Reuse existing ElasticSearch client

Instead of always creating a new ElasticSearch client, we now check for
the presence of a custom bean configuration and use that if it's
available.

Closes gh-4143
Closes gh-4146

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/elasticsearch/ElasticsearchAutoConfiguration.java

@@ -32,6 +32,7 @@ import org.elasticsearch.node.NodeBuilder;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -72,6 +73,7 @@ public class ElasticsearchAutoConfiguration implements DisposableBean {
 	private Releasable releasable;
 
 	@Bean
+	@ConditionalOnMissingBean
 	public Client elasticsearchClient() {
 		try {
 			return createClient();

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/data/elasticsearch/ElasticsearchAutoConfigurationTests.java

@@ -26,11 +26,15 @@ import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration;
 import org.springframework.boot.test.EnvironmentTestUtils;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
 
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThat;
+import static org.mockito.Mockito.mock;
 
 /**
  * Tests for {@link ElasticsearchAutoConfiguration}.
@@ -89,6 +93,17 @@ public class ElasticsearchAutoConfigurationTests {
 		assertThat(client.settings().get("http.enabled"), is(equalTo("true")));
 	}
 
+	@Test
+	public void useExistingClient() {
+		this.context = new AnnotationConfigApplicationContext();
+		this.context.register(CustomConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class,
+				ElasticsearchAutoConfiguration.class);
+		this.context.refresh();
+		assertEquals(1, this.context.getBeanNamesForType(Client.class).length);
+		assertSame(this.context.getBean("myClient"), this.context.getBean(Client.class));
+	}
+
 	@Test
 	public void createTransportClient() throws Exception {
 		// We don't have a local elasticsearch server so use an address that's missing
@@ -105,4 +120,14 @@ public class ElasticsearchAutoConfigurationTests {
 		this.context.refresh();
 	}
 
+	@Configuration
+	static class CustomConfiguration {
+
+		@Bean
+		public Client myClient() {
+			return mock(Client.class);
+		}
+
+	}
+
 }