一、单文件的上传功能

         这里是一个demo的流程图，下面按照这个流程图做了一个简单的实现，有部分判断没有加上，实际操作中，可以根据自己的需求进行增加或者修改。并且此处还是在接受文件传入后将文件进行了下载，保存到本地的操作，这个要按照具体情况具体分析，看需求是否要把上传进来的文件进行数据备份，或者直接以流的形式读进来，然后进行解析等逻辑操作后，最后关闭释放流也可以，没有说一定要上传完文件就要下载下来。

controller层 （接受前端传入的文件参数，为单个文件）

@RequestMapping( "/salary/server/excelxz")
public class SalaryExcelOperatController {@Autowiredprivate SalaryExcelOperatService salaryexcelOperatService;@PostMapping("/upload")public RespondDto uploadFile(@RequestParam("file") MultipartFile multipartFile) {SalaryExcelOperatVo excelOperatVo =salaryexcelOperatService.uploadExcel(multipartFile);return new RespondDto(excelOperatVo);
}

service层 （这里使用了easyExcel的方式实现了，一个Excel中包含多个sheet的读取操作，但本质和POI的思想是差不多的 ）

@Service
@Slf4j
public class SalaryExcelOperatServiceImpl implements SalaryExcelOperatService {@Resourceprivate SalaryExcelOperatMapper salaryexcelOperatMapper;@Resourceprivate LoginMapper loginMapper;/*** 上传 Excel 文件* 1、接收文件，保存到本地；* 2、获取本地文件路径调用 readExcel 读成ArrayList；*/@Overridepublic SalaryExcelOperatVo uploadExcel(MultipartFile multipartFile) {if (multipartFile==null) {log.error("文件不能为空");throw new RuntimeException("上传Excel文件内容为空，请重新上传！");}String fileName = multipartFile.getOriginalFilename();//判断文件是否是excel文件assert fileName != null;if (!fileName.endsWith("xls") && !fileName.endsWith("xlsx")) {log.error(fileName + "不是Excel文件!");throw new RuntimeException(fileName + "不是Excel文件!");}//保存文件到本地File dir1 = new File("/roots/uploadFile/xzExcel");if (!dir1.exists()) {dir1.mkdirs();}//统一日期格式LocalDateTime current = LocalDateTime.now();DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");String formatted = current.format(formatter);//加上三位随机数Random random = new Random();int end3 = random.nextInt(999);File file1 = new File(dir1.getAbsolutePath() + File.separator + formatted + "-" + end3 + "-" + multipartFile.getOriginalFilename());try {multipartFile.transferTo(file1);} catch (IOException e) {e.printStackTrace();}//创建返回对象SalaryExcelOperatVo的实例化对象： resultSalaryExcelOperatVo result = new SalaryExcelOperatVo();//获取excel文件sheet1 的内容ArrayList<InSalary> inSalaries1 = readExcel1(file1.getAbsolutePath());ArrayList<SalaryStaffPerOneListVo> vo1 = new ArrayList<>();SalaryStaffPerOneListVo oneListVo ;for(InSalary inSalary1:inSalaries1){oneListVo = new SalaryStaffPerOneListVo();BeanUtils.copyProperties(inSalary1,oneListVo);vo1.add(oneListVo);
}result.setSheetOne(vo1);//获取excel文件sheet2 的内容ArrayList<InSalary> inSalaries2 = readExcel2(file1.getAbsolutePath());ArrayList<SalaryStaffPerTwoListVo> vo2 = new ArrayList<>();SalaryStaffPerTwoListVo twoListVo ;for(InSalary inSalary2:inSalaries2){twoListVo = new SalaryStaffPerTwoListVo();BeanUtils.copyProperties(inSalary2,twoListVo);vo2.add(twoListVo);}result.setSheetTwo(vo2);return result;}/*** 抽离出   【读取excel文件，包含多个sheet内容的方法】* 1、工作区间 -> Sheet -> cell；* 2、每行为一个 inSalary 对象， 把所有对象用 ArrayList保存;* 从第二行开始读取，第一行表头忽略；** @param filePath ;本地保存后的文件地址* @return ArrayList<InSalary>*/private ArrayList<InSalary> readExcel1(String filePath) {ArrayList<InSalary> inSalary = new ArrayList<>();// 该监听将excel文件一行一行读入内存（必须有）SalaryExcelListener listener = new SalaryExcelListener();ExcelReader excelReader = EasyExcel.read(filePath, InSalary.class,listener).build();ReadSheet readSheet = EasyExcel.readSheet(0).build();excelReader.read(readSheet);// 这里千万别忘记关闭，读的时候会创建临时文件，到时磁盘会崩的excelReader.finish();// readList 文件中的数据，不包括表头inSalary .addAll(listener.getList());return inSalary;}private ArrayList<InSalary> readExcel2(String filePath) {ArrayList<InSalary> inSalary = new ArrayList<>();// 该监听将excel文件一行一行读入内存（必须有）SalaryExcelListener listener = new SalaryExcelListener();ExcelReader excelReader = EasyExcel.read(filePath, InSalary.class,listener).build();ReadSheet readSheet = EasyExcel.readSheet(1).build();excelReader.read(readSheet);// 这里千万别忘记关闭，读的时候会创建临时文件，到时磁盘会崩的excelReader.finish();// readList 文件中的数据，不包括表头inSalary .addAll(listener.getList());return inSalary;}

二、多文件的上传功能 

controller层 （接受前端传入的文件参数，为多个文件）

    @PostMapping(value = "/uploadExcels")public RespondDto upLoadFiles(@NonNull @RequestParam("multipartFiles") MultipartFile[] multipartFiles,@NonNull @RequestParam("types") String[] types){return fileService.upLoadFiles(multipartFiles,types);}

        这里需要说明一点，controller层的实现方式有很多中，没有说当要传入多个文件的时候一定要去使用数组的形式进行 ，在这样写之前我也尝试了其他的两种写法：

    @PostMapping("/upload")public String upload(@RequestParam("files") List<MultipartFile> files, HttpServletRequest request) {for (MultipartFile file : files) {String type1 = request.getParameter("type1");String type2 = request.getParameter("type2");// 根据type1和type2的值，对上传的文件进行特定处理// ...}return "upload success";}

    @PostMapping(value = "/uploadExcels")public RespondDto upLoadFiles(@NonNull @RequestParam("multipartFiles") List<MultipartFile> multipartFiles,@NonNull @RequestParam("types") List<MultipartFile> types){return fileService.upLoadFiles(multipartFiles,types);}

 不过实际中具体怎么写，还是看跟前端的沟通以及最终的接口文档来进行操作。

service层 （这里实现了将多个Excel一次性上传后，后端将这些Excel文件进行接收并保存到本地，并且将每个文件的名字以文件类型的名字进行重命名）

@Override
public RespondDto upLoadFiles(MultipartFile[] files, String[] types) {long MAX_SIZE = 1024 * 1024 * 10;// 文件大小限制为10MBLocalDateTime current = LocalDateTime.now();DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");String formattedDate = current.format(formatter);//加上三位随机数Random random = new Random();int randomNum = random.nextInt(999);File dir = new File("/manage/uploadFile/"+formattedDate+randomNum);if (!dir.exists()) {dir.mkdirs();}for (int i = 0; i < files.length; i++) {MultipartFile file = files[i];String type = types[i];// 判断文件或类型不能为空if (file.isEmpty() || StringUtils.isEmpty(type)) {return new RespondDto<>("文件或类型不能为空，请重新上传！");}// 判断文件大小是否合适if (file.getSize() > MAX_SIZE) {return new RespondDto<>("文件过大，上传失败！");}String originalFileName = file.getOriginalFilename();// 获取文件名和扩展名String fileExt = originalFileName.substring(originalFileName.lastIndexOf("."));String fileName = type ;File fileToSave = new File(dir.getAbsolutePath() + File.separator + fileName +fileExt);try {//文件写入 transferTofile.transferTo(fileToSave);String fileUrl =  fileToSave.getAbsolutePath();fileUrls.add(fileUrl);} catch (IOException e) {e.printStackTrace();return new RespondDto<>("文件上传失败！");}log.info("【上传文件】"+fileName+" 已保存到本地：{}", originalFileName, fileToSave.getAbsolutePath());}return new RespondDto<>(fileUrls);
}

 在postman中进行测试，结果为：

三、文件导出功能

①、导出带有图片的Excel

@RestController
@RequestMapping( "/salary/server/excel")
@Slf4j
public class ExportjxExcelsController {@Value("#{'${headerTitles}'.split(',')}")private String[] headerTitles;@AutowiredStaffMapper staffMapper;@GetMapping("/jxdownload")public void export( HttpServletResponse response ,Integer year,Integer month) throws IOException {//设置响应response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");response.setCharacterEncoding("utf-8");// 设置要导出的文件名, 这里URLEncoder.encode可以防止中文乱码 当然和easyexcel没有关系String fileName= URLEncoder.encode("XXXX数据","UTF-8").replaceAll("\\+","%20");response.setHeader("Content-disposition","attachment;filename*=utf-8''"+fileName+".xlsx");// 从数据库ensure表中读取数据List<Salary> userList =  staffMapper.getAllStaff(year, month);log.info("数据为：\n{}", userList);List<Map<String, String>> salaryList = new ArrayList<>();for (Salary salary : userList) {Map<String, String> salaryMap = new LinkedHashMap<>();salaryMap.put("userName", salary.getUserName());salaryMap.put("firstDepart", salary.getFirstDepart());salaryMap.put("secondDepart", salary.getSecondDepart());salaryMap.put("post", salary.getPost());;salaryMap.put("careDeduct", salary.getCareDeduct());salaryMap.put("personalTax", salary.getPersonalTax());salaryMap.put("actualPay", salary.getActualPay());salaryMap.put("socialUnitpart", salary.getSocialUnitpart());salaryMap.put("amonthlySalary", salary.getAmonthlySalary());salaryMap.put("achieveBonus", salary.getAchieveBonus());salaryMap.put("status", Integer.valueOf(103).equals(salary.getStatus()) ? "已确认" : "未确认");salaryMap.put("evidence", salary.getEvidence());salaryList.add(salaryMap);}//取出map键值对中的value值List<String> valueList = new ArrayList<>();for (Map<String, String> salaryMap : salaryList) {Set<Map.Entry<String, String>> entrySet = salaryMap.entrySet();for (Map.Entry<String, String> entry : entrySet) {valueList.add(entry.getValue());}}//  保存文件到本地File dir = new File("/roots/uploadFile/exportxzExcel");if (!dir.exists()) {dir.mkdirs();}//加上三位随机数Random random = new Random();int end3 = random.nextInt(999);String path = dir.getAbsolutePath() + File.separator + end3  +fileName + ".xlsx";log.info("path文件路径为:{}",path);SSExcel07Workbook ssExcel07Workbook = (new SSExcel07Workbook()).openOrCreate(path);SSExcel07Sheet sheet = ssExcel07Workbook.createSheet("sheet1");// 创建Excel表格头部（有43个字符串）//将表头数据写入到单元格中int col = 0;for (String title : headerTitles) {SSExcel07Cell cell = sheet.getCellOrCreate(0, col);cell.setCellValue(title);col++;}// 将数据写入数据到Excel文件中// 循环遍历 salaryList 中的值，写入到 Excel 文件中int row = 1;int col1 = 0;for (String strval : valueList) {// 判断当前列是否超过了最大列数，如果超过了，则重置列数，同时行数加1if (col1 >= headerTitles.length) {col1 = 0;row++;}if(col1==42){//在最后一列插入图片SSExcel07Cell imgCell = sheet.getCellOrCreate(row, 42);imgCell.insertImg(strval, 0, 0);}else {// 获取当前单元格SSExcel07Cell cell = sheet.getCellOrCreate(row, col1);// 将当前单元格的值设置为当前的 strval 值cell.setCellValue(strval);}// 将列数加1col1++;}ssExcel07Workbook.getXSSFWorkBook().write(response.getOutputStream());log.info("文件导出完成！");}
}

②、将之前上传的多个Excel按照一定的映射规则生成一个Excel文件（映射规则可以写在配置文件中，也可以写到数据库中，主要看映射关系的改动频率是多少）

@Overridepublic RespondDto writeExcel(String[] fileUrls) throws IOException {long startTime=System.currentTimeMillis (); //获取开始时间String fileUrl = null;for (String url : fileUrls) {fileUrl = url;}// 读取配置文件,configFile 是指配置文件的路径和名称。Properties config = new Properties();ClassPathResource configInputStream = new ClassPathResource("config.properties");config.load(configInputStream.getInputStream());//  保存文件到本地File excelDir = new File("/manage/uploadFile");if (!excelDir.exists()) {excelDir.mkdirs();}LocalDateTime current = LocalDateTime.now();DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");String formattedDate = current.format(formatter);//加上三位随机数Random random = new Random();int randomNum = random.nextInt(999);// 获取文件名String destExcelFileName = formattedDate + "-" + randomNum + "-" ;FileInputStream destinationFileInputStream = new FileInputStream(excelDir + destExcelFileName);Workbook destinationWorkbook = new XSSFWorkbook(destinationFileInputStream);Map<String, Workbook> workbookMap = new HashMap<>();for (String key : config.stringPropertyNames()) {String[] destArray = org.springframework.util.StringUtils.tokenizeToStringArray(key, ".");String[] srcArray = org.springframework.util.StringUtils.tokenizeToStringArray(config.getProperty(key), ".");System.out.println(srcArray[0]);if (destArray == null || srcArray == null || srcArray.length != 3 || destArray.length != 2) {continue;}Workbook sourceWorkbook = null;if (workbookMap.containsKey(srcArray[0])) {sourceWorkbook = workbookMap.get(srcArray[0]);} else {// 读取源文件//FileInputStream sourceFileInputStream = new FileInputStream(excelDir + srcArray[0] + ".xlsx");FileInputStream sourceFileInputStream = new FileInputStream(fileUrl);sourceWorkbook = new XSSFWorkbook(sourceFileInputStream);workbookMap.put(srcArray[0], sourceWorkbook);}Sheet sourceSheet = sourceWorkbook.getSheet(srcArray[1]);CellReference sourceCellRef = new CellReference(srcArray[2]);Row sourceRow = sourceSheet.getRow(sourceCellRef.getRow());Cell sourceCell = null;if (sourceRow != null) {sourceCell = sourceRow.getCell(sourceCellRef.getCol());}Sheet destinationSheet = destinationWorkbook.getSheet(destArray[0]);CellReference destCellRef = new CellReference(destArray[1]);Row destRow = destinationSheet.getRow(destCellRef.getRow());if (destRow == null) {destRow = destinationSheet.createRow(destCellRef.getRow());}Cell destCell = destRow.createCell(destCellRef.getCol());// 执行 copy 方法copyCellValue(sourceCell, destCell);}// 保存目标文件FileOutputStream outputStream = new FileOutputStream(excelDir + destExcelFileName);destinationWorkbook.write(outputStream);// 关闭资源outputStream.close();destinationFileInputStream.close();destinationWorkbook.close();workbookMap.values().forEach(k -> {try {k.close();} catch (IOException e) {}});long endTime=System.currentTimeMillis (); //获取结束时间System.out.println ( "程序运行时间： " + (endTime-startTime)/1000 + "s" );return new RespondDto<>("Excel导出成功!");}/*** copyCellValue() 方法用于将源单元格的值复制到目标单元格中。* @param sourceCell 是源单元格对象* @param destCell 是目标单元格对象*/public static void copyCellValue(Cell sourceCell, Cell destCell) {// 如果 sourceCell 和 destCell 中任意一个为 null，则不进行操作，方法直接返回。if (sourceCell == null || destCell == null) {return;}// 首先，将源单元格的单元格样式克隆到目标单元格上，然后再将源单元格的值赋给目标单元格。CellStyle sourceStyle = sourceCell.getCellStyle();CellStyle destinationStyle = destCell.getSheet().getWorkbook().createCellStyle();destinationStyle.cloneStyleFrom(sourceStyle);destCell.setCellStyle(destinationStyle);// 如果源单元格的数据类型为字符串类型，则复制字符串值；如果为布尔类型，则复制布尔值；如果为公式类型，则复制公式字符串；如果为数字类型，则复制数字值。if (sourceCell.getCellTypeEnum().equals(CellType.STRING)) {destCell.setCellValue(sourceCell.getStringCellValue());} else if (sourceCell.getCellTypeEnum().equals(CellType.BOOLEAN)) {destCell.setCellValue(sourceCell.getBooleanCellValue());} else if (sourceCell.getCellTypeEnum().equals(CellType.FORMULA)) {if (DateUtil.isCellDateFormatted(sourceCell)) {destCell.setCellValue(sourceCell.getDateCellValue());} else {destCell.setCellValue(sourceCell.getNumericCellValue());}} else if (sourceCell.getCellTypeEnum().equals(CellType.NUMERIC)) {if (DateUtil.isCellDateFormatted(sourceCell)) {destCell.setCellValue(sourceCell.getDateCellValue());} else {destCell.setCellValue(sourceCell.getNumericCellValue());}// 如果源单元格是空的，则在目标单元格中写入一个空串("")。} else if (sourceCell.getCellTypeEnum().equals(CellType.BLANK)) {destCell.setCellValue("");}}

四、注意事项

①、在使用poi的时候一定要注意，选对依赖的版本

不能想用什么依赖的版本就使用什么依赖版本，有些方法，不同的版本之间相差还是比较大的，此处我使用的版本就是3.17的，如果你使用3.9版本的依赖，就不能运行成功。

        <!--xlsx(07)--><dependency><groupId>org.apache.poi</groupId><artifactId>poi-ooxml</artifactId><version>3.17</version></dependency>

②、当在上传多个文件的时候，出现 the request was rejected because its size (10821303) exceeds the configured maximum (10485760)的报错

        这是因为springboot默认配置 multipart.max-file-size大小是1M，max-request-size默认大小是10M  故可以在yml文件中添加：

spring:servlet:multipart:max-file-size: 100MBmax-request-size: 500MB