Java利用Apache POI实现Excel文件读写操作

<!--alibaba-fastjson-->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>2.0.9.graal</version>
</dependency> 
<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-compress -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-compress</artifactId>
    <version>1.26.1</version>
</dependency>
<!-- Excel处理 -->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>4.1.2</version>
</dependency>

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import org.apache.poi.hssf.usermodel.HSSFDateUtil;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.*;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

public class ExcelHelper {

    //文件后缀
    private final static String XLSX = ".xlsx";
    private final static String XLS = ".xls";

    /**
     * json数据导出Excel
     *
     * @param json     json数据
     * @param filepath 文件路径
     * @return true 导出成功
     */
    public static boolean jsonToExcel(String json, String filepath) {
        try {
            JSONArray array = JSONArray.parseArray(json);
            Workbook workbook = new XSSFWorkbook();
            Sheet sheet = workbook.createSheet("Sheet1");
            // 创建表头
            Row header = sheet.createRow(0);
            JSONObject title = array.getJSONObject(0);
            for (String s : title.keySet()) {
                Cell cell = header.createCell(header.getLastCellNum() < 0 ? 0 : header.getLastCellNum());
                cell.setCellValue(s);
            }
            // 填充数据
            for (int i = 0; i < array.size(); i++) {
                JSONObject object = array.getJSONObject(i);
                Row row = sheet.createRow(i + 1);
                int colNum = 0;
                for (String key : object.keySet()) {
                    Object value = object.get(key);
                    row.createCell(colNum).setCellValue(String.valueOf(value));
                    colNum++;
                }
            }
            // 导出到文件
            OutputStream outputStream = new FileOutputStream(filepath);
            workbook.write(outputStream);
            workbook.close();
            return true;
        } catch (IOException e) {
            System.out.println(e.getMessage());
            return false;
        }
    }


    /**
     * Excel数据读取成json
     *
     * @param filepath 文件路径
     * @return json数据
     */
    public static JSONArray excelToJsonArray(String filepath) throws IOException, InvalidFormatException {
        File file = new File(filepath);
        String flieName = file.getName();
        Workbook book = null;
        Sheet sheet = null;
        if (flieName.endsWith(XLSX)) {
            book = new XSSFWorkbook(file);
            sheet = book.getSheetAt(0);
        }
        if (flieName.endsWith(XLS)) {
            POIFSFileSystem poifsFileSystem = new POIFSFileSystem(new FileInputStream(file));
            book = new HSSFWorkbook(poifsFileSystem);
            sheet = book.getSheetAt(0);
        }
        if (sheet != null) {
            return readSheet(sheet, book);
        }
        return new JSONArray();
    }

    /**
     * 读取Excel
     *
     * @param sheet 工作表
     * @param book  工作簿
     * @return json数据
     */
    public static JSONArray readSheet(Sheet sheet, Workbook book) throws IOException {
        int rowStart = sheet.getFirstRowNum(); // 首行下标
        int rowEnd = sheet.getLastRowNum();    // 尾行下标
        // 如果首行与尾行相同，表明只有一行，直接返回空数组
        if (rowStart == rowEnd) {
            book.close();
            return new JSONArray();
        }
        // 获取第一行JSON对象键
        Row firstRow = sheet.getRow(rowStart);
        int cellStart = firstRow.getFirstCellNum();
        int cellEnd = firstRow.getLastCellNum();
        Map<Integer, String> keyMap = new HashMap<Integer, String>();
        for (int j = cellStart; j < cellEnd; j++) {
            keyMap.put(j, getValue(firstRow.getCell(j), rowStart, j, book, true));
        }
        // 获取每行JSON对象的值
        JSONArray array = new JSONArray();
        for (int i = rowStart + 1; i <= rowEnd; i++) {
            Row eachRow = sheet.getRow(i);
            JSONObject obj = new JSONObject();
            StringBuffer sb = new StringBuffer();
            for (int k = cellStart; k < cellEnd; k++) {
                if (eachRow != null) {
                    String val = getValue(eachRow.getCell(k), i, k, book, false);
                    sb.append(val);        // 所有数据添加到里面，用于判断该行是否为空
                    obj.put(keyMap.get(k), val);
                }
            }
            if (!sb.toString().isEmpty()) {
                array.add(obj);
            }
        }
        book.close();
        return array;
    }

    /**
     * 获取每个单元格的数据
     *
     * @param cell   单元格对象
     * @param rowNum 第几行
     * @param index  该行第几个
     * @param book   主要用于关闭流
     * @param isKey  是否为键：true-是，false-不是。 如果解析Json键，值为空时报错；如果不是Json键，值为空不报错
     */
    public static String getValue(Cell cell, int rowNum, int index, Workbook book, boolean isKey) throws IOException {

        // 空白或空
        if (cell == null || cell.getCellTypeEnum() == CellType.BLANK) {
            if (isKey) {
                book.close();
                throw new NullPointerException(String.format("the key on row %s index %s is null ", ++rowNum, ++index));
            } else {
                return "";
            }
        }

        // 0. 数字 类型
        if (cell.getCellTypeEnum() == CellType.NUMERIC) {
            if (HSSFDateUtil.isCellDateFormatted(cell)) {
                Date date = cell.getDateCellValue();
                DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
                return df.format(date);
            }
            String val = cell.getNumericCellValue() + "";
            val = val.toUpperCase();
            if (val.contains("E")) {
                val = val.split("E")[0].replace(".", "");
            }
            return val;
        }

        // 1. String类型
        if (cell.getCellTypeEnum() == CellType.STRING) {
            String val = cell.getStringCellValue();
            if (val == null || val.trim().isEmpty()) {
                if (book != null) {
                    book.close();
                }
                return "";
            }
            return val.trim();
        }

        // 2. 公式 CELL_TYPE_FORMULA
        if (cell.getCellTypeEnum() == CellType.FORMULA) {
            return cell.getStringCellValue();
        }

        // 4. 布尔值 CELL_TYPE_BOOLEAN
        if (cell.getCellTypeEnum() == CellType.BOOLEAN) {
            return cell.getBooleanCellValue() + "";
        }

        // 5.	错误 CELL_TYPE_ERROR
        return "";
    }
}

public static void main(String[] args) throws IOException, InvalidFormatException {
   //导出Excel
   var json = "[{\"name\":\"张三\",\"age\":\"18\"},{\"name\":\"李四\",\"age\":\"19\"}]";
   System.out.println(jsonToExcel(json, "D:\\test.xlsx"));

   //读取Excel
   System.out.println(excelToJsonArray("D:\\test.xlsx"));
}