code: private Map<String, List<String>> mapClazztoPu(Class<?> clazz, String pu, Map<String, List<String>> clazzToPuMap)
      {
          List<String> puCol = new ArrayList<String>(1);
          if (clazzToPuMap == null)
          {
              clazzToPuMap = new HashMap<String, List<String>>();
          }
          else
          {
              if (clazzToPuMap.containsKey(clazz.getName()))
              {
                  puCol = clazzToPuMap.get(clazz.getName());
              }
          }
  
          if (!puCol.contains(pu))
          {
              puCol.add(pu);
              clazzToPuMap.put(clazz.getName(), puCol);
              String annotateEntityName = clazz.getAnnotation(Entity.class).name();
              if (!StringUtils.isBlank(annotateEntityName))
              {
                  clazzToPuMap.put(annotateEntityName, puCol);
              }
          }
  
          return clazzToPuMap;
      }
docs: Method to prepare class simple name to list of pu's mapping. 1 class can
  be mapped to multiple persistence units, in case of RDBMS, in other cases
  it will only be 1!
  
  @param clazz
  entity class to be mapped.
  @param pu
  current persistence unit name
  @param clazzToPuMap
  collection holding mapping.
  @return map holding mapping.