我有两个实体- User , UserPayment . User 以及 UserPayment 有一个 OneToMany 关系。有一个变量 setDefault 在 UserPayment . 新的时候 UserPayment ，其 setDefault 应该设置 true 以及其他 UserPayment 特别是 User 应设置为 false . 新建之后 UserPayment 是创建的，当坚持，我得到下面的错误。
实体用户

@Entity
public class User  {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "Id",nullable = false,updatable = false)
    private Long id;

    @OneToMany(mappedBy = "user",cascade = CascadeType.ALL)
    private List<UserPayment> userPaymentList;

}

实体用户支付

@Entity
public class UserPayment{

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

    private boolean defaultPayment;

    @ManyToOne
    @JoinColumn(name="user_id")
    @JsonIgnore
    private User user;

}

控制器

@RequestMapping(value = "/add",method = RequestMethod.POST)
public ResponseEntity addNewCardDetail(@RequestBody UserPayment userPayment,Principal principal) {  
    if(principal != null) {
        String username = principal.getName();
        User user = userServiceImpl.findUserByUsername(username);
        userServiceImpl.uodateUserBilling(user,userPayment);
        return new ResponseEntity("Your card has been successfully saved",HttpStatus.OK);
    }
    return new ResponseEntity("Card not saved",HttpStatus.BAD_REQUEST);
}

服务实现

@Override
public void uodateUserBilling(User user, UserPayment userPayment) {
    userPayment.setDefaultPayment(true);
    userPayment.setUser(user);
    List<UserPayment> paymentList = user.getUserPaymentList();
    for(UserPayment eachPaymnet:paymentList) {
        eachPaymnet.setDefaultPayment(false);
        paymentRepository.save(eachPaymnet);
    }    
    user.getUserPaymentList().add(userPayment);
    userRepository.save(user); 

}

错误

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.dao.InvalidDataAccessApiUsageException: Multiple representations of the same entity [com.bookstore.domain.UserPayment#53] are being merged. Detached: [com.bookstore.domain.UserPayment@6ea664ae]; Managed: [com.bookstore.domain.UserPayment@790e8792]; nested exception is java.lang.IllegalStateException: Multiple representations of the same entity [com.bookstore.domain.UserPayment#53] are being merged. Detached: [com.bookstore.domain.UserPayment@6ea664ae]; Managed: [com.bookstore.domain.UserPayment@790e8792]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:652)