HADOOP-19890: s3a: fix isolated classloader test for jdk >=17 (#8491)

* HADOOP-19890: s3a: fix isolated classloader test for jdk >=17

Author: ajfabbri

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/ITestS3AFileSystemIsolatedClassloader.java

@@ -26,6 +26,7 @@
 
 import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.Test;
+
 import software.amazon.awssdk.auth.credentials.AwsCredentials;
 import software.amazon.awssdk.auth.credentials.AwsCredentialsProvider;
 
@@ -34,8 +35,6 @@
 import org.apache.hadoop.fs.s3a.impl.InstantiationIOException;
 
 import static org.apache.hadoop.test.LambdaTestUtils.intercept;
-import static org.mockito.Mockito.doReturn;
-import static org.mockito.Mockito.spy;
 
 /**
  * Checks that classloader isolation for loading extension classes is applied
@@ -47,9 +46,9 @@ public class ITestS3AFileSystemIsolatedClassloader extends AbstractS3ATestBase {
 
   private static String customClassName = "custom.class.name";
 
-  private static class CustomCredentialsProvider implements AwsCredentialsProvider {
+  public static class CustomCredentialsProvider implements AwsCredentialsProvider {
 
-    CustomCredentialsProvider() {
+    public CustomCredentialsProvider() {
     }
 
     @Override
@@ -60,19 +59,23 @@ public AwsCredentials resolveCredentials() {
   }
 
   private static class CustomClassLoader extends ClassLoader {
-  }
 
-  private final ClassLoader customClassLoader = spy(new CustomClassLoader());
-  {
-    try {
-      doReturn(CustomCredentialsProvider.class)
-          .when(customClassLoader)
-          .loadClass(customClassName);
-    } catch (ClassNotFoundException ex) {
-      throw new RuntimeException(ex);
+    CustomClassLoader(ClassLoader parent) {
+      super(parent);
+    }
+
+    @Override
+    public Class<?> loadClass(String name) throws ClassNotFoundException {
+      if (customClassName.equals(name)) {
+        return CustomCredentialsProvider.class;
+      }
+      return super.loadClass(name);
     }
   }
 
+  private final ClassLoader customClassLoader =
+      new CustomClassLoader(ITestS3AFileSystemIsolatedClassloader.class.getClassLoader());
+
   private S3AFileSystem createNewTestFs(Configuration conf) throws IOException {
     S3AFileSystem fs = new S3AFileSystem();
     fs.initialize(getFileSystem().getUri(), conf);