Create a Post entity named Post.kt with the @Entity annotation to convert this class into an entity class. Here is the code of this model class:

@Entity
class Post(text: String, postedBy: Profile) : Serializable {

    @Id
    @GeneratedValue
    var id: Long? = 0

    var text: String? = text

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "profile_id")
    @JsonIgnoreProperties("username","password", "email","accCreatedTime","firstName","lastName",
            "contactNumber","dob","city","country")
    var postedBy: Profile? = postedBy

    @JsonIgnore
    @JsonProperty("postCreatedTime")
    var postCreatedTime: Instant? = Instant.now()

    @OneToMany(cascade = [CascadeType.ALL], fetch = FetchType.LAZY, orphanRemoval=true)
    val comments = mutableListOf<Comment>()


    @OneToMany(cascade = [CascadeType.ALL], orphanRemoval = true)
    var likes: List<LikeObj>? = mutableListOf<Comment>()
}

Here we have two elements and one constructor. Here is the constructor:

@Entity
class Post(text: String, postedBy: Profile) : Serializable {
   -----
   -----
}

It's time now to discuss some new annotations that have been used in this class:

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "profile_id")
@JsonIgnoreProperties("username","password", "email","accCreatedTime","firstName","lastName",
            "contactNumber","dob","city","country")
    var postedBy: Profile? = postedBy

@ManyToOne on the Profile variable means that this will indicate which user posted that specific status. 

@JoinColumn means its access element Profile is connected with the foreign key using profile_id.

@JsonIgnoreProperties(......) ignores the JSON properties during deserialization. In this project, when you get the post's JSON, in the profile attribute you will only find the id. Here is a simple example of a JSON:

You can see "id":0, which is the id of the post.

Now create a mutable list of the Comment and annotate it with @OneToMany, as follows:

 @OneToMany(cascade = [CascadeType.ALL], fetch = FetchType.LAZY, orphanRemoval=true)
    val comments = mutableListOf<Comment>()

@OneToMany(....) means a post can be many comments and likes. 

cascade = [CascadeType.ALL] attribute is a feature of Hibernate. It means you can apply all primary cascade types.

fetch = FetchType.LAZY means it fetches the data lazily during the first access.

orphanRemoval=true means if the post has been deleted, then all the comments and likes on this post will be deleted automatically.