code: protected void setEntityNavigationProperties(Object entity, StructuredType entityType) throws ODataException {
          for (Map.Entry<String, Object> entry : links.entrySet()) {
              String propertyName = entry.getKey();
              Object entryLinks = entry.getValue();
              LOG.debug("Found link for navigation property: {}", propertyName);
  
              StructuralProperty property = entityType.getStructuralProperty(propertyName);
              if (!(property instanceof NavigationProperty)) {
                  throw new ODataUnmarshallingException("The request contains a navigation link '" + propertyName +
                          "' but the entity type '" + entityType + "' does not contain a navigation property " +
                          "with this name.");
              }
  
              // Note: The links are processed a bit differently depending on whether we are parsing in the context
              // of a 'write operation' or 'read operation'. Only in the case of a 'write operation' it is necessary
              // to resolve the referenced entity.
              if (isWriteOperation()) {
                  // Get the referenced entity(es), but only with the key fields filled in
                  if (entryLinks instanceof List) {
                      List<String> linksList = (List<String>) entryLinks;
                      for (String link : linksList) {
                          Object referencedEntity = getReferencedEntity(link, propertyName);
                          LOG.debug("Referenced entity: {}", referencedEntity);
                          saveReferencedEntity(entity, propertyName, property, referencedEntity);
                      }
                  } else {
                      Object referencedEntity = getReferencedEntity((String) entryLinks, propertyName);
                      LOG.debug("Referenced entity: {}", referencedEntity);
                      saveReferencedEntity(entity, propertyName, property, referencedEntity);
                  }
              }
          }
      }
docs: Sets the given entity with navigation links.
  
  @param entity     entity
  @param entityType the entity type
  @throws ODataException If unable to set navigation properties