public Integer retrieveHighestBatchImportNumberForCustomer(String customerCode) {
      Integer highestNumber = null;
      String queryString = "select max(to_number(h.batchNum)) from BatchImportHistory as h where h.licNum=?";
      List<Integer> resultList = getHibernateTemplate().find(queryString, customerCode);
      if (resultList != null && resultList.size() > 0 && resultList.get(0) != null) { // Last check is important as we use MAX(...) that might return <NULL>
         logger.info("Highest batch import number: "+resultList.get(0));
         highestNumber = resultList.get(0);
      }
      return highestNumber;
   }

java.lang.IllegalStateException: No data type for node: org.hibernate.hql.ast.tree.AggregateNode
\-[AGGREGATE] AggregateNode: 'max'
    \-[METHOD_CALL] MethodNode: '('
       +-[METHOD_NAME] IdentNode: 'to_number' {originalText=to_number}
       \-[EXPR_LIST] SqlNode: 'exprList'
          \-[DOT] DotNode: 'batchimpor0_.BATCH_NUM' {propertyName=batchNum,dereferenceType=4,propertyPath=batchNum,path=h.batchNum,tableAlias=batchimpor0_,className=de.ls.spwebonline.model.domain.BatchImportHistory,classAlias=h}
             +-[ALIAS_REF] IdentNode: 'batchimpor0_.ID' {alias=h, className=de.ls.spwebonline.model.domain.BatchImportHistory, tableAlias=batchimpor0_}
             \-[IDENT] IdentNode: 'batchNum' {originalText=batchNum}

select max(to_number(BATCH_NUM)) bn from BATCH_IMPORT_HISTORY model where model.LIC_NUM='ROLAND'