The other advantage of CGLib is its licensed with the ASL 1.1. While
>> ASM's license is very liberal its not a 'typical' license and we would
>> have to go through some review with lega..pache.org to get the
>> license OK'd.
>>
>> TTFN,
>>
>> Bill Dudney
>> MyFaces - http://myfaces.apache.org
>> Cayenne - http://incubator.apache.org/projects/cayenne.html
>>
>>
>>
>> On Mar 27, 2006, at 10:29 AM, Andrus Adamchik wrote:
>>
>>> I have almost no experience with bytecode enhancement frameworks. The
>>> only reason ASM seemed attractive is because of its small footprint
>>> (generally we are trying to keep the dependency list as small as
>>> reasonably possible).
>>>
>>> I agree - ASM is too low level, and I am not against CGLib if it
>>> saves us time. But can anyone show a simple example of the
>>> differences between the two?
>>>
>>> Also with CGLib how would we solve the problem of changing
>>> CayenneDataObject code? Is there a good way to grab stuff from the
>>> existing compiled class?
>>>
>>> Andrus
>>>
>>>
>>> On Mar 27, 2006, at 6:58 PM, Jeff Genender wrote:
>>>
>>>> How about CGLib instead of ASM directly? ASM is a bit complex and
>>>> necessitates a certain knowledge of the JVM op codes. IMHO, CGLib
>>>> seems
>>>> high level enough to make this work. Thoughts?
>>>>
>>>> Jeff
>>>>
>>>> Bill Dudney wrote:
>>>>> Hi Andrus,
>>>>>
>>>>> Sorry for such a tardy reply but I'm just getting going on the JPA
>>>>> stuff...
>>>>>
>>>>> Jeff and I were at TSS Symposium last week and we had a chance to talk
>>>>> through the work for JPA. I wanted to get our thoughts into an
>>>>> email and
>>>>> off to the list so we are not duplicating work. We are planning on
>>>>> doing
>>>>> the mapping work. Jeff is going to tackle handling the annotations
>>>>> and I
>>>>> am going to handle parsing the orm.xml files and augmenting the
>>>>> mapping
>>>>> info.
>>>>>
>>>>> Other thoughts etc are inline.
>>>>>
>>>>> On Mar 7, 2006, at 2:45 AM, Andrus Adamchik wrote:
>>>>>
>>>>>> I did a little research on bytecode enhancement (CAY-460) and wanted
>>>>>> to share some thoughts.
>>>>>>
>>>>>> It turned out that it is fairly simple to modify bytecode with the
>>>>>> ASM
>>>>>> framework:
>>>>>>
>>>>>> http://asm.objectweb.org/
>>>>>>
>>>>>> I checked in a basic enhancer that adds objectId and persistenceState
>>>>>> properties to POJOs already. Coding the rest of the DataObject
>>>>>> enhancements shouldn't be a problem, however ASM code is not
>>>>>> something
>>>>>> that is easy to maintain by hand (so if say CayenneDataObject changes
>>>>>> internally, I'd like the enhancer to pick up such changes
>>>>>> automatically). I guess we may implement some sort of template based
>>>>>> approach. ASM allows to take an existing class X and generate regular
>>>>>> Java code that can act as a script for creating class X bytcode from
>>>>>> scratch. So theoretically an enhancer itself can be generated.
>>>>>>
>>>>>
>>>>> This looks interesting. I like the idea of using ASM to weave in the
>>>>> required enhancements. I looked at the code you checked in and I'm
>>>>> happy
>>>>> to start down the path of getting the rest of the required code woven
>>>>> in. I will also start looking at the template based approach. I will
>>>>> probably do this before I get to the XML work so we can start
>>>>> testing ASAP.
>>>>>
>>>>>> BTW, ASM visitor API can be used for another purpose - processing
>>>>>> annotations (CAY-456), thus solving two problems at once.
>>>>>>
>>>>>
>>>>> This looks cool (the ASM is really cool for doing this kind of work
>>>>> AFAICT). Jeff is going to head down this path.
>>>>>
>>>>>>
>>>>>> Another issue is integrating the enhancer in the provider. The
>>>>>> requirement is that enhanced classes must be accessible to the
>>>>>> application ClassLoader, so my original solution with a specialized
>>>>>> child ClassLoader won't work. I see three ways to do the integration
>>>>>> (we may implement all three of them).
>>>>>>
>>>>>> 1. "cgen" - by merging all CayenneDataObject code in the class
>>>>>> generator template. This will work for people who use Cayenne to
>>>>>> model
>>>>>> their ORM classes, but want a superclass that is not a DataObject.
>>>>>> This is not suitable for persistent classes created outside Cayenne
>>>>>> and deployed with Cayenne provider.
>>>>>>
>>>>>> 2. "cdeploy" - enhancing compiler Ant task ala JDO.
>>>>>>
>>>>>> 3. Runtime - this would use JDK 1.5 java.lang.instrument API. On the
>>>>>> one hand it is the least intrusive option, but on the other it
>>>>>> requires a special runtime parameter (-javaagent:cayenne.jar).
>>>>>>
>>>>>> Ideas, comments?
>>>>>>
>>>>>
>>>>> From my reading of the spec it looks like the ClassTransformer is
>>>>> there
>>>>> so that 3 does not require the special runtime parameter. Is there
>>>>> something that I'm missing? I am basing my assumptions on the comment
>>>>> (starting on page 148) on the addTransformer(ClassTransformer)
>>>>> method on
>>>>> the PersistenceUnitInfo class.
>>>>>
>>>>> Thoughts welcome. Also if you are doing any of this work please
>>>>> speak up
>>>>> so we don't duplicate.
>>>>>
>>>>> TTFN,
>>>>>
>>>>> Bill Dudney
>>>>> MyFaces - http://myfaces.apache.org
>>>>> Cayenne - http://incubator.apache.org/projects/cayenne.html
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>>
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