How to concatenate two fields in Solr using DIH?

Question

Right now I am trying to concatenate names and some dates when I am importing XML files using DIH.

I have been trying the solution here: https://bryanbende.com/development/2015/01/31/concatenating-fields-with-apache-solr. But I have gotten nowhere.

<updateRequestProcessorChain name="concatFields">
  <processor class="solr.CloneFieldUpdateProcessorFactory">
    <str name="source">author_fname</str>
    <str name="dest">author_name</str>
  </processor>
  <processor class="solr.CloneFieldUpdateProcessorFactory">
    <str name="source">author_lname</str>
    <str name="dest">author_name</str>
  </processor>
  <processor class="solr.ConcatFieldUpdateProcessorFactory">
    <str name="fieldName">author_name</str>
    <str name="delimiter">_</str>
  </processor>
  <processor class="solr.LogUpdateProcessorFactory"/>
  <processor class="solr.RunUpdateProcessorFactory"/>
</updateRequestProcessorChain>

<requestHandler name="/update" class="solr.UpdateRequestHandler">
     <lst name="defaults">
       <str name="update.chain">concatFields</str>
     </lst>
 </requestHandler>