Apache-poi: Auto set size with merged cells and make the font bold

Question

I'm new to this and just playing around with apache-poi to generate an excel sheet with some mock data, here is my class and I'm struck with few things, any best practices??

1. Auto set size with merged cells in the row.
2. Font bold --> For all cells in the first row.

class:

package com.example.TestProject.process;

import java.io.File;
import java.io.FileOutputStream;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;


public class WriteExcelDemo {

    public static void main(
            String[] args) {

        // Blank workbook
        XSSFWorkbook workbook = new XSSFWorkbook();

        // Create a blank sheet
        XSSFSheet sheet = workbook.createSheet("Employee Data");

        // This data needs to be written (Object[])
        Map<String, Object[]> data = new TreeMap<String, Object[]>();
        data.put("1", new Object[] {"ID", "NAME", "LASTNAME"});
        data.put("2", new Object[] {1, "Amit", "Shukla"});
        data.put("3", new Object[] {2, "Lokesh", "Gupta"});
        data.put("4", new Object[] {3, "John", "Adwards"});
        data.put("5", new Object[] {4, "Brian", "Schultz"});

        // Iterate over data and write to sheet
        Set<String> keyset = data.keySet();
        int rownum = 0;
        for (String key : keyset) {
            Row row = sheet.createRow(rownum++);
            Object[] objArr = data.get(key);
            int cellnum = 0;
            for (Object obj : objArr) {
                Cell cell = row.createCell(cellnum++);
                if (obj instanceof String)
                    cell.setCellValue((String) obj);
                else if (obj instanceof Integer)
                    cell.setCellValue((Integer) obj);
            }
        }
        try {
            // Write the workbook in file system
            FileOutputStream out = new FileOutputStream(new File("howtodoinjava_demo.xlsx"));
            workbook.write(out);
            out.close();

            System.out.println("howtodoinjava_demo.xlsx written successfully on disk.");

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

Answer 1

For autosizing columns there is Sheet.autoSizeColumn . There you can specify whether the content of merged cells should be considered or ignored. Default is to ignore merged cells. But your question is not really clear in this point since your code does not merging cells at all.

For the row style there is Row.setRowStyle . Excel takes that style when new cells are added to this row. But apache poi does not behave like this. It always uses the default cell style for new created cells. So we need a method CellStyle getPreferredCellStyle(Cell cell) which gets the preferred cell style for a given cell as Excel would do it.

And, since you are asking about best practice, please do using org.apache.poi.ss.usermodel.* as long as posible. So the code is able processing HSSF and XSSF whithout much changes.

Example:

import java.io.File;
import java.io.FileOutputStream;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.hssf.usermodel.HSSFCell;

public class WriteExcelDemo {

 static CellStyle getPreferredCellStyle(Cell cell) {
  // a method to get the preferred cell style for a cell
  // this is either the already applied cell style
  // or if that not present, then the row style (default cell style for this row)
  // or if that not present, then the column style (default cell style for this column)
  CellStyle cellStyle = cell.getCellStyle();
  // if no explicit cell style applied then cellStyle.getIndex() is 0 for XSSF
  // or 15 (0xF = the index to the default ExtendedFormatRecord (0xF)) for HSSF
  if ((cell instanceof XSSFCell && cellStyle.getIndex() == 0) || (cell instanceof HSSFCell && cellStyle.getIndex() == 15)) cellStyle = cell.getRow().getRowStyle();
  if (cellStyle == null) cellStyle = cell.getSheet().getColumnStyle(cell.getColumnIndex());
  if (cellStyle == null) cellStyle = cell.getCellStyle();
  return cellStyle;
 }

 public static void main(String[] args) throws Exception {

  // Blank workbook XSSF or HSSF
  Workbook workbook = new XSSFWorkbook();
  //Workbook workbook = new HSSFWorkbook();

  // Create needed cell styles on workbook level
  Font boldFont = workbook.createFont();
  boldFont.setBold(true);
  CellStyle headerRowStyle = workbook.createCellStyle();
  headerRowStyle.setFont(boldFont);


  // This data needs to be written (Object[])
  Map<String, Object[]> data = new TreeMap<String, Object[]>();
  data.put("1", new Object[] {"ID", "NAME", "LASTNAME"});
  data.put("2", new Object[] {1, "Amit", "Shukla"});
  data.put("3", new Object[] {2, "Lokesh", "Gupta"});
  data.put("4", new Object[] {3, "John", "Adwards"});
  data.put("5", new Object[] {4, "Brian", "Schultz"});

  // Create a blank sheet
  Sheet sheet = workbook.createSheet("Employee Data");

  // Iterate over data and write to sheet
  Set<String> keyset = data.keySet();
  int rownum = 0;
  for (String key : keyset) {
   Row row = sheet.createRow(rownum++);
   if (rownum == 1) row.setRowStyle(headerRowStyle); // row style for first row; Excel takes that style when new cells are added to this row
   Object[] objArr = data.get(key);
   int cellnum = 0;
   for (Object obj : objArr) {
    Cell cell = row.createCell(cellnum++);
    cell.setCellStyle(getPreferredCellStyle(cell)); // set the preferred cell style for the new cell as Excel would do
    if (obj instanceof String)
     cell.setCellValue((String) obj);
    else if (obj instanceof Integer)
     cell.setCellValue((Integer) obj);
   }
  }

  for (int c = 0; c < data.get("1").length; c++) {
   //sheet.autoSizeColumn(c); // autosize, merged cells should be ignored
   sheet.autoSizeColumn(c, true); // autosize, merged cells should be considered
  }

  // Write the workbook in file system
  String filepath = (workbook instanceof XSSFWorkbook)?"./howtodoinjava_demo.xlsx":"./howtodoinjava_demo.xls";
  FileOutputStream out = new FileOutputStream(new File(filepath));
  workbook.write(out);
  out.close();
  workbook.close();

  System.out.println("howtodoinjava_demo.xlsx written successfully on disk.");
 }
}