46.8.2.1 Coding the Application Client: HumanResourceClient.java

The application client, HumanResourceClient.java, found under clientmdbentity-app-client, performs the following steps:

1. Defines a topic for the application, using the java:app namespace because the topic is used in both the application client and the EJB module

2. Injects ConnectionFactory and Topic resources

3. Creates a TemporaryQueue to receive notification of processing that occurs, based on new-hire events it has published

4. Creates a JMSConsumer for the TemporaryQueue, sets the JMSConsumer's message listener, and starts the connection

5. Creates a MapMessage

6. Creates five new employees with randomly generated names, positions, and ID numbers (in sequence) and publishes five messages containing this information

The message listener, HRListener, waits for messages that contain the assigned office and equipment for each employee. When a message arrives, the message listener displays the information received and determines whether all five messages have arrived. When they have, the message listener notifies the main method, which then exits.

46.8.2.2 Coding the Message-Driven Beans for the clientmdbentity Example

This example uses two message-driven beans, both under clientmdbentity-ejb:

• EquipmentMDB.java

• OfficeMDB.java

The beans take the following steps.

1. They inject a MessageDrivenContext resource, an EntityManager, and a JMSContext.

2. The onMessage method retrieves the information in the message. The EquipmentMDB's onMessage method chooses equipment, based on the new hire's position; the OfficeMDB's onMessage method randomly generates an office number.

3. After a slight delay to simulate real world processing hitches, the onMessage method calls a helper method, compose.

4. The compose method takes the following steps.

   1. It either creates and persists the SetupOffice entity or finds it by primary key.

   2. It uses the entity to store the equipment or the office information in the database, calling either the doEquipmentList or the doOfficeNumber business method.

   3. If the business method returns true, meaning that all of the information has been stored, it retrieves the reply destination information from the message, creates a JMSProducer, and sends a reply message that contains the information stored in the entity.

   4. It removes the entity.

46.8.2.3 Coding the Entity Class for the clientmdbentity Example

The SetupOffice.java class, also under clientmdbentity-ejb, is an entity class. The entity and the message-driven beans are packaged together in an EJB JAR file. The entity class is declared as follows:

@Entity
public class SetupOffice implements Serializable {

The class contains a no-argument constructor and a constructor that takes two arguments, the employee ID and name. It also contains getter and setter methods for the employee ID, name, office number, and equipment list. The getter method for the employee ID has the @Id annotation to indicate that this field is the primary key:

@Id
public String getEmployeeId() {
    return id;
}

The class also implements the two business methods, doEquipmentList and doOfficeNumber, and their helper method, checkIfSetupComplete.

The message-driven beans call the business methods and the getter methods.

The persistence.xml file for the entity specifies the most basic settings:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" 
             xmlns="http://xmlns.jcp.org/xml/ns/persistence" 
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence 
               http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
  <persistence-unit name="clientmdbentity-ejbPU" transaction-type="JTA">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <jta-data-source>java:comp/DefaultDataSource</jta-data-source>
    <properties>
      <property name="eclipselink.ddl-generation" 
                value="drop-and-create-tables"/>
    </properties>
  </persistence-unit>
</persistence>

46.8.3.1 To Run clientmdbentity Using NetBeans IDE

1. Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server), as well as the database server (see Starting and Stopping the Java DB Server).

2. From the File menu, choose Open Project.

3. In the Open Project dialog box, navigate to:

   tut-install/examples/jms/clientmdbentity
   

4. Select the clientmdbentity folder.

5. Click Open Project.

6. In the Projects tab, right-click the clientmdbentity project and select Build.

   This command creates the following:

   • An application client JAR file that contains the client class and listener class files, along with a manifest file that specifies the main class

   • An EJB JAR file that contains the message-driven beans and the entity class, along with the persistence.xml file

   • An application EAR file that contains the two JAR files along with an application.xml file

     The clientmdbentity.ear file is created in the clientmdbentity-ear/target/ directory.

   The command then deploys the EAR file, retrieves the client stubs, and runs the application client.

46.8.3.2 To Run clientmdbentity Using Maven

1. Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server), as well as the database server (see Starting and Stopping the Java DB Server).

2. Go to the following directory:

   tut-install/examples/jms/clientmdbentity/
   

3. To compile the source files and package, deploy, and run the application, enter the following command:

   mvn install
   

   This command creates the following:

   • An application client JAR file that contains the client class and listener class files, along with a manifest file that specifies the main class

   • An EJB JAR file that contains the message-driven beans and the entity class, along with the persistence.xml file

   • An application EAR file that contains the two JAR files along with an application.xml file

   The command then deploys the application, retrieves the client stubs, and runs the application client.

46.8.3.3 Viewing the Application Output

The output in the NetBeans IDE output window or in the terminal window looks something like this (preceded by application client container output and Maven output):

SENDER: Setting hire ID to 50, name Bill Tudor, position Programmer
SENDER: Setting hire ID to 51, name Carol Jones, position Senior Programmer
SENDER: Setting hire ID to 52, name Mark Wilson, position Manager
SENDER: Setting hire ID to 53, name Polly Wren, position Senior Programmer
SENDER: Setting hire ID to 54, name Joe Lawrence, position Director
Waiting for 5 message(s)
New hire event processed:
  Employee ID: 52
  Name: Mark Wilson
  Equipment: Tablet
  Office number: 294
Waiting for 4 message(s)
New hire event processed:
  Employee ID: 53
  Name: Polly Wren
  Equipment: Laptop
  Office number: 186
Waiting for 3 message(s)
New hire event processed:
  Employee ID: 54
  Name: Joe Lawrence
  Equipment: Mobile Phone
  Office number: 135
Waiting for 2 message(s)
New hire event processed:
  Employee ID: 50
  Name: Bill Tudor
  Equipment: Desktop System
  Office number: 200
Waiting for 1 message(s)
New hire event processed:
  Employee ID: 51
  Name: Carol Jones
  Equipment: Laptop
  Office number: 262

The output from the message-driven beans and the entity class appears in the server log.

For each employee, the application first creates the entity and then finds it. You may see runtime errors in the server log, and transaction rollbacks may occur. The errors occur if both of the message-driven beans discover at the same time that the entity does not yet exist, so they both try to create it. The first attempt succeeds, but the second fails because the bean already exists. After the rollback, the second message-driven bean tries again and succeeds in finding the entity. Container-managed transactions allow the application to run correctly, in spite of these errors, with no special programming.

To undeploy the application after you have finished running it, use the Services tab or issue the mvn cargo:undeploy command.