Re: [aspectj-users] Perthis vs ITD

[Keith Kowalczykowski <keith@xxxxxxxxxxx>]

Hi Holger, thanks for the quick response. This verifies my intuition. So far
I have no issues with ITD, so I'll stick with it since its more performant.

    -Keith


On 3/16/09 6:31 PM, "Holger Hoffstätte" <holger@xxxxxxxxxx> wrote:

> Keith Kowalczykowski wrote:
>>     I am little bit confused about the differences between perthis and ITD,
>> and was hoping someone could enlighten me. I am currently using ITD to
>> inject some fields/methods into our classes. From what I gather, perthis can
>> provide similar behavior as ITD (at least for fields). Is this a correct
>> assumption? If so, what are the benefits of using ITD over perthis? In
>> summary, I'm trying to figure out if there is any advantages (performance,
>> etc) to using perthis vs ITD. Thanks for your help.

> You assume correctly - they accomplish similar things, but in different
> ways. Off the top of my head some main differences are
> 
> - perthis has naturally higher creation/access overhead/GC pressure than IDT
> 
> - with concurrent code perthis will likely have some form of contention
> for the aspect reference table, unlike IDT
> 
> - perthis does not modify the structural layout of the class, whereas ITD
> can break serialization (but then again that is broken either way ;)
> 
> - there may be some cases where methods/fields cannot be added to a class
> via IDT because they already exist..not sure if that is an actual problem
> since you can just rename them in the advice.
> 
> I'd always go for IDT first because it seems cleaner, and fall back to
> perthis if it breaks the advised class for whatever reasons. Can't
> remember when that was actually the case..
> 
> Holger
> 
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