使用Spring4 restTemplate（Java客户端和RestController）上传一个MultipartFile列表

Question

我正在尝试使用spring restTemplate将MultipartFile列表发布到我的RestController中，尽管我对客户机和控制器使用的确切语法和类型有点困惑。以下是我根据我所做的研究得出的结论...

FileUploadClient.java

public void uploadFiles(List<MultipartFile> multiPartFileList) throws IOException {
    MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
    List<Object> files = new ArrayList<>();
    for(MultipartFile file : multiPartFileList) {
        files.add(new ByteArrayResource(file.getBytes()));
    }
    map.put("files", files);

    // headers is inherited from BaseClient
    headers.setContentType(MediaType.MULTIPART_FORM_DATA);
    HttpEntity<MultiValueMap<String, Object>> request = new HttpEntity<>(map, headers);
    ResponseEntity<String> response = restTemplate.exchange(restURI + "/rest/fileupload/uploadfiles", HttpMethod.POST, request, String.class);
    if(HttpStatus.OK.equals(response.getStatusCode())) {
        System.out.println("status for /rest/fileupload/uploadfiles ---> " + response);
    }
}

@RequestMapping(value = "/uploadfiles", method = RequestMethod.POST)
public ResponseEntity<?> uploadFiles(@RequestParam("files") List<MultipartFile> files, HttpServletRequest request) {
    ResponseEntity<?> response;
    try {
        // do stuff...
        response = new ResponseEntity<>(header, HttpStatus.OK);
        System.out.println("file uploaded");
    } catch (Exception e) {
        // handle exception
    }
    return response;
}

<filter>
    <filter-name>multipartFilter</filter-name>
    <filter-class>org.springframework.web.multipart.support.MultipartFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>multipartFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!-- max upload size in bytes -->
    <property name="maxUploadSize" value="20971520" /> <!-- 20MB -->
    <!-- max size of file in memory (in bytes) -->
    <property name="maxInMemorySize" value="1048576" /> <!-- 1MB -->
</bean>

如果我没理解错的话。multipart筛选器应该将我的MultiValueMap解析为MultipartFiles列表和MultiPartTtpServletRequest？我可以让客户机访问RestController的唯一方法是将文件数据作为ByteArrayResource发送，但是在我的控制器中，RequestBody始终为null，MultipartHttpServletRequest的multipartFiles属性有一个空映射。我看了很多文章试图解决这个问题，但没有任何效果。任何帮助都将不胜感激。

Answer 1

您从FileUploadClient发送的Request负载看起来与服务器期望的不匹配。您能尝试更改以下内容吗：

MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
for(MultipartFile file : multiPartFileList) {
    map.add(file.getName(), new ByteArrayResource(file.getBytes()));
}

至

MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
List<ByteArrayResource> files = new ArrayList<>();
for(MultipartFile file : multiPartFileList) {
    files.add(new ByteArrayResource(file.getBytes()));
}
map.put("files", files);

另外，您是否可以尝试将服务器的方法签名更改为以下内容：

public ResponseEntity<?> uploadFiles(@RequestParam("files") List<MultipartFile> files, HttpServletRequest request) {

MultiValueMap<String, Object> data = new LinkedMultiValueMap<String, Object>(); 
for(MultipartFile file : multiPartFileList) { 
    ByteArrayResource resource = new ByteArrayResource(file.getBytes()) { 
        @Override 
        public String getFilename() { 
            return ""; 
        } 
    }; 
    data.add("files", resource);
} 

服务器

public ResponseEntity<?> upload(@RequestParam("files") MultipartFile[] files){