[jira] [Commented] (NIFI-7447) Objects returned from Controller Services may be invoked with the wrong ClassLoader

["ASF subversion and git services (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/NIFI-7447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17123992#comment-17123992 ] 

ASF subversion and git services commented on NIFI-7447:
-------------------------------------------------------

Commit e31c323aa70dfe8f1bc7a3f39c216f9154529654 in nifi's branch refs/heads/master from Mark Payne
[ https://gitbox.apache.org/repos/asf?p=nifi.git;h=e31c323 ]

NIFI-7447: When returning an object from a Controller Service, if that object is defined as an interface, proxy that interface. This way, any method call into the object will also change the classloader to the appropriate classloader.


> Objects returned from Controller Services may be invoked with the wrong ClassLoader
> -----------------------------------------------------------------------------------
>
>                 Key: NIFI-7447
>                 URL: https://issues.apache.org/jira/browse/NIFI-7447
>             Project: Apache NiFi
>          Issue Type: Bug
>          Components: Core Framework
>            Reporter: Mark Payne
>            Assignee: Mark Payne
>            Priority: Major
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> When a Processor calls a Controller Service, the framework changes the Thread's Context ClassLoader from the Processor's ClassLoader to the Controller Service's ClassLoader. This works well. However, when the object that is returned from a Controller Service has a method invoked, the Context ClassLoader is that of the Processor.
> This means that if the object returned attempts to load a class when its method is invoked, it's attempting to load it from the wrong ClassLoader. This can result in NoClassDefFoundError/ClassNotFoundException, etc.
> An example from the mailing list:
> ---------
> Hello,
>  
> I try to implement a groovy script where I'm using jsonOutput. 
> With nifi 1.5 the script works, but If I'm try to use the same groovy script with nifi 1.11.4, I get 
> "unable to load FastStringService"
>  
> example code :
>  
> class GroovyRecordSetWriter implements RecordSetWriter {
> ....
> @Override
>  WriteResult write(Record r) throws IOException { 
> ...
> def j = JsonOutput.toJson([name: 'John Doe', age: 42])
>  out.write(j.getBytes())
>  
> ...
> ---------
>  
> The problem here is that Controller Service returns a GroovyRecordSetWriter. When the processor calls #write, the Context Class Loader is the Processor's Context Class Loader, which knows nothing about Groovy. The call then delegates to `JsonOutput.toJson`. When this happens, Groovy, under the hood, attempts to load the `FastStringService` class using the Context Class Loader, which of course fails since the Context Class Loader is the Processor's ClassLoader and not the ScriptedRecordSetWriter's ClassLoader.



--
This message was sent by Atlassian Jira
(v8.3.4#803005)