如何使用Spring以编程方式使用Rest API中的文件？

Question

我有以下Rest资源从DB下载文件.它可以在浏览器中正常工作,但是,当我尝试从Java客户端执行此操作时,我得到406(不接受错误).

...
 @RequestMapping(value="/download/{name}", method=RequestMethod.GET, 
        produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
public @ResponseBody HttpEntity<byte[]> downloadActivityJar(@PathVariable String name) throws IOException
{
    logger.info("downloading : " + name + " ... ");
    byte[] file = IOUtils.toByteArray(artifactRepository.downloadJar(name));
    HttpHeaders header = new HttpHeaders();
    header.set("Content-Disposition", "attachment; filename="+ name + ".jar");
    header.setContentLength(file.length);

    return new HttpEntity<byte[]>(file, header);
}
...

客户端部署在具有不同端口的同一服务器上(消息提供正确的名称):

    ...
    RestTemplate restTemplate = new RestTemplate();
    String url = "http://localhost:8080/activities/download/" + message.getActivity().getName();
    File jar = restTemplate.getForObject(url, File.class);
    logger.info("File size: " + jar.length() + " Name: " + jar.getName());
    ...

我在这里错过了什么？

Answer 1

响应代码为406 Not Accepted.您需要指定一个'Accept'请求标头,该标头必须与RequestMapping的'produce'字段匹配.

RestTemplate restTemplate = new RestTemplate();
restTemplate.getMessageConverters().add(new ByteArrayHttpMessageConverter());    
HttpHeaders headers = new HttpHeaders();
headers.setAccept(Arrays.asList(MediaType.APPLICATION_OCTET_STREAM));
HttpEntity<String> entity = new HttpEntity<String>(headers);

ResponseEntity<byte[]> response = restTemplate.exchange(URI, HttpMethod.GET, entity, byte[].class, "1");

if(response.getStatusCode().equals(HttpStatus.OK))
        {       
                FileOutputStream output = new FileOutputStream(new File("filename.jar"));
                IOUtils.write(response.getBody(), output);

        }

一个小警告:不要对大文件执行此操作.RestTemplate.exchange(...)总是将整个响应加载到内存中,因此您可以获得OutOfMemory异常.为避免这种情况,请不要使用Spring RestTemplate,而是直接使用Java标准HttpUrlConnection或apache http-components.