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Updated on 2025-11-13 GMT+08:00
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What Should I Do if ClassCastException Is Reported Due to Flink JAR Package Conflicts?

Symptom

An error is reported when a job is started after introducing a third-party dependency package to Flink lib.

ClassCastException: X Cannot be cast to X

Cause Analysis

The introduced third-party dependency package conflicts with the dependency package in Flink. Precisely, the classes in the third-party dependency package are incompatible, resulting in failure to instantiate certain functions.

Solution

Method 1: Remove the conflict packages from the introduced third-party JAR. This method is recommended.

Method 2: Set classloader.resolve-order to parent-first in the flink-conf.yaml configuration file. Modify Flink class loading sequence so that the dependency packages provided by Flink are preferentially loaded.