JPA mapping to a collection of objects of same class

Question

I have an Entity which contains a collection of another Entity which itself references the same class in a collection, with the following mappings:

@Entity
@Table(name="parents")
public class Parent {
    @Id
    @GeneratedValue
    private long id;
    @ElementCollection
    @Cascade(org.hibernate.annotations.CascadeType.ALL)
    private Set<Child> children;

    public Parent() {}

    public Parent(Set<Child> children) {
        this.children = children;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public Set<Child> getChildren() {
        return children;
    }

    public void setChildren(Set<Child> children) {
        this.children = children;
    }

    @Entity
    @Table(name="children")
    public static class Child {
        @Id
        @GeneratedValue
        private long id;
        private String name;
        @ElementCollection
        @Cascade(org.hibernate.annotations.CascadeType.ALL)
        private Set<Child> dependencies;

        public Child() {}

        public Child(String name) {
            this.name = name;
            dependencies = new LinkedHashSet<>();
        }

        public long getId() {
            return id;
        }

        public void setId(long id) {
            this.id = id;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public getDependencies() {
            return dependencies;
        }

        public setDependencies(Set<Child> dependencies) {
            this.dependencies = dependencies;
        }
    }
}

But when I try to save it, I get a: java.lang.IllegalStateException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing exception

I've read in another post that I should use @Cascade(CascadeType.ALL) annotation, but as you can see, I tried doing so and it didn't solve my problem.

Please help me understand what's wrong with these mappings