Spring REST MultipartFile file is always null when do upload file

Question

@RequestMapping(value = "{fileName:.+}", method = RequestMethod.POST, consumes = { MediaType.MULTIPART_FORM_DATA_VALUE})
public ResponseEntity<ResponseEnvelope<String>> uploadFile(
         @RequestParam("ownerId") Long ownerId, 
         @PathVariable("fileName") String fileName,
         @RequestBody MultipartFile file)
         throws Exception {
    ResponseEnvelope<String> env;
    if(null == certFileContent) {
        env = new ResponseEnvelope<String>("fail");
        return new ResponseEntity<ResponseEnvelope<String>>(env, HttpStatus.OK);
    }
    service.uploadCertificate(ownerId, fileName, certFileContent.getBytes());
    env = new ResponseEnvelope<String>("success");
    return new ResponseEntity<ResponseEnvelope<String>>(env, HttpStatus.OK);
}

Why I always get the file value is null, I've configure the multipart support,see below,

Answer 1

The file should be binded to a RequestParam instead of the RequestBody as follows:

public ResponseEntity<ResponseEnvelope<String>> uploadFile(
         @RequestParam("ownerId") Long ownerId, 
         @PathVariable("fileName") String fileName,
         @RequestParam(value = "file") MultipartFile file)

This would correspond with the following HTML form:

<form method="post" action="some action" enctype="multipart/form-data">
    <input type="file" name="file" size="35"/>
</form>

Then in your dispatcher configuration specify the CommonsMultiPartResolver

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="maxUploadSize" value="5000000"/>
</bean>

Answer 2

This is what worked for me,

Previously my input field was defined as,

<input type="file" />

I was getting null file with the above line but when I added the name="file" everything worked fine!

<input type="file" name="file" />

Hope this helps!