[GitHub] [flink] sunhaibotb opened a new pull request #9744: [FLINK-13515][test] Fix ClassLoaderITCase fails on Java 11

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sunhaibotb opened a new pull request #9744: [FLINK-13515][test] Fix ClassLoaderITCase fails on Java 11
URL: https://github.com/apache/flink/pull/9744
 
 
   ## What is the purpose of the change
   
   This pull request fixes the failure of `ClassLoaderITCase` on Java 11. For a nested class instance `x`, `x.getCanonicalName()` finds and loads the enclosing class of `x` by calling the methods of the classloader where `x` resides. Thus, It is incorrect to use `candidate.getClass().getCanonicalName()` to test whether there is `SuccessException` in the classpath of the class loader where the `ClassLoaderITCase` class resides, because `candidate.getClass().getCanonicalName()` will not find and load the related classes in the classloader where the `ClassLoaderITCase` class resides. We should use `Class.forName(...)` to test the expected result.
   
   
   In addition, when calling `getCanonicalName()` , `NoClassDefFoundError` is reported in Java 8, not in Java 11,  for the following reason:
   
   In Java 8, a class named `CheckpointedStreamingProgram$1` is generated at compiling ( because there are nested classes) , and when the nested classes are loaded, the dependent class loaded is `CheckpointedStreamingProgram$1` rather than `CheckpointedStreamingProgram`. Therefore, when `getCanonicalName()` is called in `ClassLoaderITCase`, the `CheckpointedStreamingProgram` class needs to be loaded, but at this time the `ChildFirstClassloader` (an `URLClassloader`) is closed and cannot load it, so `NoClassDefFoundError` is reported. But in Java 11, the `CheckpointedStreamingProgram$1` class is not generated and the `CheckpointedStreamingProgram` class is used directly (that is the `CheckpointedStreamingProgram` class has been loaded into `ChildFirstClassloader` before closing `ChildFirstClassloader`), so no errors are reported.
   
   
   ## Brief change log
   
     - Change the expected detection logic in `ClassLoaderITCase#testCheckpointedStreamingClassloaderJobWithCustomClassLoader`
   
   
   ## Verifying this change
   
   This change is already covered by existing test.
   
   
   ## Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): (yes / **no**)
     - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: (yes / **no**)
     - The serializers: (yes / **no** / don't know)
     - The runtime per-record code paths (performance sensitive): (yes / **no** / don't know)
     - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (yes / **no** / don't know)
     - The S3 file system connector: (yes / **no** / don't know)
   
   ## Documentation
   
     - Does this pull request introduce a new feature? (yes / **no**)
     - If yes, how is the feature documented? (**not applicable** / docs / JavaDocs / not documented)
   

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