I am trying to create a new User(entity1) - it has reference to a Group (entity2) via a link table Member (entity3)
A user has a Set of groups as a class variable.
When i create my user object i want to say this user will be a member of group n (there are pre defined users that are linked to by id (1,2,3,4,5,6...) each group has some associated data in the table.
Whenever I create my user object as follows;
User user = new User();
user.setActive(1);
user.setCrby("me");
user.setUsername("username");
user.setCrdate("2016-06-20 12:42:53.610");
user.setCrwsref("...");
user.setModby("...");
user.setModdate("2016-06-20 12:42:53.610");
user.setModswref("..");
user.setBackground("Y");
user.setPassword("password");
user.setFullName("me");
Group group = new Group();
group.setId(1);
Group group2 = new Group();
group2.setId(2);
Set<Group> sets = new HashSet<Group>();
sets.add(group);
sets.add(group2);
user.setGroups(sets);
userDao.addUser(user);
I keep getting errors telling me that certain columns cannot be null. What I actually want to happen here is not to be doing an insert in to the group table but associating a user to a line in the group table. Is there a particular way I can prevent the columns in the group table being modified? I think I need to modify the mappings between the link table - this is how much pojos link right now
User
#Entity
#Table(name = "user")
public class User
{
#Id
#GeneratedValue
#Column(name = "id")
private int id;
#Column(name = "username")
private String username;
#Column(name = "password")
private String password;
#OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
#JoinTable(name = "zmember", joinColumns = {#JoinColumn(name = "username")}, inverseJoinColumns = {#JoinColumn(name = "id")})
private Set<Group> groups = new HashSet<Group>(0);
Member link table
#Entity
#Table(name = "member")
public class Member implements Serializable
{
#Id
#GeneratedValue
#Column(name = "id")
private int id;
#Id
#Column(name = "sgpid")
private int sgpid;
#Column(name = "username")
private String memberUsername;
Group
#Entity
#Table(name = "group")
public class Group
{
#Id
#GeneratedValue
#Column(name = "id")
private int id;
What is happening is there is no association to the link Member table so ideally should User have a set of member objects rather than a set of groups?
Thanks - this was quite hard to explain so sorry if it is hard to understand
This is a typical case for the #ManyToMany annotation. See for example:
https://dzone.com/tutorials/java/hibernate/hibernate-example/hibernate-mapping-many-to-many-using-annotations-1.html
The relationship from User to Group is essentially ManyToMany. You could model this is using the #ManyToMany annotation however one drawback with this approach is you cannot save additional information about the group in the join table such as 'date_joined'.
See: https://en.wikibooks.org/wiki/Java_Persistence/ManyToMany#ManyToMany
Using this approach you would not need the Join entity Member and the relationship on User would look like:
#ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
#JoinTable(name = "zmember", joinColumns = {#JoinColumn(name = "member_id", referencedColumnName = "id")}, inverseJoinColumns = {#JoinColumn(name = "group_id", referencedColumnName = "id")})
private Set<Group> groups = new HashSet<Group>(0);
The alternative to using #ManyToMany is to use a Join entity Member(ship) as you have done. This would allow you to save additional data about the relationship (by defining additional field mappings in the Join entity).
In this case the mappings would look like:
User:
public class User{
#OneToMany(mappedBy = "user", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private Set<Membership> memberships = new HashSet<Membership>(0);
//if required, you can 'hide' the join entity from client code by
//encapsulating add remove operations etc.
public void addToGroup(Group group){
Membership membershup = new Membership();
membership.setUser(this);
membership.setGroup(group);
memberships.add(membership);
)
public Set<Groupp> getGroups(){
//iterate memberships and build collection of groups
}
}
Membership:
public class Membership{
#Id
#GeneratedValue
#Column(name = "id")
private int id;
#ManyToOne
#JoinColumn(name = "user_id")
private Member member;
#ManyToOne
#JoinColumn(name = "group_id")
private Group group;
}
Group:
#Entity
#Table(name = "group")
public class Group
{
#Id
#GeneratedValue
#Column(name = "id")
private int id;
#OneToMany(mappedBy = "group", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private Set<Membership> memberships = new HashSet<Membership>(0);
}
Related
I have two jpa entities User + profile with many to many relationship like below :
User Entity
#Data
#Entity
#AllArgsConstructor
#NoArgsConstructor
#Table(name = "t_user")
public class UserEntity {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "user_id")
private Long Id;
#Column(nullable = false)
private String username;
#Column(nullable = false, length = 14)
private String siret;
#Cascade({
org.hibernate.annotations.CascadeType.SAVE_UPDATE,
org.hibernate.annotations.CascadeType.MERGE,
org.hibernate.annotations.CascadeType.PERSIST
})
#ManyToMany(fetch = FetchType.LAZY,cascade = CascadeType.MERGE)
#JoinTable(name = "t_user_profile", joinColumns = {#JoinColumn(name = "user_id")},
inverseJoinColumns = {#JoinColumn(name = "profile_id")})
private Set<ProfileEntity> profiles = new HashSet<>();
#OneToOne(fetch = FetchType.LAZY,cascade = CascadeType.ALL)
#JoinColumn(name = "ressource_id")
private RessourceEntity ressource;
}
and Profile entity :
#Data
#Entity
#AllArgsConstructor
#NoArgsConstructor
#Table(name = "t_profile")
public class ProfileEntity {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "profile_id")
private Long Id;
#Column(nullable = false)
#Enumerated(EnumType.STRING)
private Profiles profile;
#ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "profiles")
private Set<UserEntity> user = new HashSet<>();
}
The problem is when I send an http request contaning the same profiles with different users, I obtain new duplicated profiles records with new IDs in the Profile table in the database like below :
but the correct way is to add the informations ONLY in the joined table t_user_profile because profile already exists in profile table .
I tried cascade.All , persist and merge .... but the same result .
And if I remove cascade and i search for profile Id using findById and get the Id and insert... I got a problem when the profile is new and don't exist in DB and the problem is because I removed cascade ... So I want if the profile already exists , I want to add the relationship in the joined table ONLY.
I have two entities mapped Board and Tag by #ManyToMany to a join table board_tag_table.
How would I return the top 5 most common tag_id in the board_tag_table?
enter image description here
public class Board {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
#ManyToMany(fetch = FetchType.LAZY,cascade = CascadeType.ALL)
#JoinTable(name = "board_tag_table",
joinColumns = {
//primary key of Board
#JoinColumn(name = "id", referencedColumnName = "id")
},
inverseJoinColumns = {
//primary key of Tag
#JoinColumn(name = "tag_id", referencedColumnName = "tag_id")
})
private Set<Tag> tags = new HashSet<>();
}
public class Tag {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer tag_id;
private String tagname;
#JsonIgnore
#ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "tags")
private Set<Board> boards = new HashSet<>();
}
Unable to find how to query within a many to many table
you can pass through foreach and write your query in Tag repository, but I think you can't write query, because they are have list from two sides
Consider using a native query instead.
If you want to use the JPA, you can add a field (Eg. usedCount) in the Tag entity and follow the instructions here https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#repositories.limit-query-result.
The query should look like this:
List<Tag> findByUsedCount(Sort sort, Pageable pageable);
Don't look at it as trying to access the board_tag_table, and instead look at how you would do this with the java entities themselves. This would be just selecting the 5 top Tags based on the number of boards they have. "select t.tag_id, count(b) as boardCount from Tag t join t.boards b group by t.tag_id order by boardCount", then use maxResults to limit the returned values to 5
I have two entities connected with many-to-many relationship. For example:
#Entity
public class Account {
#Id
private Long id;
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(
name = "account_games",
joinColumns = {#JoinColumn(name="account_id")},
inverseJoinColumns = {#JoinColumn(name="game_id")}
)
private Set<Game> games = new HashSet<>();
}
#Entity
public class Game {
#Id
private Long id;
#ManyToMany(mappedBy = "games", fetch = FetchType.LAZY)
List<Account> accounts = new ArrayList<>();
}
So, there is a table account_games(account_id, game_id) in mysql describing entities many-to-many relations.
I don't want to have Game entity anymore. Is there a way to get rid of Game and leave gameId relation only? So, I'd like to have code something like that:
#Entity
public class Account {
#Id
private Long id;
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(
name = "account_games",
joinColumns = {#JoinColumn(name="account_id")},
inverseJoinColumns = {#JoinColumn(name="game_id")}
)
private Set<Long> gameIds = new HashSet<>();
}
without making changes in database.
I've tried different configuration on javax.persistance annotations, but none worked
You can use #ElementCollection and #CollectionTable to achieve that.
#Entity
public class Account {
#Id
private Long id;
#ElementCollection(fetch = FetchType.LAZY)
#CollectionTable(name = "account_games", joinColumns = #JoinColumn(name = "account_id"))
#Column(name = "game_id", nullable = false)
private Set<Long> gameIds = new HashSet<>();
}
You may have to change the query on how to filter data using gameId. Element Collection Query
I have 3 tables which are Person Login and Account.
Person and Login is OneToOne relation and Login has one FK which is connected Person's id column called PERSON_ID.
Person(one) and Account(many) is OneToMany relation and Account has one FK which is connected Person's id column called PERSON_ID as well .
what i want to do is when i delete one data from Account , nothing happen to Person and Login.
if i delete one data from Person which id=1, Login's PERSON_ID=1 data will be deleted , and all of the data PERSON_ID=1 from Account will be deleted as well.
if i delete one data from Login which PERSON_ID=1, Person 's id=1 data will be deleted , and all of the data PERSON_ID=1 from Account will be deleted as well.
how should i set the cascade ?
i've tried dozens of times and still can't find the logic in there, thanks!!
here's my code of all 3 tables without setting cascade:
`
#Entity
#Table(name = "PERSON")
public class Person {
#Id
#Column(name = "ID", nullable = false, unique = true)
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
#Column(name = "NAME")
private String name;
#Column(name = "SEX")
private String sex;
#OneToMany(mappedBy = "person",fetch = FetchType.LAZY)
private List<Account> account;
#OneToOne(mappedBy = "person")
private Login login;
#get..
#set..
}
`
#Entity
#Table(name = "ACCOUNT")
public class Account {
#Id
#Column(name = "ID")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
#Column(name = "ACCOUNT")
private String account;
#Column(name = "AMOUNT")
private String amount;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "PERSON_ID",referencedColumnName = "ID")
public Person person;
#get..
#set..
}
`
#Entity
#Table(name = "LOGIN")
public class Login {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID")
private long id;
#Column(name = "USERNAME")
private String userName;
#Column(name = "PASSWORD")
private String password;
#OneToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "PERSON_ID", referencedColumnName = "ID")
private Person person;
#get..
#set..
}
It's been a while, but if I'm not mistaken you need to use the cascade=REMOVE option on the OneToMany and OneToOne relationships. In the OneToOne I think you need to specify cascade=REMOVE on the side that does NOT own the relationship, that is, the side that also contains the "mappedBy" property.
Finally, I believe JPA will NOT automatically load lazy relationships and then cascade them. I'm thinking you may need to fetch the relationship before you delete the parent entity (otherwise JPA will not know what to delete).
I would like to ignore #OnetoMany field in my entity. fetch data need to get actual fields but don't want to fire query to dependent table. But deleting data from parent table needs deletion from dependent table
I have tried #Transient that ignores but the delete is also being ignored. Is there any other option to tell JPA not to fetch data from childs table when i call the parent entity?
#Entity
Table(name = "User")
public class UserEntity implements Serializable {
#Id
#Column(name = "id")
private int id;
#Column(name = "SERIAL", unique = true, nullable = false)
private String serial;
#OneToMany(mappedBy = "serialBySerialId", cascade = CascadeType.ALL)
private Set<UserActionEntity> userActionsById;
}
#Table(name = "user_action")
public class UserActionEntity implements Serializable {
#Id
#Column(name = "id")
private int id;
#Column(name = "action")
private String action;
#ManyToOne
#JoinColumn(name = "USER_ID", referencedColumnName = "ID", nullable = false)
private UserEntity userByUserId;
If you don't want to fire query to dependent table, you can use (fetch = FetchType.LAZY) on UserActionEntity property.
#OneToMany(mappedBy = "serialBySerialId", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<UserActionEntity> userActionsById;