java - 传递给持久化的分离实体 : com. carpooling.entity.Role；嵌套异常是 org.hibernate

Question

我在我的项目中使用 Spring Boot 和 Spring Data:

@Entity
public class User {
   vate Long       id;
   private String     firstName;
   private String     familyName;
   @ManyToMany( fetch = FetchType.LAZY, cascade = CascadeType.ALL )
   @JoinTable( name = "user_role", joinColumns = {
        @JoinColumn( name = "USER_ID", nullable = false, updatable = false ) }, inverseJoinColumns = {
                @JoinColumn( name = "ROLE_ID", nullable = false, updatable = false ) } )
private List<Role> roles;
//getters and setters
 }

角色类:

@Entity
 public class Role {
   @Id
   @GeneratedValue( strategy = GenerationType.IDENTITY )
   private Long       id;
   private String     roleName;

   @ManyToMany( fetch = FetchType.LAZY, mappedBy = "roles" )
    private List<User> users;
   //getters and setters
 }

添加用户方法:

public User AddUser( User user ) {
    // TODO Auto-generated method stub
    List<Role> roles = user.getRoles();
    user.setRoles( roles );
    return userRepsitory.save( user );
}

当我尝试添加新用户时，出现上面的错误，这是发送的 JSON 对象:

{"firstName":"fff","familyName":"ffff","roles":[{"id":1}, {"id":2}] }

Answer 1

由于您要级联非托管实体，因此如果您的实体确实有 id(如您的情况)，jpa 会认为它们是独立的实体，并且您需要将它们管理起来，您只需使用提供的 id 从数据库中获取角色即可。

public User AddUser( User user ) {
// TODO Auto-generated method stub
 List<Role> roles = new ArrayList<Role>();
 for(Role entry :user.getRoles()) 
    roles.add(roleDao.findOne(entry.getId()));
user.setRoles( roles );
return userRepsitory.save( user );
}