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：

@Override    public 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httpGet        HttpGet 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();}

来源地址：https://blog.csdn.net/weixin_46074829/article/details/127842719