Hibernate Unknown integral data type for ids : <p>I'm starting with Hibernate and I have an error that I just can't figure out.</p>

<p>I have the following Classes:</p>

<pre><code>@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class AbstractColumn {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private String id;
    private String name;

//Other stuff
}
</code></pre>

<p>Then I have</p>

<pre><code>@Entity
public class DoubleColumn extends AbstractColumn  implements Column {

    @ElementCollection
    private Map&lt;Double,String&gt; isNA;
    private double min=0;
    private double max=0;
    @ElementCollection
    private List&lt;Double&gt; data;
    // a lot of stuff
}
</code></pre>

<p>And finally:</p>

<pre><code>@Entity
public class DataFrame {
    @OneToMany(cascade = CascadeType.ALL)
    @PrimaryKeyJoinColumn
    private List&lt;AbstractColumn&gt; data;
    private String name;
    @Id
    @GeneratedValue
    private String id;
    @ElementCollection
    private Map&lt;String,Integer&gt; colIndex;
//more stuff
}
</code></pre>

<p>The error I'm getting is:</p>

<pre><code>Exception in thread "main" org.hibernate.id.IdentifierGenerationException: Unknown integral data type for ids : java.lang.String
    at org.hibernate.id.IdentifierGeneratorHelper.getIntegralDataTypeHolder(IdentifierGeneratorHelper.java:224)
    at org.hibernate.id.enhanced.SequenceStructure$1.getNextValue(SequenceStructure.java:98)
    at org.hibernate.id.enhanced.NoopOptimizer.generate(NoopOptimizer.java:40)
    at org.hibernate.id.enhanced.SequenceStyleGenerator.generate(SequenceStyleGenerator.java:432)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:105)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:192)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:177)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:675)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:667)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:662)
    at Main.main(Main.java:285)
</code></pre>

<p>The only hint that the error throws is that the error is in the main class here:</p>

<pre><code>DoubleColumn c1 = new DoubleColumn("Datos varios");
        c1.addData(12);
        c1.addData(11);
        c1.addData(131);
        c1.addData(121);
        c1.addData(151);
        c1.addData(116);


        DataFrame datosHibernate = new DataFrame("Dataframe Hibernate");
        datosHibernate.addColumn(c1);


        Configuration hibernateConfig = new Configuration();
        SessionFactory sessionFactory = hibernateConfig.configure().buildSessionFactory();
        Session session = sessionFactory.openSession();
        session.beginTransaction();
        session.save(datosHibernate);
        session.getTransaction().commit();
        session.disconnect();
        session.close();
        System.exit(0);
</code></pre>

<p>The ids are Strings, and I have them annotated as @GeneratedValue (I think I do not need to initialize them myself). The relation @OneToMany have the cascade annotation so it should be mapped correctly.</p>

<p>I've tried the code WITHOUT the session.save line and doesn't throw errors, so is not a problem in the code per se, it has to be something with Hibernate.</p>

<p>My configuration file is:</p>

<pre><code>&lt;hibernate-configuration&gt;
    &lt;session-factory&gt;
        &lt;property name="connection.url"&gt;jdbc:h2:E:/bd;DB_CLOSE_DELAY=-1;MVCC=TRUE&lt;/property&gt;
        &lt;property name="connection.driver_class"&gt;org.h2.Driver&lt;/property&gt;
        &lt;property name="connection.username"&gt;user&lt;/property&gt;
        &lt;property name="connection.password"&gt;&lt;/property&gt;
        &lt;property name="dialect"&gt;org.hibernate.dialect.H2Dialect&lt;/property&gt;
        &lt;property name="show_sql"&gt;true&lt;/property&gt;
        &lt;property name="hbm2ddl.auto"&gt;create&lt;/property&gt;

        &lt;mapping class="com.dataframe.estructuras.DataFrame"&gt;&lt;/mapping&gt;
        &lt;mapping class="com.dataframe.estructuras.column.AbstractColumn"/&gt;
        &lt;mapping class="com.dataframe.estructuras.column.types.DoubleColumn"/&gt;
    &lt;/session-factory&gt;
&lt;/hibernate-configuration&gt;
</code></pre>

<p>It creates the database file and I see all the SQL code generated, tables and all. Is when it tries to store the info when the thing breaks.</p>
