Java后端返回PDF预览给前端

前端要预览index.php/tags-1.html" >服务器PDF 可直接将要blob流返回给前端 即可用浏览器自带pdf预览功能打开，现有两种方式

方式1 返回blob流给前端 代码如下       

    @PostMapping(value = "/preview")    @ResponseBody    public void showPdf(HttpServletResponse response) {        try {            File file = new File("filePath");            OutputStream out = null;            try (BufferedInputStream br = new BufferedInputStream(new FileInputStream(file));            ) {                byte[] bs = new byte[1024];                int len;                response.reset(); // 非常重要                URL u = new URL("file:///" + "filePath");                String contentType = u.openConnection().getContentType();                response.setContentType(contentType);                response.setHeader("Content-Disposition", "inline;filename="                        + "preview.pdf");                out = response.getOutputStream();                while ((len = br.read(bs)) > 0) {                    out.write(bs, 0, len);                }                out.flush();                out.close();            }        } catch (Exception e) {            e.printStackTrace();        }    }

此时 前端解析可直接拿返回的文件流 例子如下

let blob = this.response;          const binaryData = [];          binaryData.push(blob);          const url = window.URL.createObjectURL(new Blob(binaryData, { type: 'application/pdf' }));          window.open(url);

但有的时候 不想返回文件流 可把文件返回为base64 （注意 base64可能超长）此时代码修改如下

        File file = new File("filePath");            OutputStream out = null;            try (BufferedInputStream br = new BufferedInputStream(new FileInputStream(file));                         ByteArrayOutputStream outStream = new ByteArrayOutputStream();            ) {                int len;                URL u = new URL("file:///" + "filePath");                String contentType = u.openConnection().getContentType();                byte[] buffer = new byte[1024];                //每次读取的字符串长度，如果为-1，代表全部读取完毕                //使用输入流从buffer里把数据读取出来                while ((len = br.read(buffer)) != -1) {                    //用输出流往buffer里写入数据，中间参数代表从哪个位置开始读，len代表读取的长度                    outStream.write(buffer, 0, len);                }                // 对字节数组Base64编码                Base64Encoder base64 = new Base64Encoder();                String base64Str = replaceEnter(base64.encode(outStream.toByteArray()));            }        } catch (Exception e) {        }

前端修改如下

 let base64 = resBase64.data.base64;      base64 = base64.replace(/[\n\r]/g, '')      const raw = window.atob(base64)      const rawLength = raw.length      const uInt8Array = new Uint8Array(rawLength)      for (let i = 0; i