SpringBoot @OneToMany　を使いMySQLのIDと紐づけしたい。

@OneToManyを使うとどうしてもNULLになってしまうのでアドバイスを頂ければ幸いです。
まだ質問の文章の作り方なれてなく、見にくくなってしまい申しわけないです・

Controller
	@RequestMapping(value = "/msg", method = RequestMethod.GET)
	public ModelAndView msgindex(@RequestParam("id")Long id,ModelAndView mav) {
		mav.setViewName("msg");
		MailAddressData mailaddressdata = service.findOne((long)id);
		mav.addObject("MailDataList",mailaddressdata);

		MsgData msgdata = new MsgData();
		mav.addObject("from", msgdata);
		MsgData list =msgservice.findOne((long)id);
		mav.addObject("datalist",list);
		return mav;
	}

	@RequestMapping(value = "/msg", method = RequestMethod.POST)
	public ModelAndView msgform(@ModelAttribute MsgData msgdata,ModelAndView mav) {
			msgservice.save(msgdata);
			return new ModelAndView("redirect:/msg");
		}
	}

@Entity
@Table(name="mailaddress")
public class MailAddressData {

	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	@Column
	private Long id;

	@Column(length = 50,nullable = false)
	private String name;

	@Column(length = 100,nullable = false)
	private String address;

	@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.LAZY)
	@Column(nullable = true)
	private List<MsgData> msgdata;







	public MailAddressData(Long id,String name,String address) {
		this.id=id;
		this.name=name;
		this.address=address;
	}
	public MailAddressData() {};




	public List<MsgData> getMsgdata() {
		return msgdata;
	}
	public void setMsgdata(List<MsgData> msgdata) {
		this.msgdata = msgdata;
	}
	public Long getId() {return id;}
	public void setId(Long id) {this.id = id;}

	public String getName() {return name;}
	public void setName(String name) {this.name = name;}

	public String getAddress() {return address;}
	public void setAddress(String address) {this.address = address;}

}

@Entity
@Table(name="mailaddress")
public class MailAddressData {

	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	@Column
	private Long id;

	@Column(length = 50,nullable = false)
	private String name;

	@Column(length = 100,nullable = false)
	private String address;

	@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.LAZY)
	@Column(nullable = true)
	private List<MsgData> msgdata;







	public MailAddressData(Long id,String name,String address) {
		this.id=id;
		this.name=name;
		this.address=address;
	}
	public MailAddressData() {};




	public List<MsgData> getMsgdata() {
		return msgdata;
	}
	public void setMsgdata(List<MsgData> msgdata) {
		this.msgdata = msgdata;
	}
	public Long getId() {return id;}
	public void setId(Long id) {this.id = id;}

	public String getName() {return name;}
	public void setName(String name) {this.name = name;}

	public String getAddress() {return address;}
	public void setAddress(String address) {this.address = address;}

}

Service
public class MsgService {

@Autowired
MsgDataRepository repository;

public MsgData save(MsgData msgdata) {
	return repository.save(msgdata);
}
public List<MsgData> getAll(){
	return repository.findAll();
}
public MsgData findOne(long id) {
	return repository.getOne(id);
}

```ここに言語を入力
<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head>
	<title>メッセージ</title>
</head>
<body>
				<div th:each="obj : ${MailDataList}">
					<a th:text="${obj.name}" ></a><a>さんのメッセージ</a><br/>

				<form action="/msg" method="POST" th:object="${from}">

					<input type="hidden" name="id" th:value="${obj.id}" />
					<input type="text" name="msg" th:text="${msg}" />

					<input type="submit" />
				</form>
				</div>

<hr />
<table>
		<tr>
			<th>名前</th>
			<th>メッセージ</th>
		</tr>
		<tr th:each="obj : ${list}">
			<td th:text="${obj.addressdata.name}"></td>
			<td th:text="${obj.msg}"></td>
		</tr>
	</table>
</body>
</html>