This example application
demonstrates Oracle's support for the Servlet 2.5 annotations and EJB
3.0 specification. It provides an example of using the new EJB 3.0 components
from a Web application.
OC4J supports the following annotations in the web container:
JSR 250 common annotations
javax.ejb.EJB annotation as defined by EJB 3.0 specification
javax.persistence.PersistenceContext and javax.persistence.PersistenceUnit as defined by EJB 3.0 Java Persistence API.
javax.xml.ws.WebserviceRef as defined by Java XML Web services 2.0
It also supports the corresponding XML elements in the web module deployment descriptor.
This demonstration uses the Employee entity to demonstrate a entity using EJB 3.0 JPA that is accessed by the web module using EmployeFacade session bean.
Entity
example using EJB 3.0
The bean class
is a plain java class that is annotated with @Entity to mark it as an entity bean.
@Entity
@Table(name = "EMP")
public class Employee implements java.io.Serializable
{
private int empNo;
private String eName;
private double sal;
@Id
@Column(name="EMPNO")
public int getEmpNo()
{
return empNo;
}
..
}
The @Table annotation
is used to specify the table name to be used by this Entity bean.
The @Id annotation is used to mark the empNo field
as the primary key of the entity bean.
The @Column annotation is used to specify that
the empNo field is mapped to the EMPNO column in the table.
Creating a Session Facade using EntityManager API
The javax.persistence.EntityManager API is used for persisting, finding and updating entity instances.
In this example, the EmployeeFacadeBean uses PersistenceContext injection to grab an EntityManager instance and then persists entity instance as follows:
@Stateless
public class EmployeeFacadeBean implements EmployeeFacade {
@PersistenceContext
private EntityManager em;
....
public void addEmployee(int empNo, String eName, double sal) {
emp = new Employee();
emp.setEmpNo(empNo);
emp.setEname(eName);
emp.setSal(sal);
em.persist(emp);
}
}
Using Dependency Injection from Web Module to use SessionBean
In this example,
the InsertServlet uses dependency injection using javax.ejb.EJB annotation to use EmployeeFacadeBean as follows:
public class InsertServlet extends HttpServlet {
@EJB private EmployeeFacade employeeFacade;
..
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int empId;
String name = "";
double sal = 0;
empId = (int) Integer.valueOf(request.getParameter("empId"));
name = request.getParameter("empName");
sal = Integer.valueOf(request.getParameter("Sal"));
try {
System.out.println("Id:" + request.getParameter("empId"));
etc - all necessary files to package the application
lib - holds the application archives that could be deployed
scripts - contains SQL script to create a table
doc - the How-to document and Javadoc's
javadoc - the javadoc of the different source files
how-to-ejb30-DIfromweb.html - this How-to page
src - the source of the demo
ejb - contains the sample entity and session bean code
web- contains application
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 J2SE 5.0
%PATH% - includes %ORACLE_HOME% /ant/bin
Configure Database
This example is based on the EMP table from the
SCOTT schema in an Oracle database. If you do not have SCOTT schema
installed in your Oracle database, or are using a database other than
Oracle, then the table will be automatically created during deployment
of your applications because automatic table creation is switched. You
can also manually create the table usingthe table.sql script in the %HOWTO_HOME%/scripts directory.
Configure Data Source
This example requires a DataSource to be configured to connect to the database
that contains the EMP table.
For OC4J, you must configure a datasource in the %ORACLE_HOME%/j2ee/home/config/data-sources.xml file
and point it at the schema that owns the EMP table.
Start OC4J stand alone using the following command after you make the above changes.
>%ORACLE_HOME%/bin/oc4j -start
If you are using an OracleAS managed install, start using the following command after you make the above changes.
> %ORACLE_HOME%/opmn/bin/opmnctl startall
4. Generate, Compile, and Deploy the Application
Ant 1.6.2 is shipped with OC4J and you have to set your PATH environment variable to $ORACLE_HOME/ant/bin.
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 ant-oracle.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 for OC4J standalone:
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-web-site)
If you are using OracleAS managed install then you have appropriately change the following properties beside changing oc4j.admin.user and oc4j.admin.password for your managed OC4J instance in OracleAS install.
opmn.host: the hostname/IP where OracleAS is running (default localhost)
opmn.port: OPMN request port (default 6003) for the OracleAS install
oc4j.instance: admin user name (default oc4jadmin)
You have to uncomment appropriate deployer.uri in the
ant-oracle.properties based on your environment i.e. a single instance
OC4J or a clustered OC4J instance/group managed by OPMN.
To build the application, type the following command
from the %HOWTO_HOME% directory:
>ant
You should now have the newly created DIfromweb.ear in your
%HOWTO_HOME%/lib directory.
This command will attempt to deploy the application archive if the build is
successful. It will first test whether OC4J is running before attempting the
deployment operation.
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 invoking the following URL from your favorite browser:
http://localhost:8888/DIfromweb
In this page, enter employee no, Name and Salary and then click on Add Employee button.
The InsertServlet will be invoked that will try to create
the entity instance invoking addEmployee method in EmployeeFacadeBean that uses EntityManager API.
You will be redirected
to a success page if your record was inserted successfully. You can also
check the database table to ensure the record was created.
Summary
In this document, you should have learned how to:
Use Dependency Injection from a web module to invoke a EJB
Deploy an execute the simple Entity using Oracle Application
Server 10g 10.1.3.1
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