Spring 3.0 MultipartFile upload

Question

I am converting Java web application to Spring framework and appreciate some advice on the issues I am facing with the file upload. Original code was written using org.apache.commons.fileupload.

1. Does Spring MultipartFile wraps org.apache.commons.fileupload or I can exclude this dependency from my POM file?

2. I have seen following example:

    @RequestMapping(value = "/form", method = RequestMethod.POST) public String handleFormUpload(@RequestParam("file") MultipartFile file) { if (!file.isEmpty()) { byte[] bytes = file.getBytes(); // store the bytes somewhere return "redirect:uploadSuccess"; } else { return "redirect:uploadFailure"; } } 

   Originally I tried to follow this example but was always getting an error as it couldn't find this request param. So, in my controller I have done the following:

    @RequestMapping(value = "/upload", method = RequestMethod.POST) public @ResponseBody ExtResponse upload(HttpServletRequest request, HttpServletResponse response) { // Create a JSON response object. ExtResponse extResponse = new ExtResponse(); try { if (request instanceof MultipartHttpServletRequest) { MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request; MultipartFile file = multipartRequest.getFiles("file"); InputStream input = file.getInputStream(); // do the input processing extResponse.setSuccess(true); } } catch (Exception e) { extResponse.setSuccess(false); extResponse.setMessage(e.getMessage()); } return extResponse; } 

and it is working. If someone can tell me why @RequestParam did not work for me, I will appreciate. BTW I do have

    <bean id="multipartResolver"
        class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="maxUploadSize" value="2097152"/>
    </bean>

in my servlet context file.

Answer 1

1. spring does not have a dependency on commons-fileupload, so you'll need it. If it's not there spring will use its internal mechanism
2. You should pass a MultipartFile as a method parameter, rather than @RequestParam(..)

Answer 2

I had to

1. add commons-fileupload dependency to my pom,
2. add multipartResolver bean (mentioned in the question),
3. use @RequestParam("file") MultipartFile file in the handleFormUpload method and
4. add enctype in my jsp : <form:form method="POST" action="/form" enctype="multipart/form-data" >

to get it to work.

Answer 3

This works for me.

@RequestMapping(value = "upload.spr", method = RequestMethod.POST)
public ModelAndView upload(@RequestParam("file") MultipartFile file, HttpServletResponse response)
{
    //  handle file here
}

Answer 4

请求参数的常规sysntax是@RequestParam（value =“Your value”，required = true），模式请求参数用于获取Url的值。

Answer 5

In a POST you will only send the params in the request body, not in the URL (for which you use @RequestParams)

Thats why your second method worked.

Answer 6

In Spring MVC 3.2 support for Servet 3.0 was introduced. So you need to include commons-file upload if you use earlier versions of Spring.