Update

streams-bootstrap-core/src/main/java/com/bakdata/kafka/ImprovedStreamsConfig.java

@@ -25,6 +25,7 @@
 package com.bakdata.kafka;
 
 import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 import lombok.NonNull;
 import lombok.Value;
@@ -50,11 +51,11 @@ public String getAppId() {
 
     /**
      * Get the bootstrap servers of the underlying {@link StreamsConfig}
-     * @return comma separated bootstrap servers config
+     * @return list of bootstrap servers
      * @see StreamsConfig#BOOTSTRAP_SERVERS_CONFIG
      */
-    public String getBoostrapServers() {
-        return String.join(",", this.streamsConfig.getList(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG));
+    public List<String> getBoostrapServers() {
+        return this.streamsConfig.getList(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG);
     }
 
     /**

streams-bootstrap-core/src/main/java/com/bakdata/kafka/StreamsCleanUpRunner.java

@@ -102,7 +102,7 @@ public static void runResetter(final Collection<String> inputTopics, final Colle
         final File tempFile = createTemporaryPropertiesFile(appId, streamsAppConfig.getKafkaProperties());
         final ImmutableList.Builder<String> argList = ImmutableList.<String>builder()
                 .add("--application-id", appId)
-                .add("--bootstrap-server", streamsAppConfig.getBoostrapServers())
+                .add("--bootstrap-server", String.join(",", streamsAppConfig.getBoostrapServers()))
                 .add("--config-file", tempFile.toString());
         final Collection<String> existingInputTopics = filterExistingTopics(inputTopics, allTopics);
         if (!existingInputTopics.isEmpty()) {

streams-bootstrap-core/src/test/java/com/bakdata/kafka/ImprovedStreamsConfigTest.java

@@ -0,0 +1,98 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2024 bakdata
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.bakdata.kafka;
+
+import java.util.List;
+import java.util.Map;
+import org.apache.kafka.streams.StreamsConfig;
+import org.assertj.core.api.SoftAssertions;
+import org.assertj.core.api.junit.jupiter.InjectSoftAssertions;
+import org.assertj.core.api.junit.jupiter.SoftAssertionsExtension;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+@ExtendWith(SoftAssertionsExtension.class)
+class ImprovedStreamsConfigTest {
+
+    @InjectSoftAssertions
+    private SoftAssertions softly;
+
+    @Test
+    void shouldGetAppId() {
+        final StreamsConfig config = new StreamsConfig(
+                Map.of(
+                        StreamsConfig.APPLICATION_ID_CONFIG, "test-app",
+                        StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "broker1:9092"
+                )
+        );
+        this.softly.assertThat(new ImprovedStreamsConfig(config).getAppId())
+                .isEqualTo("test-app");
+    }
+
+    @Test
+    void shouldGetBootstrapServersFromList() {
+        final StreamsConfig config = new StreamsConfig(
+                Map.of(
+                        StreamsConfig.APPLICATION_ID_CONFIG, "test-app",
+                        StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, List.of("broker1:9092", "broker2:9092", "broker3:9092")
+                )
+        );
+        this.softly.assertThat(new ImprovedStreamsConfig(config).getBoostrapServers())
+                .isEqualTo(List.of("broker1:9092", "broker2:9092", "broker3:9092"));
+    }
+
+    @Test
+    void shouldGetBootstrapServersFromString() {
+        final StreamsConfig config = new StreamsConfig(
+                Map.of(
+                        StreamsConfig.APPLICATION_ID_CONFIG, "test-app",
+                        StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "broker1:9092,broker2:9092,broker3:9092"
+                )
+        );
+        this.softly.assertThat(new ImprovedStreamsConfig(config).getBoostrapServers())
+                .isEqualTo(List.of("broker1:9092", "broker2:9092", "broker3:9092"));
+    }
+
+    @Test
+    void shouldGetOriginalKafkaProperties() {
+        final StreamsConfig config = new StreamsConfig(
+                Map.of(
+                        StreamsConfig.APPLICATION_ID_CONFIG, "test-app",
+                        StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "broker1:9092"
+                )
+        );
+        this.softly.assertThat(new ImprovedStreamsConfig(config).getKafkaProperties())
+                .hasSize(2)
+                .anySatisfy((key, value) -> {
+                    this.softly.assertThat(key).isEqualTo(StreamsConfig.APPLICATION_ID_CONFIG);
+                    this.softly.assertThat(value).isEqualTo("test-app");
+                })
+                .anySatisfy((key, value) -> {
+                    this.softly.assertThat(key).isEqualTo(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG);
+                    this.softly.assertThat(value).isEqualTo("broker1:9092");
+                });
+    }
+
+}