GH-2692: Fix Embedded Kafka for @nested tests

Fixes #2692

When used with `@nested`, Multiple Contexts appear causing test to break.
Contexts caching miss.

* Fix Context Customizer Factory to Work with Nested Test
* Add spring test with nested class
* Fix checkstyle violations

spring-kafka-test/src/main/java/org/springframework/kafka/test/context/EmbeddedKafkaContextCustomizerFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2019 the original author or authors.
+ * Copyright 2017-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,10 +18,10 @@
 
 import java.util.List;
 
-import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.test.context.ContextConfigurationAttributes;
 import org.springframework.test.context.ContextCustomizer;
 import org.springframework.test.context.ContextCustomizerFactory;
+import org.springframework.test.context.TestContextAnnotationUtils;
 
 /**
  * The {@link ContextCustomizerFactory} implementation to produce a
@@ -38,7 +38,7 @@ class EmbeddedKafkaContextCustomizerFactory implements ContextCustomizerFactory
 	public ContextCustomizer createContextCustomizer(Class<?> testClass,
 			List<ContextConfigurationAttributes> configAttributes) {
 		EmbeddedKafka embeddedKafka =
-				AnnotatedElementUtils.findMergedAnnotation(testClass, EmbeddedKafka.class);
+				TestContextAnnotationUtils.findMergedAnnotation(testClass, EmbeddedKafka.class);
 		return embeddedKafka != null ? new EmbeddedKafkaContextCustomizer(embeddedKafka) : null;
 	}
 

spring-kafka-test/src/test/java/org/springframework/kafka/test/condition/WithNestedClassContextTests.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2021-2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.kafka.test.condition;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.kafka.test.context.EmbeddedKafka;
+import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
+
+@EmbeddedKafka
+@SpringJUnitConfig(WithNestedClassContextTests.Config.class)
+class WithNestedClassContextTests {
+
+	private static final AtomicInteger counter = new AtomicInteger();
+
+	@Autowired
+	private TestClass outer;
+
+	@Nested
+	class NestedClass {
+
+		@Test
+		void equalsInjected(@Autowired TestClass inner) {
+			assertThat(inner).isEqualTo(outer);
+		}
+
+		@Test
+		void equalsSize(@Autowired List<TestClass> classes) {
+			assertThat(classes).hasSize(1);
+		}
+
+		@Test
+		void equalsCount() {
+			assertThat(counter.get()).isEqualTo(1);
+		}
+	}
+
+	public static class TestClass {
+	}
+
+	@Configuration
+	static class Config {
+		@Bean
+		public TestClass testClass() {
+			counter.incrementAndGet();
+			return new TestClass();
+		}
+	}
+}