[jira] [Commented] (UIMA-6057) Avoid falsely switching classloader

["Peter Klügl (JIRA)" <de...@uima.apache.org>]

    [ https://issues.apache.org/jira/browse/UIMA-6057?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16876761#comment-16876761 ] 

Peter Klügl commented on UIMA-6057:
-----------------------------------

It's maybe better to put the SimplePipeline aside. It's just a situation where the problem can occur, but it also easily solvable in three different spots.

Let me try to summarize the scenario from my perspective.

You have a pipeline with different components. Some of them are "special" as they initialize additional components within their implementation. They are not aggregated analysis engines, they are still simple anlaysis engines. These components also call the process() method for executing the internal analysis engines (which can of course again delegate to others). There are different reasons why one should create those "special" components, e.g., rapid prototyping in Ruta, Java functionality in Ruta, complex parameter mapping, external resource management and so on. This approach is not supported by the framework, but it does not cause any problems *IF* there is not class loader switch. The switch can happen for different reasons, e.g., the JCas and the analysis engines have been created using different UIMA class loader wrappers for the same class loader, which is the example of simple-pipline in uimaFIT (not really a problem anymore). However, the switch will happen if PEARs are involved. Then, the wrong class loader is set and class cast exceptions and so on will be thrown.

I think the problem is easily solved by extending the logic for the class loader switching a bit, e.g., with the patch, or by using a class loader stack or similar solutions.

What do you think?

> Avoid falsely switching classloader
> -----------------------------------
>
>                 Key: UIMA-6057
>                 URL: https://issues.apache.org/jira/browse/UIMA-6057
>             Project: UIMA
>          Issue Type: Bug
>          Components: Core Java Framework
>            Reporter: Matthias Koch
>            Priority: Major
>         Attachments: UIMA-6057.diff
>
>
> In some cases the classloader is switched back, although it hasn't be switched before processing.



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