Convert JSON to Excel in Java [Source Code]

<!-- https://mvnrepository.com/artifact/org.apache.poi/poi -->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>4.0.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml -->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>4.0.1</version>
</dependency>

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.13.2</version>
		</dependency>

package com.javacodepoint.example;

import java.io.File;
import java.io.FileOutputStream;
import java.util.ArrayList;
import java.util.Iterator;

import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.Font;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;

/**
 * 
 * @author javacodepoint.com
 *
 */
public class JsonToExcelConverter {

	private ObjectMapper mapper = new ObjectMapper();

	/**
	 * Method to convert json file to excel file
	 * @param srcFile
	 * @param targetFileExtension
	 * @return file
	 */
	public File jsonFileToExcelFile(File srcFile, String targetFileExtension) {
		try {
			if (!srcFile.getName().endsWith(".json")) {
				throw new IllegalArgumentException("The source file should be .json file only");
			} else {
				Workbook workbook = null;
				
				//Creating workbook object based on target file format
				if (targetFileExtension.equals(".xls")) {
					workbook = new HSSFWorkbook();
				} else if (targetFileExtension.equals(".xlsx")) {
					workbook = new XSSFWorkbook();
				} else {
					throw new IllegalArgumentException("The target file extension should be .xls or .xlsx only");
				}

				//Reading the json file
				ObjectNode jsonData = (ObjectNode) mapper.readTree(srcFile);
				
				//Iterating over the each sheets
				Iterator<String> sheetItr = jsonData.fieldNames();
				while (sheetItr.hasNext()) {
					
					// create the workbook sheet
					String sheetName = sheetItr.next();
					Sheet sheet = workbook.createSheet(sheetName);

					ArrayNode sheetData = (ArrayNode) jsonData.get(sheetName);
					ArrayList<String> headers = new ArrayList<String>();	
					
					//Creating cell style for header to make it bold
					CellStyle headerStyle = workbook.createCellStyle();
					Font font = workbook.createFont();
					font.setBold(true);
					headerStyle.setFont(font);
					
					//creating the header into the sheet
					Row header = sheet.createRow(0);	
					Iterator<String> it = sheetData.get(0).fieldNames();
					int headerIdx = 0;
					while (it.hasNext()) {
						String headerName = it.next();
						headers.add(headerName);
						Cell cell=header.createCell(headerIdx++);
						cell.setCellValue(headerName);
						//apply the bold style to headers
						cell.setCellStyle(headerStyle);
					}
					
					//Iterating over the each row data and writing into the sheet
					for (int i = 0; i < sheetData.size(); i++) {
						ObjectNode rowData = (ObjectNode) sheetData.get(i);
						Row row = sheet.createRow(i + 1);
						for (int j = 0; j < headers.size(); j++) {
							String value = rowData.get(headers.get(j)).asText();
							row.createCell(j).setCellValue(value);
						}
					}

					/*
					 * automatic adjust data in column using autoSizeColumn, autoSizeColumn should
					 * be made after populating the data into the excel. Calling before populating
					 * data will not have any effect.
					 */
					for (int i = 0; i < headers.size(); i++) {
						sheet.autoSizeColumn(i);
					}

				}
				
				//creating a target file
				String filename = srcFile.getName();
				filename = filename.substring(0, filename.lastIndexOf(".json")) + targetFileExtension;
				File targetFile = new File(srcFile.getParent(), filename);

				// write the workbook into target file
				FileOutputStream fos = new FileOutputStream(targetFile);
				workbook.write(fos);
				
				//close the workbook and fos
				workbook.close();
				fos.close();
				return targetFile;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}

	/**
	 * Main method to test this converter
	 * 
	 * @param args
	 */
	public static void main(String[] args) {
		
		JsonToExcelConverter converter = new JsonToExcelConverter();
		File srcFile = new File("E:/employee_info.json");		
		File xlsxFile = converter.jsonFileToExcelFile(srcFile, ".xlsx");
		System.out.println("Sucessfully converted JSON to Excel file at =" + xlsxFile.getAbsolutePath());

	}

}