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.

索引モデルが issue の本文から書いたものです。