hibernate foreign-keys one-to-many h2 bidirectional

Hibernate and H2 "Referential integrity constraint violation" for OneToMany bidirectional mapping

I have two simple beans--FatKid and Hamburgers. I need to be able to not only look up all of the hamburgers someone ate, but also who ate which particular hamburger.

FatKid.java

import java.util.List;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Table
@Entity
public class FatKid {
    
    private int id;
    private String name;
    private List<Hamburger> hamburgers;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "FATKID_ID")
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }

    @Column
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name="HAMBURGER_ID")
    public List<Hamburger> getHamburgers() {
        return hamburgers;
    }
    public void setHamburgers(List<Hamburger> hamburgers) {
        this.hamburgers = hamburgers;
    }

}

Hamburger.java

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Table
@Entity
public class Hamburger {

    private int id;
    private String description;
    private FatKid whoDoneAteMe;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "HAMBURGER_ID")
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }

    @Column
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name="FATKID_ID")
    public FatKid getWhoDoneAteMe() {
        return whoDoneAteMe;
    }
    public void setWhoDoneAteMe(FatKid whoDoneAteMe) {
        this.whoDoneAteMe = whoDoneAteMe;
    }

}

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">org.h2.Driver</property>
        <property name="hibernate.connection.url">jdbc:h2:~/routesetting</property>
        <property name="hibernate.dialect">org.hibernate.dialect.H2Dialect</property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">create-drop</property>

        <mapping class="FatKid" />
        <mapping class="Hamburger" />

    </session-factory>
</hibernate-configuration>

dependencies

<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>3.6.7.Final</version>
</dependency>

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <version>1.3.160</version>
</dependency>

<dependency>
    <groupId>javassist</groupId>
    <artifactId>javassist</artifactId>
    <version>3.9.0.GA</version>
</dependency>

client

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class OmNom {

    private static final SessionFactory sessionFactory = buildSessionFactory();

    public static void main(String[] args) {

        Session session = sessionFactory.openSession();

        session.beginTransaction();
        FatKid fk = new FatKid();
        fk.setName("Darrell");
        session.save(fk);
        session.getTransaction().commit();

        session.beginTransaction();
        Hamburger hamburger_1 = new Hamburger();
        hamburger_1.setDescription("Juicy quarter pounder with cheese");
        hamburger_1.setWhoDoneAteMe(fk);
        session.save(hamburger_1);
        session.getTransaction().commit();

        session.beginTransaction();
        Hamburger hamburger_2 = new Hamburger();
        hamburger_2.setDescription("Ground buffalo burger topped with bacon and a sunny-side egg");
        hamburger_2.setWhoDoneAteMe(fk);
        session.save(hamburger_2);
        session.getTransaction().commit();

        sessionFactory.close();

    }

    private static SessionFactory buildSessionFactory() {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            return new Configuration().configure().buildSessionFactory();
        }
        catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            throw new ExceptionInInitializerError(ex);
        }
    }

}

The output (and truncated stack trace):

Hibernate: insert into FatKid (FATKID_ID, name) values (null, ?)
Hibernate: insert into Hamburger (HAMBURGER_ID, description, FATKID_ID) values (null, ?, ?)
Hibernate: insert into Hamburger (HAMBURGER_ID, description, FATKID_ID) values (null, ?, ?)
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: could not insert: [Hamburger]
        ...
Caused by: org.h2.jdbc.JdbcSQLException: Referential integrity constraint violation: "FK43797FE95067143: PUBLIC.HAMBURGER FOREIGN KEY(HAMBURGER_ID) REFERENCES PUBLIC.FATKID(FATKID_ID)"; SQL statement:
insert into Hamburger (HAMBURGER_ID, description, FATKID_ID) values (null, ?, ?) [23506-160]
        ...

The first Hamburger is saved but it blows up on the second.

How can I get it to use the FatKid's id as their foreign key?

Solution

Your mappings look weird to me. You have a @JoinColumn in both sides of the relationship, each pointing to the primary key of the other table. That doesn't seem to be a OneToMany relationship.

Your OneToMany should tell the owner of the relationship:

@OneToMany(cascade = CascadeType.ALL, mappedBy = "whoDoneAteMe")
public List<Hamburger> getHamburgers() {
    return hamburgers;
}

and then in the other side:

@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "fatkid_id")
public FatKid getWhoDoneAteMe() {
    return whoDoneAteMe;
}

You might be able to optimize your code further too. As your FatKid objects are aware of the Hamburger objects and you have configured cascading, you could do:

    session.beginTransaction();
    FatKid fk = new FatKid();
    fk.setName("Darrell");

    Hamburger hamburger_1 = new Hamburger();
    hamburger_1.setDescription("Juicy quarter pounder with cheese");
    hamburger_1.setWhoDoneAteMe(fk);
    fk.getHamburgers().add(hamburger1);

    Hamburger hamburger_2 = new Hamburger();
    hamburger_2.setDescription("Ground buffalo burger topped with bacon and a sunny-side egg");
    hamburger_2.setWhoDoneAteMe(fk);
    fk.getHamburgers().add(hamburger2);

    session.save(fk);
    session.getTransaction().commit();

    sessionFactory.close();

The above code should save the complete object graph with just one commit operation and in a single transaction.