[hibernate-issues] [Hibernate-JIRA] Commented: (METAGEN-49) JPAMetaModelEntityProcessor.createMetaModelClasses calls remove within foreach loop (causing a ConcurrentModificationException)

[Robin Sander (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/METAGEN-49?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=39245#action_39245 ] 

Robin Sander commented on METAGEN-49:
-------------------------------------

Note that the entities in the attached test project are a sub-set of a considerably larger model. I've simply removed entity after entity while checking that the error still occurs.
It seems that either the inheritance hierarchy (User -> LocalizedDataContainer -> EntityBase) or the use of generics (or both) is the cause of the problem.
If the hierarchy is simplified or if the whole "groups" package gets removed the bug does not occur anymore.

> JPAMetaModelEntityProcessor.createMetaModelClasses calls remove within foreach loop (causing a ConcurrentModificationException)
> -------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: METAGEN-49
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/METAGEN-49
>             Project: Hibernate Metamodel Generator
>          Issue Type: Bug
>          Components: processor
>    Affects Versions: 1.1.0.Final
>         Environment: Hibernate 3.6.0, Java 6 (1.6.0_22), Mac OS X 10.6.5
>            Reporter: Robin Sander
>            Assignee: Hardy Ferentschik
>         Attachments: metagen49.zip
>
>
> Running the annotation processor causes a ConcurrentModificationException.
> I'm using Maven and the maven-processor-plugin 1.3.7 but from looking into the sources I guess this bug occurs in any environment.
> JPAMetaModelEntityProcessor.createMetaModelClasses iterates of a Collection<MetaEntity> using a foreach loop and calls remove
> on the same collection which causes a ConcurrentModificationException.
> Obviously an iterator should be used instead.
> Here are the lines concerned:
> {code:java} 
>  Collection<MetaEntity> toProcessEntities = context.getMetaEmbeddables();
>  while ( !toProcessEntities.isEmpty() ) {
>   Set<MetaEntity> processedEntities = new HashSet<MetaEntity>();
>   int toProcessCountBeforeLoop = toProcessEntities.size();
>   for ( MetaEntity entity : toProcessEntities ) {
>     // see METAGEN-36
>     if ( generatedModelClasses.contains( entity.getQualifiedName() ) ) {
>       toProcessEntities.remove( entity );  // XXX this causes a ConcurrentModificationException
>       continue;
>   }
>  ...
> {code}
> Here is the stacktrace:
> {code}
> ...
> [INFO] diagnostic Note: Hibernate JPA 2 Static-Metamodel Generator 1.1.0.Final
> An annotation processor threw an uncaught exception.
> Consult the following stack trace for details.
> java.util.ConcurrentModificationException
> 	at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
> 	at java.util.HashMap$ValueIterator.next(HashMap.java:822)
> 	at org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor.createMetaModelClasses(JPAMetaModelEntityProcessor.java:153)
> 	at org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor.process(JPAMetaModelEntityProcessor.java:133)
> 	at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:625)
> 	at com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(JavacProcessingEnvironment.java:554)
> 	at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:699)
> 	at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:981)
> 	at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:727)
> 	at com.sun.tools.javac.main.Main.compile(Main.java:353)
> 	at com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:115)
> 	at org.bsc.maven.plugin.processor.AbstractAnnotationProcessorMojo.executeWithExceptionsHandled(AbstractAnnotationProcessorMojo.java:261)
> 	at org.bsc.maven.plugin.processor.AbstractAnnotationProcessorMojo.execute(AbstractAnnotationProcessorMojo.java:129)
> 	at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:490)
> {code}

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