Hibernate - OneToMany join with Map by key from another column

package logic.database.entity;

​

import org.hibernate.annotations.Fetch;

import org.hibernate.annotations.FetchMode;

​

import javax.persistence.*;

import java.util.Date;

import java.util.Map;

​

@Table(name = "groups")

public class GroupEntity

{

    @Id

    @GeneratedValue

    private Long id;

​

    private String name;

​

    @Fetch(value = FetchMode.SELECT)

    @OneToMany(fetch = FetchType.LAZY)

    @JoinColumn(name = "groupId", insertable = false, updatable = false) // groupId property is located in ItemEntity

    @MapKey(name = "type")                 // type property is located in ItemEntity

    private Map<String, ItemEntity> items; // should keep all items accessed by type property from ItemEntity

                                           // type property from ItemEntity has String type so map key is String type too

​

    // getters and setters here...

}

package logic.database.entity;

​

import org.hibernate.annotations.Fetch;

import org.hibernate.annotations.FetchMode;

​

import javax.persistence.*;

import java.util.Date;

import java.util.List;

​

@Table(name = "items")

public class ItemEntity

{

    @Id

    @GeneratedValue

    private Long id;

​

    private String name;

    private String description;

    private String type;        // in our case it is unique key in database with groupId property

                                // so in MySQL it should be: UNIQUE KEY (`group_id`, `type`)

​

    private Long groupId;       // groupId and group properties describe same relation

​

    @Fetch(value = FetchMode.JOIN)

    @ManyToOne(fetch = FetchType.EAGER)

    @JoinColumn(name = "id", insertable = false, updatable = false) // id property is located in GroupEntity

    private GroupEntity group;  // groupId and group properties describe same relation

​

    // getters and setters here...

}