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
}
Related
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.
I have one table called image and another table called duplicate. There are two OneToMany relations are associated.
I am not quite sure whether below implementation is the right approach for that. Moreover whether we require that second private List<DuplicateEntity> duplicateEntities2; ?
ImageEntity:
#Entity
#Table(name = "image")
public class ImageEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "filename")
private String fileName;
#OneToMany(mappedBy = "imageEntity1")
private List<DuplicateEntity> duplicateEntities1;
#OneToMany(mappedBy = "imageEntity2")
private List<DuplicateEntity> duplicateEntities2;
}
DuplicateEntity:
#Entity
#Table(name = "duplicate")
public class DuplicateEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne
#JoinColumn(name = "image_a_id")
private ImageEntity imageEntity1;
#ManyToOne
#JoinColumn(name = "image_b_id")
private ImageEntity imageEntity2;
}
I'm trying to map with Hibernate an entity Product with self reference to other products.
The JSON sent to create a project is like this:
{"name":"chair", "description":"red chair",
"parent": {"name":"table","description":"red table"}
}
When I receive this json, I need to persist on DB the child product and set PARENT_PRODUCT_ID with the productId from parent attribute.
Some help, please?
public class Product implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Column(name = "ID")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer productId;
#Column(name = "NAME")
private String name;
#Column(name = "DESCRIPTION")
private String description;
#OneToMany(cascade=CascadeType.ALL)
#JoinColumn(name="PRODUCT_ID")
private List<Image> images;
#OneToMany(cascade=CascadeType.ALL)
#JoinColumn(name="PRODUCT_ID")
private List<Product> children;
#ManyToOne
#JoinColumn(name = "PARENT_PRODUCT_ID")
private Product parent;
Image.java:
#Entity
#Table
public class Image implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Column(name = "ID")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer imageId;
#Column(name = "TYPE")
private String type;
#ManyToOne
#JoinColumn(name = "PRODUCT_ID", nullable = false)
private Product product;
In the oneToMany relationships, I think it should be like:
#OneToMany(cascade=CascadeType.ALL, mappedBy="parent")
private List<Product> children;
I'm having two entities Car and CarDescription where CarDescription is depending on another foreign key from the table Language.
What I' trying to accomplish is to have a HashMap in Car such that whenever I'm having a Car entity-object I am able to access all descriptions from the language id.
Entity Car.java
#Entity
#Table(name = "Car")
public class Car extends AbstractTimestampEntity implements Serializable {
private static final long serialVersionUID = -5041816842632017838L;
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
private Long id;
#OneToMany(mappedBy="car")
#MapKeyColumn(name = "language_ID")
// #MapKey(name = "language") // does not work either
private Map<Long, CarDescription> carDescription = new HashMap<>(0);
}
Entity CarDescription.java
#Entity
#Table( name="car_description",
uniqueConstraints = {
#UniqueConstraint(columnNames={"language_id", "name"})
}
)
public class CarDescription extends AbstractTimestampEntity implements Serializable {
private static final long serialVersionUID = 2840651722666001938L;
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name = "ID", unique = true, nullable = false)
private Long id;
#NotNull
#ManyToOne
private Car car;
#NotNull
#OneToOne
private Language language;
// ..
}
Entity Language.java
#Entity
public class Language implements Serializable {
private static final long serialVersionUID = 3968717758435500381L;
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name="ID")
private Long id;
// ..
}
The problem I am having is that the mapping gives me a map from each CarDescription.id to CarDescription.
How can I accomplish a correct mapping?
In CarDescription you need to add the languageId property:
#Column(name = "language_id", insertable = false, updatable = false)
private Long languageId;
#NotNull
#OneToOne
#JoinColumn(name = "language_id")
private Language language;
public void setLanguage(Language language) {
this.languageId = language.getId();
this.language = language;
}
Then you can use it in the Car entity like this:
#OneToMany(mappedBy="car")
#MapKey(name = "languageId")
private Map<Long, CarDescription> carDescription = new HashMap<>(0);
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.