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背景：在旧系统的基础上，导出一些工单信息时，现需要新添加处理人的签名或者签章，这就涉及图片的上传、下载、写入等几个操作。

1、EasyExcel工具类

（1）支持下拉框的导出。

import com.alibaba.excel.EasyExcelFactory;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.write.builder.ExcelWriterBuilder;
import com.alibaba.excel.write.handler.SheetWriteHandler;
import com.alibaba.excel.write.handler.WriteHandler;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
import com..common.handler.DropDownHandler;
import com..modules.device.convert.ImageCellWriteHandler;
import com..modules.device.domain.vo.DeviceAndTypeVO;
import lombok.extern.slf4j.Slf4j;
import lombok.var;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFClientAnchor;import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.util.List;@Slf4j
public class ExcelExportUtil {private static final String CHARACTER = "UTF-8";private static final String CONTENT_TYPE = "application/vnd.ms-excel;charset=utf-8";private static final String CONTENT_DISPOSITION = "Content-Disposition";private static final String CACHE_CONTROL = "Cache-Control";private static final String NO_STORE = "no-store";private static final String MAX_AGE = "max-age=0";private static final String PASSWORD = "excel_unlock";private static final Integer colSplit = 0;private static final Integer rowSplit = 1;private static final Integer leftmostColumn = 0;private static final Integer topRow = 1; 
/*** 通用导出 Excel 方法（支持下拉框和每行图片插入）** @param response         HttpServletResponse* @param data             导出数据，数据行顺序与 Excel 中顺序一致（表头在第0行，第一条数据为第1行）* @param clazz            数据模型 Class* @param fileName         导出文件名（不包含后缀）* @param dropDownHandler  下拉框处理器（可选，可传 null）* @param imagesList       每条记录对应的图片数据列表，List中每个元素为 byte[2] 数组，*                         第0位为签名图片， 第1位为签章图片（可有可无）* @param signCol          签名图片插入列（0-based）* @param signatureCol     签章图片插入列（0-based）* @throws IOException     I/O 异常时抛出*/public static void exportExcel(HttpServletResponse response, List<?> data, Class<?> clazz, String fileName,Object dropDownHandler, List<byte[][]> imagesList,int signCol, int signatureCol) throws IOException {String fullFileName = fileName + ".xlsx";String encodedFileName = URLEncoder.encode(fullFileName, StandardCharsets.UTF_8.toString());response.setCharacterEncoding(CHARACTER);response.setContentType(CONTENT_TYPE);response.setHeader(CONTENT_DISPOSITION, "attachment; filename=" + encodedFileName);response.setHeader(CACHE_CONTROL, NO_STORE);response.addHeader(CACHE_CONTROL, MAX_AGE);ServletOutputStream out = null;ExcelWriter excelWriter = null;try {out = response.getOutputStream();ExcelWriterBuilder writerBuilder = EasyExcelFactory.write(out, clazz);// 注册下拉框处理器（需确保 dropDownHandler 是 WriteHandler 类型）if (dropDownHandler != null && dropDownHandler instanceof WriteHandler) {writerBuilder.registerWriteHandler((WriteHandler) dropDownHandler);}excelWriter = writerBuilder.build();WriteSheet writeSheet = EasyExcelFactory.writerSheet(fileName).build();excelWriter.write(data, writeSheet);// 获取 Workbook 和 SheetWorkbook workbook = excelWriter.writeContext().writeWorkbookHolder().getWorkbook();Sheet sheet = workbook.getSheetAt(0);// 遍历数据行插入图片（从第1行开始）if (imagesList != null && !imagesList.isEmpty()) {for (int i = 0; i < data.size(); i++) {int targetRowIndex = i + 1; // 数据行从第1行开始if (i < imagesList.size()) {byte[][] images = imagesList.get(i);if (images != null) {insertImages(sheet, workbook, targetRowIndex, images, signCol, signatureCol);}}}}// 必须显式调用 finish 确保数据写入流excelWriter.finish();out.flush();} catch (Exception e) {throw new IOException("导出 Excel 失败: " + e.getMessage(), e);} finally {// 手动关闭资源（注意顺序：先关闭 excelWriter，再关闭流）if (excelWriter != null) {excelWriter.finish(); // finish() 包含关闭操作}if (out != null) {try {out.close();} catch (IOException e) {log.error("关闭输出流异常: ", e);}}}}/*** 通用的图片插入方法，在指定的 Excel 行中插入签名和签章图片** @param sheet         目标 Sheet* @param workbook      Excel Workbook* @param targetRow     目标行索引（0-based；表头为0，第一条数据为1）* @param images        byte[2] 数组，其中 images[0] 为签名图片，images[1] 为签章图片* @param signCol       签名图片插入列（0-based）* @param signatureCol  签章图片插入列（0-based）*/private static void insertImages(Sheet sheet, Workbook workbook, int targetRow, byte[][] images,int signCol, int signatureCol) {if (sheet == null || workbook == null) {return;}Row row = sheet.getRow(targetRow);if (row == null) {row = sheet.createRow(targetRow);}Drawing<?> drawing = sheet.createDrawingPatriarch();if (images[0] != null && images[0].length > 0) {int pictureIdx = workbook.addPicture(images[0], Workbook.PICTURE_TYPE_PNG);ClientAnchor anchor = new XSSFClientAnchor(0, 0, 1023, 255, signCol, targetRow, signCol + 1, targetRow + 1);drawing.createPicture(anchor, pictureIdx);}if (images[1] != null && images[1].length > 0) {int pictureIdx = workbook.addPicture(images[1], Workbook.PICTURE_TYPE_PNG);ClientAnchor anchor = new XSSFClientAnchor(0, 0, 1023, 255, signatureCol, targetRow, signatureCol + 1, targetRow + 1);drawing.createPicture(anchor, pictureIdx);}}
}

（2）无下拉框实现

/*** 配合insertImages(Sheet sheet, Workbook workbook, byte[] signImage, byte[] signatureImage,*                                      int targetRowIndex, int signCol, int signatureCol) 方法使用* @param response* @param data* @param clazz* @param fileName* @param signImage* @param signatureImage* @param targetRow* @param signCol* @param signatureCol* @throws IOException*/public static void exportExcel(HttpServletResponse response, List<?> data, Class<?> clazz, String fileName,byte[] signImage, byte[] signatureImage,int targetRow, int signCol, int signatureCol) throws IOException {String encodedFileName = URLEncoder.encode(fileName + ".xlsx", "UTF-8");response.setCharacterEncoding("UTF-8");response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");response.setHeader("Content-Disposition", "attachment; filename=" + encodedFileName);response.setHeader("Cache-Control", "no-store");response.addHeader("Cache-Control", "max-age=0");ExcelWriter excelWriter = null;ServletOutputStream out = null;try {out = response.getOutputStream();excelWriter = EasyExcelFactory.write(out, clazz).build();WriteSheet writeSheet = EasyExcelFactory.writerSheet(fileName).build();excelWriter.write(data, writeSheet);// 获取 Workbook 和 SheetWorkbook workbook = excelWriter.writeContext().writeWorkbookHolder().getWorkbook();Sheet sheet = workbook.getSheetAt(0);// 插入图片insertImages(sheet, workbook, signImage, signatureImage, targetRow, signCol, signatureCol);// 必须显式调用 finish 确保写入完成excelWriter.finish();out.flush();} finally {// 手动关闭资源（EasyExcel 3.x 中 finish() 已包含关闭操作）if (excelWriter != null) {excelWriter.finish(); // 确保资源释放}if (out != null) {out.close();}}}/*** 通用inserImages方法，和没有的DropDownHandler dropDownHandler参数的exportExcel方法一起配合使用* @param sheet* @param workbook* @param signImage* @param signatureImage* @param targetRowIndex* @param signCol* @param signatureCol*/private static void insertImages(Sheet sheet, Workbook workbook, byte[] signImage, byte[] signatureImage,int targetRowIndex, int signCol, int signatureCol) {if (sheet == null || workbook == null) {log.warn("插入图片失败: sheet 或 workbook 为空");return;}// 确保目标行存在Row row = sheet.getRow(targetRowIndex);if (row == null) {row = sheet.createRow(targetRowIndex);}Drawing<?> drawing = sheet.createDrawingPatriarch();// 插入签名图片if (signImage != null && signImage.length > 0) {int pictureIdx = workbook.addPicture(signImage, Workbook.PICTURE_TYPE_PNG);ClientAnchor anchor = new XSSFClientAnchor(0, 0, 1023, 255, signCol, targetRowIndex, signCol + 1, targetRowIndex + 1);drawing.createPicture(anchor, pictureIdx);}// 插入签章图片if (signatureImage != null && signatureImage.length > 0) {int pictureIdx = workbook.addPicture(signatureImage, Workbook.PICTURE_TYPE_PNG);ClientAnchor anchor = new XSSFClientAnchor(0, 0, 1023, 255, signatureCol, targetRowIndex, signatureCol + 1, targetRowIndex + 1);drawing.createPicture(anchor, pictureIdx);}}

2、实体类和自定义转换类

//使用自定义转换器，写入空内容，但表头显示“签名”@ExcelProperty(value = "处理人签名", converter = ImageHeaderConverter.class, index = 15)private byte[] signImage;// 使用自定义转换器，写入空内容，但表头显示“签名”@ExcelProperty(value = "处理人签章", converter = ImageHeaderConverter.class, index = 16)private byte[] signatureImage;/*** 自定义Converter*/
public class ImageHeaderConverter implements Converter<byte[]> {@Overridepublic Class supportJavaTypeKey() {return byte[].class;}@Overridepublic WriteCellData<?> convertToExcelData(byte[] value, ExcelContentProperty contentProperty, GlobalConfiguration globalConfiguration) {// 返回空数据，防止自动转换报错，但表头信息仍会根据@ExcelProperty的value显示return new WriteCellData<>("");}@Overridepublic CellDataTypeEnum supportExcelTypeKey() {return null;}public byte[] convertToJavaData(CellData cellData, ExcelContentProperty contentProperty, GlobalConfiguration globalConfiguration) {return new byte[0];}
}

3、根据图片路径下载图片工具类

public class ImagesUtils {public static byte[] downloadImage(String imageUrl) {if (imageUrl == null || imageUrl.trim().isEmpty()) {log.warn("下载图片失败: imageUrl 为空");return null;}HttpURLConnection connection = null;try {URL url = new URL(imageUrl);connection = (HttpURLConnection) url.openConnection();connection.setRequestMethod("GET");connection.setConnectTimeout(10000);  // 增加超时时间到10秒connection.setReadTimeout(10000);connection.setInstanceFollowRedirects(true); // 允许自动重定向// 检查 HTTP 响应码int statusCode = connection.getResponseCode();if (statusCode != HttpURLConnection.HTTP_OK) {log.warn("下载图片失败: {}，HTTP状态码: {}，响应消息: {}",imageUrl, statusCode, connection.getResponseMessage());return null;}try (InputStream inputStream = connection.getInputStream();ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {byte[] buffer = new byte[4096];  // 增大缓冲区提升读取效率int bytesRead;while ((bytesRead = inputStream.read(buffer)) != -1) {outputStream.write(buffer, 0, bytesRead);}return outputStream.toByteArray();}} catch (Exception e) {log.warn("下载图片失败: {}，错误类型: {}，详细信息: {}",imageUrl, e.getClass().getSimpleName(), e.getMessage(), e); // 输出完整异常return null;} finally {if (connection != null) {connection.disconnect(); // 显式断开连接}}}
}

4、业务逻辑实现

// 1. 查询 Channel_SIGN_SIGNATURE 表，获取所有处理记录List<ChannelSignSignature> processList = channelSignSignatureMapper.selectList(new LambdaQueryWrapper<ChannelSignSignature>().in(ChannelSignSignature::getDisposeChannelId, ids));if (CollectionUtils.isEmpty(processList)) {return ReposeResult.failed(ResultCode.CHANNEL_EXPORT_NULL);}//根据前端传入的ids顺序排序处理记录Map<Long, ChannelSignSignature> processMap = processList.stream().collect(Collectors.toMap(ChannelSignSignature::getDisposeChannelId, Function.identity()));List<ChannelSignSignature> sortedProcessList =  new ArrayList<>();for (Long id :ids) {if (!processMap.containsKey(id)) {return ReposeResult.failed("部分导出ID未保存处理记录，请先处理记录再导出");}sortedProcessList.add(processMap.get(id));}// 2. 获取所有处理人姓名（保持原顺序）List<String> userNames = sortedProcessList.stream().map(ChannelSignSignature::getChannelRecordName).collect(Collectors.toList());// 3. 批量查询用户信息（userId 映射表）Map<String, Long> userIdMap;if (CollectionUtils.isEmpty(userNames)) {userIdMap = new HashMap<>();} else {List<User> users = userMapper.selectList(new LambdaQueryWrapper<User>().in(User::getUsername, userNames));userIdMap = users.stream().collect(Collectors.toMap(User::getUsername, User::getId, (u1, u2) -> u1));}// 4. 查询用户签名 & 签章Map<Long, List<String>> signMap = new HashMap<>();Map<Long, List<String>> signatureMap = new HashMap<>();if (!userIdMap.isEmpty()) {// 4.1 批量查询用户签名（userId -> 签名列表）List<UserSign> userSigns = userSignMapper.selectList(new LambdaQueryWrapper<UserSign>().in(UserSign::getUserId, userIdMap.values()));signMap = userSigns.stream().collect(Collectors.groupingBy(UserSign::getUserId,LinkedHashMap::new,Collectors.mapping(UserSign::getContent, Collectors.toList())));// 4.2 批量查询用户签章（userId -> 签章列表）List<UserSignature> userSignatures = userSignatureMapper.selectList(new LambdaQueryWrapper<UserSignature>().in(UserSignature::getUserId, userIdMap.values()));signatureMap = userSignatures.stream().collect(Collectors.groupingBy(UserSignature::getUserId,LinkedHashMap::new,Collectors.mapping(UserSignature::getContent, Collectors.toList())));}Integer grading = UserUtils.getUser().getGrading();HashMap<Integer, String[]> dropDownMap = new HashMap<>();String[] results = Arrays.stream(ChannelResultEnum.values()).map(ChannelResultEnum::getDesc).toArray(String[]::new);dropDownMap.put(13, results);List<ChannelVO> channels = channelMapper.selectJoinList(ChannelVO.class, new MPJLambdaWrapper<>(DataChannel.class).selectAll(DataChannel.class).select(Dept::getDeptName).selectAs(Period::getDescription, "period").select(BenchInfo::getBench).selectCollection(MachineInfo.class, ChannelVO::getMachineInfos).leftJoin(ChannelModel.class, ChannelModel::getChannelId, DataChannel::getId).leftJoin(MachineInfo.class, MachineInfo::getId, ChannelModel::getModelId).leftJoin(Dept.class, Dept::getId, DataChannel::getDeptId).leftJoin(Period.class, Period::getId, DataChannel::getPeriodId).leftJoin(BenchInfo.class, BenchInfo::getId, DataChannel::getBenchId).ge(ObjectUtils.isNotEmpty(grading), DataChannel::getGrading, grading).in(DataChannel::getId, ids));channels.forEach(channelVO -> {List<String> models = channelVO.getMachineInfos().stream().map(MachineInfo::getModel).collect(Collectors.toList());channelVO.setModel(String.join(",", models));});//根据前端传入的ids顺序排序channelVOMap<Long, ChannelVO> channelVoMap= channels.stream().collect(Collectors.toMap(ChannelVO::getId, Function.identity()));List<ChannelVO> sortedChannelVOs = new ArrayList<>();for (Long id:ids) {if (!channelVoMap.containsKey(id)) {return ReposeResult.failed("部分导出ID未保存检查记录，请先保存处理记录再导出");}sortedChannelVOs.add(channelVoMap.get(id));}List<ExportChannelDTO> exportChannelDTOS = CopyUtils.copyList(sortedChannelVOs, ExportChannelDTO.class);// 5. 按 `userNames` 生成 `signUrls` 和 `signatureUrls`（保证顺序）List<String> signUrls = new ArrayList<>();List<String> signatureUrls = new ArrayList<>();for (String userName : userNames) {Long userId = userIdMap.get(userName);if (userId != null) {List<String> signs = signMap.getOrDefault(userId, Collections.emptyList());List<String> signatures = signatureMap.getOrDefault(userId, Collections.emptyList());// 如果有签名，添加签名；如果有签章，添加签章；如果都有，则都添加if (!signs.isEmpty()) {signUrls.addAll(signs);} else {signUrls.add(null);}if (!signatures.isEmpty()) {signatureUrls.addAll(signatures);} else {signatureUrls.add(null);}} else {// 处理人无签名/签章，则填充 nullsignUrls.add(null);signatureUrls.add(null);}}// 7. 赋值到 DTOfor (int i = 0; i <  exportChannelDTOS.size(); i++) {ExportChannelDTO dto =  exportChannelDTOS.get(i);// 取签名图片if (signUrls.get(i) != null) {dto.setSignImage(downloadImage(BASE_IMAGE_URL + signUrls.get(i)));} else {dto.setSignImage(null);}// 取签章图片if (signatureUrls.get(i) != null) {dto.setSignatureImage(downloadImage(BASE_IMAGE_URL + signatureUrls.get(i)));} else {dto.setSignatureImage(null);}}// 8. 构造图片数据列表，与 checkDTOS 顺序一致List<byte[][]> imagesList = exportChannelDTOS.stream().map(dto -> new byte[][]{dto.getSignImage() != null ? dto.getSignImage() : new byte[0],dto.getSignatureImage() != null ? dto.getSignatureImage() : new byte[0]}).collect(Collectors.toList());ExcelExportUtil.exportExcel(response,exportChannelDTOS,ExportChannelDTO.class,ConstantUtil.DATA_CHANNEL,new DropDownHandler(dropDownMap),imagesList,15,16);log.info("---导出数据通道信息完成---");         

代码不可直接使用，只是自己记录一下，方便下次使用，你完全可以使用AI来帮你写这些部分。