Spring MVC - 将 XML 参数编组到多部分请求中的对象 (JAXB)

Question

我使用带有 apache commons 多部分解析器支持的 Spring MVC 创建了一个文件上传服务，该服务指定应将文件作为多部分 HTTP Post 请求的一部分附加。该请求还包含一个参数，其中包含带有有关该对象的元数据的 XML 字符串。可以使用 JAXB 来编组 XML。

其他不是多部分的服务透明地处理编组，例如：

@RequestMapping(value = "/register", method = RequestMethod.POST)
    @ResponseStatus(HttpStatus.CREATED)
    public ModelAndView createUser(@RequestBody CreateUserDTO createUserDTO) throws Exception {
        UserDTO user = userService.createUser(createUserDTO);
        return createModelAndView(user);
    }

这里 CreateUserDTO 是一个自动编组的 JAXB 注释对象。 在多部分情况下，我希望具有相同的透明度。理想情况下，我想做以下事情：

RequestMapping(method = RequestMethod.POST)
    @ResponseStatus(HttpStatus.CREATED)
    public ModelAndView createAttachment(@RequestParam AttachmentDTO attachment,
                                         HttpServletRequest request) throws Exception {

        final MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
        AttachmentDTO attachment = null;
        final MultipartFile dataFile = multipartRequest.getFile("data");

        AttachmentDTO createdAttachment = attachmentService.createAttachment(attachment,
                dataFile);

        return createModelAndView(createdAttachment);
}

不幸的是，这不起作用。我可以将附件参数绑定为字符串，但自动编组不起作用。我的解决办法是手动进行如下编组，但我不喜欢这种方法（特别是因为参数可能以 JSON 和 XML 形式指定）：

    @Autowired
    private Jaxb2Marshaller jaxb2Marshaller;

    @Autowired
    private ObjectMapper jacksonMapper;  

    @RequestMapping(method = RequestMethod.POST)
    @ResponseStatus(HttpStatus.CREATED)
    public ModelAndView createAttachment(@RequestParam(ATTACHMENT_PARAMETER) String attachmentString,
                                                 final HttpServletRequest request) throws Exception {

            final MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
            AttachmentDTO attachment = null;
            try {
                attachment = (AttachmentDTO)jaxb2Marshaller.unmarshal(new StreamSource(new StringReader(attachmentString)));
            } catch (XmlMappingException e) {
                //Try JSON
                try {
                    attachment = jacksonMapper.readValue(attachmentString, AttachmentDTO.class);
                } catch (IOException e1) {
                    throw new BadRequestException("Could not interpret attachment parameter, both JSON and XML parsing failed");
                }
            }

有谁对解决此问题有更好的建议吗？

为了完整起见，我还在这里指定了相关的 Spring 配置：

<bean id="viewResolver" class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
        <property name="order" value="1"/>
        <property name="favorPathExtension" value="true"/>
        <property name="ignoreAcceptHeader" value="false"/>
        <property name="mediaTypes">
            <map>
                <entry key="xml" value="application/xml"/>
                <entry key="json" value="application/json"/>
            </map>
        </property>
        <property name="viewResolvers">
            <list>
                <bean class="org.springframework.web.servlet.view.BeanNameViewResolver"/>
                <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
                    <property name="prefix" value="/WEB-INF/jsp/"/>
                    <property name="suffix" value=".jsp"/>
                </bean>
            </list>
        </property>
        <property name="defaultViews">
            <list>
                <bean class="org.springframework.web.servlet.view.xml.MarshallingView">
                    <property name="modelKey" value="object"/>
                    <property name="marshaller" ref="jaxbMarshaller"/>
                </bean>
                <bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView">
                    <property name="objectMapper" ref="jaxbJacksonObjectMapper"/>
                </bean>
            </list>
        </property>
    </bean>

    <!--Use JAXB OXM marshaller to marshall/unmarshall following class-->
    <bean id="jaxbMarshaller"
          class="org.springframework.oxm.jaxb.Jaxb2Marshaller">
        <property name="contextPath" value="com.behindmedia.btfd.model.dto"/>
    </bean>

    <bean id="jaxbJacksonObjectMapper" class="org.codehaus.jackson.map.ObjectMapper"/>

    <!-- allows for integration of file upload functionality -->
    <bean class="org.springframework.web.multipart.commons.CommonsMultipartResolver" id="multipartResolver">
        <property name="maxUploadSize" value="100000000"/>
    </bean>