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

Question

So I have two simple beans -- FatKid and Hamburgers. Now, for reasons unbeknownst to me I need to be able to not only look up all of the hamburgers someone ate, but also who ate which particular hamburger. Onto the code!

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);
        }
    }

}

So when I run the code I end up with 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]
        ...

So the first Hamburger is saved but it then blows up on the second. Both should be able to use the FatKid's id as their foreign key but it doesn't seem to work. Any insight would be greatly appreciated.

Thanks, Kevin

Answer 1

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.