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

[Hardy Ferentschik]

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?

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 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.

--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



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