Polish

This commit makes sure that no high-level client is auto-configured if
a low-level client is registered as a bean.

See gh-22358

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/elasticsearch/ElasticsearchRestClientAutoConfiguration.java

@@ -50,6 +50,7 @@ import org.springframework.util.StringUtils;
  */
 @Configuration(proxyBeanMethods = false)
 @ConditionalOnClass(RestHighLevelClient.class)
+@ConditionalOnMissingBean(RestClient.class)
 @EnableConfigurationProperties(ElasticsearchRestClientProperties.class)
 public class ElasticsearchRestClientAutoConfiguration {
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/elasticsearch/ElasticsearchRestClientAutoConfigurationTests.java

@@ -45,6 +45,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
 
 /**
  * Tests for {@link ElasticsearchRestClientAutoConfiguration}.
@@ -69,6 +70,13 @@ class ElasticsearchRestClientAutoConfigurationTests {
 				.hasSingleBean(RestHighLevelClient.class));
 	}
 
+	@Test
+	void configureWhenCustomRestClientShouldBackOff() {
+		this.contextRunner.withBean("customRestClient", RestClient.class, () -> mock(RestClient.class))
+				.run((context) -> assertThat(context).doesNotHaveBean(RestHighLevelClient.class)
+						.hasSingleBean(RestClient.class).hasBean("customRestClient"));
+	}
+
 	@Test
 	void configureWhenCustomRestHighLevelClientShouldBackOff() {
 		this.contextRunner.withUserConfiguration(CustomRestHighLevelClientConfiguration.class)