@Entity
public class Blog {
    @ManyToMany(cascade = CascadeType.ALL)
    private List<Tag> tags = new ArrayList<Tag>();
}

@Entity
public class Tag {

}

@Entity
public class Tag {
    @ManyToMany(mappedBy = “tags”)
    private List<Blog> blogs = new ArrayList<Blog>();
}

@Entity
public class Blog {
    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(
        name="blog_tag_relation",
        joinColumns=@JoinColumn(name="blog_id", referencedColumnName="id"),
        inverseJoinColumns=@JoinColumn(name="tag_id", referencedColumnName="id")
    )
    private List<Tag> tags = new ArrayList<Tag>();
}

@Entity
class BlogTag {
    @ManyToOne
    private Blog blog;

    @ManyToOne
    private Tag tag;

    private Date createdTime;
}

@Entity
public class Blog {
    @OneToMany(mappedBy = "blog")
    private final List<BlogTag> blogTags = new ArrayList<BlogTag>();

    public List<Tag> getTags() {
        return blogTags.stream().map(BlogTag::getTag).collect(Collectors.toList());
    }
}

@Entity
public class Tag {
    @OneToMany(mappedBy = "tag")
    private final List<BlogTag> blogTags = new ArrayList<BlogTag>();

    public List<Blog> getBlogs() {
        return blogTags.stream().map(BlogTag::getBlog).collect(Collectors.toList());
    }
}