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https://issues.apache.org/jira/browse/KAFKA-17150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17866541#comment-17866541
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Greg Harris commented on KAFKA-17150:
-------------------------------------
The difference seems to be caused by the difference between these two calls:
[https://github.com/apache/kafka/blob/b015a83f6d286965af999c39c0902584fb6fb9de/clients/src/main/java/org/apache/kafka/common/utils/Utils.java#L428]
which passes the class alias into Class.forName, and
[https://github.com/apache/kafka/blob/b015a83f6d286965af999c39c0902584fb6fb9de/clients/src/main/java/org/apache/kafka/common/config/ConfigDef.java#L776]
which uses the alias to first load the class, and then calls Class.forName
with the full name of the class.
These diverged a long time ago in KAFKA-8550 and the same bug resurfaced when
we added more validation surrounding the converter classes.
> Connect converter validation does not accept class aliases
> ----------------------------------------------------------
>
> Key: KAFKA-17150
> URL: https://issues.apache.org/jira/browse/KAFKA-17150
> Project: Kafka
> Issue Type: Bug
> Components: connect
> Affects Versions: 3.8.0
> Reporter: Greg Harris
> Priority: Blocker
> Fix For: 3.8.0
>
>
> Connect allows users to specify aliases instead of full classes when
> configuring plugins. For example, the following configuration is valid:
> {noformat}
> {
> "connector.class": "FileStreamSource",
> "topic": "anything",
> "key.converter": "JsonConverter"
> }{noformat}
> In <= 3.7.1 this will pass validation and function correctly.
> In 3.8.0-rc1 this will instead fail with this error message:
> {noformat}
> [2024-07-16 13:58:54,250] ERROR Failed to instantiate key converter class
> JsonConverter; this should have been caught by prior validation logic
> (org.apache.kafka.connect.runtime.AbstractHerder:462)
> java.lang.ClassNotFoundException: JsonConverter
> at java.base/java.lang.Class.forName0(Native Method)
> at java.base/java.lang.Class.forName(Class.java:534)
> at java.base/java.lang.Class.forName(Class.java:513)
> at org.apache.kafka.common.utils.Utils.loadClass(Utils.java:426)
> at org.apache.kafka.common.utils.Utils.newInstance(Utils.java:415)
> at
> org.apache.kafka.connect.runtime.AbstractHerder.validateConverterConfig(AbstractHerder.java:460)
> at
> org.apache.kafka.connect.runtime.AbstractHerder.validateKeyConverterConfig(AbstractHerder.java:528)
> at
> org.apache.kafka.connect.runtime.AbstractHerder.validateConnectorConfig(AbstractHerder.java:734)
> at
> org.apache.kafka.connect.runtime.AbstractHerder.lambda$validateConnectorConfig$3(AbstractHerder.java:574)
> at
> java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
> at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
> at
> java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
> at
> java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
> at java.base/java.lang.Thread.run(Thread.java:1583){noformat}
> and this error will eventually be shown to the user:
> {noformat}
> Connector configuration is invalid and contains the following 1 error(s):
> Failed to load class JsonConverter: JsonConverter{noformat}
> When the full class name is specified, the class is found and passes
> validation.
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