spring-boot上傳文件MultiPartFile獲取不到文件問題解決

1.現象是在spring-boot里加入 commons-fileupload jar並且配置了mutilPart的bean，在upload的POST請求后，發現

multipartRequest.getFiles("file")=null，有點奇怪，查了文檔資料才解決。

 <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="maxUploadSize" value="104857600"/>
        <property name="maxInMemorySize" value="4096"/>
    </bean>

2.原因是：spring-boot自帶的org.springframework.web.multipart.MultipartFile
和Multipart產生沖突，如果同時使用了MultipartResolver 和ServletFileUpload，就會在iter.hasNext()返回false.然后整個循環就跳出去了。整個問題產生的原因是Spring框架先調用了MultipartResolver 來處理http multi-part的請求。這里http multipart的請求已經消耗掉。后面又交給ServletFileUpload ，那么ServletFileUpload 就獲取不到相應的multi-part請求。因此將multipartResolve配置去除，問題就解決了。

3. 單文件的話只需要一個變量即，多文件上傳的話就將MultipartFile改為數組，然后分別上傳保存即可。

@RequestMapping(value="/multipleSave", method=RequestMethod.POST )
    public @ResponseBody String multipleSave(@RequestParam("file") MultipartFile[] files){
        String fileName = null;
        String msg = "";
        if (files != null && files.length >0) {
            for(int i =0 ;i< files.length; i++){
                try {
                    fileName = files[i].getOriginalFilename();
                    byte[] bytes = files[i].getBytes();
                    BufferedOutputStream buffStream = 
                            new BufferedOutputStream(new FileOutputStream(new File("/tmp/" + fileName)));
                    buffStream.write(bytes);
                    buffStream.close();
                    msg += "You have successfully uploaded " + fileName";
                } catch (Exception e) {
                    return "You failed to upload " + fileName + ": " + e.getMessage();
                }
            }
            return msg;
        } else {
            return "Unable to upload. File is empty.";
        }
    }
}

4.spring-boot 配置上傳文件和請求文件的最大值限制：
直接在application.properties中
multipart.maxFileSize=128KB
multipart.maxRequestSize=128KB

 

5. spring-boot-starter-web are already added as dependencies. To upload files with Servlet containers, you need to register aMultipartConfigElement class (which would be <multipart-config> in web.xml). Thanks to Spring Boot, everything is auto-configured for you! spring-boot-upload鏈接