Single-directional OneToMany mapping with 3 classes using 1 single class

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Single-directional OneToMany mapping with 3 classes using 1 single class

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#1 by (0 votes)

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Good evening,

I have the following structure:

@Entity
public class Endereco {
   private String logradouro;
   private String numero;
   private String cep;
   private String bairro;
   private String complemento;
}

@Entity
public class Cliente {
    @OneToMany
    private Set<Endereco> enderecos;
    // Outros atributos...
}

@Entity
public class Fornecedor {
    @OneToMany
    private Set<Endereco> enderecos;
    // Outros atributos...
}

@Entity
public class Procurador {
    @OneToMany
    private Set<Endereco> enderecos;
    // Outros atributos...
}

@Entity
public class Fiador {
    @OneToMany
    private Set<Endereco> enderecos;
    // Outros atributos...
}

How do I create a relationship for all Client, Vendor, Proxy, and Guarantor classes to use the same "ENDERECOS" table or something similar?

java hibernate jpa

asked by anonymous 15.10.2016 / 04:23

1 answer

@protocol is not working Pass Coordinates from Activity to MapsFragment

score 0 · Accepted Answer

If you do not want join tables , you must use inheritance and register the foreign key in the Endereco table. The superclass would look something like:

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class ObjetoComEndereco {
    @Id
    private Long id;

    @OneToMany(cascade = CascadeType.ALL, mappedBy="objetoComEndereco")
    private List<Endereco> enderecos = Lists.newArrayList();
}

Note that mappedBy is required. If not used, Hibernate will create an auxiliary table and use UNION to retrieve the addresses.

The other classes extend ObjetoComEndereco . For example:

@Entity
public class Cliente extends ObjetoComEndereco {
    // Outros atributos...
}

The class Endereco changes to:

@Entity
public class Endereco {
    @Id
    private Long id;

    @ManyToOne
    private ObjetoComEndereco objetoComEndereco;
}

Hibernate will only create 5 tables:

create table cliente (
    id bigint not null,
    primary key (id)
)

create table endereco (
    id bigint not null,
    objeto_com_endereco_id bigint,
    primary key (id)
)

create table fiador (
    id bigint not null,
    primary key (id)
)

create table fornecedor (
    id bigint not null,
    primary key (id)
)

create table procurador (
    id bigint not null,
    primary key (id)
)

A proxy query, for example, produces this SQL:

/* criteria query */ select
    this_.id as id1_4_0_,
from
    procurador this_

As the address list is lazy , Hibernate makes another query when it is time to access it:

select
    enderecos0_.objeto_com_endereco_id as objeto_c2_1_0_,
    enderecos0_.id as id1_1_0_,
    enderecos0_.id as id1_1_1_,
    enderecos0_.objeto_com_endereco_id as objeto_c2_1_1_ 
from
    endereco enderecos0_ 
where
    enderecos0_.objeto_com_endereco_id=?

If it is eager the query changes to:

/* criteria query */ select
    this_.id as id1_4_1_,
    enderecos2_.objeto_com_endereco_id as objeto_c2_1_3_,
    enderecos2_.id as id1_1_3_,
    enderecos2_.id as id1_1_0_,
    enderecos2_.objeto_com_endereco_id as objeto_c2_1_0_ 
from
    procurador this_ 
left outer join
    endereco enderecos2_ 
        on this_.id=enderecos2_.objeto_com_endereco_id