I am doing an application where I need 2 entities: User and Car.
public class User{
private long id;
private String name;
}
public class Car{
private long id;
private User firstUser;
private User secondUser;
}
So my table cars_info info will contain
RENT(date), FIRST_USER(id), SECOND_USER(id)
How do I connect this using hibernate? I need unidirectional relation. I tried OneToOne, ManyToOne but neither of that works.
Check that you're properly naming the column on your CAR table vs the reference column on the USER table. Example below:
#Entity
#Table(name = "USER")
public class User {
#Id
#Column(name = "USER_ID")
private long id;
#Column(name = "NAME")
private String name;
}
#Entity
#Table(name = "CAR")
public class Car {
#Id
#Column(name = "CAR_ID")
private long id;
#ManyToOne
#JoinColumn(name = "FIRST_USER_ID", referencedColumnName = "USER_ID")
private User firstUser;
#ManyToOne
#JoinColumn(name = "SECOND_USER_ID", referencedColumnName = "USER_ID")
private User secondUser;
}
Related
I have two entites as follows
user entity
#Entity
#Table(name = "user")
#Getter
#Setter
public class UserEntity{
#Id
#GeneratedValue(strategy = GeneratedType.IDENTITY)
#Column(name = "user_id")
private Long userId;
#Column(name = "user_name")
private String name;
#OneToOne(Cascade=CascadeType.ALL, mappedBy="user")
private UserAddressEntity addressEntity;
}
user address entity
#Entity
#Table(name = "user_address")
#Getter
#Setter
public class UserAddressEntity{
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "user_id")
private Long userId;
#Column(name = "address")
private String address;
#OneToOne
#JoinColumn(name = "user_id", nullable = false, referencedColumnName = "user_id")
private UserEntity user;
}
I am saving user entity as follows in service class
#Service
public class UserService{
#Autowired
private UserRepository userRepository;
public void saveUser(){
UserEntity userEntity=new UserEntity();
UserAddressEntity userAddressEntity=new UserAddressEntity();
//logic here
userEntity.setAddressEntity(userAddressEntity);
userRepository.save(userEntity);
}
}
After saving entity user_id column is not being saved in user_address table. It's value is saved as null.I can't seem to find where the issue is.
EDIT:
I have added following to entities after answer referred in comments but I am getting this error
Infinite recursion (StackOverflowError)
#Entity
#Table(name = "user")
#Getter
#Setter
public class UserEntity{
#Id
#GeneratedValue(strategy = GeneratedType.IDENTITY)
#Column(name = "user_id")
private Long userId;
#Column(name = "user_name")
private String name;
#OneToOne(Cascade=CascadeType.ALL, mappedBy="user")
private UserAddressEntity addressEntity;
//added this
public void setAddressEntity(UserAddressEntity addressEntity){
if (!addressEntity.equals(this.addressEntity)){
this.addressEntity=addressEntity;
addressEntity.setUser(this);
}
}
#Entity
#Table(name = "user_address")
#Getter
#Setter
public class UserAddressEntity{
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "user_id")
private Long userId;
#Column(name = "address")
private String address;
#OneToOne
#JoinColumn(name = "user_id", nullable = false, referencedColumnName = "user_id")
private UserEntity user;
//added this
public void setUser(UserEntity user){
if (!user.equals(this.user){
this.user=user;
}
}
}
You need to set the relationship correctly in UserService.saveUser():
userEntity.setAddressEntity(userAddressEntity);
userAddressEntity.setUser(userEntity);
Also, use regular getters/setters, no need to add logic there.
The recommended/best way to map a #OneToOne is to use #MapsId. With that approach, you don’t need at all a bidirectional association.
I would advise you to take look at link below, there you have answer to your question with example how to save and map between objects.
https://vladmihalcea.com/the-best-way-to-map-a-onetoone-relationship-with-jpa-and-hibernate/
I've got following two tables:
Customer
id
name
Order
id
product_name
customer_id
with a 1 to 1 relation
and java entities:
#Data
public class Customer{
#Id
private Long id;
private String name;
}
#Data
public class Order{
#Id
private Long id;
#Column("id")
private Customer customer; //i want to somehow map this
private String productName;
}
and a controller
#Controller
public class MyController{
//...
#GetMapping("/")
public String getmap(Model m){
System.out.println(repository.findAll()) //prints "nullrows" due to wrong sql statement
return "mytemplate";
}
}
my current issue is, that spring is executing following sql statement:
SELECT Order.id, Order.product_name, Customer.id, Customer.name
FROM Order LEFT OUTER JOIN Customer ON Customer.id = Order.id
what i actually want is to join on Customer.id = Order.customer_id while leaving the classes as they are i.e. the customer reference needs to stay in order.
i've tried every annotation that i could find so far and have made no progress.
EDIT:
I am not allowed to use jpa/hibernate
One workaround is to do the following:
#Data
public class Customer{
#Id
private Long id;
private String name;
}
#Data
public class Order{
#Id
private Long customerId;
private Long id;
#Column("id")
private Customer customer; //i want to somehow map this
private String productName;
}
causing this to automatically join on Customer.id = Order.customer_id
This does not look like a good fix however.
You can use #OneToOne and #JoinColumn annotations for your One-to-One relationship:
#Data
public class Customer{
#Id
#Column(name = "id")
private Long id;
#Column(name = "name")
private String name;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "order_id", referencedColumnName = "id")
private Order order;
}
#Data
public class Order{
#Id
#Column(name = "id")
private Long id;
#Column(name = "product_name")
private String productName;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "customer_id", referencedColumnName = "id")
private Customer customer;
}
I have question. I have 3 entities Book->Part->Page with relationships.
Book.java
#Entity
#Table(name = "Book")
public class Book{
#ID
#Column(name = "id")
private Long id;
#OneToMany
#JoinColumn(name="bookid", referencedColumnName="id")
private Set<Part> parts = new HashSet<Part>;
}
Part.java
#Entity
#Table(name = "Part")
public class Part{
#ID
#Column(name = "id")
private Long id;
#Column(name="bookid")
private Long bookid;
#ManyToMany
#JoinTable(name="partpage",
joinColumns = #JoinColumn(name = "id")
inverseJoinColumns = #JoinColumn(name = "pageid")
private Set<Page> pages = new HashSet<Page>;
}
Page.java
#Entity
#Table(name = "Page")
public class part{
#ID
#Column(name = "pageid")
private Long id;
#Column(name="color")
private String color;
#Column(name="type")
private String type;
}
I have query = "Select b FROM book b". This query returns all books with all relation parts and pages.
What I need.
I need count how many pages with color = green and type = comedy in each Book. Is it possible to do it in one query?
Thank you all.
I want to make a friend system via hibernate, and I need to check user-friend's corresponding time when this user had related to other.
I hope table columns like following code:
table 1:
int id;
String name;
table 2:
int user_id;
int friend_id;
Date startdate;
POJO code:
public class User {
private int id;
private String name;
private Map<User,Date> friends;
}
I think you need nothing more then JPA. Something like this:
#Entity
#Table(name = "users")
public class User implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column
private String name;
#ElementCollection(fetch = FetchType.EAGER)
#CollectionTable(name = "friendship", joinColumns = #JoinColumn(name = "user_id"))
#MapKeyColumn(name = "friend_id")
#Column(name = "start_date")
private Map<Long, Date> friendshipMap;
... getters/setters ...
}
I have the following two classes, one ReqCandAssociation can have many Comments and it is mapped like so. I need to figure out a way that when I delete a ReqCandAssociation it deletes all of its associated comments. Thanks
#Entity
#Table(name = "candidate_jobReq")
public class ReqCandAssociation implements Serializable {
#Id
private Integer candidateId;
#Id
private Integer jobId;
#Column(name = "reqStatus")
private String reqStatus;
#ManyToOne
#PrimaryKeyJoinColumn(name="candidateId", referencedColumnName="id")
private Candidate candidate;
#ManyToOne
#PrimaryKeyJoinColumn(name="jobId", referencedColumnName="id")
private JobReq jobReq;
public ReqCandAssociation(){
}
Second class
#Entity
#Table(name="comment")
public class Comment {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Integer id;
#Column(name="commentText")
private String commentText;
#Column(name="commentDate")
private Date commentDate;
#ManyToOne
#PrimaryKeyJoinColumn(name="reqCandAssociationId", referencedColumnName="id")
private ReqCandAssociation reqCandAssociation;
#ManyToOne
#PrimaryKeyJoinColumn(name="userId", referencedColumnName="id")
private User user;
Change this to the following, i'm making it bidirectional mapping.
#Entity
#Table(name = "candidate_jobReq")
public class ReqCandAssociation implements Serializable {
#Id
private Integer candidateId;
#Id
private Integer jobId;
#Column(name = "reqStatus")
private String reqStatus;
#OneToMany(cascade = { CascadeType.ALL }) //this is added here.
#JoinColumn(name ="reqCandAssociationId")
private Set<Comment> comments;
-----
Readup more on the cascade options. All cascade types are all|none|save-update|delete|all-delete-orphan|delete-orphan
The cascade all will delete all the comments associated to this class.