This example application demonstrates Oracle's support for
the EJB 3.0 specification in JDK 1.4 environment. Because annotations
are only available in JDK 1.5, this will show how to configure many of
the feature with an xml-only deployment. It demonstrates:
a sparse ejb-jar.xml file
how to perform field and property injection of ejb refernces
how to perform field and property injection of environment
entries
how to declare life cycle callbacks
This demonstration uses the WeatherReport bean to demonstrate
a simple stateless EJB using EJB 3.0 and JDK 1.4.
Stateless Session Bean example using
EJB 3.0 and JDK 1.4
The
following is the remote interface for the WeatherReport
EJB.
package oracle.ejb30;
public interface WeatherReport {
public String
getTemperatorFor(String cityName);
public String
getTemperatorFor(String cityName, boolean celcius);
}
The bean class is a plain java class that implements a
business interface:
package oracle.ejb30;
public class WeatherReportBean implements WeatherReport {
protected Map weatherMap;
// both Strings are configured
for injection in the ejb-jar.xml file
private String celciusString;
private String fahrenheitString;
private TemperatureConverter
temperatureConverter;
. . .
public String
getTemperatureFor(String cityName) {
return
getTemperatureFor(cityName, false);
}
// this setter is configured
for injection in the ejb-jar.xml file
public void
setTemperatureConverter(TemperatureConverter converter) {
this.temperatureConverter
= converter;
}
}
The
following is a callback listener class
for the WeatherReport EJB.
package oracle.ejb30;
public interface LifecycleListener {
public void
initializeWeatherData(Object obj) {
.
. .
}
}
Note that none of the classes make use of annotations, but
instead rely on a simplified deployment descriptor.
Here's the content of the simplified deployment descriptor. It
denotes the EJB name, bean class, remote/local
interface(s), session type, injected references, and the callback
listener. The remainder is defaulted.
The <field> and
<property> tags for
reference injection have not been officially defined in the spec and
are subject to change
The values of the <field>
and <property> tags
correspond to the fields and setters on the bean that are to be injected
The <lifecycle-callbacks>
tag and subtags have not been officially defined in the spec and are
subject to change
If you want to declare the life cycle callbacks on the bean
itself, omit the <callback-listener>
tag
The supported life cycle tags are <post-construct>,
<pre-destroy>, <post-activate>,
and <pre-passivate> and
those used should be listed as subtags of a single
<lifecycle-callbacks> tag per bean.
an example of configuring interceptors in xml can be found
in the interceptor How-To
TemperatureConverter shows the minimal amount of xml
currently needed to deploy a stateless session bean
Sample EJB Client
Note that the EJB home
interface is no longer required, and a bean instance is not created by
invoking the create() method. Instead, we can directly invoke a method
on the EJB, as shown in the following client accessor:
Context context = new InitialContext();
System.out.println("Looking up WeatherReport");
WeatherReport report =
(WeatherReport)context.lookup("java:comp/env/ejb/WeatherReport");
System.out.println(weatherReport.getTemperatureFor("Las Vegas"));
System.out.println(weatherReport.getTemperatureFor("Ottawa", true));
Prerequisites
What you need to know
In order to complete the example application, you should be familiar
with the following:
EJB 3.0
For further information on EJB 3.0, see the following
documents on OTN:
etc - all necessary files to package the
application
lib - holds the application archives
that could be deployed
doc - the How-to document and Javadoc's
javadoc - the javadoc of the different
source files
how-to-ejb30-jdk14.html - this How-to
page
src - the source of the demo
ejb - contains the sample SLSB code
client - contains
application client code
2.
Configure the Environment
Ensure the following environment variables are defined:
%ORACLE_HOME% - The directory where you
installed OC4J.
%JAVA_HOME% - The directory where you
installed the JDK
3.
Start the Oracle Application Server EJB 3.0 Preview
An Oracle Application Server EJB 3.0 Preview container
must be running. Start it using the following command:
>%ORACLE_HOME%/bin/ejb30 -start
4.
Generate, Compile, and Deploy the Application
Ensure Ant 1.6.2 or above is installed on your machine and
configured correctly. On some operating systems, Ant does not currently
support the use of environment variables. If this is the case for your
operating system, please modify the common.xml file located in the
%HOWTO_HOME% directory.
Edit ant-oracle.properties (in the demodirectory)
and ensure the following properties are set to the
correct values, as indicated below:
oc4j.host: host where OC4J is running
(default localhost)
oc4j.admin.port: RMI port number
(default 23791)
oc4j.admin.user: admin user name
(default oc4jadmin)
oc4j.admin.password: admin user password
(default welcome)
oc4j.binding.module: website name where
deployed web modules are bound (default http-web-site)
To build the application, type the following command from the %HOWTO_HOME%
directory:
>ant
You should now have the newly created ejb30-jdk14.ear
in your
%HOWTO_HOME%/lib directory.
This command would also attempt to deploy the application if the build
is
successful. It will first test whether OC4J is running.
Note that you can also deploy the application separately .
Ensure the %ORACLE_HOME% environment variable is
defined, and from the %HOWTO_HOME% directory, type
the command:
>ant deploy
5.
Run the Application
Run the sample by providing the following command, including a
name as the program argument:
>ant run
You will the following output from the Client
[java] Looking up WeatherReport [java] 60.0 degrees Fahrenheit [java] 53.0 degrees Fahrenheit [java] 18.0 degrees Fahrenheit [java] -7.777777777777778 degrees Celsius [java] No weather data available for LasVegas
Summary
In this document, you should have learned how to:
Develop and deploy a simple stateless session bean using
EJB 3.0 and configured entirely using xml
Deploy an execute a simple stateless session bean in the
Oracle Application Server EJB 3.0 Preview running JDK 1.4
Bookmark
