PDF和图片互转，拓展知识点，合并pddf元素（三）

拓展知识点，合并pddf元素，依据pdf编辑元素数据合并输出pdf文件，在开发过程中的发散思维，记录一下

代码逻辑：

/**
 * 依据pdf编辑元素数据合并输出pdf文件
 */
@RequestMapping(value = "/v1/pdfEdit/mergeImageOutPdf/{fileInfoId}", method = RequestMethod.GET)
public void mergeImageOutPdf(HttpServletRequest request, HttpServletResponse response, @PathVariable("fileInfoId") String fileInfoId) {
    try {
        //准备
        Map<String, Object> qmap = new HashMap<>();
        qmap.clear();
        qmap.put("fileInfoId", fileInfoId);
        qmap.put("isDelete", Constants.NO_INT);
        FileAttachmentPo fileAttachmentPo = null;
        List<FileAttachmentPo> fileAttachmentPoList = fileAttachmentFacade.queryByMap(qmap);
        if (fileAttachmentPoList != null && !fileAttachmentPoList.isEmpty()) {
            fileAttachmentPo = fileAttachmentPoList.get(0);
        }
        //
        qmap.clear();
        qmap.put("fileInfoId", fileInfoId);
        qmap.put("isDelete", Constants.NO_INT);
        List<PdfEditPo> pdfEditPoList = pdfEditFacade.queryByMap(qmap);
        Map<String, String> listMapKeyPageNo = new HashMap<>();
        for (int i = 0; i < pdfEditPoList.size(); i++) {
            PdfEditPo item = pdfEditPoList.get(i);
            listMapKeyPageNo.put(item.getPageNo(), item.getBase64Decoder());
        }
        List<String> base64DecoderList = new ArrayList<>();
        for (int i = 1; i < pdfEditPoList.size() + 1; i++) {
            base64DecoderList.add(listMapKeyPageNo.get(i + ""));
        }

        //开始合并
        PDDocument pdDocument = new PDDocument();

        PDPageContentStream contentStream = null;
        ByteArrayInputStream byteIn = null;

        for (int i = 0; i < base64DecoderList.size(); i++) {
            //base64Decoder 解析为图片
            BASE64Decoder decoder = new BASE64Decoder();
            String base64Decoder = base64DecoderList.get(i);
            byte[] decoderBytes = decoder.decodeBuffer(base64Decoder.split(",")[1]);
            byteIn = new ByteArrayInputStream(decoderBytes);    //将b作为输入流；
            BufferedImage image = ImageIO.read(byteIn);

            //图片格式化为 pdf文档页面
            PDPage pdPage = new PDPage(new PDRectangle(image.getWidth(), image.getHeight()));
            pdDocument.addPage(pdPage);

            //输出为pdf数据
            contentStream = new PDPageContentStream(pdDocument, pdPage);
            PDImageXObject pdImageXObject = LosslessFactory.createFromImage(pdDocument, image);
            contentStream.drawImage(pdImageXObject, 0, 0, image.getWidth(), image.getHeight());

            //
            contentStream.close();
            byteIn.close();
        }
        //设置MIME类型
        response.setContentType("application/octet-stream");
        //或者为response.setContentType("application/x-msdownload");
        String fileName = fileAttachmentPo.getFileName();
        //设置头信息,设置文件下载时的默认文件名，同时解决中文名乱码问题
        response.addHeader("Content-disposition", "attachment;filename=" + new String(fileName.getBytes(), "ISO-8859-1"));

        //保存文件 或则 字节流
        //pdDocument.save(filename);
        pdDocument.save(response.getOutputStream());
        pdDocument.close();
    } catch (Exception e) {
        logger.error("依据pdf编辑元素数据合并输出pdf文件服务器出现异常", e);
        //return AjaxResult.error(AjaxResult.ERROR_CODE, messageSource.getMessage("server.error", null, "服务器出现异常，请联系管理员", getLocal()));
    }
}