Let BFAwareGeneratorStrategy extend ClassLoaderAwareGeneratorStrategy

This commit updates BeanFactoryAwareGeneratorStrategy to extend 
ClassLoaderAwareGeneratorStrategy in order to avoid duplication of the
common generate() implementation.

Closes gh-24396

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassEnhancer.java

@@ -35,8 +35,8 @@ import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.beans.factory.support.SimpleInstantiationStrategy;
 import org.springframework.cglib.core.ClassGenerator;
+import org.springframework.cglib.core.ClassLoaderAwareGeneratorStrategy;
 import org.springframework.cglib.core.Constants;
-import org.springframework.cglib.core.DefaultGeneratorStrategy;
 import org.springframework.cglib.core.SpringNamingPolicy;
 import org.springframework.cglib.proxy.Callback;
 import org.springframework.cglib.proxy.CallbackFilter;
@@ -207,13 +207,11 @@ class ConfigurationClassEnhancer {
 	 * Also exposes the application ClassLoader as thread context ClassLoader for the time of
 	 * class generation (in order for ASM to pick it up when doing common superclass resolution).
 	 */
-	private static class BeanFactoryAwareGeneratorStrategy extends DefaultGeneratorStrategy {
-
-		@Nullable
-		private final ClassLoader classLoader;
+	private static class BeanFactoryAwareGeneratorStrategy extends
+			ClassLoaderAwareGeneratorStrategy {
 
 		public BeanFactoryAwareGeneratorStrategy(@Nullable ClassLoader classLoader) {
-			this.classLoader = classLoader;
+			super(classLoader);
 		}
 
 		@Override
@@ -228,36 +226,6 @@ class ConfigurationClassEnhancer {
 			return new TransformingClassGenerator(cg, transformer);
 		}
 
-		@Override
-		public byte[] generate(ClassGenerator cg) throws Exception {
-			if (this.classLoader == null) {
-				return super.generate(cg);
-			}
-
-			Thread currentThread = Thread.currentThread();
-			ClassLoader threadContextClassLoader;
-			try {
-				threadContextClassLoader = currentThread.getContextClassLoader();
-			}
-			catch (Throwable ex) {
-				// Cannot access thread context ClassLoader - falling back...
-				return super.generate(cg);
-			}
-
-			boolean overrideClassLoader = !this.classLoader.equals(threadContextClassLoader);
-			if (overrideClassLoader) {
-				currentThread.setContextClassLoader(this.classLoader);
-			}
-			try {
-				return super.generate(cg);
-			}
-			finally {
-				if (overrideClassLoader) {
-					// Reset original thread context ClassLoader.
-					currentThread.setContextClassLoader(threadContextClassLoader);
-				}
-			}
-		}
 	}