HQL Many to Many JOIN with extra columns - mysql

Question

I have a many to many relationship in Hibernate with additional colums so I have an extra java class for the model and another class with the primary key... now in HQL I need a query that retrieve those data but I have problems with Join condition.
This is my First class:
#Entity
#Table(name = "Firsts")
public class First {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
#OneToMany(mappedBy = "primaryKey.second")
private List<FirstsSeconds> seconds = new LinkedList<>();
#Column(name="description")
private String description;
...
}
The Second class:
#Entity
#Table(name="Seconds")
public class Second {
#Id
private String code;
#OneToMany(mappedBy = "primaryKey.first")
private List<FirtsSeconds> firsts = new LinkedList<>();
...
}
And the table manyToMany with additional columns:
#Entity
#Table(name = "firsts_seconds")
#AssociationOverrides({ #AssociationOverride(name = "primaryKey.first", joinColumns = #JoinColumn(name = "id")),
#AssociationOverride(name = "primaryKey.second", joinColumns = #JoinColumn(name = "code")) })
public class FirstsSeconds{
#EmbeddedId
private FirstsSecondsId primaryKey = new FirstsSecondsId();
#Column(name = "extra", nullable = false)
private String extra;
...
}
So the id class:
#Embeddable
public class FirstsSecondsId {
#ManyToOne
private First first;
#ManyToOne
private Second second;
...
}
Finally to get HQL result I create a new class with the field that I want:
public class NewObject
public CargoOrder(String firstDescription, String fsExtra) {
this.firstDescription = firstDescription;
this.fsExtra = fsExtra;
}
...
First of all I want First descrption and extra from FirstsSecond, so this is my query with JOIN fr.seconds as fs:
#Query("SELECT new com.mypackage.NewObject("
+ "fr.description as firstDescription, fs.extra as fsExtra) "
+ "FROM First as fr"
+ "JOIN fr.seconds as fs")
public List<NewObject> findManyToMany();
But I have no results :(... in this case I have to specify the where condition?
#Query("SELECT new com.mypackage.NewObject("
+ "fr.description as firstDescription, fs.extra as fsExtra) "
+ "FROM First as fr"
+ "JOIN fr.seconds as fs WHERE fr.first = fs.primaryKey.first")
public List<NewObject> findManyToMany();
Thats not compile on JOIN fr.seconds as fs WHERE fr.first = fs.primaryKey.first...
Kind regards.

Answer 1

Solved... debugging with spring.jpa.show_sql = true in application-properties I see that there was a bad matching in the join condition, I mapped wrong keys:
In First class it's primaryKey.first (not second):
#OneToMany(mappedBy = "primaryKey.first")
private List<FirstsSeconds> seconds = new LinkedList<>();
And in Second primaryKey.second (not first):
#OneToMany(mappedBy = "primaryKey.second")
private List<FirstsSeconds> firsts = new LinkedList<>();