Below are my entity classes Instructor and Courses having OnetoMany Relations, where all CRUD Operation is working but while fetching Instructor I don't want courses to be fetched. But when I execute GET instructor By Id, It also fetches courses in Postman. This should be avoided.
public class Instructor {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private Long id;
private String firstName;
private String lastName;
private String email;
#OneToMany(mappedBy = "instructor", cascade = {CascadeType.ALL})
#JsonManagedReference
private List < Course > courses;
}
public class Course {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String title;
#ManyToOne(fetch =FetchType.LAZY)
#JoinColumn(name = "instructor_id")
#JsonBackReference
private Instructor instructor;
}
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 entities as below:
Course
#Entity
public class Course {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToMany(mappedBy = "course", cascade = {CascadeType.PERSIST, CascadeType.REMOVE, CascadeType.MERGE})
private List<Comment> comments;
Comment
#Entity
public class Comment {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String comment;
#ManyToOne(targetEntity = Course.class)
private Course course; //Error: 'Many To One' attribute type should not be 'Course'
I follow luv2code.com course but he use Spring MVC and it work just find, but when I do this in spring boot, it always show the error, please help me fix this!
Try something like this:
#Entity
public class Course {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToMany(mappedBy = "course")
private List<Comment> comments;
And your comment entity:
#Entity
public class Comment {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String comment;
#ManyToOne(cascade = CascadeType.ALL)
private Course course;
#Entity
public class Course {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToMany(cascade = CascadeType.ALL,
fetch = FetchType.LAZY,
orphanRemoval = true)
private List<Comment> comments = new ArrayList<Comment>();
#Entity
public class Comment {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String comment;
}
You don't to define ManyToOne Mapping in your comment Entity.
Simple Fetch Problem I'm facing in a straight-forward OneToMany Relationship: One Author Many Books.
Here's Author :
#Entity
#Table(name = "authors")
public class AuthorEntity {
#Id
#GeneratedValue
private UUID id;
#Column(name = "first_name")
private String firstName;
#Column(name = "last_name")
private String lastName;
#OneToMany(
mappedBy = "author",
orphanRemoval = true,
fetch = FetchType.EAGER
)
private List<BookEntity> books; // Getters and Setters
}
Here's Book:
#Entity
#Table(name = "books")
public class BookEntity {
#Id
#Column(name = "id")
#GeneratedValue
private UUID id;
#Column(name = "title")
private String title;
#ManyToOne(optional = false)
#JoinColumn(
name = "author_id",
referencedColumnName = "id"
)
private AuthorEntity author;
// Getters and Setters
}
I saved an author and a book through their respective repositories and I checked everything is fine, and here's my query to fetch the author :
SELECT a FROM AuthorEntity a JOIN a.books WHERE a.id = :authorId
Now when I try to access author.getBooks() it says it is null, why doesn't it fetch ? Why do I always have to fetch the books separately ? What's the right query ?
I have some trouble with joining tables using Spring Boot JPA
I need to do this kind of joining:
**book2user — book to user
id INT NOT NULL AUTO_INCREMENT
time DATETIME NOT NULL
type_id INT NOT NULL
book_id INT NOT NULL
user_id INT NOT NULL**
Here are my Entity classes:
#Entity
#Table(name = "user")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
private String hash;
private Date reg_time;
private Integer balance = 0;
private String name;
// getters and setters
public class Book {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
#ManyToOne
#JoinColumn(name = "author_id", referencedColumnName = "id")
private Author author;
#ManyToOne
#JoinColumn(name = "genre_id", referencedColumnName = "id")
private Genre genre;
private String title;
private String slug;
private String description;
private String priceOld;
private String price;
private String image;
private boolean is_bestseller;
private Date pub_date;
// getters and setters
In order to do this kind of joining I should create another entity class ??
Something like this should work:
#Entity
#Table("book2user")
public class Book2User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private LocalDateTime time;
private Integer typeId;
#OneToOne
private Book book;
#OneToOne
#JoinColumn(name = "user_id") //optional, if the name of the table and field matches.
private User user;
}
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)