我用springjpa和angular构建了一个api rest。此api有一个列表字段“tags”，可通过postman with post方法正确发布：

但当我转到部署在heroku中的api时，tags字段是空的：

{"id":3164,"name":"Iñaki","surname":"Williams","dni":"19238191G","address":"calle almanaque,Madrid","mail":"williams@iñaqui.com","phone":"9373482382","linkedln":"https://www.linkedin.com/

在/sara-b-54b93543/“，”state“：”por validar“，”rating“：”67“，”availability“：”tardes“，”tags“：[]}]
我的Maven模型：

@Entity
@Table(name="experts")
public class Expert {

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

    private String name;
    private String surname;
    private String dni;
    private String address;
    private String mail;
    private String phone;
    private String linkedln;
    private String state;
    private String rating;
    private String availability;

    @ManyToMany(mappedBy="expert", cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Tag> tags = new ArrayList<>();

    public Expert() {
    }

    public Expert(String name, String surname, String dni, String address, String mail, String phone, String linkedln, String state, String rating, List<Tag> tags, String availability) {
        this.name = name;
        this.surname = surname;
        this.dni = dni;
        this.address = address;
        this.mail = mail;
        this.phone = phone;
        this.linkedln = linkedln;
        this.state = state;
        this.rating = rating;
        this.tags = tags;
        this.availability = availability;
    }

我的标签型号：

@Entity
@Table(name="tags")
public class Tag {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable(
           name = "experts_tags",
           joinColumns = {@JoinColumn(name="tag_id", referencedColumnName = "id")},
           inverseJoinColumns = {@JoinColumn(name="expert_id", referencedColumnName = "id")}
   )
    private List<Expert> expert = new ArrayList<>();

    public Tag() {
    }

expertdao中的postexpert方法：

@Override
    public Expert postExpert(Expert expert) {
         this.manager.persist(expert);
         return expert;
    }

知道为什么会这样吗？？谢谢您！！！