@joincolunm with foreignKey Hibernate

Question

Hello I wanted to make a foreign key, but I don’t understand the syntax.

In the Endereco class:

@Embeddable
@Table(name = "tab_endereco")
public class Endereco {

@Column(length = 40, nullable = false)
private String logradouro;

@Column(length = 40, nullable = false)
private String bairro;

@JoinColumn(columnDefinition = "char(3)", nullable = false, foreignKey = @ForeignKey(name="fk_cidade"))
private Cidade cidade;

In the City class, where we catch the acronym:

@Entity
@Table(name = "tab_cidade")
public class Cidade {


@Id
@JoinColumn(columnDefinition = "char(3)", nullable = false, referencedColumnName = "fk_cidade")
private String sigla;

@Column(length = 40, nullable = false)
private String nome;

@Column(columnDefinition = "char(2)", nullable = false)
private Estado estado;

Answer 1

Hello, here’s an example of how you can create relationship in your classes.

State-class:

@Entity
public class Estado {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;
private String nome;
private String sigla;

As for the City Class, in this class I took the liberty of putting as primary key a field of Id, I don’t know if I would understand your need, but you can change according to the rules of your project:

@Entity
public class Cidade {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long cidadeId;
private String nome;

@ManyToOne
@JoinColumn(name = "estadoId")
private Estado estado;

Finally the class address, in this class did not put the state field because the City already has a state bound to it:

public class Endereço {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;
private String logradouro;

@ManyToOne
@JoinColumn(name = "cidadeId")
private Cidade cidade;

So come on:

@Id = Specifies the unique identification attribute of the object to be persisted;

@GeneratedValue(strategy=GenerationType.IDENTITY) = When using this annotation SGDB is responsible for generating the ID value of the object incrementally;

@ManyToOne = Sets a cardinality ratio of many to one, ie Many addresses are in a single city for example;

In your code I realized that you had used a note @Embeddable, in my example I removed because this annotation is used when working with composite key.

Thanks.