Introduction to EJB 3.0 Using JDeveloper and Oracle Application Server
Introduction to EJB 3.0 Using JDeveloper 10g and
OC4J
Using JDeveloper, this tutorial provides an introduction to
building the data model for an application using the new Enterprise JavaBeans
3.0 specification.
Approximately 30 minutes
The tutorial covers the following topics:
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In the tutorial, you implement a persistence model by developing
and deploying Session and Entity beans. These beans use the EJB 3.0 annotations
and the new POJO (Plain Old Java Object) model persistence. You will use the
Entity Manager API to create, update, delete and query the POJO persistence
model.
As part of the tutorial, you will create a database connection
and an OC4J application connection. Once complete, the application could be
deployed to Oracle Application Server 10g for enterprise-wide access.
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You create persistence objects for the DEPARTMENTS and
EMPLOYEES tables. The persistence objects are implemented as Entity Beans. Methods
are created for adding a new department, retrieving department data, and returning
the email for an employee. These methods are implemented as session beans.
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Before you begin, you should:
| 1. |
Have access to or have installed Oracle JDeveloper 10g
Release 3 (10.1.3) Production edition. You can download it from Oracle
Technology Network.
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| 2. |
Have access to or have installed the Oracle Sample Schemas,
included with Oracle Database 10g.
The tutorial uses the HR schema. Specifically, the pages
work with the EMPLOYEES table.
Instructions for installing the HR schema and creating
a connection to it in JDeveloper are available online at:
http://www.oracle.com/technology/obe/obe1013jdev/common/OBEConnection.htm
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| 3. |
Start JDeveloper. Double-click the JDeveloper executable
(<JDEV_HOME>\jdeveloper.exe) found in the root directory where you
unzipped it.
If the Migrate User Settings dialog box opens, click
NO.
Close the Tip of the Day window.
|
| 4. |
The JDeveloper IDE should now be displayed.
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In this section, you create a database connection to the Human
Resources (HR) schema.
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1.
|
In the Application Navigator, click the Connections
tab to create a database connection.
|
2.
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Right-click the Database node in the Connection Navigator,
and select the New Database Connection option.
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3.
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Click Next on the Welcome page of the Create Database
Connection wizard. In Step 1 of 4, enter hrconn as the
connection name, and then click Next.
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| 4. |
In Step 2 of 4 of the Create Database Connection wizard, enter hr
as the username and hr as the password. Select the Deploy
Password check box, and then click Next.
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| 5. |
In Step 3 of 4 of the Create Database Connection wizard, make sure that
the following values are specified:
| Driver |
thin |
| Host Name |
localhost |
| JDBC Port |
1521 |
| SID |
ORCL |
Click Next.
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| 6. |
In Step 4 of 4 of the Create Database Connection wizard, click the Test
Connection button.
If the database is available and the connection
details are correct, you see the word Success! displayed in the
Status window.
If an error occurs, verify the connection settings, click Back to
make any necessary changes, and then retest the connection.
If the connection is successful, click Finish to complete the connection.
|
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When you work in JDeveloper, you organize your work
in projects within applications. JDeveloper provides several templates that
you can use to create an application and projects. The templates are preconfigured
with a basic range of technologies that are needed for developing various types
of applications, and you create your working environment by selecting the template
that fits your needs. You can then configure it to add any other technologies
that you plan to use.
In this topic, you choose the basic application and
a new project, with no predefined technology.
To create a new application with a new project, perform
the following steps:
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1.
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In JDeveloper, click the Applications
tab. In the Application navigator, right-click Applications
and select New Application from the shortcut menu.
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2.
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In the Create Application dialog
box, enter HRApp as the application name. Specify buslogic
as the application package prefix, and select the No Template
option. Click OK.
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| 3. |
In the Create Project dialog box, rename the project from Project1 to
EJB_Project, hence providing a more meaningful name.
Then click OK.
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| 4. |
In the Application Navigator, right-click the EJB_Project
node and select the Project Properties option from the
context menu.
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| 5. |
In the Project Properties dialog, select the Compiler node and check the Use
Javac option, then OK.
|
| 6. |
Click the Save All icon  to
save your work.
|
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The business or persistence model provides data access and validation
for an application. When data is managed by the business model, the data
is always
validated by the model, regardless of the client implementation. This cleanly
separates the validation and business rules from the user interface.
In this section of the tutorial, you create the persistence model
for departments and employees using EJB 3.0 entity beans.
To create EJB 3.0 entity beans, perform the following steps:
1. |
In the Application Navigator, right-click the
EJB_Project node and choose the New option.
|
2. |
In the New Gallery dialog box, expand the Business Tier
node in Categories. Click EJB in the Items list,
then select CMP
Entity Beans from tables. Click OK.
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| 3. |
In Step 1 of 5 of the Create
CMP Entity Beans from Tables wizard,
select the Enterprise
JavaBeans 3.0 (J2EE 5.0) option, and then click Next.
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| 4. |
In Step 2 of 5, select hrconn as
the connection name.
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| 5. |
In step 3 of 5, for the HR Schema and the Tables
Objects Types, click the Query button, and
then select the Departments and Employees
tables from the Available list and shuttle them to the Selected list.
Click
Next.
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| 6. |
In step 4 of 5, enter buslogic.persistence as the package
name. Click Next.
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7. |
Click Next in step 5 of 5 and then Finish
to create the entity beans.
Click the Save All icon to
save your work.
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8. |
Double-click the Departments.java node in the Application
Navigator to open it in the source editor.
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9. |
A NamedQuery metadata
statement has been created by default. It retrieves
all rows from the departments table.
@NamedQuery(name="findAllDepartments",
query="select object (o)
from Departments o")
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10. |
Because you will insert new rows in the Departments
table, you need to specify that the primary key values come from a
database sequence.
Scroll down to the @Id statement
and replace it by the following statements:
@Id (generate=SEQUENCE,generator="DEPARTMENT_SEQ_GEN")
@SequenceGenerator(name="DEPARTMENT_SEQ_GEN", sequenceName="DEPARTMENTS_SEQ",allocationSize=1)
Press Alt + Enter to automatically add the required import statement
and manually add the following import statement:
import static javax.persistence.GeneratorType.*;
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11. |
Double-click the Employees.java node in the Application
Navigator to open it in the source editor.
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12. |
You will add another named query. To support this, you will add the EJB
3.0 metadata statements shown in bold text below, so that your resulting
code looks like this:
@NamedQueries({
@NamedQuery(name="findAllEmployees", query="select object(o)
from Employees
o")
,
@NamedQuery(name="getEmail",query="SELECT OBJECT(employees)
FROM Employees "
+
"
employees WHERE employees.employeeId =:empid")
})
Press Alt + Enter to accept the suggested import statement:
import javax.persistence.NamedQueries;
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13. |
Right-click the EJB_Project node in the Application
Navigator and choose the Make option to compile your
Java classes.
|
14. |
Verify that the Message - Log window does not report any error.
|
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In this section, you create a session bean that implements
a method to find employee and department records.
| 1. |
Right-click the EJB_Project project node in the Application
Navigator, and select the New option from the context
menu. Open the Business Tier category and choose the
Session Bean item. Click OK.
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| 2. |
Click Next on the Welcome page of the Create Enterprise
JavaBean wizard. In step 1 of 4, enter HRAppFacade
as the EJB name. Leave the options unchanged, and then click Next.
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| 3. |
In Step 2 of 4, make sure all entity methods are selected, then click
Next.
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| 4. |
In Step 3 of 4, make sure that the full name for Bean Class is buslogic.HRAppFacadeBean,
and then click Next.
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| 5. |
In step 4 of 4, select only the Implement a Remote Interface
option. Click Next and then Finish.
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| 6. |
The Application Navigator should look like this:
If not, select the EJB_Project node and select the
Refresh option from the View menu option (View
| Refresh).
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| 7. |
The session bean is made up of two files: HRAppFacadeBean
- contains the session code.
HRAppFacade - a local interface containing the detail code
Open the Structure pane (View | Structure) and
click the HRAppFacadeBean in the Application Navigator.
The Structure pane should look like this displaying the HRAppFacade classes:
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| 8. |
In the Structure pane, double-click the HRAppFacade
interface to edit the code and add the following method declarations:
public void addDepartment(String
department_name, long location_id) throws NamingException;
public String getEmail(long empid) throws NamingException;
Press Alt + Enter to add the suggested import statement.
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| 9. |
Double-click the HRAppFacadeBean
class to open it in the code editor. Then click
the light bulb icon next to the class declaration and select
Implement Methods.
Select both addDepartment and
getEmail methods, and click OK.
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| 10. |
Change the code of the newly implemented
methods to the following:
public void addDepartment(String department_name, long location_id)
throws NamingException
{
Departments dept = new Departments();
dept.setDepartmentName(department_name);
dept.setLocationId(location_id);
this.persistEntity(dept);
}
public String getEmail(long
empid)
{
Employees emp = (Employees)this.em.createNamedQuery("getEmail").setParameter("empid",empid).getSingleResult();
return emp.getEmail();
}
Press Alt + Enter to add the
suggested import statement
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| 11. |
Right-click the EJB_Project project and select the
Make option to compile your project.
|
| 12. |
Verify that the Messages - Log window does not report any error.
|
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| 1. |
The first step in creating the client is to run the HRAppFacadeBean
using the OC4J server that is provided within JDeveloper. This server
allows you to create J2EE applications and test them within JDeveloper,
thereby eliminating the need to run an external server during the development
/ testing cycle.
In the Application Navigator, right-click HRAppFacadeBean
and select Run.
This will launch the embedded server and deploy the
HRAppFacadeBean.
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| 2. |
The next steps are to create a test client.
In the Application Navigator, right-click HRAppFacadeBean
and select New Sample Java Client.
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| 3. |
In the Sample EJB Java Client Details dialog box, select Connect
to OC4J Embedded in JDeveloper.
Click OK.
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| 4. |
Double-click the HRAppFacadeClient node to open the
file in the source editor. In the Main method, comment out the call
to the findAllDepartments
and findAllEmployees methods.
// System.out.println( hRAppFacade.findAllDepartments(
) );
// System.out.println( hRAppFacade.findAllEmployees( ) );
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| 5. |
In HRAppFacadeClient, add the following statements
to create a new department by using the addDepartments() method.
String
department_name = "IT Administration 12";
long location_id = 1500;
hRAppFacade.addDepartment( department_name, location_id );
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| 6. |
Specify the employee ID of the employee for whom
you want to view the e-mail. For example:
long
empid = 100;
Call the getEmail() method and print the e-mail for the employee_id
argument:
System.out.println(hRAppFacade.getEmail(
empid ));
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| 7. |
Some Java Virtual Machines may not recognize the -javaagent runtime
option that JDeveloper uses to run this sample client.
To avoid any runtime issues with this option, follow the next few steps
to change how JDeveloper uses the JVM.
Right-click the EJB Project in the Application Navigator
and select Project Properties from the context menu to open the
Project Properties for the EJB_Project.
|
| 8. |
Select the Run/Debug category.
Select the default Run Configuration and click Edit.
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| 9. |
Select the Launch Settings category in the Edit Run Configuration
wizard.
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| 10. |
Use the Virtual Machine drop list and select Client as the JVM
type.
Click OK to apply the change and close the Edit Run Configuration
window. Click OK again to close the Project Properties window.
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| 11. |
In the Application Navigator, right-click the HRAppFacadeClient
file and select Run.
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| 12. |
Ensure that the e-mail (SKING) for the
customer you specified is being returned.
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| 13. |
Ensure that a new department is added to the table, utilizing the sequence
that you specified for the ID. On the Connection page, expand Database
> HR > Tables > DEPARTMENTS, and click the Data
tab in the editor.
|
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In this tutorial, you created persistence services and
accessed them using EJB 3.0. Additionally, you used a client to test the deployed
EJBs.
You've learned how to:
 |
Configure
an application and a project |
|
Create a persistence
model using EJB 3.0 |
|
Create the Data Model
using a session bean |
|
Create the Client
class and test your application |
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