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Java后端返回PDF預(yù)覽給前端的實(shí)現(xiàn)

更新時(shí)間：2023年09月27日 16:33:14 作者：YuiDesu

前端要預(yù)覽服務(wù)器PDF 可直接將要blob流返回給前端,即可用瀏覽器自帶pdf預(yù)覽功能打開(kāi),本文就來(lái)介紹一下如何實(shí)現(xiàn),感興趣的可以了解一下

前端要預(yù)覽服務(wù)器PDF 可直接將要blob流返回給前端即可用瀏覽器自帶pdf預(yù)覽功能打開(kāi)，現(xiàn)有兩種方式

方式1 返回blob流給前端代碼如下

    @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();
        }
    }

此時(shí) 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);

但有的時(shí)候不想返回文件流可把文件返回為base64 （注意 base64可能超長(zhǎng)）此時(shí)代碼修改如下

        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];
                //每次讀取的字符串長(zhǎng)度，如果為-1，代表全部讀取完畢
                //使用輸入流從buffer里把數(shù)據(jù)讀取出來(lái)
                while ((len = br.read(buffer)) != -1) {
                    //用輸出流往buffer里寫入數(shù)據(jù)，中間參數(shù)代表從哪個(gè)位置開(kāi)始讀，len代表讀取的長(zhǎng)度
                    outStream.write(buffer, 0, len);
                }
                // 對(duì)字節(jié)數(shù)組Base64編碼
                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 < rawLength; ++i) {
        uInt8Array[i] = raw.charCodeAt(i)
      }
      const url = window.URL.createObjectURL(new Blob([uInt8Array], { type: resBase64.data.contentType }));
      window.open(url);

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