private String getSamzaProperty(SystemStream systemStream, String property, String defaultValue) {
    String streamVal = getSamzaProperty(systemStream, property);

    return streamVal != null ? streamVal : defaultValue;
  }
Gets a Samza property, with a default value used if no property value is found.
See getSamzaProperty(SystemStream, String).

@param systemStream the SystemStream for which the property value will be retrieved.
@param property the samza property key (including the "samza." prefix); for example, for both
                "streams.streamId.samza.prop.key" and "systems.system.streams.streamName.samza.prop.key", this
                argument should have the value "samza.prop.key"
@param defaultValue the default value to use if the property value is not found
samza-core/src/main/java/org/apache/samza/config/StreamConfig.java