Estoy usandohbmddl.auto configurado para crear en el archivo de configuración de hibernación y usarlo para conectarse a la base de datos derby en modo de red (no incrustado, no sé si eso es relevante).

Aquí está mihibernate.cfg.xml

    <!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">org.apache.derby.jdbc.ClientDriver</property>
        <property name="connection.url">jdbc:derby://localhost:1527/HibernateDb;create=true</property>
        <property name="connection.username">admin</property>
        <property name="connection.password">admin</property>

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

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.DerbyDialect</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>

        <!-- Names the annotated entity class -->
        <mapping class="org.asif.javabrains.dto.UserDetails"/>

    </session-factory>

</hibernate-configuration>

Pero cuando ejecuto el programa java que está usando esto, también conocido como la clase de servicio, parece que no dejo caer la base de datos y la recrea. como dice el comentario (tomé el archivo de configuración de los ejemplos de hibernación).

~~~~ ACTUALIZACIÓN ~~~~

legué a la conclusión de que hbm2ddl no estaba descartando el esquema en función del siguiente comportamiento

Tengo 2 clases que se ven de la siguiente manera

@Entity
public class UserDetails {

    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private int userId;
    private String userName;

    @OneToMany
    @JoinTable(name="USER_VEHICLE",
               joinColumns=@JoinColumn(name="USER_ID"),
               inverseJoinColumns = @JoinColumn(name="VEHICLE_ID")
    )    
    private Collection<Vehicle> vehicles = new ArrayList<Vehicle>() ;

        /* getters and setters */
}

@Entity
public class Vehicle {
    @Id @GeneratedValue
    private int vehicleId;
    private String vehicleName;
    @ManyToOne
    @JoinColumn(name="USER_ID")
    private UserDetails user;

        /* getters and setters */
}

y la configuración de hibernación correspondiente es

 <!--boiler plate-->

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

    <!-- Names the annotated entity class -->
    <mapping class="org.asif.javabrains.dto.UserDetails"/>
    <mapping class="org.asif.javabrains.dto.Vehicle"/>

  <!--boiler plate-->

Ahora cuando cambio las clases anteriores a

  @Entity
    public class UserDetails {

        @Id @GeneratedValue(strategy=GenerationType.AUTO)
        private int userId;
        private String userName;

        @OneToMany(mappedBy="user")
        private Collection<Vehicle> vehicles = new ArrayList<Vehicle>() ;
    //rest is same

@Entity
public class Vehicle {
    @Id @GeneratedValue
    private int vehicleId;
    private String vehicleName;
    @ManyToOne
    @JoinColumn(name="USER_ID")
    private UserDetails user;
      //rest is same

Lo siguiente se imprime en la consola

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Hibernate: insert into UserDetails (userId, userName) values (default, ?)
Hibernate: values identity_val_local()
Hibernate: insert into Vehicle (vehicleId, USER_ID, vehicleName) values (default, ?, ?)
Exception in thread "main" org.hibernate.exception.SQLGrammarException: could not insert: [org.asif.javabrains.dto.Vehicle]
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelectingDelegate.java:64)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2345)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2852)
    at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:320)
    at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:203)
    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:129)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
    at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
    at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:713)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:701)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:697)
    at org.asif.javabrains.hibernate.HibernateTest.main(HibernateTest.java:33)
Caused by: java.sql.SQLSyntaxErrorException: 'USER_ID' is not a column in table or VTI 'ADMIN.VEHICLE'.
    at org.apache.derby.client.am.SQLExceptionFactory40.getSQLException(Unknown Source)
    at org.apache.derby.client.am.SqlException.getSQLException(Unknown Source)
    at org.apache.derby.client.am.Connection.prepareStatement(Unknown Source)
    at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:534)
    at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:116)
    at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelectingDelegate.java:54)
    ... 16 more
Caused by: org.apache.derby.client.am.SqlException: 'USER_ID' is not a column in table or VTI 'ADMIN.VEHICLE'.
    at org.apache.derby.client.am.Statement.completeSqlca(Unknown Source)
    at org.apache.derby.client.net.NetStatementReply.parsePrepareError(Unknown Source)
    at org.apache.derby.client.net.NetStatementReply.parsePRPSQLSTTreply(Unknown Source)
    at org.apache.derby.client.net.NetStatementReply.readPrepareDescribeOutput(Unknown Source)
    at org.apache.derby.client.net.StatementReply.readPrepareDescribeOutput(Unknown Source)
    at org.apache.derby.client.net.NetStatement.readPrepareDescribeOutput_(Unknown Source)
    at org.apache.derby.client.am.Statement.readPrepareDescribeOutput(Unknown Source)
    at org.apache.derby.client.am.PreparedStatement.readPrepareDescribeInputOutput(Unknown Source)
    at org.apache.derby.client.am.PreparedStatement.flowPrepareDescribeInputOutput(Unknown Source)
    at org.apache.derby.client.am.PreparedStatement.prepare(Unknown Source)
    at org.apache.derby.client.am.Connection.prepareStatementX(Unknown Source)
    ... 20 more

Esto parece desaparecer cuando borro manualmente las tablas y las ejecuto nuevamente. ¿Qué podría estar causando este comportamiento?