And again: How to solve 'Repeated column in mapping for collection'?

Question

I'm trying to use HashMap in entity Player and my HashMap is a compound of Integer and another entity (entity ResourceOnPlayerAccount) that is in a One-To-Many relationship, so I can prevent duplicated entries but still can keep the newest entry. My code worked well with a HashSet but that way I couldn't keep the newest entries.

I already searched for another post. Among these posts, I found this one Another Repeated column in mapping for entity error But in this post, the problem seems to be the repeated call of a column, but in my code, I can't find something like that. And also I couldn't find an example with a HashMap.

I added the Player entity as followed:

Player.java

@Entity
@Table(name="player")
public class Player {

    // define fields

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="id")
    private int id;

    @Column(name="user_name")
    private String userName;

    @Column(name="password")
    private String password;

    @Column(name="display_name")
    private String displayName;

    @Column(name="email")
    private String email;

    // define relationships

//    @OneToMany(cascade = CascadeType.ALL)
//    @JoinColumn(name = "player_id")
//    private Set<ResourceOnPlayerAccount> resourceOnPlayerAccountSet;

    @OneToMany
    @MapKeyColumn(name = "player_id")
    private Map<Integer, ResourceOnPlayerAccount> resourceOnPlayerAccountMap;
...

The commented lines are my previous implementation with HashSet that had worked.

Following is the other entity class:

ResourceOnPlayerAccount.java

@Entity
@Table(name = "resources_on_player_account")
public class ResourceOnPlayerAccount {

    // define fields

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private int id;

    @Column(name = "amount")
    private double amount;

    @Column(name = "resource_id")
    private int resourceId;
...

I just want to make sure that a player does not have duplicate resources in his account and that existing amounts of resources can be updated.

score 2 · Accepted Answer · answered Aug 06 '19 at 08:32

2

@MapKeyColumn is used in a Map<Basic, Basic> situation.

In your case, it is Map<Basic, Entity>. For this @MapKey is used:

Specifies the map key for associations of type java.util.Map when the map key is itself the primary key or a persistent field or property of the entity that is the value of the map.

answered Aug 06 '19 at 08:32

Maciej Kowalski

25,605
12
54
63

I changed the annotation. Now I get the following error message: `Map key property not found: com.avanoah.projectf.springdemo.projectfwebversion.entity.ResourceOnPlayerAccount.player_id` – Constantin Beer Aug 06 '19 at 08:34
it should be name of persistent field, not db column. So playerId or whatever you called it in your entity. – Maciej Kowalski Aug 06 '19 at 08:36
Oh ok. I didn't had add the player_id column from the db to the `ResourceOnPlayerAccount` entity. But I did it now and changed `@MapKey(name = "player_id)` to `@MapKey(name = "playerId)`. But got the following error message: `Schema-validation: missing table [player_resource_on_player_account_map]`. If you want I could edit my post and add the updated code. – Constantin Beer Aug 06 '19 at 09:04
1

Most likely you are missing mappedBy on the OneToMany – Maciej Kowalski Aug 06 '19 at 09:05
Thank you! That was it. Know it compiles. I just have to check now if it works as wished with the updates of the resources. :) – Constantin Beer Aug 06 '19 at 09:23

And again: How to solve 'Repeated column in mapping for collection'?

1 Answers1