The concept for one-to-one mapping. Explain the mapping

Question

How to define a One-to-One relation between 2 classes ? I think I am going wrong somewhere,conceptually. I don\'t know what ,but it is.

Let us suppose t

Answer 1

The problem is in the relation between your xml mapping and your Java code.

If you specify

there needs to be a field named "name_pm" in your Country POJO.

You don't have such a field.

If your Country class has a field for the corresponding PM object, that field's name should be used here.

If neither class has a reference to the other, you need to add one.

What I would probably do with your code is to add a field to country and use its name in the mapping.

public class Country {
    private int c_id;
    private String name_c;
    private PM c_pm;

    public int getC_id() {
        return c_id;
    }

    public void setC_id(int c_id) {
        this.c_id = c_id;
    }

    public String getName_c() {
        return name_c;
    }

    public void setName_c(String name_c) {
        this.name_c = name_c;
    }

    public PM getC_pm() {
        return c_pm;
    }

    public void setC_pm(PM c_PM) {
        this.c_pm = c_pm;
    }

}

Mapping:

Disclaimer:

I haven't tested any of this, and I'm not sure of exactly how the mapping should be done with a shared primary key. If anyone else feels like providing a tested version, I'll happily upvote another answer or let this one turn "community wiki".