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From "Richard Eckart de Castilho (JIRA)" <...@uima.apache.org>
Subject [jira] [Commented] (UIMA-5554) Strange exception when trying to get JCas FS class through reflection
Date Mon, 11 Sep 2017 14:56:00 GMT

    [ https://issues.apache.org/jira/browse/UIMA-5554?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16161396#comment-16161396
] 

Richard Eckart de Castilho commented on UIMA-5554:
--------------------------------------------------

A lot of information! It sounds like JCas has become quite a bit more restricted in v3 - and/or
I don't manage to wrap my head around the new approach yet.

First, wrt. 4: I'm happily mixing JCas (with non-built-in classes) and CAS all the time -
even then reinitializing the type system.

JCas classes are global per classloader. Type-systems are local per CAS. I could have a CAS
initialized with typesystem X and types A+B and a second CAS with typesystem Y and the types
C+D, even under the regime of a single classloader. The typesystems are committed individually
per CAS. I understand you say that the JCas classes are independently committed per classloader
- and this seems to be somehow tied to the committing of the typesystems in the CASes. I still
don't understand why these two processes have to be coupled though because they have different
scopes. 

Typesystem merging is something that can happen at the level of CASes. However, since JCas
classes are static (we usually generate them via jcasgen at build time), typesystem merging
cannot have any effect on them. 

So I still don't understand this "ordering" of things. As I see it, the "the UIMA type system
be assembled, merged, and committed" before a the CAS API can be used and certainly before
JCas classes can access any data in the CAS. But this "assembling, merging and committing"
happens at runtime. JCas classes *predate* this -they are created at build-time.

> Strange exception when trying to get JCas FS class through reflection
> ---------------------------------------------------------------------
>
>                 Key: UIMA-5554
>                 URL: https://issues.apache.org/jira/browse/UIMA-5554
>             Project: UIMA
>          Issue Type: Bug
>          Components: Core Java Framework
>    Affects Versions: 3.0.0SDK-beta
>            Reporter: Richard Eckart de Castilho
>
> I am trying to get a class object for a JCas FS type using reflection:
> {noformat}
> Class.forName(typeName);
> {noformat}
> However, it produces this strange error.
> {noformat}
> java.lang.ExceptionInInitializerError
> 	at java.lang.Class.forName0(Native Method)
> 	at java.lang.Class.forName(Class.java:264)
> ...
> Caused by: org.apache.uima.cas.CASRuntimeException: A JCas class field "sofa" is being
initialized by non-framework (user) code before Type System Commit for a type system with
a corresponding type. Either change the user load code to not do initialize, or to defer it
until after the type system commit.
> 	at org.apache.uima.cas.impl.TypeSystemImpl.getAdjustedFeatureOffset(TypeSystemImpl.java:2575)
> 	at org.apache.uima.jcas.cas.AnnotationBase.<clinit>(AnnotationBase.java:71)
> 	... 27 more
> {noformat}
> Is it considered harmful to try getting a class object for a JCas FS class?



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