Transfer only contents of Kafka and ZooKeeper properties files

src/main/java/io/strimzi/test/container/StrimziKafkaContainer.java

@@ -75,6 +75,7 @@ public class StrimziKafkaContainer extends GenericContainer<StrimziKafkaContaine
     private boolean useKraft;
     private Function<StrimziKafkaContainer, String> bootstrapServersProvider = c -> String.format("PLAINTEXT://%s:%s", getHost(), this.kafkaExposedPort);
     private String clusterId;
+    private MountableFile serverPropertiesFile;
 
     // proxy attributes
     private ToxiproxyContainer proxyContainer;
@@ -282,6 +283,11 @@ protected void containerIsStarting(final InspectContainerResponse containerInfo,
             command += "bin/kafka-server-start.sh config/kraft/server.properties" + kafkaConfigurationOverride;
         }
 
+        Utils.asTransferableBytes(serverPropertiesFile).ifPresent(properties -> copyFileToContainer(
+                properties,
+                this.useKraft ? "/opt/kafka/config/kraft/server.properties" : "/opt/kafka/config/server.properties"
+        ));
+
         LOGGER.info("Copying command to 'STARTER_SCRIPT' script.");
 
         copyFileToContainer(
@@ -354,7 +360,7 @@ public String getBootstrapServers() {
 
     /**
      * Get the cluster id. This is only supported for KRaft containers.
-     * @return The cluster id. 
+     * @return The cluster id.
      */
     public String getClusterId() {
         return clusterId;
@@ -442,8 +448,12 @@ public StrimziKafkaContainer withPort(final int fixedPort) {
      * @return StrimziKafkaContainer instance
      */
     public StrimziKafkaContainer withServerProperties(final MountableFile serverPropertiesFile) {
-        withCopyFileToContainer(serverPropertiesFile,
-                this.useKraft ? "/opt/kafka/config/kraft/server.properties" : "/opt/kafka/config/server.properties");
+        /*
+         * Save a reference to the file and delay copying to the container until the container
+         * is starting. This allows for `useKraft` to be set either before or after this method
+         * is called.
+         */
+        this.serverPropertiesFile = serverPropertiesFile;
         return self();
     }
 

src/main/java/io/strimzi/test/container/StrimziZookeeperContainer.java

@@ -112,7 +112,8 @@ protected void containerIsStarting(InspectContainerResponse containerInfo, boole
      * @return StrimziZookeeperContainer instance
      */
     public StrimziZookeeperContainer withZooKeeperPropertiesFile(final MountableFile zooKeeperPropertiesFile) {
-        withCopyFileToContainer(zooKeeperPropertiesFile, "/opt/kafka/config/zookeeper.properties");
+        Utils.asTransferableBytes(zooKeeperPropertiesFile)
+            .ifPresent(properties -> withCopyToContainer(properties, "/opt/kafka/config/zookeeper.properties"));
         return this;
     }
 

src/main/java/io/strimzi/test/container/Utils.java

@@ -7,11 +7,17 @@
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.StringWriter;
+import java.io.UncheckedIOException;
 import java.net.ServerSocket;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Optional;
 import java.util.function.BooleanSupplier;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.testcontainers.images.builder.Transferable;
+import org.testcontainers.utility.MountableFile;
 
 /**
  * Utils contains auxiliary static methods, which are used in whole project.
@@ -81,6 +87,32 @@ static long waitFor(String description, long pollIntervalMs, long timeoutMs, Boo
         }
     }
 
+    /**
+     * Converts the contents of {@code file} to a new Transferable. If the file is
+     * null, an empty Optional is returned. This method reads the contents of the
+     * file to avoid preservation of the file's owner and group attributes when
+     * copying into the container.
+     *
+     * @param file the source file
+     * @return an Optional containing the Transferable contents of file, or an empty
+     *         Optional when the file is null.
+     */
+    static Optional<Transferable> asTransferableBytes(MountableFile file) {
+        if (file != null) {
+            final byte[] data;
+
+            try {
+                data = Files.readAllBytes(Path.of(file.getFilesystemPath()));
+            } catch (IOException e) {
+                throw new UncheckedIOException(e);
+            }
+
+            return Optional.of(Transferable.of(data));
+        }
+
+        return Optional.empty();
+    }
+
     /**
      * Finds a free server port which can be used by the web server
      *
@@ -90,7 +122,7 @@ public static int getFreePort()   {
         try (ServerSocket serverSocket = new ServerSocket(0)) {
             return serverSocket.getLocalPort();
         } catch (IOException e) {
-            throw new RuntimeException("Failed to find free port", e);
+            throw new UncheckedIOException("Failed to find free port", e);
         }
     }
 }