Duplicate spring jpa

Tag

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

    @Id
    @GeneratedValue
    private Long id;

    private String name;

    @ManyToMany(mappedBy = "tags")
    private Set<Post> posts = new HashSet<>();

    public Tag() {}

    public Tag(String name) {
        this.name = name;
    }

    //Getters and setters ommitted for brevity

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Set<Post> getPosts() {
        return posts;
    }

    public void setPosts(Set<Post> posts) {
        this.posts = posts;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Tag tag = (Tag) o;
        return Objects.equals(name, tag.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name);
    }
}


@Entity(name = "Post")
@Table(name = "post")
public class Post {

    @Id
    @GeneratedValue
    private Long id;

    private String title;

    public Post() {}

    public Post(String title) {
        this.title = title;
    }

    @ManyToMany(cascade = {
            CascadeType.PERSIST,
            CascadeType.MERGE
    })
    @JoinTable(name = "post_tag",
            joinColumns = @JoinColumn(name = "post_id"),
            inverseJoinColumns = @JoinColumn(name = "tag_id")
    )
    private Set<Tag> tags = new HashSet<>();

    //Getters and setters ommitted for brevity

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Set<Tag> getTags() {
        return tags;
    }

    public void setTags(Set<Tag> tags) {
        this.tags = tags;
    }

    public void addTag(Tag tag) {
        tags.add(tag);
        tag.getPosts().add(this);
    }

    public void removeTag(Tag tag) {
        tags.remove(tag);
        tag.getPosts().remove(this);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Post)) return false;
        return id != null && id.equals(((Post) o).id);
    }

    @Override
    public int hashCode() {
        return 31;
    }
}


Test:

Post post1 = new Post("JPA with Hibernate");
		Post post2 = new Post("Native Hibernate");

		Tag tag1 = new Tag("Java");
		Tag tag2 = new Tag("Hibernate");

		post1.addTag(tag1);
		post1.addTag(tag2);

		post2.addTag(tag1);

		postRepository.save(post1);
		postRepository.save(post2);