// concatenate all the values for multi-valued field
Fieldable[] fields = solrDoc.getFieldables(fieldName);
if (fields != null && fields.length > 0) {
ArrayList<String> valueList = new ArrayList<String>();
for (Fieldable fd : fields) {
Object fieldObj = fieldType.toObject(fd);
if (fieldObj != null)
valueList.add(fieldObj.toString());
}
fieldValue = StringUtil.listToString(valueList, ",");
}