Map columns of separate tables into a single object and vice versa

Question

Situation 1

I have the following tables, very simple:

.......................

And I have the following classes:

Client:

@Entity
public class Cliente implements Serializable {

    private static final long serialVersionUID = 7402770378598465859L;

    private Short id;
    private String nome;

    @Column(name="data_nascimento")
    private LocalDate dataNascimento;

    private Contato contato;

    //Constructor
    // get e sets
}

Contact:

@Entity
public class Contato implements Serializable {

    private static final long serialVersionUID = -5040500676803061821L;

    private String telefone;
    private String celular;

    //Constructor
    // get e sets
}

Official:

@Entity
public class Funcionario implements Serializable{

    private static final long serialVersionUID = -5718684144972644433L;

    private Short id;
    private String nome;
    private String rg;
    private String cpf;
    private boolean ativo;
    private Contato contato;

    //Constructor
    // get e sets
}

Situation 2

I have the following tables, very simple:

And I have the following classes:

Client:

@Entity
public class Cliente implements Serializable {

    private static final long serialVersionUID = 7402770378598465859L;

    private Short id;
    private String nome;

    @Column(name = "data_nascimento")
    private LocalDate dataNascimento;

    private String telefone;
    private String celular;

    // Constructor
    // get e sets
}

Official:

@Entity
public class Funcionario implements Serializable {

    private static final long serialVersionUID = -5718684144972644433L;

    private Short id;    
    private String nome;
    private String rg;
    private String cpf;
    private boolean ativo;
    private String telefone;
    private String celular;

    // Constructor
    // get e sets
}

Issues

1 - In "Situation 1", we have 2 tables and 3 classes, in which the properties telephone and cellular class Contact are represented as columns in tables Official and Client in the database, how this situation is mapped using JPA?

2 - In "Situation 2", we have 3 tables and 2 classes, in which the columns of the "Contact" table of the database are represented in the application as class properties Official and Client, how do I map using JPA in this situation?

3 - In the Customer class we have the property dataNascization which stores an object of the type java.time.LocalDate. To JPA(2.1) and/or Hibernate(4.3.5.Final) provides some annotation or other means for mapping this object? If not, there is some other alternative than to re-use the java.util.Date?

4 - This is a question of curiosity about SQL, the type attribute BIT currently has some difference from TINYINT(1)?

Answer 1

Responding to situation 1 and 2:

What you need to solve situation 1 is in situation 2 and vice versa, that is, in situation 1 you have 2 tables and the code of situation 2 is noted for 2 entities. You also have the possibility, in situation 1, to create the Contact class without it is noted for JPA and make the others inherit from it. In situation 2, the attributes belong to the Contacts table, so they cannot be annotated in other entities. In that case do the following (alternative solution to situation 2):

1. Create the entity Contact;
2. Replace the phone and cell attributes of the classes with a variable of type Contact;

3. Make the note using @Onetoone as it is in the relationship.

   @Entity
   public class Contato implements Serializable {
   
       private static final long serialVersionUID = -5040500676803061821L;
   
       private String telefone;
       private String celular;
   
       //Constructor
       // get e sets
   }
   
   @Entity
   public class Cliente implements Serializable {
   
       private static final long serialVersionUID = 7402770378598465859L;
   
       private Short id;
       private String nome;
   
       @Column(name="data_nascimento")
       @Temporal(DATE)
       private Calendar dataNascimento;
   
       @OneToOne(fetch=FetchType.LAZY)
       private Contato contato;
   
       //Constructor
       // get e sets
   }
   
   @Entity
   public class Funcionario implements Serializable{
   
       private static final long serialVersionUID = -5718684144972644433L;
   
       private Short id;
       private String nome;
       private String rg;
       private String cpf;
       private boolean ativo;
   
       @OneToOne(fetch=FetchType.LAZY)
       private Contato contato;
   
       //Constructor
       // get e sets
   }
   

Responding to 3, see that I changed the date of birth type to Calendar and put the @Temporal annotation.

About the BIT in relation to TINYINT(1) is that the BIT by default in some databases is recognized as a boolean field, that is, it will always accept 0 or 1 or FALSE or TRUE. On the other hand, TINYINT stores integer values greater than 1 or less than 0, depending on how it was defined, and even defining it thus TINYINT(1) does not change its behavior. So if you are going to work with boolean values, use BIT.

Note: If the relationship is 1 to 1, remove the Contact table from the database and place the attributes in the Customer and Employee. It will facilitate your side and prevent excessive use of Join. :D

Updated:

If you want to keep the table separate and use its attributes in the entities you can use the @Embeddable annotation.

Oracle Javadoc Embeddable