private String getColumnPrefix(String parentPrefix, ResultMapping resultMapping) {
   final StringBuilder columnPrefixBuilder = new StringBuilder();
   if (parentPrefix != null) columnPrefixBuilder.append(parentPrefix);
   if (resultMapping.getColumnPrefix() != null)
     columnPrefixBuilder.append(resultMapping.getColumnPrefix());
   final String columnPrefix =
       columnPrefixBuilder.length() == 0
           ? null
           : columnPrefixBuilder.toString().toUpperCase(Locale.ENGLISH);
   return columnPrefix;
 }
 private void createRowKeyForMappedProperties(
     ResultMap resultMap,
     ResultSetWrapper rsw,
     CacheKey cacheKey,
     List<ResultMapping> resultMappings,
     String columnPrefix)
     throws SQLException {
   for (ResultMapping resultMapping : resultMappings) {
     if (resultMapping.getNestedResultMapId() != null
         && resultMapping.getResultSet() == null) { // Issue #392
       final ResultMap nestedResultMap =
           configuration.getResultMap(resultMapping.getNestedResultMapId());
       createRowKeyForMappedProperties(
           nestedResultMap,
           rsw,
           cacheKey,
           nestedResultMap.getConstructorResultMappings(),
           prependPrefix(resultMapping.getColumnPrefix(), columnPrefix));
     } else if (resultMapping.getNestedQueryId() == null) {
       final String column = prependPrefix(resultMapping.getColumn(), columnPrefix);
       final TypeHandler<?> th = resultMapping.getTypeHandler();
       List<String> mappedColumnNames = rsw.getMappedColumnNames(resultMap, columnPrefix);
       if (column != null
           && mappedColumnNames.contains(column.toUpperCase(Locale.ENGLISH))) { // Issue #114
         final Object value = th.getResult(rsw.getResultSet(), column);
         if (value != null) {
           cacheKey.update(column);
           cacheKey.update(value);
         }
       }
     }
   }
 }