2 Replies Latest reply on Oct 3, 2005 12:20 PM by Emmanuel Bernard

    Issues with inheritance

    Jon Åkerström Newbie

      I have encountered issues with entity enheritance. Here is my case:

      I basically followed the instructions in the tutorial when i coded.

      First I have a base entity class called Message like this:

      
      package ejb3.language.system;
      import java.io.Serializable;
      import javax.persistence.Column;
      import javax.persistence.DiscriminatorColumn;
      import javax.persistence.DiscriminatorType;
      import javax.persistence.EmbeddedId;
      import javax.persistence.Entity;
      import javax.persistence.Inheritance;
      import javax.persistence.InheritanceType;
      
      @Entity
      @Inheritance(strategy = InheritanceType.SINGLE_TABLE, discriminatorType = DiscriminatorType.STRING)
      @DiscriminatorColumn(name = "TYPE", columnDefinition="VARCHAR(255)", nullable = true)
      public class Message implements Serializable
      {
      
       private static final long serialVersionUID = 1L;
      
       private MessagePK pk;
       private String value;
      
       @EmbeddedId
       public MessagePK getPk() {
       return pk;
       }
       public void setPk(MessagePK pk) {
       this.pk = pk;
       }
      
       @Column(columnDefinition="text")
       public String getValue() {
       return value;
       }
       public void setValue(String value) {
       this.value = value;
       }
      }
      


      This entity bean has a composite primary key class like this:

      package ejb3.language.system;
      import java.io.Serializable;
      import javax.persistence.AccessType;
      import javax.persistence.Embeddable;
      
      @Embeddable(access = AccessType.PROPERTY)
      public class MessagePK implements Serializable
      {
       private static final long serialVersionUID = 1L;
      
       private String object_member;
       private int object_id;
       private String url;
      
       public int getObject_id() {
       return object_id;
       }
       public void setObject_id(int object_id) {
       this.object_id = object_id;
       }
       public String getObject_member() {
       return object_member;
       }
       public void setObject_member(String object_member) {
       this.object_member = object_member;
       }
       public String getUrl() {
       return url;
       }
       public void setUrl(String url) {
       this.url = url;
       }
      }
      


      I then have some classes that inherits from the base class in order to achieve different "types" to be stored within the same table. Like this one:

      package ejb3.language.system;
      import java.io.Serializable;
      import javax.persistence.Entity;
      import javax.persistence.JoinColumn;
      import javax.persistence.ManyToOne;
      import javax.persistence.Table;
      import com.lightminds.ppdb.ejb3.country.Country;
      
      @Table(name="Message")
      @Entity
      @Inheritance(strategy = InheritanceType.SINGLE_TABLE, discriminatorType = DiscriminatorType.STRING, discriminatorValue = "Country")
      public class Message_CountryView extends Message implements Serializable
      {
       private static final long serialVersionUID = 1L;
      
       private Country country;
      
       @ManyToOne
       @JoinColumn(name = "object_id", insertable=false, updatable=false)
       public Country getCountry()
       {
       return country;
       }
      
       public void setCountry(Country country)
       {
       this.country = country;
       }
      }
      


      All fine. And all deployes well on latest RC2 release of EJB3. I can successfully add both Messages and Country and other into the table with the normal persist stuff. However when I try to fetch a specific row in the database represented by one of the inherited clasess I get errors.

      First If I try something like this:

      MessagePK pk = new MessagePK();
      pk.setObject_id(1);
      pk.setObject_member("test2");
      pk.setUrl("www.mysite.org");
      Message_CountryView message = MyEntityManager.find(Message_CountryView.class, pk);
      


      I get the following error:


      org.hibernate.exception.GenericJDBCException: could not load an entity: [ejb3.language.system.Message_CountryView#component[url,object_id,object_member]{object_id=1, url=www.mysite.org, object_member=test2}]
      .......
      Caused by: java.sql.SQLException: Invalid value for getInt() - 'test2' in column 3


      and if I manually create a query like this:
      Message_CountryView message = (Message_CountryView)MyEntityManager.createQuery("SELECT mcv FROM Message_CountryView mcv WHERE mcv.pk = :key").setParameter("key", pk).getSingleResult();
      


      I get a similar error:

      org.hibernate.exception.DataException: could not execute query
      .........
      Caused by: java.sql.SQLException: Operand should contain 3 column(s)


      Also note that if I create an entry with the type of the base class. I.e Message - both the above "finds" works if the row returned is of the base class type, but If I query for an entry that is represented by one of the inherited classes I get the above errors even if I query for the base class (Message message = MyEntityManager.find(Message.class, pk);)

      Thanks in advance