Refine the configuration callbacks in the ClientConfiguration.

Original Pull Request #2237
Closes #2149

src/main/asciidoc/reference/elasticsearch-clients.adoc

@@ -38,16 +38,17 @@ ElasticsearchClient elasticsearchClient; <.>
 @Autowired
 RestClient restClient;                   <.>
 ----
+
 the following can be injected:
 
 <.> an implementation of `ElasticsearchOperations`
-<.> the `co.elastic.clients.elasticsearch.ElasticsearchClient` that is used. This is new Elasticsearch client 
+<.> the `co.elastic.clients.elasticsearch.ElasticsearchClient` that is used.
-implementation.
+This is new Elasticsearch client implementation.
 <.> the low level `RestClient` from the Elasticsearch libraries
 ====
 
-Basically one should just use the `ElasticsearchOperations` to interact with the Elasticsearch cluster. When using 
+Basically one should just use the `ElasticsearchOperations` to interact with the Elasticsearch cluster.
-repositories, this instance is used under the hood as well.
+When using repositories, this instance is used under the hood as well.
 
 [[elasticsearch.clients.reactiverestclient]]
 == Reactive Rest Client
@@ -81,16 +82,17 @@ ReactiveElasticsearchClient elasticsearchClient; <.>
 @Autowired
 RestClient restClient;                           <.>
 ----
+
 the following can be injected:
 
 <.> an implementation of `ElasticsearchOperations`
-<.> the `org.springframework.data.elasticsearch.client.elc.ReactiveElasticsearchClient` that is used. This is based 
+<.> the `org.springframework.data.elasticsearch.client.elc.ReactiveElasticsearchClient` that is used.
-on the new Elasticsearch client implementation.
+This is based on the new Elasticsearch client implementation.
 <.> the low level `RestClient` from the Elasticsearch libraries
 ====
 
-Basically one should just use the `ReactiveElasticsearchOperations` to interact with the Elasticsearch cluster. When 
+Basically one should just use the `ReactiveElasticsearchOperations` to interact with the Elasticsearch cluster.
-using repositories, this instance is used under the hood as well.
+When using repositories, this instance is used under the hood as well.
 
 [[elasticsearch.clients.resthighlevelclient]]
 == High Level REST Client (deprecated)
@@ -231,12 +233,49 @@ Default is 5 sec.
 <.> Optionally set headers.
 <.> Add basic authentication.
 <.> A `Supplier<Header>` function can be specified which is called every time before a request is sent to Elasticsearch - here, as an example, the current time is written in a header.
-<.> a function configuring the low level REST client (the same for the imperative and reactive stack)
+<.> a function to configure the created client (see <<elasticsearch.clients.configuration.callbacks>>), can be added multiple times.
 ====
 
 IMPORTANT: Adding a Header supplier as shown in above example allows to inject headers that may change over the time, like authentication JWT tokens.
 If this is used in the reactive setup, the supplier function *must not* block!
 
+[[elasticsearch.clients.configuration.callbacks]]
+=== Client configuration callbacks
+
+The `ClientConfiguration` class offers the most common parameters to configure the client. In the case this is not 
+enough, the user can add callback functions by using the `withClientConfigurer(ClientConfigurationCallback<?>)` method.
+
+The following callbacks are provided:
+
+==== Configuration of the low level Elasticsearch `RestClient`:
+
+====
+[source,java]
+----
+ClientConfiguration.builder()
+    .withClientConfigurer(ElasticsearchClients.ElasticsearchRestClientConfigurationCallback.from(restClientBuilder -> {
+        // configure the Elasticsearch RestClient
+        return restClientBuilder;
+    }))
+    .build();
+----
+====
+
+==== Configuration of the HttpAsyncClient used by the low level Elasticsearch `RestClient`:
+
+====
+[source,java]
+----
+ClientConfiguration.builder()
+    .withClientConfigurer(ElasticsearchClients.ElasticsearchHttpClientConfigurationCallback.from(httpAsyncClientBuilder -> {
+        // configure the HttpAsyncClient
+        return httpAsyncClientBuilder;
+    }))
+    .build();
+----
+====
+
+
 === Elasticsearch 7 compatibility headers
 
 When using the deprecated `RestHighLevelClient` and accessing an Elasticsearch cluster that is running on version 8, it is necessary to set the compatibility headers

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchClients.java

@@ -56,7 +56,6 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
-import org.springframework.web.reactive.function.client.WebClient;
 
 /**
  * Utility class to create the different Elasticsearch clients
@@ -229,14 +228,20 @@ public final class ElasticsearchClients {
 
 			for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurer : clientConfiguration
 					.getClientConfigurers()) {
-				if (clientConfigurer instanceof ElasticsearchClientConfigurationCallback) {
+				if (clientConfigurer instanceof ElasticsearchHttpClientConfigurationCallback restClientConfigurationCallback) {
-					ElasticsearchClientConfigurationCallback restClientConfigurationCallback = (ElasticsearchClientConfigurationCallback) clientConfigurer;
 					clientBuilder = restClientConfigurationCallback.configure(clientBuilder);
 				}
 			}
 
 			return clientBuilder;
 		});
+
+		for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurationCallback : clientConfiguration
+				.getClientConfigurers()) {
+			if (clientConfigurationCallback instanceof ElasticsearchRestClientConfigurationCallback configurationCallback) {
+				builder = configurationCallback.configure(builder);
+			}
+		}
 		return builder;
 	}
 
@@ -360,37 +365,39 @@ public final class ElasticsearchClients {
 
 	/**
 	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
-	 * the RestClient with a {@link HttpAsyncClientBuilder}
+	 * the Elasticsearch RestClient's Http client with a {@link HttpAsyncClientBuilder}
 	 *
 	 * @since 4.4
 	 */
-	public interface ElasticsearchClientConfigurationCallback
+	public interface ElasticsearchHttpClientConfigurationCallback
 			extends ClientConfiguration.ClientConfigurationCallback<HttpAsyncClientBuilder> {
 
-		static ElasticsearchClientConfigurationCallback from(
+		static ElasticsearchHttpClientConfigurationCallback from(
-				Function<HttpAsyncClientBuilder, HttpAsyncClientBuilder> clientBuilderCallback) {
+				Function<HttpAsyncClientBuilder, HttpAsyncClientBuilder> httpClientBuilderCallback) {
 
-			Assert.notNull(clientBuilderCallback, "clientBuilderCallback must not be null");
+			Assert.notNull(httpClientBuilderCallback, "httpClientBuilderCallback must not be null");
 
 			// noinspection NullableProblems
-			return clientBuilderCallback::apply;
+			return httpClientBuilderCallback::apply;
 		}
 	}
 
 	/**
 	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
-	 * the ReactiveElasticsearchClient with a {@link WebClient}
+	 * the RestClient client with a {@link RestClientBuilder}
 	 *
-	 * @since 4.4
+	 * @since 5.0
 	 */
-	public interface WebClientConfigurationCallback extends ClientConfiguration.ClientConfigurationCallback<WebClient> {
+	public interface ElasticsearchRestClientConfigurationCallback
+			extends ClientConfiguration.ClientConfigurationCallback<RestClientBuilder> {
 
-		static WebClientConfigurationCallback from(Function<WebClient, WebClient> webClientCallback) {
+		static ElasticsearchRestClientConfigurationCallback from(
+				Function<RestClientBuilder, RestClientBuilder> restClientBuilderCallback) {
 
-			Assert.notNull(webClientCallback, "webClientCallback must not be null");
+			Assert.notNull(restClientBuilderCallback, "restClientBuilderCallback must not be null");
 
 			// noinspection NullableProblems
-			return webClientCallback::apply;
+			return restClientBuilderCallback::apply;
 		}
 	}
 }

src/main/java/org/springframework/data/elasticsearch/client/erhlc/ReactiveRestClients.java

@@ -72,7 +72,9 @@ public final class ReactiveRestClients {
 	 * the ReactiveElasticsearchClient with a {@link WebClient}
 	 *
 	 * @since 4.3
+	 * @deprecated
 	 */
+	@Deprecated
 	public interface WebClientConfigurationCallback extends ClientConfiguration.ClientConfigurationCallback<WebClient> {
 
 		static WebClientConfigurationCallback from(Function<WebClient, WebClient> webClientCallback) {

src/main/java/org/springframework/data/elasticsearch/client/erhlc/RestClients.java

@@ -252,7 +252,9 @@ public final class RestClients {
 	 * the RestClient with a {@link HttpAsyncClientBuilder}
 	 *
 	 * @since 4.3
+	 * @deprecated since 5.0
 	 */
+	@Deprecated
 	public interface RestClientConfigurationCallback
 			extends ClientConfiguration.ClientConfigurationCallback<HttpAsyncClientBuilder> {
 

src/main/java/org/springframework/data/elasticsearch/client/erhlc/WebClientProvider.java

@@ -35,7 +35,6 @@ import java.util.function.Function;
 import javax.net.ssl.SSLContext;
 
 import org.springframework.data.elasticsearch.client.ClientConfiguration;
-import org.springframework.data.elasticsearch.client.elc.ElasticsearchClients;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.client.reactive.ClientHttpConnector;
 import org.springframework.http.client.reactive.ReactorClientHttpConnector;
@@ -240,11 +239,6 @@ public interface WebClientProvider {
 					ReactiveRestClients.WebClientConfigurationCallback webClientConfigurationCallback = (ReactiveRestClients.WebClientConfigurationCallback) clientConfigurer;
 					webClient = webClientConfigurationCallback.configure(webClient);
 				}
-
-				if (clientConfigurer instanceof ElasticsearchClients.WebClientConfigurationCallback) {
-					ElasticsearchClients.WebClientConfigurationCallback webClientConfigurationCallback = (ElasticsearchClients.WebClientConfigurationCallback) clientConfigurer;
-					webClient = webClientConfigurationCallback.configure(webClient);
-				}
 			}
 			return webClient;
 		};

src/test/java/org/springframework/data/elasticsearch/client/RestClientsTest.java

@@ -103,7 +103,8 @@ public class RestClientsTest {
 			defaultHeaders.add("def2", "def2-1");
 
 			AtomicInteger supplierCount = new AtomicInteger(1);
-			AtomicInteger clientConfigurerCount = new AtomicInteger(0);
+			AtomicInteger httpClientConfigurerCount = new AtomicInteger(0);
+			AtomicInteger restClientConfigurerCount = new AtomicInteger(0);
 
 			ClientConfigurationBuilder configurationBuilder = new ClientConfigurationBuilder();
 			configurationBuilder //
@@ -120,26 +121,36 @@ public class RestClientsTest {
 			if (clientUnderTestFactory instanceof ERHLCUnderTestFactory) {
 				configurationBuilder
 						.withClientConfigurer(RestClients.RestClientConfigurationCallback.from(httpClientBuilder -> {
-							clientConfigurerCount.incrementAndGet();
+							httpClientConfigurerCount.incrementAndGet();
 							return httpClientBuilder;
 						}));
 			} else if (clientUnderTestFactory instanceof ReactiveERHLCUnderTestFactory) {
 				configurationBuilder.withClientConfigurer(ReactiveRestClients.WebClientConfigurationCallback.from(webClient -> {
-					clientConfigurerCount.incrementAndGet();
+					httpClientConfigurerCount.incrementAndGet();
 					return webClient;
 				}));
 			} else if (clientUnderTestFactory instanceof ELCUnderTestFactory) {
 				configurationBuilder.withClientConfigurer(
-						ElasticsearchClients.ElasticsearchClientConfigurationCallback.from(httpClientBuilder -> {
+						ElasticsearchClients.ElasticsearchHttpClientConfigurationCallback.from(httpClientBuilder -> {
-							clientConfigurerCount.incrementAndGet();
+							httpClientConfigurerCount.incrementAndGet();
 							return httpClientBuilder;
 						}));
+				configurationBuilder.withClientConfigurer(
+						ElasticsearchClients.ElasticsearchRestClientConfigurationCallback.from(restClientBuilder -> {
+							restClientConfigurerCount.incrementAndGet();
+							return restClientBuilder;
+						}));
 			} else if (clientUnderTestFactory instanceof ReactiveELCUnderTestFactory) {
 				configurationBuilder
-						.withClientConfigurer(ElasticsearchClients.ElasticsearchClientConfigurationCallback.from(webClient -> {
+						.withClientConfigurer(ElasticsearchClients.ElasticsearchHttpClientConfigurationCallback.from(webClient -> {
-							clientConfigurerCount.incrementAndGet();
+							httpClientConfigurerCount.incrementAndGet();
 							return webClient;
 						}));
+				configurationBuilder.withClientConfigurer(
+						ElasticsearchClients.ElasticsearchRestClientConfigurationCallback.from(restClientBuilder -> {
+							restClientConfigurerCount.incrementAndGet();
+							return restClientBuilder;
+						}));
 			}
 
 			ClientConfiguration clientConfiguration = configurationBuilder.build();
@@ -162,7 +173,8 @@ public class RestClientsTest {
 				);
 			}
 
-			assertThat(clientConfigurerCount).hasValue(1);
+			assertThat(httpClientConfigurerCount).hasValue(1);
+			assertThat(restClientConfigurerCount).hasValue(clientUnderTestFactory.getExpectedRestClientConfigCalls());
 		});
 	}
 
@@ -328,11 +340,16 @@ public class RestClientsTest {
 		}
 
 		protected abstract String getDisplayName();
+
+		protected Integer getExpectedRestClientConfigCalls() {
+			return 0;
+		}
 	}
 
 	/**
 	 * {@link ClientUnderTestFactory} implementation for the old {@link RestHighLevelClient}.
 	 */
+	@Deprecated
 	static class ERHLCUnderTestFactory extends ClientUnderTestFactory {
 
 		@Override
@@ -363,7 +380,6 @@ public class RestClientsTest {
 				}
 			};
 		}
-
 	}
 
 	/**
@@ -376,6 +392,11 @@ public class RestClientsTest {
 			return "ElasticsearchClient";
 		}
 
+		@Override
+		protected Integer getExpectedRestClientConfigCalls() {
+			return 1;
+		}
+
 		@Override
 		ClientUnderTest create(ClientConfiguration clientConfiguration) {
 
@@ -403,6 +424,7 @@ public class RestClientsTest {
 	 * {@link ClientUnderTestFactory} implementation for the
 	 * {@link org.springframework.data.elasticsearch.client.erhlc.ReactiveElasticsearchClient}.
 	 */
+	@Deprecated
 	static class ReactiveERHLCUnderTestFactory extends ClientUnderTestFactory {
 
 		@Override
@@ -446,6 +468,11 @@ public class RestClientsTest {
 			return "ReactiveElasticsearchClient (ELC based)";
 		}
 
+		@Override
+		protected Integer getExpectedRestClientConfigCalls() {
+			return 1;
+		}
+
 		@Override
 		ClientUnderTest create(ClientConfiguration clientConfiguration) {