java实现传入URL下载图片并压缩，导出到excel

记录工作中使用导出excel功能，导出的excel带图片。前端传过来的是图片的url，那么请求参数就是字符串类型的url，把这条url转成流，生成文件并输出，返回值类型就是文件类型file。下面是先把图片下载，再压缩的工具类：

/*** URL转成图片并压缩*/
public class UrlImageUtil {public static File downloadAndCompress(String url,float quality) throws IOException{/*** 下载图片*/File file = null;InputStream inputStream = null;FileOutputStream fos = null;try {file = File.createTempFile("image", "jpg");URL urlFile = new URL(url);inputStream = urlFile.openStream();fos = new FileOutputStream(file);byte[] bytes = new byte[8192];int bytesRead = 0;while ((bytesRead = inputStream.read(bytes,0,8192)) != -1){fos.write(bytes,0,bytesRead);}} catch (Exception e) {e.printStackTrace();}finally {try {if (null != fos){fos.close();}if (null != inputStream){inputStream.close();}} catch (IOException e) {e.printStackTrace();}}/*** 指定压缩图片的方式、参数等*/ImageWriter imageWriter = ImageIO.getImageWritersByFormatName("jpg").next();ImageWriteParam imageWriteParam = new JPEGImageWriteParam(null);imageWriteParam.setCompressionMode(imageWriteParam.MODE_EXPLICIT);imageWriteParam.setCompressionQuality(quality);imageWriteParam.setProgressiveMode(imageWriteParam.MODE_DISABLED);ColorModel colorModel = ImageIO.read(file).getColorModel();imageWriteParam.setDestinationType(new javax.imageio.ImageTypeSpecifier(colorModel,colorModel.createCompatibleSampleModel(32,32)));FileOutputStream out;if (!file.exists()){throw new FileNotFoundException("文件不存在");}else{BufferedImage bufferedImage = ImageIO.read(file);out = new FileOutputStream(file);imageWriter.reset();imageWriter.setOutput(ImageIO.createImageOutputStream(out));imageWriter.write(null,new IIOImage(bufferedImage,null,null),imageWriteParam);out.flush();out.close();}return file;}
}

下面是导出的实现方法：

/*** 导出excel的接口* @param response* @param workerListReqVO* @throws IOException*/@GetMapping(value = "/imageExportXls")public void imageExportXls(HttpServletResponse response, WorkerListReqVO workerListReqVO) throws IOException {try {int a = 0;HSSFWorkbook workbook = new HSSFWorkbook();HSSFSheet sheet = workbook.createSheet();String fileName = "人员信息表" + DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss").format(LocalDateTime.now());int rowNum = 1;String[] headers = {"姓名","性别","年龄","身份证号","工种","头像"};HSSFRow row = sheet.createRow(0);for (int i = 0; i < headers.length; i++) {sheet.setColumnWidth(i,4000);HSSFCell cell = row.createCell(i);HSSFRichTextString text = new HSSFRichTextString(headers[i]);cell.setCellValue(text);}List<WorkerListRespVO> list = workerBasicInfoService.queryWorkerInfoExport(workerListReqVO);for (WorkerListRespVO worker : list) {HSSFRow row1 = sheet.createRow(rowNum);row1.setHeight((short) 1000);row1.createCell(0).setCellValue(worker.getWorkerName());row1.createCell(1).setCellValue(worker.getGender_dictText());row1.createCell(2).setCellValue(String.valueOf(worker.getAge()));row1.createCell(3).setCellValue(worker.getIdCardNumber());row1.createCell(4).setCellValue(worker.getWorkType_dictText());if (worker.getHeadImageUrl() == null) {row1.createCell(5).setCellValue("暂无头像");} else {File file = UrlImageUtil.downloadAndCompress(worker.getHeadImageUrl(), 0.0005f);setImage(workbook, sheet, a, file);}rowNum++;a++;}response.reset();String excelFileName = new String(fileName.getBytes(), "iso-8859-1");response.setHeader("Disposition","attachment;filename=" + excelFileName + ".xls");response.setContentType("application/octet-stream;charset=UTF-8");OutputStream os = response.getOutputStream();workbook.write(os);os.flush();os.close();} catch (Exception e) {e.printStackTrace();response.sendRedirect("error.action");}}public void setImage(HSSFWorkbook workbook,HSSFSheet sheet,int a,File file){HSSFPatriarch patriarch = sheet.createDrawingPatriarch();ByteArrayOutputStream byteArrayOps = new ByteArrayOutputStream();try {BufferedImage image = ImageIO.read(file);ImageIO.write(image,"jpg",byteArrayOps);HSSFClientAnchor anchor = new HSSFClientAnchor(50, 55, 900, 200, (short) 5, a + 1, (short) 5, a + 1);anchor.setAnchorType(ClientAnchor.AnchorType.MOVE_DONT_RESIZE);patriarch.createPicture(anchor,workbook.addPicture(byteArrayOps.toByteArray(),HSSFWorkbook.PICTURE_TYPE_JPEG));} catch (IOException e) {e.printStackTrace();}}

注意在传入多条url，只要有一条无效的url那它就不会有文件file生成，运行时会直接抛出空指针异常导致无法成功导出，所以注意做判空操作。

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