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

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Listing 7. ejb-jar.xml

<?xml version="1.0"?>
<!DOCTYPE ejb-jar PUBLIC
"-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN"
"http://java.sun.com/dtd/ejb-jar_2_0.dtd">
<ejb-jar>
  <enterprise-beans>
    <entity>
    <ejb-name>Catalog</ejb-name>
    <local-home>CatalogLocalHome</local-home>
    <local>CatalogLocal</local>
    <ejb-class>CatalogBean</ejb-class>
    <persistence-type>Container</persistence-type>
    <prim-key-class>String</prim-key-class>
    <reentrant>False</reentrant>
      <cmp-version>2.x</cmp-version>
      <abstract-schema-name>Catalog</abstract-schema-name>
      <cmp-field>
        <field-name>catalogId</field-name>
      </cmp-field>
      <cmp-field>
        <field-name>journal</field-name>
      </cmp-field>
      <cmp-field>
        <field-name>publisher</field-name>
      </cmp-field>
        <query>
         <query-method>
           <method-name>findByJournal</method-name>
           <method-params>
            <method-param>java.lang.String</method-param>
           </method-params>
         </query-method>
         <ejb-ql>
           <![CDATA[SELECT DISTINCT OBJECT(obj)  FROM Catalog obj WHERE obj.journal = ?1 ]]>
         </ejb-ql>
       </query>
      </entity>
    </enterprise-beans>
    <relationships>

    <ejb-relation>
      <ejb-relation-name>Catalog-Editions</ejb-relation-name>
      <ejb-relationship-role>
        <ejb-relationship-role-name>
          Catalog-Has-Editions
        </ejb-relationship-role-name>
        <multiplicity>One</multiplicity>
        <relationship-role-source>
          <ejb-name>Catalog</ejb-name>
        </relationship-role-source>
        <cmr-field>
          <cmr-field-name>editions</cmr-field-name>
          <cmr-field-type>java.util.Collection</cmr-field-type>
        </cmr-field>
      </ejb-relationship-role>
      <ejb-relationship-role>
        <ejb-relationship-role-name>
          Editions-Belong-To-Catalog
        </ejb-relationship-role-name>
        <multiplicity>One</multiplicity>
        <cascade-delete />
        <relationship-role-source>
          <ejb-name>Edition</ejb-name>
        </relationship-role-source>
      </ejb-relationship-role>
    </ejb-relation>
  </relationships>
</ejb-jar>

An EJB 3.0 entity bean class is a POJO and does not implement the EntityBean interface. In an EJB 3.0 entity bean, the local interface, the local home interface, and the deployment descriptors are not required. Only a bean class annotated with the metadata annotation @Entity is required. The finder methods specified in EJB 2.0 deployment descriptor ejb-jar.xml, with the <query/> elements, are included in the EJB 3.0 bean class with the @NamedQuery annotation. The CMR relationships specified in ejb-jar.xml with <ejb-relation/> elements are included in the EJB 3.0 bean class with metadata annotations. The primary key field in EJB 3.0 is specified with the annotation @Id. Some of the EJB 3.0 metadata annotations are listed in Table 1.

Next page: Table 1. EJB 3.0 Metadata Annotations