Java 通过SpringRESTAPI将另一个对象中的对象发布到mongoDB

我正在为库中的成员创建一个基本crud应用程序。我创建了一个SpringAPI来获取这些值并将其插入数据库。所以当我用邮递员检查时，会显示一个错误。（500：内部服务器错误）
下图显示了我试图发送的请求。

如上所示，我正在成员对象中发送另一个对象，一旦我删除了最新版本，就不会出现任何错误，即会发布值

我想解决这个问题，请帮我解决

API

@PostMapping("/m")
public Member save(@RequestBody Member member){
    repository.save(member);
    return member;
}

Member.java

@Document(collection = "Members")
public class Member {

@Id
private String id;
private String name;
private Book latestBook;
private String gender;
private int contact;

public Member() {
}

public Member(String id, String name, Book latestBook, String gender, int contact) {
    this.id= id;
    this.name = name;
    this.startMembershipDate = startMembershipDate;
    this.gender = gender;
    this.contactNum = contactNum;
}

 //getters , setters and toString method

}

public class Book{

private String name;
private String author;
private int year;

public Book(String name, String author, int year) {
    this.name= name;
    this.author= author;
    this.year = year;
}
    //getters , setters and toString method
}

Book.java

@Document(collection = "Members")
public class Member {

@Id
private String id;
private String name;
private Book latestBook;
private String gender;
private int contact;

public Member() {
}

public Member(String id, String name, Book latestBook, String gender, int contact) {
    this.id= id;
    this.name = name;
    this.startMembershipDate = startMembershipDate;
    this.gender = gender;
    this.contactNum = contactNum;
}

 //getters , setters and toString method

}

public class Book{

private String name;
private String author;
private int year;

public Book(String name, String author, int year) {
    this.name= name;
    this.author= author;
    this.year = year;
}
    //getters , setters and toString method
}

我想问题出在图书课上，所以请帮我解决这个问题。
不仅对于发布，对于删除也不起作用。

解决了这个问题

@Document(collection = "Members")
public class Member {

@Id
private String id;
private String name;
private Book latestBook = new Book();
private String gender;
private int contact;

public Member() {
}

public Member(String id, String name, Book latestBook, String gender, int contact) {
    this.id= id;
    this.name = name;
    this.startMembershipDate = startMembershipDate;
    this.gender = gender;
    this.contactNum = contactNum;
}

 //getters , setters and toString method

}

////////////////////////

public class Book{

private String name;
private String author;
private int year;

Book(){}

public Book(String name, String author, int year) {
    this.name= name;
    this.author= author;
    this.year = year;
}
    //getters , setters and toString method
}

---

您能发布错误跟踪以查看问题所在吗？好的，您需要使用DBRef注释来链接一对一映射。请跟随