How to make excel cells readonly using apache poi - apache-poi

Question

In my case I need to protect single cell, to achieve this initially I used HSSFCellStyle and setLocked(true) and protect the sheet using Sheet.protectSheet("password"). This will protect non empty cell also so I am using DataValidation with single option, It is working as expected but it allows to delete the cell content without validation.Below is my sample code.Thanks in advance for your help.
String errorBoxTitle = "Warning";
String errorBoxMessage = "Invalid Data";
String [] valueArr = {"cellValue"};
CellRangeAddressList cellValueAddress = new CellRangeAddressList(row.getRowNum(), row.getRowNum(), cell.getColumnIndex(), cell.getColumnIndex());
DVConstraint cellValueConstraint = DVConstraint.createExplicitListConstraint(valueArr);
DataValidation cellValueValidation = new HSSFDataValidation(cellValueAddress , cellValueConstraint );
cellValueValidation .setSuppressDropDownArrow(true);
cellValueValidation .createErrorBox(errorBoxTitle, errorBoxMessage);
cellValueValidation .setEmptyCellAllowed(false);
sheet.addValidationData(cellValueValidation );

Answer 1

A cell either can be locked or not locked. If it is locked, then it cannot be changed and also not be deleted. If a cell is not locked, then of course it also can be deleted. So since data validation needs to be used in not locked cells, data validation is not an option to protect against deleting.
If the goal is to have only some cells locked when the sheet is protected but most of the cells shall be not locked, then the only way is creating a cell style having setLocked(false) set and applying that cell style to all cells which shall be not locked. That is because it is the default in Excel that cells are locked when the sheet is protected.
If new cells in whole columns shall be not locked, then this notLocked cell style can be set as the default column style.
In the following example only the header cells A1:C1 and all cells in columns greater than C are locked. The cells in A2:C4 are not locked because the notLocked cell style is applied to that cells. Also the empty cells in columns A:C for rows greater than 4 are not locked because the notLocked cell style is applied as the default column style for columns A:C.
import java.io.FileOutputStream;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.poi.ss.usermodel.*;
public class CreateExcelDefaultColumnStyleNotLocked {
public static void main(String[] args) throws Exception {
//Workbook workbook = new XSSFWorkbook(); String filePath = "./CreateExcelDefaultColumnStyleNotLocked.xlsx";
Workbook workbook = new HSSFWorkbook(); String filePath = "./CreateExcelDefaultColumnStyleNotLocked.xls";
CellStyle notLocked = workbook.createCellStyle();
notLocked.setLocked(false);
Sheet sheet = workbook.createSheet();
Row row = sheet.createRow(0);
Cell cell = null;
for (int c = 0; c < 3; c++) {
cell = row.createCell(c);
cell.setCellValue("Col " + (c+1));
}
for (int r = 1; r < 4; r++) {
row = sheet.createRow(r);
for (int c = 0; c < 3; c++) {
cell = row.createCell(c);
cell.setCellValue(r * (c+1));
cell.setCellStyle(notLocked);
}
}
sheet.setDefaultColumnStyle(0, notLocked);
sheet.setDefaultColumnStyle(1, notLocked);
sheet.setDefaultColumnStyle(2, notLocked);
sheet.protectSheet("");
FileOutputStream out = new FileOutputStream(filePath);
workbook.write(out);
out.close();
workbook.close();
}
}