Java Reference
In-Depth Information
Setter injection methods are invoked by the container before any business methods
on the bean instance. Multiple resources may be injected using the @Resources
annotation. For example, in the following code snippet two resources of type javax.
sql.DataSource are injected.
@Resource(name="ds1", type="javax.sql.DataSource"),
@Resource(name="ds2", type="javax.sql.DataSource")
} )
JNDI resources injected with the dependency mechanism may be looked up in the
java:comp/env namespace. For example, if the JNDI name of a resource of type
javax.sql.DataSource is catalogDB , the resource may be looked up as follows.
InitialContext ctx = new InitialContext();
Javax.sql.DataSource ds = ctx.lookup("java:comp/env/catalogDB");
Simplified Session Beans
In EJB 2.x, a session bean is required to implement the SessionBean interface. An
EJB 3.0 session bean class is a POJO ( Plain Old Java Object ) and does not implement
the SessionBean interface.
An EJB 2.x session bean class includes one or more ejbCreate methods, the callback
methods ejbActivate , ejbPassivate , ejbRemove , and setSessionContext , and
the business methods defined in the local/remote interface. An EJB 3.0 session bean
class includes only the business methods.
In EJB 3.0, EJB component interfaces and home interfaces are not required for
session beans. A remote interface in an EJB 2.x session EJB extends the javax.ejb.
EJBObject interface; a local interface extends the javax.ejb.EJBLocalObject
interface. A home interface in an EJB 2.x session EJB extends the javax.ejb.EJBHome
interface; a local home interface extends the javax.ejb.EJBLocalHome interface. In
EJB 3.0 the home/local home and remote/local interfaces are not required. The EJB
interfaces are replaced with a POJI ( Plain Old Java Interface ) business interface.
If a business interface is not included with the session bean class, a POJI business
interface gets generated from the session bean class by the EJB server.
An EJB 2.x session EJB includes a deployment descriptor that specifies the EJB name,
the bean class name, and the interfaces. The deployment descriptor also specifies
the bean type of Stateless/Stateful. In EJB 3.0, a deployment descriptor is not
required for a session bean. An example EJB 2.x session bean, which implements the
SessionBean interface, is listed next:
Search WWH ::

Custom Search