spring mvc upload file

spring 封装了文件上传功能，使用spring mvc上传文件需要完成下面的工作：

1. 配置MultipartFileResolver

    在spring容器中注入MultipartFileResolver bean

 <bean id="commonsMultipartResolver"  class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="defaultEncoding" value="utf-8"/>
        <property name="maxInMemorySize" value="1073741824"/>
        <property name="maxUploadSize" value="50000000"/>
 </bean>

应用该功能需要apche的commons-fileupload和commons-io依赖，因为它们提供底层api，spring是对它们的一种封装

2. jsp文件创建表单

<form id="upload_form" action="/upload/example" method="post" enctype="multipart/form-data" onsubmit="return sub();" >
    <textarea rows="4" name="description" class="form-control  ng-pristine ng-valid ng-touched" placeholder="填写something"></textarea>
    <span class="gray weight">上传歌曲：</span><input id="target_file" name="file" type="file" />
    <button id="submit_btn" class="inputBtn">确定上传</button>
</form>
<script type="text/javascript">
function sub() {//简单的验证
   var file = $("#week_song_file").val();
   if(file==null||file.indexOf(".mp3")==-1){
   alert("请选择mp3格式的文件");
   return false;
                   }
   return true;
          }                                        
</script>

文件的提交有其它方式，比如ajax或jquery的上传插件，这里只做示例

3. controller中文件上传处理

@Controller
public class UploadController {
    @Autowired
    MultipartResolver resolver;
   @RequestMapping(value="/member/{uid}/weeksong/upload",method = RequestMethod.POST)
   @ResponseBody
   public String upload(@PathVariable long uid,HttpSession session,HttpServletRequest request){
        String result="ok";
        if(resolver.isMultipart(request)){
                MultipartHttpServletRequest multipartRequest=resolver.resolveMultipart(request);
                MultipartFile file=multipartRequest.getFile("file");//此处文件名字‘file’要于表单中提交的一致
                String description=multipartRequest.getParameter("description");
                //处理file....
            }
        }else{
            result="type error";
        }
        return result;
    }
}

接收文件的方法中有另一种方式： 

@RequestMapping(value="/member/{uid}/weeksong/upload",method = RequestMethod.POST)
@ResponseBody
public String upload(@PathVariable long uid,HttpSession session,@RequestParam("file")MultipartFile file,@RequestParam String description){
//handle file...
}

直接将上传的文件以变量的形式封装到一个MultipartFile类型的对象file中，这是出现错误：java.lang.IllegalArgumentException: Expected MultipartHttpServletRequest: is a MultipartResolver configured? 具体原因还要研究一下