如何使用 MockMvc 解决 MethodArgumentConversionNotSupportedException？

Question

我正在为接受 MultipartFile 的控制器方法编写单元测试 和一个自定义对象 MessageAttachment。到目前为止，我可以看到 MultipartFile 是请求的正确格式，但 MessageAttachment 不是。

messageAttachment 的解析抛出服务器端 500 错误 MethodArgumentConversionNotSupportedException。

在测试中将 MessageAttachment 转换为 MockMultipartFile 似乎是一个问题。这类似于此处显示的示例 -

问题：

如何使用 MockMvc 解决 MethodArgumentConversionNotSupportedException？

正在测试的控制器方法

 @RequestMapping(value = "/", method = RequestMethod.POST, consumes = "multipart/form-data", produces = "application/json")
        public ResponseEntity<MessageAttachment> handleFileUpload(@RequestParam(value = "file", required = true) MultipartFile file, @RequestParam(value = "messageAttachment") MessageAttachment messageAttachment) {

            //do stuff with the file and attachment passed in..  
            MessageAttachment attachment = new MessageAttachment();

            return ResponseEntity.accepted().header(HttpHeaders.CONTENT_DISPOSITION,
                    "attachment; filename=\"" + file.getOriginalFilename() + "\"").body(attachment);
        }

MockMvc 测试

@Test
public void shouldSaveUploadedFile() throws Exception {


        // Given
        ObjectMapper mapper = new ObjectMapper();

        MessageAttachment messageAttachment = new MessageAttachment();  
        messageAttachment.setTimestamp(new Date());

        MockMultipartFile multipartFile = new MockMultipartFile("file", "test.txt", "text/plain",
                "Spring Framework".getBytes());

        //Mapping the msgAttachment to a MockMultipartFile HERE
        MockMultipartFile msgAttachment = new MockMultipartFile("messageAttachment", "","application/json",
                 mapper.writeValueAsString(messageAttachment).getBytes());

        // When
        this.mockMvc.perform(MockMvcRequestBuilders.multipart("/media/")
                .file(multipartFile)
                .file(msgAttachment)).andDo(MockMvcResultHandlers.print());

}

MockMvcResultHandlers.print()

的控制台输出

MockHttpServletRequest:                                                                                                                                                                                                                         
      HTTP Method = POST                                                                                                                                                                                                                        
      Request URI = /media/                                                                                                                                                                                                                     
       Parameters = {}                                                                                                                                                                                                                          
          Headers = {Content-Type=[multipart/form-data]}                                                                                                                                                                                        
             Body = <no character encoding set>                                                                                                                                                                                                 
    Session Attrs = {}                                                                                                                                                                                                                          

Handler:                                                                                                                                                                                                                                        
             Type = com.fizz.buzz.fizzapi.controller.MediaUploadController                                                                                                                                                             
           Method = public org.springframework.http.ResponseEntity<com.fizz.buzz.fizzapi.model.MessageAttachment> com.fizz.buzz.fizzapi.controller.MediaUploadController.handleFileUpload(org.springframework.web.multipart.Mu
ltipartFile,com.fizz.buzz.fizzapi.model.MessageAttachment,javax.servlet.http.HttpServletRequest)                                                                                                                                       

Async:                                                                                                                                                                                                                                          
    Async started = false                                                                                                                                                                                                                       
     Async result = null                                                                                                                                                                                                                        

Resolved Exception:                                                                                                                                                                                                                             
             Type = org.springframework.web.method.annotation.MethodArgumentConversionNotSupportedException                                                                                                                                     

ModelAndView:                                                                                                                                                                                                                                   
        View name = null                                                                                                                                                                                                                        
             View = null                                                                                                                                                                                                                        
            Model = null                                                                                                                                                                                                                        

Answer 1

对于请求的 application/json 部分，您需要使用 @RequestPart 而不是 @RequestParam。 @RequestPart 的 javadoc 状态

Supported method argument types include MultipartFile in conjunction with Spring's MultipartResolver abstraction, javax.servlet.http.Part in conjunction with Servlet 3.0 multipart requests, or otherwise for any other method argument, the content of the part is passed through an HttpMessageConverter taking into consideration the 'Content-Type' header of the request part. This is analogous to what @RequestBody does to resolve an argument based on the content of a non-multipart regular request.

Note that @RequestParam annotation can also be used to associate the part of a "multipart/form-data" request with a method argument supporting the same method argument types. The main difference is that when the method argument is not a String, @RequestParam relies on type conversion via a registered Converter or PropertyEditor while @RequestPart relies on HttpMessageConverters taking into consideration the 'Content-Type' header of the request part. @RequestParam is likely to be used with name-value form fields while @RequestPart is likely to be used with parts containing more complex content (e.g. JSON, XML).

据推测，您没有注册 Converter，也没有注册 PropertyEditor 来解析该部分的内容，而 JSON 的 HttpMessageConverter 是自动注册的已注册（取决于您的 Spring MVC/Boot 版本）如果您在类路径上有 Jackson。