spring MVC接口-下载PDF文件添加水印

spring MVC接口-下载PDF文件添加水印

PDF文件下载接口动态添加水印, 本文以七牛云存储为例

主要步骤

1. Java获取url文件流
2. 文件流动态添加水印
3. 文件流下载

核心代码

添加maven

<dependency>
    <groupId>com.itextpdfgroupId>
    <artifactId>itextpdfartifactId>
    <version>5.2.0version>
dependency>
<dependency>
    <groupId>com.itextpdfgroupId>
    <artifactId>itext-asianartifactId>
    <version>5.2.0version>
dependency>

1.通过url获取文件输出流

这里是写死的PDF文件, 其他文件请自行测试

    /**
     * 通过url获取 OutputStream
     *
     * @param outputStream
     * @param url
     * @throws IOException
     */
    public static void getFile(OutputStream outputStream, String url) throws IOException {
        RestTemplate restTemplate = new RestTemplate();

        final String APPLICATION_PDF = "application/pdf";
        HttpHeaders headers = new HttpHeaders();
        InputStream inputStream = null;
        try {
            List list = new ArrayList<>();
            list.add(MediaType.valueOf(APPLICATION_PDF));
            headers.setAccept(list);

            ResponseEntity<byte[]> response = restTemplate.exchange(
                    url,
                    HttpMethod.GET,
                    new HttpEntity<byte[]>(headers),
                    byte[].class);

            byte[] result = response.getBody();

            inputStream = new ByteArrayInputStream(result);

            int len = 0;
            byte[] buf = new byte[1024];
            while ((len = inputStream.read(buf, 0, 1024)) != -1) {
                outputStream.write(buf, 0, len);
            }
            outputStream.flush();

        } finally {
            if (inputStream != null) {
                inputStream.close();
            }
            if (outputStream != null) {
                outputStream.close();
            }
        }
    }

2.添加水印

需要将第一步的输出流转为输入流, 然后进行水印添加

    /**
     * outputStream转inputStream
     */
    public static ByteArrayInputStream parse(OutputStream out) throws Exception {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        baos = (ByteArrayOutputStream) out;
        ByteArrayInputStream swapStream = new ByteArrayInputStream(baos.toByteArray());
        return swapStream;
    }

   /**
     * InputStream pdf文件加文字水印转成 OutputStream
     *
     * @param is
     * @param text
     * @param os 这里传入的是response响应输出流
     * @throws Exception
     */
    public static void addTextfMark(InputStream is, String text, OutputStream os) throws Exception {
        PdfReader reader = new PdfReader(is, "pdf".getBytes());

        // 如果是web项目，直接下载应该放到response的流里面
        PdfStamper stamp = new PdfStamper(reader, os);
        int pageSize = reader.getNumberOfPages();

        // 每页的高度
        float pageHeight = reader.getPageSize(1).getHeight();
        // 每页的宽度
        float pageWidth = reader.getPageSize(1).getWidth();


        try {
            // 每页显示多少行
            int lineNum = (int) (pageHeight / IAMGE_HEIGHT); // 行数
            // 每两行显示两个 左边一个，右边一个
            int middleX = (int) pageWidth / 2;
            int middleH = (int) pageHeight / 2;
            // 循环每一页
            for (int i = 1; i <= pageSize; i++) {
                // 循环每一页的每一行
                for (int j = 0, k = 0; j < lineNum; j = j + 2, k++) {
                    PdfContentByte under = stamp.getOverContent(i);// 在图片上
                    under.beginText();
                    // 支持中文 仅 5.2.0版本
                    BaseFont bf = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H",BaseFont.EMBEDDED);
                    under.setFontAndSize(bf, 40);
                    under.setTextMatrix(10, 10);

                    // 设置透明度
                    PdfGState gs = new PdfGState();
                    gs.setFillOpacity(0.2f);//设置透明度为0.2
                    under.setGState(gs);

                    under.setColorFill(BaseColor.GRAY);
                    under.showTextAligned(Element.ALIGN_LEFT, text, middleX / 2, middleH / 2, 45);
                    under.showTextAligned(Element.ALIGN_LEFT, text, middleX + middleX / 2, middleH + middleH / 2, 45);

                    // 0 0 0 表示左下脚 最后一个0是角度，0表示横着 45 表示斜着
                    under.showTextAligned(Element.ALIGN_LEFT, text, middleX / 2, middleH / 2, 45);
                    under.showTextAligned(Element.ALIGN_LEFT, text, middleX + middleX / 2, middleH + middleH / 2, 45);
                    under.endText();
                }
            }
        } catch (Exception e) {
            throw e;
        } finally {
            stamp.close();// 关闭
            reader.close();
        }
    }

3.完整方法调用过程

    /**
     * 下载处理PDF附件
     *
     * @param response
     * @param fileName
     * @param resourceUrl
     * @param content
     * @throws Exception
     */
    public static void downloadFile(String viewType, HttpServletResponse response, String fileName, String resourceUrl, String content) throws Exception {
        viewType = StringUtil.isNotEmpty(viewType)?viewType:"attachment";
        if(!"attachment".equals(viewType) && !"inline".equals(viewType)){
            throw new BizException("文件查看类型有误");
        }
        response.setContentType("application/pdf");//attachment
        response.setHeader("Content-disposition", viewType+";filename=" + new String(fileName.getBytes(), "iso-8859-1"));
        OutputStream ouputStream = response.getOutputStream();
        OutputStream ouputStreamTemp = new ByteArrayOutputStream();
        CRMUtil.getFile(ouputStreamTemp, resourceUrl);
        InputStream bis = PDFUtils.parse(ouputStreamTemp);
        PDFUtils.addTextfMark(bis, content, ouputStream);
        ouputStream.flush();
        ouputStream.close();
    }

接口

    /**
     * 下载附件
     *
     * @param request
     * @param response
     */
    @GetMapping("/download")
    public void disclosureDownload(HttpServletRequest request,HttpServletResponse response,
                                             @RequestParam(name = "ticket", required = false) String ticket,
                                             @RequestParam(name = "viewType", required = false) String viewType, // inline/attachment
                                             @RequestParam(name = "disclosureId", required = false) String disclosureId){
            try {
                PDFUtils.downloadFile(viewType, response,"文件名", resourceUrl, "水印文字");
            } catch (Exception e) {
                e.printStackTrace();
                throw new BizException("附件下载失败:"+e.getMessage());
            }
    }