常用组件：
WorkbookFactory excel的文档对象
Sheet excel的表单
Row excel的行
Cell excel的格子单元
Font excel字体
样式：
CellStyle cell样式
实现步骤：
1.添加maven依赖
<!-- https://mvnrepository.com/artifact/org.apache.poi/poi -->
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>3.9</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml -->
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>3.9</version>
</dependency>
2.编写Controller
使用spring webflux文件下载就没有之前基于servlet容器的javax.servlet.http.HttpServletResponse了，取而代之的是org.springframework.http.server.reactive.ServerHttpResponse。
@GetMapping("/cars/download/{carId}")
public Mono<Void> downloadByWriteWith(ServerHttpResponse response, @PathVariable("carId") String carId) throws IOException {
return manager.downloadByWriteWith(response, carId);
}
3.编写Manager
public Mono<Void> downloadByWriteWith(ServerHttpResponse response, String carId)
throws IOException {
//spring webflux文件下载零拷贝（Zero-copy）
ZeroCopyHttpOutputMessage zeroCopyResponse = (ZeroCopyHttpOutputMessage) response;
//设置文件下载响应头
response.getHeaders().set(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=car.xlsx");
response.getHeaders().setContentType(MediaType.APPLICATION_OCTET_STREAM);
return getCar(carId).flatMap(x -> getCarModel(x)).flatMap(s -> {
try {
String relTarget = "/static/car.xlsx";
//声明输入流
InputStream inputStream = null;
//声明输出流
OutputStream fout = null;
//声明临时文件
File targetFile = null;
// getResourceAsStream不以’/'开头时默认是从此类所在的包下取资源，以’/'开头则是从ClassPath根下获取。其只是通过path构造一个绝对路径，最终还是由ClassLoader获取资源。
inputStream = this.getClass().getResourceAsStream(relTarget);
//创建临时文件(在默认临时文件目录中创建一个空文件，使用给定前缀和后缀生成其名称。)
targetFile = File.createTempFile("car", "");
//excel的文档对象（WorkbookFactory）
final Workbook wb = WorkbookFactory.create(inputStream);//WorkbookFactory可以读取xls格式或xlsx格式
//获取该工作区的第一个sheet
Sheet sheet = wb.getSheetAt(0);
//创建样式类
CellStyle cellStyle = wb.createCellStyle();
// 设置自动换行
cellStyle.setWrapText(true);
// 水平居中
cellStyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);
// 垂直居中
cellStyle.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
// 设置字体
Font font = wb.createFont();
font.setFontName("仿宋_GB2312");
// 设置字体粗细
font.setBoldweight(HSSFFont.DEFAULT_CHARSET);
// 设置字体大小
font.setFontHeightInPoints((short) 14);
// 选择需要用到的字体格式
cellStyle.setFont(font);
// 设置边框
cellStyle.setBorderBottom(HSSFCellStyle.BORDER_THIN); // 下边框
cellStyle.setBorderLeft(HSSFCellStyle.BORDER_THIN);// 左边框
cellStyle.setBorderTop(HSSFCellStyle.BORDER_THIN);// 上边框
cellStyle.setBorderRight(HSSFCellStyle.BORDER_THIN);// 右边框
String departmentName = Optional.ofNullable(s.getDepartmentName()).orElse("");
String applicantName = Optional.ofNullable(s.getApplicantName()).orElse("");
String drivingTime = Optional.ofNullable(s.getDrivingTime()).map(x -> DateUtils.dateFormat(DateUtils.sdfTimeDate, x)).orElse("");
String reason = Optional.ofNullable(s.getReason()).map(x -> x + "\n时间：" + drivingTime).orElse("");
String license = Optional.ofNullable(s.getLicense()).orElse("");
String destination = Optional.ofNullable(s.getDestination()).orElse("");
String people = Optional.ofNullable(s.getPeople()).map(String::valueOf).map(x -> x + "（人）").orElse("");
String days = Optional.ofNullable(s.getDays()).map(String::valueOf).map(x -> x + "（天）").orElse("");
String pickTime = Optional.ofNullable(s.getPickTime()).map(x -> DateUtils.dateFormat(DateUtils.sdfTimeDate, x)).orElse("");
String pickAutograph = Optional.ofNullable(s.getPickAutograph()).map(String::valueOf).orElse("");
String firstApprovalName = Optional.ofNullable(s.getFirstApproval()).map(x -> x.getApprovalName() + " <====> " + (x.getApprovalStatus() == 1 ? "未审" : x.getApprovalStatus() == 2 ? "同意" : "拒绝")).orElse("无");
String secondApprovalName = Optional.ofNullable(s.getSecondApproval()).map(x -> x.getApprovalName() + " <====> " + (x.getApprovalStatus() == 1 ? "未审" : x.getApprovalStatus() == 2 ? "同意" : "拒绝")).orElse("无");
String threeApprovalName = Optional.ofNullable(s.getThreeApproval()).map(x -> x.getApprovalName() + " <====> " + (x.getApprovalStatus() == 1 ? "未审" : x.getApprovalStatus() == 2 ? "同意" : "拒绝")).orElse("无");
String returnTime = Optional.ofNullable(s.getReturnTime()).map(x -> DateUtils.dateFormat(DateUtils.sdfTimeDate, x)).orElse("");
String returnKilometre = Optional.ofNullable(s.getReturnKilometre()).map(String::valueOf).orElse("");
String returnAutograph = Optional.ofNullable(s.getReturnAutograph()).map(String::valueOf).orElse("");
//设置该工作区的第一个sheet名字
wb.setSheetName(0, "名字");
Row row = sheet.getRow(1); //获取第二行（0开始）
//设置第二行（0开始）第二列（0开始）的值和样式
Cell cell = row.createCell(1);
cell.setCellValue(departmentName);
cell.setCellStyle(cellStyle);
//设置第二行（0开始）第四列（0开始）的值和样式
Cell cell1 = row.createCell(3);
cell1.setCellValue(applicantName);
cell1.setCellStyle(cellStyle);
Row row1 = sheet.getRow(2);
Cell cell2 = row1.createCell(1);
cell2.setCellValue(reason);
cell2.setCellStyle(cellStyle);
Row row2 = sheet.getRow(3);
Cell cell3 = row2.createCell(1);
cell3.setCellValue(license);
cell3.setCellStyle(cellStyle);
Cell cell4 = row2.createCell(3);
cell4.setCellValue(destination);
cell4.setCellStyle(cellStyle);
Row row3 = sheet.getRow(4);
Cell cell5 = row3.createCell(1);
cell5.setCellValue(people);
cell5.setCellStyle(cellStyle);
Cell cell6 = row3.createCell(3);
cell6.setCellValue(days);
cell6.setCellStyle(cellStyle);
Row row4 = sheet.getRow(5);
Cell cell7 = row4.createCell(1);
cell7.setCellValue(pickTime);
cell7.setCellStyle(cellStyle);
Cell cell8 = row4.createCell(3);
cell8.setCellValue(pickAutograph);
cell8.setCellStyle(cellStyle);
Row row5 = sheet.getRow(7);
Cell cell9 = row5.createCell(1);
cell9.setCellValue(firstApprovalName);
cell9.setCellStyle(cellStyle);
Row row6 = sheet.getRow(8);
Cell cell10 = row6.createCell(1);
cell10.setCellValue(secondApprovalName);
cell10.setCellStyle(cellStyle);
Row row7 = sheet.getRow(9);
Cell cell11 = row7.createCell(1);
cell11.setCellValue(threeApprovalName);
cell11.setCellStyle(cellStyle);
Row row8 = sheet.getRow(10);
Cell cell12 = row8.createCell(1);
cell12.setCellValue(returnTime);
cell12.setCellStyle(cellStyle);
Cell cell13 = row8.createCell(3);
cell13.setCellValue(returnKilometre);
cell13.setCellStyle(cellStyle);
Row row9 = sheet.getRow(11);
Cell cell14 = row9.createCell(1);
cell14.setCellValue(returnAutograph);
cell14.setCellStyle(cellStyle);
//将临时文件输出
fout = new BufferedOutputStream(new FileOutputStream(targetFile));
//写入工作区
wb.write(fout);
//这里将数据写入ServerHttpResponse
return zeroCopyResponse.writeWith(targetFile, 0, targetFile.length());
} catch (Exception e) {
throw new RuntimeException(e);
}
});
}
4.测试
测试的话可以使用swagger或者postman，甚至你前端技术足够ok的话也可以写个简单的页面进行测试，我是用的是postman进行的测试，下面就是我测试的结果了：
转载：https://blog.csdn.net/qq_42322632/article/details/115704260
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