前言

java将多个base64数据合并成一个pdf下载

一、Maven引入jar包

<dependency>
    <groupId>cn.gtmap.ahcalib</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.10</version>
</dependency>

二、将base64转成byte[]

public static byte[] base64StringToByte(String base64String) {
        BASE64Decoder decoder = new BASE64Decoder();
        ByteArrayOutputStream baos = null;
        try {
            byte[] bytes = decoder.decodeBuffer(base64String);
            baos = new ByteArrayOutputStream();
            baos.write(bytes); //把byte写进输出流里
            return baos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (baos != null){
                    baos.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return new byte[0];
    }

三、合并pdf

private String getCombinePdf(String fileName, List<byte[]> byteList) {
        String path = System.getProperty("catalina.home") + "/egov-home/bdc/data/temp/";
        File folder = new File(path);
        if (!folder.exists()) {
            folder.mkdirs();
        }
        String filePath = path + fileName + ".pdf";
        Document doc = new Document(PageSize.A4, 20, 20, 20, 20);
        try {
            PdfWriter.getInstance(doc, new FileOutputStream(filePath));
            doc.open();
            Image image = null;
            for (byte[] bs: byteList) {
                image = Image.getInstance(bs);
                float heigth = image.getHeight();
                float width = image.getWidth();
                int percent = getPercent2(heigth, width);
                // 设置图片居中显示
                image.setAlignment(Image.MIDDLE);
                image.scalePercent(percent+3);// 表示是原来图像的比例;
                //添加到PDF文档
                doc.add(image);
                //下一页，每张图片一页
                doc.newPage();
            }
            doc.close();
        } catch (DocumentException e) {
            logger.info("DocumentException: " + e);
        } catch (FileNotFoundException e) {
            logger.info("FileNotFoundException: " + e);
        } catch (MalformedURLException e) {
            logger.info("MalformedURLException: " + e);
        } catch (IOException e) {
            logger.info("IOException: " + e);
        }
        return filePath;
    }

public static int getPercent2(float h, float w) {
        int p = 0;
        float p2 = 0.0f;
        p2 = 530 / w * 100;
        p = Math.round(p2);
        return p;
    }

四、下载pdf

 String filePath = getCombinePdf(fileName, byteList);
        File file = new File(filePath);
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(file);
            byte[] bytes = new byte[fis.available()];
            fis.read(bytes);
            HttpHeaders headers = new HttpHeaders();
            fileName = URLEncoder.encode(fileName,"UTF-8") + ".pdf";
            headers.setContentDispositionFormData("attachment", fileName);//告知浏览器以下载方式打开
            headers.add("Content-Disposition", "attachment;filename*=UTF-8''" + fileName);
            headers.setContentType(MediaType.APPLICATION_PDF);
            return new ResponseEntity<byte[]>(bytes, headers, HttpStatus.OK);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }