Add a buildProperty function to KafkaStreamsBuilder in commons

This allows the usecases to create its own Properties object if
needed.

application-kafkastreams-commons/src/main/java/spesb/commons/kafkastreams/KafkaStreamsBuilder.java

@@ -112,25 +112,31 @@ public abstract class KafkaStreamsBuilder {
   protected abstract Topology buildTopology();
 
   /**
-   * Builds the {@link KafkaStreams} instance.
+   * Build the {@link Properties} for a {@code KafkaStreams} application.
+   *
+   * @return A {@code Properties} object.
    */
-  public KafkaStreams build() {
-    // Check for required attributes for building properties.
-    Objects.requireNonNull(this.bootstrapServers, "Bootstrap server has not been set.");
-    Objects.requireNonNull(this.applicationName, "Application name has not been set.");
-    Objects.requireNonNull(this.applicationVersion, "Application version has not been set.");
-
-    // Build properties.
-    final Properties properties = PropertiesBuilder
+  protected Properties buildProperties() {
+    return PropertiesBuilder
         .bootstrapServers(this.bootstrapServers)
         .applicationId(this.applicationName + '-' + this.applicationVersion)
         .set(StreamsConfig.NUM_STREAM_THREADS_CONFIG, this.numThreads, p -> p > 0)
         .set(StreamsConfig.COMMIT_INTERVAL_MS_CONFIG, this.commitIntervalMs, p -> p >= 0)
         .set(StreamsConfig.CACHE_MAX_BYTES_BUFFERING_CONFIG, this.cacheMaxBytesBuff, p -> p >= 0)
         .build();
+  }
+
+  /**
+   * Builds the {@link KafkaStreams} instance.
+   */
+  public KafkaStreams build() {
+    // Check for required attributes for building properties.
+    Objects.requireNonNull(this.bootstrapServers, "Bootstrap server has not been set.");
+    Objects.requireNonNull(this.applicationName, "Application name has not been set.");
+    Objects.requireNonNull(this.applicationVersion, "Application version has not been set.");
 
     // Create the Kafka streams instance.
-    return new KafkaStreams(this.buildTopology(), properties);
+    return new KafkaStreams(this.buildTopology(), this.buildProperties());
   }
 
 }