How to map a unidirectional @OneToOne relationship with the mapping column on the child side?

Hibernate ORM
1

Hi there!

Background:
Here is an example of 2 tables:

    CREATE TABLE parent
    (
        id      serial PRIMARY KEY
    );
    
    CREATE TABLE child
    (
        id        serial PRIMARY KEY
        parent_id int REFERENCES parent (id)
    );

And the corresponding Entities:

    @Entity
    public class Parent {
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Integer id;
    
        @OneToOne(mappedBy = "parent", cascade = CascadeType.ALL, fetch = FetchType.LAZY, optional = false)
        private Child child;
    
        public void createChild(Child child) {
           child.setParent(this);
           this.child = child;
        }
    }
    
    @Entity
    public class Child {
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Integer id;
    
        private String name;
    
        @OneToOne(fetch = FetchType.LAZY)
        @JoinColumn(name = "parent_id")
        private Parent parent;
    }

Question:
Is it possible to get rid of the bidirectional mapping and keep the @OneToOne only on the parent side while still using parent_id in Child? (Having only parentId instead of Parent on the Child side is also appropriate)

PS:
I know that it’s possible to have unidirectional mapping if I add child_id in the parent like this, but that’s not the case:

    @Entity
    public class Parent {
    
        @OneToOne(cascade = CascadeType.ALL)
        @JoinColumn(name = "child_id", referencedColumnName = "id")
        private Child child;
    }

    @Entity
    public class Child {
        // nothing here
    }
2

A user recently opened a Jira exactly for this: [HHH-18495] - Hibernate JIRA.

Please see also the comments section and add your thoughts and suggestions there.

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