eureka 经过网关transferRequest下载文件，用form表单、a标签或location下载，ajax不支持文件流，只支持字符串类型xml、json

/**
 * Rest模板对象，用于http访问
 * 当前对象已经使用@LoadBanlnced 实现的负载均衡
 */
@Autowired
@Qualifier("siteRestTemplate")
RestTemplate restTemplate;

//网关接口

@RequestMapping("/transferRequest/download")
public void transferRequest(String action, String site, String params, String method, Integer timeout, HttpServletResponse httpServletResponse) {
    //这里只需要把服务提供者的applicaitonName和接口名称写上即可
    String url = "http://" + site + action;
    HttpHeaders headers = getHttpHeadersByRequest(request);
    headers.setContentType(MediaType.MULTIPART_FORM_DATA);
    MultiValueMap postParams = getPostParams(params);
    HttpEntity> httpEntity = new HttpEntity(postParams, headers);
    HttpMethod requestMethod = "GET".equals(method) ? HttpMethod.GET : HttpMethod.POST;
　　//如果改用实体类接收，文件的二进制数组会自动转换为字符串，需要重新转换为文件二进制数组，暂时没找到办法转换
    ResponseEntity response = restTemplate.exchange(url, requestMethod, httpEntity, byte[].class);
    LOGGER.info("中转请求返回：" + response.getStatusCode() + " | " + response.getBody());
    try {
        HttpHeaders obj = response.getHeaders();
        String filename = String.valueOf(obj.get("filename"));
        if(filename != null && filename.length()>0){
            filename = filename.replace("[","").replace("]","");
        }
　　　　　　//下载接口已经已经处理中文乱码，此处不能再处理，否则会显示不了中文
        httpServletResponse.setHeader("Content-Disposition", "attachment;filename=" +filename);

        OutputStream outputStream = httpServletResponse.getOutputStream();
        outputStream.write(response.getBody());
        outputStream.flush();
        outputStream.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

　　//下载接口

　　@RequestMapping("/liu")
    @ResponseBody
    public void liu(HttpServletResponse response, HttpServletRequest request){
        try {
            File file = new File("D:\\ytzz\\yulin\\excleFilePath\\登记台账2020-05-21-18-06-53.xls");
            byte[] bytes = FileUtils.readFileToByteArray(file);
            response.setHeader("filename", URLEncoder.encode(file.getName(), "UTF-8"));
            response.getOutputStream().write(bytes);
            response.getOutputStream().close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }