How to create dependent drop downs in excel sheet generated using POI?

Question

we have a function in our java based web application where user can download an excel sheet template from the web application. Fill their data in this template and then uplo

Answer 1

I was about to suggest AurA's solution but it looks like you'll have to build the validation list at run-time indeed.

You should have a look at the POI Quick Guide, it seems they have exactly what you need:

hssf.usermodel (binary .xls format)

HSSFWorkbook workbook = new HSSFWorkbook();
HSSFSheet sheet = workbook.createSheet("Data Validation");
CellRangeAddressList addressList = new CellRangeAddressList(0, 0, 0, 0);
DVConstraint dvConstraint = DVConstraint.createExplicitListConstraint(new String[]{"10", "20", "30"});
DataValidation dataValidation = new HSSFDataValidation(addressList, dvConstraint);
dataValidation.setSuppressDropDownArrow(false);
sheet.addValidationData(dataValidation);

xssf.usermodel (.xlsx format)

XSSFWorkbook workbook = new XSSFWorkbook();
XSSFSheet sheet = workbook.createSheet("Data Validation");
XSSFDataValidationHelper dvHelper = new XSSFDataValidationHelper(sheet);
XSSFDataValidationConstraint dvConstraint = (XSSFDataValidationConstraint)
dvHelper.createExplicitListConstraint(new String[]{"11", "21", "31"});
CellRangeAddressList addressList = new CellRangeAddressList(0, 0, 0, 0);
XSSFDataValidation validation = (XSSFDataValidation)dvHelper.createValidation(
dvConstraint, addressList);
validation.setShowErrorBox(true);
sheet.addValidationData(validation);

Answer 2

You can get drop-down list (after clicking right mouse button) in case you've added (using POI) suggestions to the rows upper the first row that is visible to the user and should be filled (thus the rows beneath the header contain suggestions and are hgidden).

You won't get (AFAIK) category dependancy with POI or even pure excel (without VBA) drop-down list (that holds suggestions on the basis of values entered earlier).

What you can do, is to use POI to fill helper sheet with appropriate raw data and use VBA to dynamically generate drop-downs that would allow to pick a value from a list.