Setting filter on headers of an Excel sheet via POI

I generate a sheet, pretty bog standard headers and columns of data.

I want to turn on the "Filter" function for the sheet, so the user can easily sort and filter the data.

Can I so this using POI?

Save the first and last cell from filter area, and execute:

sheet.setAutoFilter(new CellRangeAddress(firstCell.getRow(), lastCell.getRow(), firstCell.getCol(), lastCell.getCol()));

For example, from the below sheet.

>x         (x, y)
  0123456  
0|--hhh--|   h = header
1|--+++--|   + = values
2|--+++--|   - = empty fields
3|--+++--|
4|-------|

first cell will be the header above the first + (2,1) cell. The last will be the last + cell (5,3)

easiest way of adding filter on header :

sheet.setAutoFilter(new CellRangeAddress(0, 0, 0, numColumns));
sheet.createFreezePane(0, 1);

If you also want to set a filter programmatically, you could use the following:

void setAutoFilter(final XSSFSheet sheet, final int column, final String value) {
	sheet.setAutoFilter(CellRangeAddress.valueOf("A1:Z1"));
	
	final CTAutoFilter sheetFilter = sheet.getCTWorksheet().getAutoFilter();
	final CTFilterColumn filterColumn = sheetFilter.addNewFilterColumn();
	filterColumn.setColId(column);
	final CTFilter filter = filterColumn.addNewFilters().insertNewFilter(0);
	filter.setVal(value);

    // We have to apply the filter ourselves by hiding the rows: 
	for (final Row row : sheet) {
		for (final Cell c : row) {
			if (c.getColumnIndex() == column && !c.getStringCellValue().equals(value)) {
				final XSSFRow r1 = (XSSFRow) c.getRow();
				if (r1.getRowNum() != 0) { // skip header
					r1.getCTRow().setHidden(true);
				}
			}
		}
	}
}

Relevant Gradle dependencies:

	// https://mvnrepository.com/artifact/org.apache.poi/poi
compile group: 'org.apache.poi', name: 'poi', version: '3.9'

// https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml
compile group: 'org.apache.poi', name: 'poi-ooxml', version: '3.9'

// https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml-schemas
compile group: 'org.apache.poi', name: 'poi-ooxml-schemas', version: '3.9'

// https://mvnrepository.com/artifact/org.apache.poi/ooxml-schemas
compile group: 'org.apache.poi', name: 'ooxml-schemas', version: '1.3'

I figured out how to do this with NPOI.
You add a CT_AutoFilter to the CT_Table.

I am guessing the it works the same for POI as NPOI.

    cttable.autoFilter = new CT_AutoFilter();
    cttable.autoFilter.@ref = "A1:C5";   // value is data and includes header.

Use sheet.setAutoFilter(CellRangeAddress.valueOf("B1:H1"));

We have to specify only the header cells of the tabular data. Here in my example header starts from cell B1 and ends at cell H1.
Excel will automatically find the data below it and show it in the filter options.