Bring back Elasticsearch RestClient auto-configuration

Prior to this commit, Spring Boot would only auto-configure
the `RestHighLevelClient` and `RestClientBuilder` if the `RestHighLevelClient`
was present. This was done in 1d73d4e.

This commit brings back the exposing of the `RestClient` bean in
Spring Boot when exposing the `RestHighLevelClient` or
when the `RestHighLevelClient` is not present.
It allows for using the Spring Boot auto configuration and its customizers
of the `RestClientBuilder` in a similar way as it is done for the `RestTeamplateBuilder`
and the `WebClient.Builder`.
Now the presence of the `org.elasticsearch.client:elasticsearch-rest-high-level-client` is optional.
This opens the door for potentially adding support to the new
[Elasticsearch Java Client](https://github.com/elastic/elasticsearch-java) that is based on the same `RestClient`

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/elasticsearch/ElasticSearchRestHealthContributorAutoConfiguration.java

@@ -19,7 +19,6 @@
 import java.util.Map;
 
 import org.elasticsearch.client.RestClient;
-import org.elasticsearch.client.RestHighLevelClient;
 
 import org.springframework.boot.actuate.autoconfigure.health.CompositeHealthContributorConfiguration;
 import org.springframework.boot.actuate.autoconfigure.health.ConditionalOnEnabledHealthIndicator;
@@ -42,16 +41,16 @@
  * @since 2.1.1
  */
 @Configuration(proxyBeanMethods = false)
-@ConditionalOnClass(RestHighLevelClient.class)
-@ConditionalOnBean(RestHighLevelClient.class)
+@ConditionalOnClass(RestClient.class)
+@ConditionalOnBean(RestClient.class)
 @ConditionalOnEnabledHealthIndicator("elasticsearch")
 @AutoConfigureAfter(ElasticsearchRestClientAutoConfiguration.class)
 public class ElasticSearchRestHealthContributorAutoConfiguration
-		extends CompositeHealthContributorConfiguration<ElasticsearchRestHealthIndicator, RestHighLevelClient> {
+		extends CompositeHealthContributorConfiguration<ElasticsearchRestHealthIndicator, RestClient> {
 
 	@Bean
 	@ConditionalOnMissingBean(name = { "elasticsearchHealthIndicator", "elasticsearchHealthContributor" })
-	public HealthContributor elasticsearchHealthContributor(Map<String, RestHighLevelClient> clients) {
+	public HealthContributor elasticsearchHealthContributor(Map<String, RestClient> clients) {
 		return createContributor(clients);
 	}
 

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/elasticsearch/ElasticsearchRestHealthIndicator.java

@@ -50,6 +50,13 @@ public class ElasticsearchRestHealthIndicator extends AbstractHealthIndicator {
 
 	private final JsonParser jsonParser;
 
+	/**
+	 * Create a health indicator using the RestHighLevelClient.
+	 * @param client the RestHighLevelClient that used to get the RestClient
+	 * @deprecated since 2.7.0 for removal in 2.9.0 in favor of
+	 * {@link #ElasticsearchRestHealthIndicator(RestClient)}
+	 */
+	@Deprecated
 	public ElasticsearchRestHealthIndicator(RestHighLevelClient client) {
 		this(client.getLowLevelClient());
 	}

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

@@ -17,12 +17,11 @@
 package org.springframework.boot.autoconfigure.elasticsearch;
 
 import org.elasticsearch.client.RestClient;
-import org.elasticsearch.client.RestHighLevelClient;
 
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientConfigurations.RestClientBuilderConfiguration;
+import org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientConfigurations.RestClientConfiguration;
 import org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientConfigurations.RestClientSnifferConfiguration;
 import org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientConfigurations.RestHighLevelClientConfiguration;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
@@ -38,11 +37,10 @@
  */
 @SuppressWarnings("deprecation")
 @Configuration(proxyBeanMethods = false)
-@ConditionalOnClass(RestHighLevelClient.class)
-@ConditionalOnMissingBean(RestClient.class)
+@ConditionalOnClass(RestClient.class)
 @EnableConfigurationProperties({ ElasticsearchProperties.class, ElasticsearchRestClientProperties.class,
 		DeprecatedElasticsearchRestClientProperties.class })
-@Import({ RestClientBuilderConfiguration.class, RestHighLevelClientConfiguration.class,
+@Import({ RestClientBuilderConfiguration.class, RestHighLevelClientConfiguration.class, RestClientConfiguration.class,
 		RestClientSnifferConfiguration.class })
 public class ElasticsearchRestClientAutoConfiguration {
 

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

@@ -37,6 +37,7 @@
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
 import org.springframework.boot.context.properties.PropertyMapper;
 import org.springframework.context.annotation.Bean;
@@ -112,27 +113,45 @@ private HttpHost createHttpHost(URI uri) {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	@ConditionalOnMissingBean(RestHighLevelClient.class)
+	@ConditionalOnClass(RestHighLevelClient.class)
+	@ConditionalOnMissingBean({ RestHighLevelClient.class, RestClient.class })
 	static class RestHighLevelClientConfiguration {
 
 		@Bean
 		RestHighLevelClient elasticsearchRestHighLevelClient(RestClientBuilder restClientBuilder) {
 			return new RestHighLevelClient(restClientBuilder);
 		}
 
+		@Bean
+		RestClient elasticsearchRestClient(RestHighLevelClient restHighLevelClient) {
+			return restHighLevelClient.getLowLevelClient();
+		}
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnMissingClass("org.elasticsearch.client.RestHighLevelClient")
+	@ConditionalOnMissingBean(RestClient.class)
+	static class RestClientConfiguration {
+
+		@Bean
+		RestClient elasticsearchRestClient(RestClientBuilder restClientBuilder) {
+			return restClientBuilder.build();
+		}
+
 	}
 
 	@Configuration(proxyBeanMethods = false)
 	@ConditionalOnClass(Sniffer.class)
-	@ConditionalOnSingleCandidate(RestHighLevelClient.class)
+	@ConditionalOnSingleCandidate(RestClient.class)
 	static class RestClientSnifferConfiguration {
 
 		@Bean
 		@ConditionalOnMissingBean
 		@SuppressWarnings("deprecation")
-		Sniffer elasticsearchSniffer(RestHighLevelClient client, ElasticsearchRestClientProperties properties,
+		Sniffer elasticsearchSniffer(RestClient client, ElasticsearchRestClientProperties properties,
 				DeprecatedElasticsearchRestClientProperties deprecatedProperties) {
-			SnifferBuilder builder = Sniffer.builder(client.getLowLevelClient());
+			SnifferBuilder builder = Sniffer.builder(client);
 			PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
 			Duration interval = deprecatedProperties.isCustomized() ? deprecatedProperties.getSniffer().getInterval()
 					: properties.getSniffer().getInterval();

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

@@ -16,20 +16,27 @@
 
 package org.springframework.boot.autoconfigure.elasticsearch;
 
+import java.io.InputStream;
 import java.time.Duration;
 import java.util.HashMap;
 import java.util.Map;
 
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
 import org.elasticsearch.action.get.GetRequest;
 import org.elasticsearch.action.index.IndexRequest;
+import org.elasticsearch.client.Request;
 import org.elasticsearch.client.RequestOptions;
+import org.elasticsearch.client.Response;
+import org.elasticsearch.client.RestClient;
 import org.elasticsearch.client.RestHighLevelClient;
 import org.junit.jupiter.api.Test;
 import org.testcontainers.elasticsearch.ElasticsearchContainer;
 import org.testcontainers.junit.jupiter.Container;
 import org.testcontainers.junit.jupiter.Testcontainers;
 
 import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.boot.testsupport.testcontainers.DockerImageNames;
 
@@ -41,6 +48,7 @@
  * @author Brian Clozel
  * @author Vedran Pavic
  * @author Evgeniy Cheban
+ * @author Filip Hrisafov
  */
 @Testcontainers(disabledWithoutDocker = true)
 class ElasticsearchRestClientAutoConfigurationIntegrationTests {
@@ -53,7 +61,7 @@ class ElasticsearchRestClientAutoConfigurationIntegrationTests {
 			.withConfiguration(AutoConfigurations.of(ElasticsearchRestClientAutoConfiguration.class));
 
 	@Test
-	void restClientCanQueryElasticsearchNode() {
+	void restHighLevelClientCanQueryElasticsearchNode() {
 		this.contextRunner
 				.withPropertyValues("spring.elasticsearch.uris=" + elasticsearch.getHttpHostAddress(),
 						"spring.elasticsearch.connection-timeout=120s", "spring.elasticsearch.socket-timeout=120s")
@@ -69,4 +77,42 @@ void restClientCanQueryElasticsearchNode() {
 				});
 	}
 
+	@Test
+	void restClientCanQueryElasticsearchNode() {
+		this.contextRunner
+				.withPropertyValues("spring.elasticsearch.uris=" + elasticsearch.getHttpHostAddress(),
+						"spring.elasticsearch.connection-timeout=120s", "spring.elasticsearch.socket-timeout=120s")
+				.run((context) -> {
+					RestClient client = context.getBean(RestClient.class);
+					Request index = new Request("PUT", "/test/_doc/2");
+					index.setJsonEntity("{" + "  \"a\": \"alpha\"," + "  \"b\": \"bravo\"" + "}");
+					client.performRequest(index);
+					Request getRequest = new Request("GET", "/test/_doc/2");
+					Response response = client.performRequest(getRequest);
+					try (InputStream input = response.getEntity().getContent()) {
+						JsonNode result = new ObjectMapper().readTree(input);
+						assertThat(result.path("found").asBoolean()).isTrue();
+					}
+				});
+	}
+
+	@Test
+	void restClientCanQueryElasticsearchNodeWithoutHighLevelClient() {
+		this.contextRunner.withClassLoader(new FilteredClassLoader(RestHighLevelClient.class))
+				.withPropertyValues("spring.elasticsearch.uris=" + elasticsearch.getHttpHostAddress(),
+						"spring.elasticsearch.connection-timeout=120s", "spring.elasticsearch.socket-timeout=120s")
+				.run((context) -> {
+					RestClient client = context.getBean(RestClient.class);
+					Request index = new Request("PUT", "/test/_doc/3");
+					index.setJsonEntity("{" + "  \"a\": \"alpha\"," + "  \"b\": \"bravo\"" + "}");
+					client.performRequest(index);
+					Request getRequest = new Request("GET", "/test/_doc/3");
+					Response response = client.performRequest(getRequest);
+					try (InputStream input = response.getEntity().getContent()) {
+						JsonNode result = new ObjectMapper().readTree(input);
+						assertThat(result.path("found").asBoolean()).isTrue();
+					}
+				});
+	}
+
 }