Allow to customize the auto-configured JestClient

This commit adds a `HttpClientConfigBuilderCustomizer` to further tune
the auto-configured `JestClient`.

Closes gh-7762

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/elasticsearch/jest/HttpClientConfigBuilderCustomizer.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2016 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
+ *
+ *      http://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.boot.autoconfigure.elasticsearch.jest;
+
+import io.searchbox.client.config.HttpClientConfig;
+
+/**
+ * Callback interface that can be implemented by beans wishing to further customize the
+ * {@link HttpClientConfig} via {@link HttpClientConfig.Builder} retaining its default
+ * auto-configuration.
+ *
+ * @author Stephane Nicoll
+ * @since 1.5.0
+ */
+public interface HttpClientConfigBuilderCustomizer {
+
+	/**
+	 * Customize the {@link HttpClientConfig.Builder}.
+	 * @param builder the builder to customize
+	 */
+	void customize(HttpClientConfig.Builder builder);
+
+}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/elasticsearch/jest/JestAutoConfiguration.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.elasticsearch.jest;
 
+import java.util.List;
+
 import com.google.gson.Gson;
 import io.searchbox.client.JestClient;
 import io.searchbox.client.JestClientFactory;
@@ -50,10 +52,14 @@ public class JestAutoConfiguration {
 
 	private final ObjectProvider<Gson> gsonProvider;
 
+	private final List<HttpClientConfigBuilderCustomizer> builderCustomizers;
+
 	public JestAutoConfiguration(JestProperties properties,
-			ObjectProvider<Gson> gsonProvider) {
+			ObjectProvider<Gson> gsonProvider,
+			ObjectProvider<List<HttpClientConfigBuilderCustomizer>> builderCustomizersProvider) {
 		this.properties = properties;
 		this.gsonProvider = gsonProvider;
+		this.builderCustomizers = builderCustomizersProvider.getIfAvailable();
 	}
 
 	@Bean(destroyMethod = "shutdownClient")
@@ -82,8 +88,18 @@ public class JestAutoConfiguration {
 			builder.gson(gson);
 		}
 		builder.multiThreaded(this.properties.isMultiThreaded());
-		return builder.connTimeout(this.properties.getConnectionTimeout())
+		builder.connTimeout(this.properties.getConnectionTimeout())
-				.readTimeout(this.properties.getReadTimeout()).build();
+				.readTimeout(this.properties.getReadTimeout());
+		customize(builder);
+		return builder.build();
+	}
+
+	private void customize(HttpClientConfig.Builder builder) {
+		if (this.builderCustomizers != null) {
+			for (HttpClientConfigBuilderCustomizer customizer : this.builderCustomizers) {
+				customizer.customize(builder);
+			}
+		}
 	}
 
 }

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/elasticsearch/jest/JestAutoConfigurationTests.java

@@ -22,6 +22,7 @@ import java.util.Map;
 
 import com.google.gson.Gson;
 import io.searchbox.client.JestClient;
+import io.searchbox.client.config.HttpClientConfig;
 import io.searchbox.client.http.JestHttpClient;
 import io.searchbox.core.Index;
 import io.searchbox.core.Search;
@@ -39,6 +40,7 @@ import org.springframework.boot.test.util.EnvironmentTestUtils;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
 import org.springframework.util.SocketUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -84,6 +86,14 @@ public class JestAutoConfigurationTests {
 		assertThat(client.getGson()).isSameAs(this.context.getBean("customGson"));
 	}
 
+	@Test
+	public void customizerOverridesAutoConfig() {
+		load(BuilderCustomizer.class, "spring.elasticsearch.jest.uris=http://localhost:9200");
+		JestHttpClient client = (JestHttpClient) this.context.getBean(JestClient.class);
+		assertThat(client.getGson()).isSameAs(
+				this.context.getBean(BuilderCustomizer.class).getGson());
+	}
+
 	@Test
 	public void proxyHostWithoutPort() {
 		this.thrown.expect(BeanCreationException.class);
@@ -147,4 +157,26 @@ public class JestAutoConfigurationTests {
 
 	}
 
+	@Configuration
+	@Import(CustomGson.class)
+	static class BuilderCustomizer {
+
+		private final Gson gson = new Gson();
+
+		@Bean
+		public HttpClientConfigBuilderCustomizer customizer() {
+			return new HttpClientConfigBuilderCustomizer() {
+				@Override
+				public void customize(HttpClientConfig.Builder builder) {
+					builder.gson(BuilderCustomizer.this.gson);
+				}
+			};
+		}
+
+		Gson getGson() {
+			return this.gson;
+		}
+
+	}
+
 }

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -3615,6 +3615,15 @@ configured:
 	spring.elasticsearch.jest.password=secret
 ----
 
+You can also register an arbitrary number of beans implementing
+`HttpClientConfigBuilderCustomizer` for more advanced customizations. The example below
+tunes additional HTTP settings:
+
+[source,java,indent=0]
+----
+include::{code-examples}/elasticsearch/jest/JestClientCustomizationExample.java[tag=customizer]
+----
+
 To take full control over the registration, define a `JestClient` bean.
 
 

spring-boot-docs/src/main/java/org/springframework/boot/elasticsearch/jest/JestClientCustomizationExample.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2012-2016 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
+ *
+ *      http://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.boot.elasticsearch.jest;
+
+import io.searchbox.client.config.HttpClientConfig;
+
+import org.springframework.boot.autoconfigure.elasticsearch.jest.HttpClientConfigBuilderCustomizer;
+
+/**
+ * Example configuration for using a {@link HttpClientConfigBuilderCustomizer} to
+ * configure additional HTTP settings.
+ *
+ * @author Stephane Nicoll
+ */
+public class JestClientCustomizationExample {
+
+	/**
+	 * A {@link HttpClientConfigBuilderCustomizer} that applies additional HTTP settings
+	 * to the auto-configured jest client.
+	 */
+	// tag::customizer[]
+	static class HttpSettingsCustomizer implements HttpClientConfigBuilderCustomizer {
+
+		@Override
+		public void customize(HttpClientConfig.Builder builder) {
+			builder.maxTotalConnection(100)
+					.defaultMaxTotalConnectionPerRoute(5);
+		}
+	}
+	// end::customizer[]
+}