按照示例写springmvc写的xml接口，报argument type mismatch

api：
`@RequestMapping(path = "/aaaa", `
    `method = RequestMethod.POST, `
    `produces = MediaType.APPLICATION_XML_VALUE)`
`public AAA aaaa(@RequestBody AAA aaa) {`
      `return person;`
` }`

入参类：
`@Data`
`@XmlAccessorOrder(XmlAccessOrder.ALPHABETICAL)`
`@XmlRootElement(name = "aaa")`
`public class AAA {`
    `@XmlElement(name = "bbb")`
    `private String bbb;`
`}`

postman请求正文：
``
  ``
    `sss`
  ``
``

另写一个无入参的接口，也是返回AAA，在postman那里是可以看到正确的xml格式的响应正文

Start with the Spring MVC endpoint using @RequestBody AAA and the AAA class with JAXB annotations. Reproduce the POST request from Postman with the provided XML, then compare it with the no-argument endpoint that returns XML correctly. Done means the request no longer produces an argument type mismatch and the XML response remains correct.

Written by the indexing model from the issue text.