Migrating EJB 2.1 Entity and Session Beans to EJB 3.0

The nuts and bolts

By Deepak Vohra • Get more from this author

Posted in Developer, 25th April 2006 06:02 GMT

Listing 5. EJB 3.0 Session Bean Client Class

public class CatalogClient {
    @Inject CatalogBean;
    CatalogBean catalogBean;

    String publisher="OReilly";
    String journal=catalogBean.getJournal(publisher);
    System.out.println("Journal for Publisher: "+publisher +" "+journal);
}

Migrating an Entity Bean

In this section, we shall migrate an EJB 2.1 entity bean to the EJB 3.0 specification. An EJB 2.1 entity bean implements the EntityBean interface. An entity bean consists of getter/setter CMP (container managed persistence) field methods, getter/setter CMR (container managed relationships) field methods, callback methods and ejbCreate/ejbPostCreate methods. The example entity bean, CatalogBean.java, that will be migrated to EJB 3.0, includes a local component interface, CatalogLocal.java, a local home interface, catalogLocalHome.java and the ejb-jar.xml deployment descriptor. The EJB 2.1 entity bean is listed in Listing 6.

Listing 6. CatalogBean.java. EJB 2.1 Entity Bean

import javax.ejb.EntityBean;
import javax.ejb.EntityContext;

public class CatalogBean implements EntityBean {
    private EntityContext ctx;

    public abstract void setCatalogId();
    public abstract String getCatalogId();

    public abstract void setJournal();
    public abstract String getJournal();

    public abstract void setPublisher();
    public abstract String getPublisher();

    public abstract void setEditions(java.util.Collection editions);

    public abstract java.util.Collection getEditions();

    public String ejbCreate(String catalogId) {
        setCatalogId(catalogId);
        return null;
    }

    public void ejbRemove() {}
    public void ejbActivate() {}
    public void ejbPassivate() {}
    public void ejbLoad() {}
    public void ejbStore() {}

    public void setEntityContext(EntityContext ctx) {
        this.ctx=ctx;
    }

    public void unsetEntityContext() {
        ctx = null;
    }
}

The ejb-jar.xml deployment descriptor specifies the EJB classes/interfaces, CMP fields, EJB QL queries, and CMR relationships. The CatalogBean entity bean includes a finder method, findByJournal; and a CMR relationship with another entity bean, Edition. The ejb-jar.xml for the CatalogBean EJB is listed in Listing 7.

Next page: Listing 7. ejb-jar.xml