[hibernate-dev] Jandex 2.0 Beta - Java 8 Type Annotations, Generics, & Offline Reflection

[Gunnar Morling]

2014-12-01 21:24 GMT+01:00 Hardy Ferentschik <hardy at hibernate.org>:

> Hi,
>
> I think this email of Jason is worth forwarding to hibernate-dev.
> Jandex 2 sounds really interesting for all Hibernate projects. To a
> certain degree Jandex offers now
> a lot of the things Steve tried to do with the reflight stuff. I am not
> sure whether Jandex can completely
> replace it, but t can be for sure of help. Especially interesting to me is
> the fully resolved type information.
>
> In Search we have been talking for a long time to get rid of Commons
> Annotations. It is basically already possible
> now (using Jandex 1), but it got pushed back so far. Now with Jandex 2 we
> definitely should make the switch. Maybe Search 5.1?
>

Out of interest, what would be the benefit for Search?

>
> Last but not least Validator, there we have been talking about Jandex for
> a while as well. The new version would not have
> the benefit of being able to remove the dependency to classmate.
>

I guess you mean it *would have* the benefit, right?

Of course that comes at the price of adding another dependency, so that's
not really an advantage per se for me :)

I think we should have a look at this Beta and provide feedback to Jason if
> we find any problems. I am for sure to have a look
> at it in the context of Validator.
>

I find being able to re-use the index generated by the application
container very useful. It would give a nice performance boost out of the
box when using HV on WildFly/EAP.

The type annotation stuff may be useful, but it's not that this information
cannot be accessed via reflection at all. There are known issues with
corner cases, though. So Jandex may improve the situation for us.

Are there other advantages you expect from a HV perspective?

I'm asking to make sure we're on the same page regarding what we expect
from using Jandex in terms of user-visible features/improvements.


>
> --Hardy
>
>
> ----- Forwarded message from Jason Greene  -----
>
> I normally don’t spam you guys with Beta announcements, but since many of
> you are using Jandex, and this release has significant changes, in
> particular additional APIs, I wanted to make sure there was an opportunity
> for feedback before going final.
>
> For those unfamiliar with Jandex, it was originally created as an
> efficient bytecode based annotation indexer for AS7, but over time has
> evolved to also act as a reflection library that does not require
> class-loading nor complete linkage (you can analyze partial class graphs).
>
> For those interested in playing with runtime Java 8 Type annotations,
> which will likely end up in EE8 APIs, this release will likely be quite
> useful to you, since standard Java reflection does not currently expose
> this data.
>
> A brief guide for using Jandex is located here:
> https://github.com/wildfly/jandex
>
> Full notes are below.
>
> Thanks!
>
>
>
> Jandex 2.0
> —————
>
> - Binary and Source Compatibility
>
>   All previous code *using* Jandex 1.1 should compile and run against 2.0.
>   However, any code that extended “closed" contracts (e.g.
> AnnotationTarget)
>   will require updating.
>
> - Offline reflective APIs and improvements
>
>   All methods and fields, whether annotated or not are all accessible, and
>   supporting APIs were created to enable access to the information.
>
>   Generics information is provided in a familiar pattern similar to Java
>   reflection but with usability improvements. Type information is fully
>   resolved.
>
>   Method and field access now supports binary searchable. Annotations are
>   categorized and filtered at various levels.
>
>   All need to cast has been eliminated from the framework.
>
> - Implemented offline index persistence
>
>   The format is radically different to support the storage of
>   generics, type annotations, and the aggressive interning used to
>   reduce memory usage. Monster deployment (713MB of class data)
>   only requires 26MB of storage. JDK, which has 128MB of class data is
>   requires only 4.8 MB. Compressing the indexes by including them in a jar
>   reduces the capacity even further to about 14MB and 2.6 MB respectively.
>
>   Loading time is extremely efficient, at 1 second to load the 26MB
>   index for the monster deployment.
>
>   A portability layer is provided to convert the pervious
>   offline index formats into the new internal model.
>
> - Full Java 8 type annotation support
>
>   Java 8 type annotations all you to use annotations almost anywhere.
>   For example, the following is now allowed:
>
>   @A Map<@B Comparable<@F Object @C [] @D [] @E []>, @G List <@H D>> b;
>   @H O1. at E O2<@F S, @G T>. at D O3. at A Nested<@B U, @C V> bar6;
>
>   A new set of APIs were developed to represent all of this information in
>   a useful way to the developer
>
> - Detailed class nesting information available
>
>   CDI needed a way to determine the enclosing class information for
>   all types of inner classes. This is all calculated and presented via
>   a few easy methods
>
> - Memory optimization work
>
>   The overhead required to store all offline reflection
>   info + generics is significant. Implemented a variety of graph
>   reduction strategies.
>
>   End results of a monster deployment containing 713MB of class data
>   (> 100k classes > 1 million methods) = 120MB of memory usage. The
>   JDK has 128MB of class data, which Jandex uses
>   only 20MB of heap to store.
>
> --
> Jason T. Greene
> WildFly Lead / JBoss EAP Platform Architect
> JBoss, a division of Red Hat
>
>
>
> ----- End forwarded message -----
>
> ----- End forwarded message -----
>
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