最近在做一個(gè)項(xiàng)目滚停，用Spring boot開發(fā)，需要接收微信小程序傳過來的圖片粥惧，壓縮后發(fā)送到影像系統(tǒng)中保存键畴，涉及到上傳文件，現(xiàn)列舉出兩種RestTemplate上傳文件的方案突雪。

1. restTemplate從服務(wù)器文件系統(tǒng)中選文件上傳起惕。

從文件系統(tǒng)上傳文件時(shí)，需要把文件轉(zhuǎn)換成FileSystemResource咏删，然后放入HttpEntity中即可惹想。代碼如下：

public UploadImageResponseVO uploadImg(String fileLocal) throws IOException {
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        headers.setConnection("Keep-Alive");
        headers.setCacheControl("no-cache");
        FileSystemResource resource = new FileSystemResource(new File(fileLocal));
        HttpEntity<FileSystemResource> httpEntity = new HttpEntity<>(resource);
        ResponseEntity<Resource> responseEntity = restTemplate.postForEntity(serverUrl, httpEntity, Resource.class);
        //對讀到的內(nèi)容映射成對應(yīng)的實(shí)體類
        XmlMapper xmlMapper = new XmlMapper();
        UploadImageResponseVO uploadImageResponseVO = xmlMapper.readValue(responseEntity.getBody().getInputStream(), UploadImageResponseVO.class);
        logger.debug("responseEntity: {} ", uploadImageResponseVO);
        return uploadImageResponseVO;
    }

2. restTemplate轉(zhuǎn)發(fā)接收的文件，直接上傳圖片督函。

用multipart形式上傳文件時(shí)嘀粱，需要用到MultiValueMap<String, Object>類，用它裝載文件對象以及multipart的表單數(shù)據(jù)辰狡。
這里涉及到一個(gè)文件锋叨，從request中拿文件往MultiValueMap放時(shí)，不能直接request.getFile()給multiValueMap宛篇，這樣在restTemplate上傳文件時(shí)娃磺，messageConverter轉(zhuǎn)化時(shí)會報(bào)錯(cuò)，需要把request.getFile("file").getResource()的數(shù)據(jù)給multiValueMap些己。代碼如下：

public UploadResponseVO resendUpload(String url,StandardMultipartHttpServletRequest request) throws IOException {
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        MultiValueMap<String, Object> parts = new LinkedMultiValueMap<>();
        parts.add("file",request.getFile("file").getResource());
        Enumeration<String> enumeration= request.getParameterNames();
        while(enumeration.hasMoreElements()){
            String key = enumeration.nextElement();
            parts.add(key,request.getParameter(key));
        }
        HttpEntity<MultiValueMap<String, Object>> httpEntity = new HttpEntity<>(parts, headers);
        ResponseEntity<UploadResponseVO> responseEntity = restTemplate.postForEntity(url,httpEntity,UploadResponseVO.class);
        return responseEntity.getBody();
    }