传递null值的Spring web PUT方法

Spring MVC 提交时 put null 代码:

<form:form action="../${user.id}" method="post" commandName="user">
                    <div class="form-group">
                        <label for="name">First Name</label>
                        <form:input path="name" class="form-control" id="name"
                            placeholder="Full Name" />
                    </div>
<input type="hidden" name="_method" value="put" />

                    <input type="submit" class="btn btn-success" value="SAVE">
                </form:form>

我在接收端的put映射

@PutMapping(path = "/{id}")
    public String updateUser(@PathVariable(value = "id") long id, @ModelAttribute("user") User user, Model model) {
        userService.updateUser(user);
        model.addAttribute("user", userService.findById(id));
        return "redirect:/users/" + id;
    }

<context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/spring/root-context.xml</param-value>
    </context-param>

    <!-- Creates the Spring Container shared by all Servlets and Filters -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <!-- Processes application requests -->
    <servlet>
        <servlet-name>appServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/spring/appServlet/servlet-context.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
        <async-supported>true</async-supported>
    </servlet>

    <servlet-mapping>
        <servlet-name>appServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

我还有一个 post 请求,该请求工作正常,但此请求正在变为null。请帮我解决这个问题

注意:Id仍在获取值,但对象 user 不是