Propagating foreign key with Spring Data - mysql

Question

I am developing an Spring Boot app based on Spring Data Rest(which uses Hibernate underneath) and mySQL database. This app is incapable to populate the foreign keys of the referenced entries(because I expect Hibernate does it for me).
Entities:
#Entity
public class Producto {
private Integer id;
private String nombre;
private List<Formato> listaFormatos;
public Producto() {
}
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getNombre() {
return nombre;
}
public void setNombre(String nombre) {
this.nombre = nombre;
}
#OneToMany(mappedBy = "producto", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
public List<Formato> getListaFormatos() {
return listaFormatos;
}
public void setListaFormatos(List<Formato> listaFormatos) {
this.listaFormatos = listaFormatos;
}
}
#Entity
public class Formato {
private Integer id;
private Integer cantidad;
private String unidadMedida;
private Producto producto;
public Formato() {
}
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
#ManyToOne
#JoinColumn(name = "producto_id", referencedColumnName = "id")
public Producto getProducto() {
return producto;
}
public void setProducto(Producto producto) {
this.producto = producto;
}
public Integer getCantidad() {
return cantidad;
}
public void setCantidad(Integer cantidad) {
this.cantidad = cantidad;
}
public String getUnidadMedida() {
return unidadMedida;
}
public void setUnidadMedida(String unidadMedida) {
this.unidadMedida = unidadMedida;
}
}
Repository:
public interface ProductoRepository extends CrudRepository<Producto, Integer> {
}
application.properties
spring.datasource.url = jdbc:mysql://localhost:3306/x1
spring.datasource.username = x2
spring.datasource.password = x3
spring.jpa.show-sql=true
spring.jpa.database=mysql
spring.jpa.hibernate.ddl-auto=create-drop
pom.xml
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-rest</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jersey</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-mail</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
Let's say that the request I am sending in JSON format looks like this:
{"nombre": "x",
"listaFormatos": [
{"cantidad": 1,
"unidadMedida":"kg"},
{"cantidad": 2,
"unidadMedida":"g"}
]
}
The output of all this is that I persist an 'producto' and 2 'formato' without foreign key. Because of that, I believe I cannot bring a producto with its formats
Does anyone know why the foreign key is not being propagated?

Answer 1

Empty FKs usually happening when you are not setting the back references.
Consider the following:
Parent p = new Parent();
...
Child c = new Child();
...
p.setChild(c);
c.setParent(p); // this is the line you are probably missing
Of course, you can put this logic into the Parent#setChild method as well.