Merge pull request #16702 from Steffen Folman Qvistgaard

* gh-16702:
  Polish "Provide control over how a Cassandra Cluster is created"
  Provide control over how a Cassandra Cluster is created

Closes gh-16702

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cassandra/CassandraAutoConfiguration.java

@@ -40,6 +40,7 @@ import org.springframework.util.StringUtils;
  * @author Phillip Webb
  * @author Eddú Meléndez
  * @author Stephane Nicoll
+ * @auther Steffen F. Qvistgaard
  * @since 1.3.0
  */
 @Configuration(proxyBeanMethods = false)
@@ -50,7 +51,8 @@ public class CassandraAutoConfiguration {
 	@Bean
 	@ConditionalOnMissingBean
 	public Cluster cassandraCluster(CassandraProperties properties,
-			ObjectProvider<ClusterBuilderCustomizer> builderCustomizers) {
+			ObjectProvider<ClusterBuilderCustomizer> builderCustomizers,
+			ObjectProvider<ClusterFactory> clusterFactory) {
 		PropertyMapper map = PropertyMapper.get();
 		Cluster.Builder builder = Cluster.builder()
 				.withClusterName(properties.getClusterName())
@@ -71,7 +73,7 @@ public class CassandraAutoConfiguration {
 				.toCall(builder::withoutJMXReporting);
 		builderCustomizers.orderedStream()
 				.forEach((customizer) -> customizer.customize(builder));
-		return builder.build();
+		return clusterFactory.getIfAvailable(() -> Cluster::buildFrom).create(builder);
 	}
 
 	private QueryOptions getQueryOptions(CassandraProperties properties) {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cassandra/ClusterFactory.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2012-2019 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
+ *
+ *      https://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.cassandra;
+
+import com.datastax.driver.core.Cluster;
+import com.datastax.driver.core.Cluster.Initializer;
+
+/**
+ * {@code CassandraClusterFactory} provides control over the creation of a {@Cluster} from
+ * an {@link Initializer}.
+ *
+ * @auther Steffen F. Qvistgaard
+ * @since 2.2.0
+ */
+@FunctionalInterface
+public interface ClusterFactory {
+
+	/**
+	 * Creates a {@link Cluster} from the given {@link Initializer}.
+	 * @param initializer the {@Code Initializer}
+	 * @return the {@code Cluster}
+	 */
+	Cluster create(Initializer initializer);
+
+}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/cassandra/CassandraAutoConfigurationTests.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.autoconfigure.cassandra;
 
 import com.datastax.driver.core.Cluster;
+import com.datastax.driver.core.Cluster.Initializer;
 import com.datastax.driver.core.PoolingOptions;
 import org.junit.jupiter.api.Test;
 
@@ -115,6 +116,14 @@ public class CassandraAutoConfigurationTests {
 				});
 	}
 
+	@Test
+	public void clusterFactoryIsCalledToCreateCluster() {
+		this.contextRunner.withUserConfiguration(ClusterFactoryConfig.class)
+				.run((context) -> assertThat(
+						context.getBean(TestClusterFactory.class).initializer)
+								.isNotNull());
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class MockCustomizerConfig {
 
@@ -135,4 +144,26 @@ public class CassandraAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class ClusterFactoryConfig {
+
+		@Bean
+		public TestClusterFactory clusterFactory() {
+			return new TestClusterFactory();
+		}
+
+	}
+
+	static class TestClusterFactory implements ClusterFactory {
+
+		private Initializer initializer = null;
+
+		@Override
+		public Cluster create(Initializer initializer) {
+			this.initializer = initializer;
+			return Cluster.buildFrom(initializer);
+		}
+
+	}
+
 }