@Entity
@Table(name = "person_conversation_meta")
@IdClass(ConversationMeta.Id.class)
public class ConversationMeta {
  public static class Id implements Serializable {
    private int conversation;
    private int person;

    public Id() {
    }

    public Id(int conversation, int person) {
      this.conversation = conversation;
      this.person = person;
    }

    public int getConversation() {
      return conversation;
    }

    public void setConversation(int conversation) {
      this.conversation = conversation;
    }

    public int getPerson() {
      return person;
    }

    public void setPerson(int person) {
      this.person = person;
    }

    @Override
    public boolean equals(Object o) {
      if (this == o) return true;
      if (o == null || getClass() != o.getClass()) return false;

      Id id = (Id)o;

      if (conversation != id.conversation) return false;
      if (person != id.person) return false;

      return true;
    }

    @Override
    public int hashCode() {
      int result = conversation;
      result = 31 * result + person;
      return result;
    }
  }

  @javax.persistence.Id
  @ManyToOne(optional = false, fetch = FetchType.LAZY)
  @JoinColumn(name = "person_id", nullable = false)
  private Person person;

  @javax.persistence.Id
  @ManyToOne(optional = false, fetch = FetchType.LAZY)
  @JoinColumn(name = "conversation_id", nullable = false)
  private Conversation conversation;

  @Column(name = "is_read", nullable = false)
  private boolean read;

  @Column(nullable = false)
  private boolean starred;

  public Person getPerson() {
    return person;
  }

  public void setPerson(Person person) {
    this.person = person;
  }

  public Conversation getConversation() {
    return conversation;
  }

  public void setConversation(Conversation conversation) {
    this.conversation = conversation;
  }

  public boolean isRead() {
    return read;
  }

  public void setRead(boolean read) {
    this.read = read;
  }

  public boolean isStarred() {
    return starred;
  }

  public void setStarred(boolean starred) {
    this.starred = starred;
  }
}

CriteriaQuery<ConversationMeta> criteriaQuery = criteriaBuilder.createQuery(ConversationMeta.class);
Root<ConversationMeta> conversationMeta = criteriaQuery.from(ConversationMeta.class);
criteriaQuery.where(criteriaBuilder.equal(conversationMeta.get(ConversationMeta_.conversation), conversation));