Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.MappingException: Could not determine type for: java.util.Collection, for columns: [org.hibernate.mapping.Column(countries)]
   at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:737)
   at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:121)
   at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:51)
   at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
   at ch.admin.insieme.persistence.driver.JPATestDriver.main(JPATestDriver.java:21)
Caused by: org.hibernate.MappingException: Could not determine type for: java.util.Collection, for columns: [org.hibernate.mapping.Column(countries)]
   at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:266)
   at org.hibernate.mapping.SimpleValue.isValid(SimpleValue.java:253)
   at org.hibernate.mapping.Property.isValid(Property.java:185)
   at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:440)
   at org.hibernate.mapping.RootClass.validate(RootClass.java:192)
   at org.hibernate.cfg.Configuration.validate(Configuration.java:1102)
   at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1287)
   at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:915)
   at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:730)
   ... 4 more

package ch.admin.insieme.persistence.model;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;

import javax.persistence.JoinColumn;
import javax.persistence.MappedSuperclass;
import javax.persistence.OneToMany;

@MappedSuperclass
public abstract class AddressGen extends InternalModelObject implements Address {

   private String city;
   private String zipCode;
   private String street;

   @OneToMany(targetEntity = CountryImpl.class)
   @JoinColumn(name = "ADDRESS_ID")
   private Collection<Country> countries = new HashSet<Country>();

   public AddressGen() {
      // TODO Auto-generated constructor stub
   }

   public AddressGen(String city, String zipCode, String street,
         Collection<Country> countries) {
      setContent(city, zipCode, street, countries);
   }

   public void setContent(String city, String zipCode, String street,
         Collection<Country> countries) {
      checkConstraint(city, zipCode, street, countries);
      this.city = city;
      this.zipCode = zipCode;
      this.street = street;
      this.countries = countries;
   }
   
   public String getCity() {
      return city;
   }

   public String getZipCode() {
      return zipCode;
   }

   public String getStreet() {
      return street;
   }

   public Collection<Country> getCountries() {
      return Collections.unmodifiableCollection(countries);
   }

   public void setCity(String city) {
      setContent(city, getZipCode(), getStreet(), getCountries());
   }

   public void setStreet(String street) {
      setContent(getCity(), getZipCode(), street, getCountries());
   }

   public void setZipCode(String zipCode) {
      setContent(getCity(), zipCode, getStreet(), getCountries());
   }
   
   public abstract void checkConstraint(String city, String zipCode, String street,
         Collection<Country> countries);

}

import java.util.Collection;

import javax.persistence.Entity;


@Entity
public class AddressImpl extends AddressGen {
   
   public AddressImpl() {
      // TODO Auto-generated constructor stub
   }

   public AddressImpl(String stadt, String plz, String strasse,
         String postfach, Collection<Country> countries) {
      super(stadt, plz, strasse, countries);
   }

   @Override
   public void checkConstraint(String city, String zipCode, String street,
         Collection<Country> countries) {
      // TODO Auto-generated method stub
      
   }
}

import javax.persistence.MappedSuperclass;

@MappedSuperclass
public abstract class CountryGen extends InternalModelObject implements Country{
   
   private String countryName;
   private String countryCode;
   
   public CountryGen() {
      // TODO Auto-generated method stub
   }
   
   public CountryGen(String countryName, String countryCode) {
      setContent(countryName, countryCode);
   }
   
   public String getCountryCode() {
      return countryCode;
   }
   
   public void setCountryCode(String countryCode) {
      setContent(getCountryName(), countryCode);
   }

   public String getCountryName() {
      return countryName;
   }
   
   public void setCountryName(String countryName) {
      setContent(countryName, getCountryCode());
   }

   public void checkConstraint(String countryName, String countryCode) {
      // Check criteria
   }

   public void setContent(String countryName, String countryCode) {
      checkConstraint(countryName, countryCode);
      this.countryName = countryName;
      this.countryCode = countryCode;
   }
   
   public abstract void checkConstraint();
}

import javax.persistence.Entity;

@Entity
public class CountryImpl extends CountryGen{

   public CountryImpl() {
      // TODO Auto-generated method stub
   }
   
   public CountryImpl(String countryName, String countryCode) {
      super(countryName, countryCode);
   }

   @Override
   public void checkConstraint() {
      // TODO Auto-generated method stub
      
   }
}

//@MappedSuperclass
public class InternalModelObject {

//   @Id
//   @GeneratedValue(strategy=GenerationType.AUTO)
   private Long id;
}

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_1_0.xsd"
  version="1.0">
 
  <mapped-superclass
    class="ch.admin.insieme.persistence.model.InternalModelObject"
    access="FIELD" metadata-complete="true">
    <attributes>
      <id name="id">
        <column name="ID" />
        <generated-value strategy="AUTO" />
      </id>
    </attributes>
  </mapped-superclass>
 
</entity-mappings>

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence     http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">

   <persistence-unit name="JPATestPU" transaction-type="RESOURCE_LOCAL">
      <provider>org.hibernate.ejb.HibernatePersistence</provider>

        <mapping-file>META-INF/orm.xml</mapping-file>
      
      <properties>
         <property name="hibernate.connection.driver_class" value="org.apache.derby.jdbc.ClientDriver"/>
         <property name="hibernate.connection.url" value="jdbc:derby://localhost:1527/jpatest;create=true"/>
         <property name="hibernate.connection.username" value="APP"/>
         <property name="hibernate.connection.password" value="APP"/>
         
         <property name="hibernate.dialect" value="org.hibernate.dialect.DerbyDialect"/>
         <property name="hibernate.hbm2ddl.auto" value="create"/>
         <property name="hibernate.show_sql" value="true"/>
         <property name="hibernate.format_sql" value="true"/>
      </properties>
   </persistence-unit>

</persistence>

public class JPATestDriver {

   public static void main(String[] args) {

      EntityManagerFactory emf = Persistence
            .createEntityManagerFactory("JPATestPU");
      EntityManager em = emf.createEntityManager();
      EntityTransaction t = em.getTransaction();

      t.begin();

      Collection<Country> countries = new HashSet<Country>();
      Country country = new CountryImpl("CH", "0041");
      countries.add(country);
      em.persist(country);

      Address adress = new AddressImpl("Bern", "3012", "Holzikofenweg",
            "4711", countries);

      em.persist(adress);

      t.commit();
      em.close();
   }
}