How can i map multiple classes to one table in hibernate?

Question

From my research it seems not likely that its possible, but here is my use case.

I have a table called user with an address id.

I'd like to map a UserReference and User class to this table where UserReference does not contain the Address object (to save sql joining time) and User does contain the Address object (in case it's needed).

I can't use since it expects a join table, and I can't just define two separate classes because a get() seems to return double of every row (one for User, one for UserReference).

Does anyone know how I could go about this?

---

I guess I should try to explain myself better.

public class UserReference {
    private int id;
    private String name;
}

public class User extends UserReference {
    private Address;
}

I'd like to map both UserReference and User so that I can query for UserReference when I only need the basic details, and User whenever I need the full object.

I understand that I can simply have Address be lazy loaded but I have a two tier system which unproxies all objects once it passes through the layers.

---

edit:

Perhaps my question was too ambigious but based on the answers it doesn't seem very possible to do what I want. Thanks anyway everyone.

Answer 1

Your question is not very clear to me but I'll try to answer as per my understanding. It depends upon what you really want to persist and what you want as a java entity.

Consider you want to represent User class with a database table i.e. represent User as entity in JPA. Now you can Create an Embeddable class which will be part of another class.

So you can map an Address class in User Entity and make the Address class as Embeddable using @Embeddable annotation package com.thejavageek.embeddabledemo;

import javax.persistence.Embeddable;

@Embeddable
public class Address {

    private String area;
    private String city;
    private String pincode;

    public String getArea() {
        return area;
    }

    public void setArea(String area) {
        this.area = area;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getPincode() {
        return pincode;
    }

    public void setPincode(String pincode) {
        this.pincode = pincode;
    }

}

and you can embed this embeddable class as below

package com.thejavageek.embeddabledemo;

import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.TableGenerator;

@Entity
public class Person {

    @TableGenerator(name = "person_gen", table = "id_gen", pkColumnName = "gen_name", valueColumnName = "gen_val", allocationSize = 100)
    @Id
    @GeneratedValue(strategy = GenerationType.TABLE, generator = "person_gen")
    private String idperson;
    private String name;

    @Embedded
    private Address address;

    public String getIdperson() {
        return idperson;
    }

    public void setIdperson(String idperson) {
        this.idperson = idperson;
    }

    public String getName() {
        return name;
    }

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

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

}

Answer 2

UserReference.java

@Entity
@DiscriminatorColumn(name = "type")
@DiscriminatorValue(value = "UserReference")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class UserReference extends BaseEntity {

    private String name;
}

User.java

@Entity
@DiscriminatorValue(value = "User")
public class User extends UserReference {
    @OneToOne
    @JoinColumn(name = "address_id")
    private Address address;

}