code: public List<Object> findByRelation(String colName, Object colValue, Class entityClazz)
      {
          EntityMetadata m = KunderaMetadataManager.getEntityMetadata(kunderaMetadata, entityClazz);
          // you got column name and column value.
          DBCollection dbCollection = mongoDb.getCollection(m.getTableName());
  
          BasicDBObject query = new BasicDBObject();
  
          query.put(colName, MongoDBUtils.populateValue(colValue, colValue.getClass()));
          KunderaCoreUtils.printQuery("Find by relation:" + query, showQuery);
          DBCursor cursor = dbCollection.find(query);
          DBObject fetchedDocument = null;
          List<Object> results = new ArrayList<Object>();
          while (cursor.hasNext())
          {
              fetchedDocument = cursor.next();
              populateEntity(m, results, fetchedDocument);
          }
  
          return results.isEmpty() ? null : results;
      }
docs: Method to find entity for given association name and association value.
  
  @param colName
  the col name
  @param colValue
  the col value
  @param entityClazz
  the entity clazz
  @return the list