I made 2 one-to-one relationships with 2 foreign keys, but I can't make a constraint or how could I make the 2 unique keys be a unique key in the new table?
#Table(name = "cart")
public class Cart {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false)
private Long id;
private int quantity;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "product_id")
private Product products;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "user_id")
private User users;
}
#Entity
#Table(name = "Products")
public class Product {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
private int quantity;
private Double price;
private String image;
It spells my 2 keys correctly, for example
user_id = 2 , product_id =2 would be ok
but if I enter another user_id=2, product_id=2 should not work, but for me it is entered in the database
You can use #PrimaryKeyJoinColumn in the #OneToOne relation:
#OneToOne(cascade = CascadeType.ALL)
#PrimaryKeyJoinColumn(name = "product_id", referencedColumnName = "id")
private Product products;
Related
I have two table user(id,name) and user_mails(id,email,user_id) user to user_mails have one to many relation.
I have created following entity in spring boot
User
#Entity
#Table(name = "user")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private int id;
#Column(name = "name", nullable = false)
private String name;
#OneToMany(mappedBy = "user", cascade = CascadeType.ALL)
private Set<UserMail> userMails =new HashSet<UserMail>(0);
//Getter setter and constructor
}
UserMail
#Entity
#Table(name = "user_mails")
public class UserMail {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
#Column(name = "email", nullable = false)
private String name;
#ManyToOne(fetch = FetchType.LAZY, optional = false)
#JoinColumn(name = "user_id")
private User user;
It is showing following output on calling controller
[{"id":1,"name":"Ram","userMails":[{"id":2,"name":"ram#b.com","user":{"id":1,"name":"Ram","userMails":[{"id":2,"name":"ram#b.com","user":{"id":1,"name":"Ram","userMails":[{"id":2,"name":"ram#b.com","user":{"id":1,"name":"Ram","userMails":[{"id":2,"name":"ram#b.com","user":{"id":1,"name":"Ram","userMails":[{"id":2,"name":"ram#b.com","user":{"id":1,"name":"Ram","userMails":[{"id":2,"name":"ram#b.com","user":{"id":1,"name":"Ram","userMails":
and more
I want to access all users with all mail ids also want to acces mail id with user details
What changes should I do to get proper result
I have 2 class
public class User {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String age;
#OneToOne
#JoinColumn(name = "address_id", referencedColumnName = "id")
private Address address;
}
and
public class Address {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String building;
private String country;
#OneToOne(mappedBy = "address")
private User user;
}
in my table address, I have a few rows.
When I insert table user with data
{
"id":null,
"name":"Foo",
"age":"18",
"address":{
"id":1,
"building":"Too",
"country":"ABS"
}
}
Table user have 1 row with address_id =1.
I insert same data as above
Table user have 2 row with address_id =1.
My answer is: why 2 table connected by one to one can happen the above case?
You can find your answer here
Why #OneToOne is allowing duplicate associations?
Basically, #JoinColumn(name = "address_id", referencedColumnName = "id") alone doesn't serve the semantics of one-to-one in the database, you need to add unique=true into the #JoinColumn, which makes it #JoinColumn(name = "address_id", referencedColumnName = "id", unique = true).
Side-note: I suggest you drop your tables and then re-creating them before trying this out. If you are using Hibernate, you can set hibernate.hbm2ddl.auto to create-drop
I have a ManyToMany relationship that is broken down into 2 OneToMany relation. A Book can belong to multiple Categories and a Category can have many Books.
When I query for Book, the categories list just get empty. How can I get a list of all Categories that a Book belong to ? Am I missing something ?
#Entity
public class Book {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
#NotBlank(message = "Please input book title")
private String title;
private Integer publishYear;
private String publisher;
private String language;
private Integer numberOfPages;
private String avatarUrl;
#OneToMany(targetEntity = BookCategory.class, cascade = CascadeType.ALL)
#JoinColumn(name = "category", nullable = false, insertable = false, updatable = false)
private Set<BookCategory> categories = new LinkedHashSet<>();
}
#Entity
public class Category {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
#Column(nullable = false)
#NotBlank(message = "Please input category name")
private String name;
}
#Entity
public class BookCategory {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
#ManyToOne
#JoinColumn(name = "book", nullable = false)
private Book book;
#ManyToOne
#JoinColumn(name = "category", nullable = false)
private Category category;
}
Try using mappedBy attribute with #OneTOMany annotation on the 'One' side of the OneToMany relation.
Or you can also try using the following:
#ManyToMany
#JoinTable(
name = “book”_category,
joinColumns = #JoinColumn(name = “book_id”),
inverseJoinColumns = #JoinColumn(name = “category_id))
Read more:
https://vladmihalcea.com/the-best-way-to-use-the-manytomany-annotation-with-jpa-and-hibernate/
I want to query data from two tables,
location field in Translation is a foreign key from id field of Location
#Entity
#Table(name = "Translation")
#Data
public class Translation {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
#NotNull private String language;
#NotNull private String name;
#NotNull private String description;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "location", nullable = false, insertable = false, updatable = false)
#Fetch(FetchMode.JOIN)
private Location location;
}
#Entity
#Table(name = "Location")
#Data
public class Location {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
#NotNull private String code;
#NotNull private String type;
private Double longitude;
private Double latitude;
#Column(name = "parent_id")
private Integer parentId;
#OneToMany(targetEntity = Translation.class, mappedBy="id", fetch = FetchType.EAGER)
private Set<Translation> translations;
}
————————————————————————————————————————
But when I use a query
#Query(
"SELECT new com.afkl.travel.exercise.model.RetrieveLocationResponse("
+ "loc.code, tran.name, loc.type, loc.latitude, loc.longitude, tran.description, loc.parentId)"
+ "FROM Location loc LEFT JOIN loc.translation tran")
List<RetrieveLocationResponse> fetchLeftJoin();
All the fields related to Translation is null, having no idea what happened
UPDATE
The following ones work for me.
#OneToMany(mappedBy = "location", cascade = CascadeType.ALL)
#JsonIgnore
private Set<Translation> translations;
#ManyToOne
#JoinColumn(name = "location")
private Location location;
try
#OneToMany(mappedBy = "location", cascade = CascadeType.ALL)
#JsonIgnore
private Set<Translation> translations;
#ManyToOne
#JoinColumn(name = "location")
private Location location;
I have a problem with the relationship oneToMany. I created tables in SQLite DB, this is my tables:
My CategoryModel:
#Entity
#Table(name = "Category")
#JsonIgnoreProperties({ "hibernateLazyInitializer", "handler" })
public class CategoryModel {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String category_name;
private String category_description;
private String image_path;
#JsonIgnore
#OneToMany( mappedBy = "category")
private Set<ProductModel> category;
My ProducCategory:
#Entity
#Table(name = "Product_Category")
#JsonIgnoreProperties({ "hibernateLazyInitializer", "handler" })
public class ProductModel {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.AUTO)
private Long product_id;
private Long category_id;
private String name;
private String description;
private int numberOfProduct;
private String image;
private int price;
#ManyToOne
#JoinColumn(name = "country_id", nullable = false)
private CategoryModel category;
I can get data from the Category table well but when I call data from the Product_Category table I have the error:
SQL error or missing database (no such column: productmod0_.country_id)
country_id does not exist anywhere in your tables.
What you want is : #JoinColumn(name = "category_id", nullable = false)