KafkaProperties: Use Class.getName() idiom for serializer registration

Change-Id: I8d17e0483ecdfe9a207e0a12c7910aba4799abae
diff --git a/src/main/java/com/googlesource/gerrit/plugins/kafka/config/KafkaProperties.java b/src/main/java/com/googlesource/gerrit/plugins/kafka/config/KafkaProperties.java
index 04195a2..ad79bca 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/kafka/config/KafkaProperties.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/kafka/config/KafkaProperties.java
@@ -20,11 +20,14 @@
 import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
+import org.apache.kafka.common.serialization.StringSerializer;
 
 @Singleton
 public class KafkaProperties extends java.util.Properties {
   private static final long serialVersionUID = 0L;
 
+  public static final String KAFKA_STRING_SERIALIZER = StringSerializer.class.getName();
+
   private final String topic;
 
   @Inject
@@ -42,8 +45,8 @@
     put("batch.size", 16384);
     put("linger.ms", 1);
     put("buffer.memory", 33554432);
-    put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
-    put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
+    put("key.serializer", KAFKA_STRING_SERIALIZER);
+    put("value.serializer", KAFKA_STRING_SERIALIZER);
   }
 
   private void applyConfig(PluginConfig config) {