GH-374: Support bootstrap server property as a list

Resolves #374

* support read bootstrap server config when it is defined as list

* update copyright year of the affected classes to 2024

Author: emmanuelsilva

src/main/java/reactor/kafka/receiver/ReceiverOptions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2023 VMware Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2016-2024 VMware Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -570,7 +570,15 @@ default String clientId() {
      */
     @NonNull
     default String bootstrapServers() {
-        return (String) Objects.requireNonNull(consumerProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG));
+        Object bootstrapServers = Objects.requireNonNull(consumerProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG));
+
+        if (bootstrapServers instanceof List) {
+            @SuppressWarnings("unchecked")
+            List<String> listOfBootstrapServers = (List<String>) bootstrapServers;
+            return String.join(",", listOfBootstrapServers);
+        }
+
+        return (String) bootstrapServers;
     }
 
     /**

src/main/java/reactor/kafka/sender/SenderOptions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2023 VMware Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2016-2024 VMware Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@
 import java.time.Duration;
 import java.util.Map;
 import java.util.Objects;
+import java.util.List;
 import java.util.Properties;
 
 import javax.naming.AuthenticationException;
@@ -286,7 +287,15 @@ default String transactionalId() {
      */
     @NonNull
     default String bootstrapServers() {
-        return (String) Objects.requireNonNull(producerProperty(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG));
+        Object bootstrapServers = Objects.requireNonNull(producerProperty(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG));
+
+        if (bootstrapServers instanceof List) {
+            @SuppressWarnings("unchecked")
+            List<String> listOfBootstrapServers = (List<String>) bootstrapServers;
+            return String.join(",", listOfBootstrapServers);
+        }
+
+        return (String) bootstrapServers;
     }
 
     @NonNull

src/test/java/reactor/kafka/receiver/ReceiverOptionsTest.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2016-2024 VMware Inc. or its affiliates, All Rights Reserved.
+ *
+ * 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 reactor.kafka.receiver;
+
+import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public class ReceiverOptionsTest {
+
+    @Test
+    public void getBootstrapServersFromSingleServerList() {
+        Map<String, Object> producerProperties = new HashMap<>();
+        producerProperties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, Collections.singletonList("localhost:9092"));
+
+        ReceiverOptions<Integer, String> senderOptions = ReceiverOptions.create(producerProperties);
+        String bootstrapServers = senderOptions.bootstrapServers();
+
+        assertEquals("localhost:9092", bootstrapServers);
+    }
+
+    @Test
+    public void getBootstrapServersFromMultipleServersList() {
+        Map<String, Object> producerProperties = new HashMap<>();
+        List<String> serverList = Arrays.asList("localhost:9092", "localhost:9093", "localhost:9094");
+        producerProperties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, serverList);
+
+        ReceiverOptions<Integer, String> senderOptions = ReceiverOptions.create(producerProperties);
+        String bootstrapServers = senderOptions.bootstrapServers();
+
+        assertEquals("localhost:9092,localhost:9093,localhost:9094", bootstrapServers);
+    }
+
+    @Test
+    public void getBootstrapServersFromString() {
+        Map<String, Object> producerProperties = new HashMap<>();
+        producerProperties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
+
+        ReceiverOptions<Integer, String> senderOptions = ReceiverOptions.create(producerProperties);
+        String bootstrapServers = senderOptions.bootstrapServers();
+
+        assertEquals("localhost:9092", bootstrapServers);
+    }
+
+}

src/test/java/reactor/kafka/sender/SenderOptionsTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020-2021 VMware Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2020-2024 VMware Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,10 +16,14 @@
 
 package reactor.kafka.sender;
 
+import org.apache.kafka.clients.producer.ProducerConfig;
 import org.junit.Test;
 
 import java.time.Duration;
+import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
@@ -33,4 +37,38 @@ public void senderOptionsCloseTimeout() {
         assertEquals(Duration.ofMillis(100), senderOptions.closeTimeout(Duration.ofMillis(100)).closeTimeout());
     }
 
+    @Test
+    public void getBootstrapServersFromSingleServerList() {
+        Map<String, Object> producerProperties = new HashMap<>();
+        producerProperties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, Collections.singletonList("localhost:9092"));
+
+        SenderOptions<Integer, String> senderOptions = SenderOptions.create(producerProperties);
+        String bootstrapServers = senderOptions.bootstrapServers();
+
+        assertEquals("localhost:9092", bootstrapServers);
+    }
+
+    @Test
+    public void getBootstrapServersFromMultipleServersList() {
+        Map<String, Object> producerProperties = new HashMap<>();
+        List<String> serverList = Arrays.asList("localhost:9092", "localhost:9093", "localhost:9094");
+        producerProperties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, serverList);
+
+        SenderOptions<Integer, String> senderOptions = SenderOptions.create(producerProperties);
+        String bootstrapServers = senderOptions.bootstrapServers();
+
+        assertEquals("localhost:9092,localhost:9093,localhost:9094", bootstrapServers);
+    }
+
+    @Test
+    public void getBootstrapServersFromString() {
+        Map<String, Object> producerProperties = new HashMap<>();
+        producerProperties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
+
+        SenderOptions<Integer, String> senderOptions = SenderOptions.create(producerProperties);
+        String bootstrapServers = senderOptions.bootstrapServers();
+
+        assertEquals("localhost:9092", bootstrapServers);
+    }
+
 }