CODEWITHSUNDEEP
javahibernate
Edgaras Karka
Edgaras Karka

Reputation: 7852

Java hibernate get all Entities

I have two Java Hibernate entities user and userPick:

@Entity
@Table(name="users")
public class User{

  @Column(length=50)
  private String name;

  @OneToMany
  private List<UserPick> userPicks = new ArrayList<UserPick>(0);
  ...

and

@Entity
@Table(name="usersPicks")
public class UserPick {
  ...
  User user; // this line no exist in code 
             // I want get it when load all picks
             // I am confused here or I can do it, because in user is
             // List<userPick> and it sounds like circle
             // user.getUserPicks().getUser().getUserPicks()....  
  ...

When I load user everythings ok. 

public User findByUserName(String name) {

    Criteria criteria = session.createCriteria(User.class);
    criteria.add(Restrictions.eq("name",name));

    List<User> users = criteria.list();

    if (users.size() > 0) {
        return users.get(0);
    } else {
        return null;
    }

}

But I looking way how I can get all usersPick's in one list and get picks users, something like:

public List<UserPick> getAllPicks(){
   Criteria criteria = session.createCriteria(UserPick.class);
   List<UserPick> picks = criteria.list();
   return picks;
}

I want to print pick user name System.out.print(picks.get(0).getUser().getName())

Upvotes: 2

Views: 3083

Answers (2)

v.ladynev
v.ladynev

Reputation: 19956

It is ok to have an association to User in the UserPick. To associate User and UserPick by a foreign key fk_user in the UserPick, please, add mappedBy = "user" to User and make association to User lazy in the UserPick. To specify a foreign key column name you need @JoinnColumn(name = "fk_user"). 

@Entity
@Table(name="users")
public class User{

  @Column(length=50)
  private String name;

  @OneToMany(mappedBy = "user")
  private List<UserPick> userPicks = new ArrayList<UserPick>();

}

@Entity
@Table(name="usersPicks")
public class UserPick {

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinnColumn(name = "fk_user") 
  private User user;

}

And you can fetch users by the way suggested by @StanislavL (except that you don't need to make an alias to user)

public List<UserPick> getAllPicks(){
   Criteria criteria = session.createCriteria(UserPick.class)
       .setFetchMode("user", FetchMode.JOIN);
   return criteria.list();
}

Even if an association to User in UserPick is not lazy It is not a problem because of Hibernate uses a cache to set the same User to all user's UserPick.

Upvotes: 3

StanislavL
StanislavL

Reputation: 57381

criteria.setFetchMode("user", FetchMode.JOIN)
.createAlias("user", "user")

The FetchMode.JOIN should solve n+1 query problem

Upvotes: 1

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