I have a datamodel, which has:
a User entity which has a few fields specific to 2 users in the application
another entity UserDetails, which contains details specific to one particular type of user in the application besides the fields in User entity
Both entities share the same primary key. I am new to JPA. What kind of mappings should be there between the two?
#Entity
class User{
#Id
#Column(name="USER_ID")
private int id;
}
#Entity
class UserDetails{
#Id
#OneToOne(optional = false, fetch = FetchType.EAGER)
#JoinColumn(name = "USER_ID")
private User user;
...
}
The above mapping gives issues on fetching UserDetails for a particular User.
It requires that both Entities share the same primary key USER_ID.
You didn't mention the issues with the above mapping. It looks OK, but I would use a separate primary key for UserDetails table.
#Entity
class UserDetails{
#Id
private int id;
#OneToOne(optional = false, fetch = FetchType.EAGER)
#JoinColumn(name = "USER_ID")
private User user;
...
}
Also, it is a good practise to use bidirectional relationships, for eaiser navigation i.e. getting user details from User, you would just use user.getUserDetails(); so in User class:
#Entity
class User{
#Id
#Column(name="USER_ID")
private int id;
#OneToOne(mappedBy = "user")
private UserDetails userDetails;
}
In this case use OneToOne relationship. But make sure your database table UserDetailshas foreign key relationship to User table. Use below code to implement it using JPA and Hibernate.
#Entity
class User{
#Id
#Column(name="USER_ID")
private int id;
// getters and setters
}
#Entity
class UserDetails{
#Id
#Column(name="USER_DETAILS_ID")
private int userDetailsId;
#OneToOne(optional = false, fetch = FetchType.LAZY)
#JoinColumn(name = "USER_ID")
private User user;
// getters and setters
}
Related
I have a one to many relation on post class, and on the relation table I have one to one relation with user. Everything works find, but i want to be able to remove the relation, keeping the user entity, is that possible?
At this moment with the annotation orphanRemoval = true when I remove from post Detail list an element, this its removed from post_details table but the user is removed too.
#Entity
#Table(name = "ta_post")
public class Post{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private Date fcDate;
#OneToMany(mappedBy="post", cascade=CascadeType.ALL, orphanRemoval = true)
private List<PostDetails>;
}
#Entity
#Table(name = "ta_user")
public class User{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private int mail;
}
#Entity
#Table(name = "ta_post_details")
public class PostDetails{
private int id;
#ManyToOne
#JoinColumn(name="post_id")
private Post post;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name="user_id")
private User user;
private String postComments;
}
You must remove the CascadeType.ALL from the PostDetails. If you want to be able to change the User through the PostDetails, you can set the CascadeType to PERSIST or MERGE. If you want to create a PostDetail along with an User, you need to include the CascadeType CREATE.
I'd guess you are creating the user somewhere else and you just associate one with a Post, so removing the CascadeType.ALL should be enough to not delete your User from the database.
So i'm learning from these simple examples, there're 2 tables, USERS and USER_DETAILS, simple enough, each user has user_details and it's 1-to-1 relationship. So this sample is like this,
#Entity
#Table(name = "USERS")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "USR_ID")
private long id;
#Column(name = "USERNAME", nullable = false, unique = true)
private String username;
#Column(name = "PASSWORD")
private String password;
#OneToOne(cascade = CascadeType.ALL, mappedBy = "user", fetch = FetchType.LAZY)
private UserDetail userDetail;
//Setter and getter methods
}
#Entity
#Table(name = "USER_DETAILS")
public class UserDetail {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "USR_DET_ID")
private long id;
#Column(name = "FIRST_NAME")
private String firstName;
#Column(name = "LAST_NAME")
private String lastName;
#Column(name = "EMAIL")
private String email;
#Column(name = "DBO")
private LocalDate dob;
#OneToOne(fetch=FetchType.LAZY)
#JoinColumn(name = "USR_ID")
private User user;
//Setter and Getter methods
}
If you look at mappedBy, it's in the User not UserDetails.
Q1: so USER is the owner, if it calls save(),
USER_DETAILS table will be updated as well ?
Q2: same examples put mappedBy in the USER_DETAILS side,
why people want to do this ?
How to determine which side to put mappedBy ?
Thanks for your help !
Q2: same examples put mappedBy in the USER_DETAILS side,
why people want to do this ?
How to determine which side to put mappedBy ?
In a bidirectional relationship, each entity has a relationship field
or property that refers to the other entity. Through the relationship
field or property, an entity class’s code can access its related
object. If an entity has a related field, the entity is said to “know”
about its related object.
There is a bidirectional one-to-one relationship in your example. Both User and UserDetail entities have a relationship field. #OneToOne annotation specified on both the entities.
For one-to-one bidirectional relationships, the owning side
corresponds to the side that contains the corresponding foreign key.
The owner of the relationship is UserDetail entity. The owner has #JoinColumn annotation to specify foreign key (USR_ID).
Inverse side of relationship (User) has mappedBy attribute.
Q1: so USER is the owner, if it calls save(),
USER_DETAILS table will be updated as well ?
In your example UserDetail is the owner. Therefore the saving process:
User user = new User(); // Ignoring the constructor parameters...
UserDetail userDetail = new UserDetail();
user.setUserDetail(userDetail);
userDetail.setUser(user);
userRepository.save(user);
You only need to save the parent. It will save the child as well.
In a db, I have User and Role entities. The share a many-to-many relation as a Role entity can be assigned to multiple User entities and on the other hand a User entity can be assigned to multiple Role entities.
My entity classes look like this
UserEntity
#Entity
public class UserEntity implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
#Column(unique = true, nullable = false)
private String username;
#ManyToMany
private Set<RoleEntity> roles;
...
}
RoleEntity
#Entity
public class RoleEntity implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
#Column(unique = true, nullable = false)
private String name;
#ManyToMany(mappedBy = "roles")
private Set<UserEntity> users;
...
}
With this configuration I am able to map the entities with each other. I am also able to delete a User entity. But I am not able to delete a Role entity as long as a relation exists.
If I add cascade = CascadeType.REMOVE the Rolegets deleted, but with it the User too of course.
To only way to get this working currently is to define a #JoinTable on both sides. But this seems more like a workaround. What am I doing wrong? As this is a regular use case, there got to be solution to this, although I haven found it yet...
You need the join table, it's not a work around. Remember you are mapping your object oriented model to a relational model. The only way to express many-to-many relationship in the relational model is defining a #JoinTable.
UPDATE: Adding comment in the answer
You sould define the #JoinTable just in one entity, for example UserEntity and mappedBy="roles" in RolesEntity inherits the definitions of #JoinColumn and #JoinTable names.
Then you need to define the cascade operations you want to perform in both sides of the relationship.
In RoleEntity
#ManyToMany(mappedBy = "roles")
private Set<UserEntity> users;
In UserEntity
#ManyToMany
#JoinTable(...)
private Set<RoleEntity> roles;
I am very new to hibernate and I am working with JPA and Hibernate4. Trying to insert parent object in child as onetoone relationship.
I went through some tutorials but All the example in the web shows, inserting both parent and child tables.
I want to insert data in child table only.
I have two tables called user and department.
User table consists of user details with department as onetoone relationship, as follows,
#Entity
#Table(name = "User")
public class UserEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "_id")
private String id;
#Column(name = "firstName")
private String firstName;
#Column(name = "lastName")
private String lastName;
#OneToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "departmentId")
private Department departmentId;
// getters and setters...
}
Below is my Department entity,
#Entity
#Table(name = "Department")
public class Department {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "_id")
private String id;
#Column(name = "name")
private String name;
// getters and setters...
}
In department table there is only 4 data. I want to insert data only in user data while insert into it and don't want to insert in Department.
How can I do that.Please assist.
You have to use mappedBy for this, as mentoned below in child Table, Department in your case
#OneToOne(mappedBy="department")
private UserEntity user;
These posts explain you better this,
JPA JoinColumn vs mappedBy
Understanding mappedBy annotation in Hibernate
You need to specify the relationship owner using mappedBy property in the OneToOne mapping in the owner side, here in your case in the Department class, you should add:
#OneToOne(mappedBy="department")
private UserEntity user;
I updated your code, to included the stated annotation and also renamed the Department property in your UserEntity class from departmentId to department to avoid confusion between relationship owner and its id:
#Entity
#Table(name = "User")
public class UserEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "_id")
private String id;
#Column(name = "firstName")
private String firstName;
#Column(name = "lastName")
private String lastName;
#OneToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "departmentId")
private Department department;
// getters and setters...
}
Below is the Department entity,
#Entity
#Table(name = "Department")
public class Department {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "_id")
private String id;
#Column(name = "name")
private String name;
#OneToOne(mappedBy="department")
private UserEntity user;
// getters and setters...
}
This will give you the right mapping with the expected behaviour.
In the #OneToOne annotation, the default value for parameter optional is true. So your annotation is the same as #OneToOne(fetch = FetchType.EAGER, optional = true). This means you can simply leave the Department in a UserEntity instance empty. In that case, persisting it results in persisting only a user entity and no department.
Even if you created a Department instance and assigned it to a UserEntity instance, persisting the UserEntity would not automatically persist the Department, since you don't have any cascade parameter in your annotation. If you don't automatically cascade persists, you would have to persist the Department first and then persist the corresponding user entity.
Maybe you're asking about using existing departments for your user entities. In that case, you first need to get the department via Hibernate (or the JPA API) from an entity manager. The entity instance you get is managed by Hibernate, and you can then set it in a UserEntity and persist that, to have it refer to the department.
Finally, I think one department will probably have more than one user. It might make more sense to have a #ManyToOne annotation instead of #OneToOne, indicating multiple users can refer to the same department, but that depends on your domain model.
I'm facing difficulties with saving objects with jpa repositories. I have two entities. One to one related:
#Entity(name="USER")
public class User {
#Id
#GeneratedValue
#Column(name = "USER_ID")
private Long userId;
private String username;
#OneToOne(mappedBy = "user", cascade = CascadeType.ALL)
#PrimaryKeyJoinColumn
#LazyCollection(LazyCollectionOption.FALSE)
private Wallet wallet;
and the Wallet
#Entity(name = "WALLET")
public class Wallet implements Serializable {
#Id
#GeneratedValue
#Column(name = "WALLET_ID")
private Long id;
#OneToMany(mappedBy = "wallet")
#Cascade({org.hibernate.annotations.CascadeType.ALL})
#LazyCollection(LazyCollectionOption.FALSE)
private List<Paper> papers;
#OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
#PrimaryKeyJoinColumn
private User user;
I have the issue with this situation - hibernate is not saving the wallet when I'm adding new user:
public String addUser(#PathVariable("userName") String userName) {
UserDto userDto = new UserDto();
userDto.setUsername(userName);
WalletDto walletDto = new WalletDto();
userDto.setWalletDto(walletDto);
userService.addUser(userDto);
return userDto.toString();
}
and the addUser:
#Override
#Transactional
public void addUser(UserDto userDto) {
userRepository.save(userConverter.convertToEntity(userDto));
}
where save is jpa method.
EDIT:
public void addUser(UserDto userDto) {
User user = userConverter.convertToEntity(userDto);
Wallet wallet = walletConverter.convertToEntity(userDto.getWallet());
user.setWallet(wallet);
userRepository.save(user);
}
and really strange thing:
12:30:06,619 DEBUG EntityPrinter:121 - com.private.model.Wallet{id=6, papers=null, user=com.private.model.User#7}
12:30:06,619 DEBUG EntityPrinter:121 - com.private.model.User{username=xyzasew, userId=7, wallet=com.private.model.Wallet#6}
and in Wallet table there is no user trail = )
Edit. Almost there I hope = ):
I want wallet to be the master of user and paper, accordingly to Your advices I've eddited a bit entities:
#Entity(name = "WALLET")
public class Wallet implements Serializable {
#Id
#GeneratedValue
#Column(name = "WALLET_ID")
private Long id;
#OneToMany(mappedBy = "wallet", cascade = CascadeType.ALL)
#LazyCollection(LazyCollectionOption.FALSE)
private List<Paper> papers;
#OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "wallet")
private User user;
and user:
#Entity(name="USER")
public class User {
#Id
#GeneratedValue
#Column(name = "USER_ID")
private Long userId;
private String username;
#OneToOne(cascade = CascadeType.ALL)
private Wallet wallet;
however wallet still does not have the user_id, and the user got it!
mappedBy basically means i am not the owner for the relationship, key is on the other side. Putting mappedBy on both side means nobody is the owner of the relationship.
Theoretically
Using "mappedBy" attribute of mapping annotations(like #OneToOne, #OneToMany, #ManyToMany) for bi-directional relationship. This attribute allows you to refer the associated entities from both sides. If "X" has association with "Y" then you can get X from Y and Y from X.
MappedBy signals hibernate that the key for the relationship is on the other side.
The annotation #JoinColumn indicates that this entity is the owner of the relationship. That is, the corresponding table has a column with a foreign key to the referenced table, whereas the attribute mappedBy indicates that the entity in this side is the inverse of the relationship, and the owner resides in the "other" entity.
Practically
#Entity
public class X implements Serializable {
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name="y_fk")
public Y getY() {
...
}
#Entity
public class Y implements Serializable {
#OneToOne(mappedBy = "y")
public X getX() {
...
}
Since this is annotated with mappedBy it shows that this is NOT the owner, and that the Owner is X (the field that is annotated). name attribute is telling Hibernate where to find the information about the FK mapping (inside X there is a getY() method). No additional fields will be created in Y.
Improvements to be done in the above code
#LazyCollection:
defines the lazyness option on #ManyToMany and #OneToMany
associations. LazyCollectionOption can be TRUE (the collection is lazy
and will be loaded when its state is accessed)
User.Java Entity changes can be reduced to below
#OneToOne(cascade = CascadeType.ALL)
private Wallet wallet;