We Keep Coding

In the Entity class there are two references to the same field in the database

I am studying a training project - working with databases.
Here is a class describing the entity
#Entity
#Table(name = "pricelists", schema = "inventories")
public class PriceList {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "id_inventory", insertable = false, updatable = false)
private Long idInventory;
#ManyToOne
#JoinColumn(name = "id_inventory", nullable = false)
private Inventory inventory;
private Integer price;
}
And there are two variables that refer to the same "id_inventory" field in the database table. Is it possible to do this? Is this not a mistake?

You should leave that
#Entity
#Table(name = "pricelists", schema = "inventories")
public class PriceList {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne
#JoinColumn(name = "id_inventory", nullable = false)
private Inventory inventory;
private Integer price;
}
I hope that will work.

How to persist objects and its nested objects at once?

I'm with some problems trying to persist an object and its items, here're my classes:
#Entity(name = "Contract")
#Table(name = "contract")
public class Contract implements Serializable{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(unique = true, nullable = false)
private Long id;
#OneToMany(mappedBy = "idContract", cascade = CascadeType.ALL,fetch = FetchType.EAGER)
private List<ContractItem> contractItem;
//getters & setters...
}
.
#Entity(name = "ContractItem")
#Table( name = "contract_item")
public class ContractItem implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(unique = true, nullable = false)
private Long id;
#Column(name = "id_contract")
private Long idContract;
//getters & setters...
}
I'm extending JpaRepository im my repositories and using .save(contract) to persist but every time my application only persists the contract not de items, I've already tried CascadeType.ALL, MERGE and PERSIST in which either the result is the same, or I get an exception that my idContract must not be null.
Need some help here guys, thanks in advance !

How to maintain foreign key relationship in hibernate

I have two classes and I want to have a one to many relation between them, for e.g.:
Home(id<int>, rooms<string>)
Vehicle(id<int>, home_id<int>, name<string>)
I need to have a relation between Home and Vehicle class using Home.id and vehicle.home_id.
Please suggest any example which I can use here for CURD operation to implement REST service.

I need to have a relation between Home and Vehicle class using Home.id
and vehicle.home_id.
Your entities should look like this :
Vehicle Entity
#Entity
#Table(name = "vehicle", catalog = "bd_name", schema = "schema_name")
#XmlRootElement
public class Vehicle implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "id")
private Integer id;
#Column(name = "name")
private String name;
#JoinColumn(name = "home_id", referencedColumnName = "id")
#ManyToOne
private Home homeId;
//constructor getter & setters
}
Home Entity
#Entity
#Table(name = "home", catalog = "bd_name", schema = "schema_name")
#XmlRootElement
public class Home implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "id")
private Integer id;
#Column(name = "room")
private Character room;
#OneToMany(mappedBy = "homeId")
private List<Vehicle> vehicleList;
//constructor getter & setters
}

Hibernate/JPA incorrect join in Spring Boot Application

See code below for my 2 entity classes - when I call the findAll() method from my OrigRepository class, it joins these two tables using both primary keys. I want the join to be between the primary key of the Orig table and the foreign key entry in the MsgResponse table ("OrigID") - any sugggestions?
Orig Entity
#Entity
#Table(name = "originator")
public class Orig {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "OrigID")
private int OrigID;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "OrigID")
private MsgResponse responseInfo;
}
MsgResponse Entity
#Entity
#Table(name = "message_response")
public class MsgResponse {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "ID")
private int responseId;
#Column(name = "OrigID")
private int OrigId;
#OneToOne(mappedBy="responseInfo")
private Orig OrigInfo;
}

I suggest you to see the jpa documentation
here.
Example 1 should be your case

Try to swap relation ownership, that is:
#Entity
#Table(name = "originator")
public class Orig {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "OrigID")
private int OrigID;
#OneToOne(mappedBy="origInfo")
private MsgResponse responseInfo;
}
#Entity
#Table(name = "message_response")
public class MsgResponse {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "ID")
private int responseId;
// #Column(name = "OrigID")
// private int origId;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "OrigID")
private Orig origInfo;
}
Note that the #JoinColum annotation is in now in the MsgResponse entity. This is because in a #OneToOne the join column refers to the source entity (see here).
Hope this could help.

JPA modelling, one-to-one relation?

I am new to JPA and stuggles with defining the relations between my classes. I have a class called Player and a class called Game. A game holds references to two Player instances. The question is, how should this be modelled?
This is my current code:
#Entity
#Table(name = "t_player")
#JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL)
public class Player {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Basic
#Column(name = "name")
private String name;
#Basic
#Column(name = "uuid")
private final String uuid = UUID.randomUUID().toString();
I think this is ok, but my problem is in the Game class:
#Entity
#Table(name = "t_game")
#JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL)
public class Game {
public Game() {
}
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Basic
#Column(name = "uuid")
private final String uuid = UUID.randomUUID().toString();
#OneToOne
#PrimaryKeyJoinColumn
#JoinColumn(name = "id")
private Player player_1;
#OneToOne
#PrimaryKeyJoinColumn
#JoinColumn(name = "player_2")
private Player player_2;
public Game(Player player_1, Player player_2) {
this.player_1 = player_1;
this.player_2 = player_2;
}
}
This is not working, my table t_game only has two field; id and uuid. Where is my problem?

Remove the PrimaryKeyJoinColumn annotation, as I don't think it is what you meant to use, as it conflicts with the joincolumn definition. Use the joincolumn annotation instead to define the foreign key field name and the field it references if necessary.