Hello Russ,

No, the sources are only generated once. I've double checked that. That was my 
first thought. 

It just occurred to me that I have a unit test with an annotated model in my 
annotation processor project and it behaves correctly (I just did some tests). 
There the annotation processor is not run if the processed annotations have not 
been modified, which is entirely correct. If I change something in the 
annotation and build again (without doing clean) it regenerates and compiles 
fine without duplicate class exception. The problem in my other code where I 
have the problem is, I just realized that the annotation processor is run when 
it should not be! 

When I do "mvn install" and then directly a new "mvn install" nothing what so 
ever have changed in the annotations being processed! Still the annotation 
processor is triggered for some reason in this case!  The interesting question 
here is how does the annotation processor framework determine if a processor 
needs to run or not ? It can't have a clue about what the processor will be 
generating, so how does it determine this ? Also, this invocation when it 
shouldn't only occurs when built with maven, but I realize that does not 
necessarily  mean that maven is at fault. Hmm. I have some more troubleshooting 
to do here.

/Tommy
 

19 jul 2013 kl. 18:33 skrev Russell Gold <r...@gold-family.us>:

> Hi Tommy,
> 
> I am not seeing this problem, myself.
> 
> When you get the duplicate class problem, do you find multiple copies of the 
> generated source in your target directory? Multiple copies of the same class 
> files? AFAIK that is the only way you should ever see a duplicate class 
> exception
> 
> - Regards,
> Russ
> 
> On Jul 19, 2013, at 11:40 AM, Tommy Svensson <to...@natusoft.se> wrote:
> 
>> Hello Russ,
>> 
>> No, that is not exactly my case. I just tried to build from the IDE  to 
>> confirm my suspicion that the problem only occurred in maven. I'm using 
>> Intellij Idea 12 and it is nice enough to recognize that my project is a 
>> maven project. When I tell it to "make" or "rebuild" it does build itself 
>> not using maven, but it uses the same target paths as maven would. It tries 
>> to avoid the problem you describe. 
>> 
>> My problem is that as long as I build with maven I have to do a "mvm clean 
>> install" every time since an "mvn install" … "mvn install" will fail on the 
>> second install with a duplicate class exception for the generated code. As I 
>> said, I suspect that maven have already built the previously generated 
>> classes before annotation procession is run by maven and when the annotation 
>> processor produces new versions of the same classes they are compiled again 
>> and produces exactly the same class file targets as already produced before 
>> during the build. This causes the duplicate class exception. That is at 
>> least my theory. 
>> 
>> /Tommy
>> 
>> 
>> 19 jul 2013 kl. 17:28 skrev Russell Gold <r...@gold-family.us>:
>> 
>>> Hi Tommy,
>>> 
>>> I've run into some problems along these lines, but in my case, it only 
>>> happens when I build first using Maven and then try to recompile in the 
>>> IDE. The problem appears to be that the two disagree on where the generated 
>>> classes go (there was a change in one of the JDK releases, I believe).
>>> 
>>> I work around that by doing a clean compile in maven before starting IDE 
>>> work.
>>> 
>>> Is that your problem? Or are you only seeing this by only doing repeated 
>>> Maven builds? I don't have that problem.
>>> 
>>> - Russ
>>> 
>>> On Jul 19, 2013, at 11:22 AM, Tommy Svensson <to...@natusoft.se> wrote:
>>> 
>>>> Hello,
>>>> 
>>>> I have found a problem when using auto triggered annotation processors 
>>>> (META-INF/services/javax.annotation.Processor) with maven builds! The 
>>>> problem occurs when the code have been built once and the annotation 
>>>> processors have been triggered and generated code.  If I then build again 
>>>> without doing a clean in between then I get a duplicate class exception 
>>>> for each generated class. I suspect this is because maven have already 
>>>> build the previous versions before annotation processing is triggered and 
>>>> when the newly updated/generated sources  are compiled it conflicts the 
>>>> the previous built classes. 
>>>> 
>>>> This problem does not occur when I build in the IDE not using maven. Then 
>>>> the annotation processing behaves as expected. I suspect that if the 
>>>> processor weren't specified in 
>>>> META-INF/services/javax.annotation.Processor, and was run manually with 
>>>> apt-maven-plugin it would work better, but that is not an option. I wan't 
>>>> my processor to be able to be used the standard Java way, and with maven, 
>>>> without having 2 versions of it. I have found a way to identify in the 
>>>> processor when there already are old sources available and don't 
>>>> regenerate then, which will make it run in maven, but will then not update 
>>>> the generated sources without first doing a clean when annotations are 
>>>> updated. This is of course not a good solution. 
>>>> 
>>>> Is there any other known way to solve this problem with maven ? I'm using 
>>>> version 3.1 of the maven-compiler-plugin.
>>>> 
>>>> Any help is appreciated.
>>>> 
>>>> Best Regards,
>>>> Tommy Svensson
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
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>>> -----------------
>>> Come read my webnovel, Take a Lemon <http://www.takealemon.com>, 
>>> and listen to the Misfile radio play 
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>>> 
>>> 
>>> 
>> 
>> 
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> -----------------
> Come read my webnovel, Take a Lemon <http://www.takealemon.com>, 
> and listen to the Misfile radio play 
> <http://www.gold-family.us/audio/misfile.html>!
> 
> 
> 
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