java通过httpclient携带请求头参数获取第三方文件流接口并实现实现文件下载

创建httpclient 请求，并在header携带指定key，也可根据实际需要携带token等信息。获取第三方接口返回的文件输入流并写到本地response中，实现返回文件流，前端通过js的a标签进行下载。

代码如下：

@Overridepublic void YKDownload(String fileId, HttpServletResponse response, HttpServletRequest request) {logger.info("下载盈科附件， 参数：附件id = " + fileId);// 创建默认的httpClient实例.CloseableHttpClient httpclient = HttpClients.createDefault();// 创建httpGetHttpGet httpGet = new HttpGet("xxxxx" + fileId);try {// 设置请求头参数httpGet.setHeader("xxxx-Key", "xxxxxx");CloseableHttpResponse httpResponse = httpclient.execute(httpGet);// 获取第三方接口放在Response中的文件名Header[] headers = httpResponse.getHeaders("content-disposition");if (headers != null && headers.length > 0) {String contentDispositionValue = headers[0].getValue();// 设置文件名，这里没用加密文件名，可以自己设置response.addHeader("Content-Disposition", contentDispositionValue);}response.setContentType("application/octet-stream;charset=utf-8");HttpEntity entity = httpResponse.getEntity();InputStream inputStream = entity.getContent(); //获取输入流//保存流 从这里到重置游标//附件第一次下载没问题再下载有时候就报错，然后参照其他博主的方法，将流先保存下来ByteArrayOutputStream bos = new ByteArrayOutputStream();BufferedInputStream br = new BufferedInputStream(inputStream);byte[] b = new byte[1024];for (int c = 0; (c = br.read(b)) != -1;){bos.write(b, 0, c);}b = null;br.close();inputStream = new ByteArrayInputStream(bos.toByteArray());// 第一次读流StringBuffer out = new StringBuffer();byte[] b1 = new byte[1024];for (int n; (n = inputStream.read(b1)) != -1;) {out.append(new String(b1, 0, n));//这个可以用来读取文件内容 并且文件内容有中文读取出来也不会乱码}// 判断文件是否存在String resultHtml = out.toString();int firstIndex = resultHtml.indexOf("\n");if(firstIndex < 0){logger.info("文件不存在或异常"+resultHtml);}// 重置游标inputStream.reset();// 输出文件ServletOutputStream outputStream = response.getOutputStream();try {byte[] oBuff = new byte[1024];int iSize;while (-1 != (iSize = inputStream.read(oBuff))) {outputStream.write(oBuff, 0, iSize);}outputStream.flush();} finally {IOUtils.close(outputStream);IOUtils.close(inputStream);}outputStream.close();} catch (Exception e) {logger.info("下载盈科附件， 原因：" + e.getMessage());e.printStackTrace();} finally {try {httpclient.close();} catch (IOException e) {e.printStackTrace();}}}

前端js代码

function fileYKDownload(fileId, fileName) {//创建XMLHttpRequest对象var httpRequest = new XMLHttpRequest();//打开连接，将请求参数拼在url后面httpRequest.open('GET', __baseUrl + '/v3/query/accessories/download?fileId=' + fileId, true);//设置期望的返回值类型httpRequest.responseType = "blob";//设置请求头，将认证信息放入请求头中httpRequest.setRequestHeader("PRIVATETOKEN",$.getCookie(__token));//请求成功回调函数httpRequest.onload = function (oEvent) {if (httpRequest.status === 200) {// 这里文件名可以从response中获取，为了方便我直接js方法传的文件名// var fileName = decodeURI(httpRequest.getResponseHeader("Content-Disposition"));console.log(fileName);var response = httpRequest.response;//数据转换为文件下载var elink = document.createElement('a');elink.download = fileName;elink.style.display = 'none';var blob = new Blob([response]);elink.href = URL.createObjectURL(blob);document.body.appendChild(elink);elink.click();document.body.removeChild(elink);}}//发送请求httpRequest.send();}