The Java EE 5 Tutorial

An Application Example That Deploys a Message-Driven Bean on Two Servers

This section, like the preceding one, explains how to write, compile, package, deploy, and run a pair of Java EE modules that use the JMS API and run on two Java EE servers. The modules are slightly more complex than the ones in the first example.

The modules use the following components:

An application client that is deployed on the local server. It uses two connection factories, one ordinary one and one that is configured to communicate with the remote server, to create two publishers and two subscribers and to publish and to consume messages.
A message-driven bean that is deployed twice: once on the local server, and once on the remote one. It processes the messages and sends replies.

In this section, the term local server means the server on which both the application client and the message-driven bean are deployed (earth in the preceding example). The term remote server means the server on which only the message-driven bean is deployed (jupiter in the preceding example).

The section covers the following topics:

You will find the source files for this section in tut-install/javaeetutorial5/examples/jms/sendremote/. Path names in this section are relative to this directory.

Overview of the `sendremote` Example Modules

This pair of modules is somewhat similar to the modules in An Application Example That Consumes Messages from a Remote Server in that the only components are a client and a message-driven bean. However, the modules here use these components in more complex ways. One module consists of the application client. The other module contains only the message-driven bean and is deployed twice, once on each server.

The basic steps of the modules are as follows.

You start two Java EE servers, one on each system.
On the local server (earth), you create two connection factories: one local and one that communicates with the remote server (jupiter). On the remote server, you create a connection factory that has the same name.
The application client looks up the two connection factories (the local one and the one that communicates with the remote server) to create two connections, sessions, publishers, and subscribers. The subscribers use a message listener.
Each publisher publishes five messages.
Each of the local and the remote message-driven beans receives five messages and sends replies.
The client’s message listener consumes the replies.

Figure 32–4 illustrates the structure of this application. M1 represents the first message sent using the local connection factory, and RM1 represents the first reply message sent by the local MDB. M2 represents the first message sent using the remote connection factory, and RM2 represents the first reply message sent by the remote MDB.

Figure 32–4 A Java EE Application That Sends Messages to Two Servers

Diagram of application showing an application client
sending messages to two servers and receiving the replies

Writing the Module Components for the `sendremote` Example

Writing the components of the modules involves two tasks:

Coding the Application Client: `MultiAppServerClient.java`

The application client class, multiclient/src/java/MultiAppServerClient.java, does the following.

It injects resources for two connection factories and a topic.
For each connection factory, it creates a connection, a publisher session, a publisher, a subscriber session, a subscriber, and a temporary topic for replies.
Each subscriber sets its message listener, ReplyListener, and starts the connection.
Each publisher publishes five messages and creates a list of the messages the listener should expect.
When each reply arrives, the message listener displays its contents and removes it from the list of expected messages.
When all the messages have arrived, the client exits.

Coding the Message-Driven Bean: `ReplyMsgBean.java`

The message-driven bean class, replybean/src/ReplyMsgBean.java, does the following:

Uses the @MessageDriven annotation:
```
@MessageDriven(mappedName="jms/Topic")
```
Injects resources for the MessageDrivenContext and for a connection factory. It does not need a destination resource because it uses the value of the incoming message’s JMSReplyTo header as the destination.
Uses a @PostConstruct callback method to create the connection, and a @PreDestroy callback method to close the connection.

The onMessage method of the message-driven bean class does the following:

Casts the incoming message to a TextMessage and displays the text
Creates a connection, a session, and a publisher for the reply message
Publishes the message to the reply topic
Closes the connection

On both servers, the bean will consume messages from the topic jms/Topic.

Creating Resources for the `sendremote` Example

This example uses the connection factory named jms/ConnectionFactory and the topic named jms/Topic. These objects must exist on both the local and the remote servers.

This example uses an additional connection factory, jms/JupiterConnectionFactory, which communicates with the remote system; you created it in Creating Administered Objects for Multiple Systems. This connection factory must exist on the local server.

The build.xml file for the multiclient module contains targets that you can use to create these resources if you deleted them previously.

Using Two Application Servers for the `sendremote` Example

If you are using NetBeans IDE, you need to add the remote server in order to deploy the message-driven bean there. To do so, perform these steps:

In NetBeans IDE, click the Services tab.
Right-click the Servers node and choose Add Server. In the Add Server Instance dialog, perform these steps:
1. Select Sun Java System Application Server (the default) from the Server list.
2. In the Name field, specify a name slightly different from that of the local server, such as Sun Java System Application Server (1).
3. Click Next.
4. For the Platform Folder location, you can either browse to the location of the Application Server on the remote system or, if that location is not visible from the local system, use the default location on the local system.
5. Select the Register Remote Domain radio button.
6. Click Next.
7. Type the system name of the host in the Host field.
8. Click Next.
9. Type the administrative username and password for the remote system in the Admin Username and Admin Password fields.
10. Click Finish.
  
  There may be a delay while NetBeans IDE registers the remote domain.

Building, Deploying, and Running the `sendremote` Modules Using NetBeans IDE

To package the modules using NetBeans IDE, perform these steps:

In NetBeans IDE, choose Open Project from the File menu.
In the Open Project dialog, navigate to tut-install/javaeetutorial5/examples/jms/sendremote/.
Select the replybean folder.
Select the Open as Main Project check box.
Click Open Project.
Right-click the replybean project and choose Build.

This command creates a JAR file that contains the bean class file.
Choose Open Project from the File menu.
Select the multiclient folder.
Select the Open as Main Project check box.
Click Open Project.
Right-click the multiclient project and choose Build.

This command creates a JAR file that contains the client class file and a manifest file.

To deploy the multiclient module on the local server, perform these steps:

Right-click the multiclient project and choose Properties.
Select Run from the Categories tree.
From the Server list, select Sun Java System Application Server (the local server).
Click OK.
Right-click the multiclient project and choose Undeploy and Deploy.

To deploy the replybean module on the local and remote servers, perform these steps:

Right-click the replybean project and choose Properties.
Select Run from the Categories tree.
From the Server list, select Sun Java System Application Server(the local server).
Click OK.
Right-click the replybean project and choose Undeploy and Deploy.
Right-click the replybean project again and choose Properties.
Select Run from the Categories tree.
From the Server list, select Sun Java System Application Server (1) (the remote server).
Click OK.
Right-click the replybean project and choose Undeploy and Deploy.

You can use the Services tab to verify that multiclient is deployed as an App Client Module on the local server and that replybean is deployed as an EJB Module on both servers.

To run the application client, right-click the multiclient project and choose Run.

This command returns a JAR file named multiclientClient.jar and then executes it.

On the local system, the output of the appclient command looks something like this:

running application client container.
Sent message: text: id=1 to local app server
Sent message: text: id=2 to remote app server
ReplyListener: Received message: id=1, text=ReplyMsgBean processed message: text: id=1 to local
 app server
Sent message: text: id=3 to local app server
ReplyListener: Received message: id=3, text=ReplyMsgBean processed message: text: id=3 to local
 app server
ReplyListener: Received message: id=2, text=ReplyMsgBean processed message: text: id=2 to remote
 app server
Sent message: text: id=4 to remote app server
ReplyListener: Received message: id=4, text=ReplyMsgBean processed message: text: id=4 to remote
 app server
Sent message: text: id=5 to local app server
ReplyListener: Received message: id=5, text=ReplyMsgBean processed message: text: id=5 to local
 app server
Sent message: text: id=6 to remote app server
ReplyListener: Received message: id=6, text=ReplyMsgBean processed message: text: id=6 to remote
 app server
Sent message: text: id=7 to local app server
ReplyListener: Received message: id=7, text=ReplyMsgBean processed message: text: id=7 to local
 app server
Sent message: text: id=8 to remote app server
ReplyListener: Received message: id=8, text=ReplyMsgBean processed message: text: id=8 to remote
 app server
Sent message: text: id=9 to local app server
ReplyListener: Received message: id=9, text=ReplyMsgBean processed message: text: id=9 to local
 app server
Sent message: text: id=10 to remote app server
ReplyListener: Received message: id=10, text=ReplyMsgBean processed message: text: id=10 to remote
 app server
Waiting for 0 message(s) from local app server
Waiting for 0 message(s) from remote app server
Finished
Closing connection 1
Closing connection 2

On the local system, where the message-driven bean receives the odd-numbered messages, the output in the server log looks like this (wrapped in logging information):

ReplyMsgBean: Received message: text: id=1 to local app server
ReplyMsgBean: Received message: text: id=3 to local app server
ReplyMsgBean: Received message: text: id=5 to local app server
ReplyMsgBean: Received message: text: id=7 to local app server
ReplyMsgBean: Received message: text: id=9 to local app server

On the remote system, where the bean receives the even-numbered messages, the output in the server log looks like this (wrapped in logging information):

ReplyMsgBean: Received message: text: id=2 to remote app server
ReplyMsgBean: Received message: text: id=4 to remote app server
ReplyMsgBean: Received message: text: id=6 to remote app server
ReplyMsgBean: Received message: text: id=8 to remote app server
ReplyMsgBean: Received message: text: id=10 to remote app server

Undeploy the modules after you finish running the client. To undeploy the modules, perform these steps:

Click the Services tab.
Expand the Servers node.
Expand the Sun Java System Application Server node (the local system).
Expand the Applications node.
Expand the EJB Modules node.
Right-click replybean and choose Undeploy.
Expand the App Client Modules node.
Right-click multiclient and choose Undeploy.
Expand the Sun Java System Application Server (1) node (the remote system).
Expand the Applications node.
Expand the EJB Modules node.
Right-click replybean and choose Undeploy.

To remove the generated files, follow these steps:

Right-click the replybean project and choose Clean.
Right-click the multiclient project and choose Clean.

Building, Deploying, and Running the `sendremote` Modules Using Ant

To package the modules, perform these steps:

Go to the following directory:

tut-install/javaeetutorial5/examples/jms/sendremote/multiclient/

Type the following command:
ant
This command creates a JAR file that contains the client class file and a manifest file.
Change to the directory replybean:
cd ../replybean
Type the following command:
ant
This command creates a JAR file that contains the bean class file.

To deploy the replybean module on the local and remote servers, perform the following steps:

Verify that you are still in the directory replybean.
Type the following command:
ant deploy
Ignore the message that states that the application is deployed at a URL.
Type the following command:
ant deploy-remote -Dsys=remote-system-name
Replace remote-system-name with the actual name of the remote system.

To deploy and run the client, perform these steps:

Change to the directory multiclient:
cd ../multiclient
Type the following command:
ant run

On the local system, the output looks something like this:

running application client container.
Sent message: text: id=1 to local app server
Sent message: text: id=2 to remote app server
ReplyListener: Received message: id=1, text=ReplyMsgBean processed message: text: id=1 to local
 app server
Sent message: text: id=3 to local app server
ReplyListener: Received message: id=3, text=ReplyMsgBean processed message: text: id=3 to local
 app server
ReplyListener: Received message: id=2, text=ReplyMsgBean processed message: text: id=2 to remote
 app server
Sent message: text: id=4 to remote app server
ReplyListener: Received message: id=4, text=ReplyMsgBean processed message: text: id=4 to remote
 app server
Sent message: text: id=5 to local app server
ReplyListener: Received message: id=5, text=ReplyMsgBean processed message: text: id=5 to local
 app server
Sent message: text: id=6 to remote app server
ReplyListener: Received message: id=6, text=ReplyMsgBean processed message: text: id=6 to remote
 app server
Sent message: text: id=7 to local app server
ReplyListener: Received message: id=7, text=ReplyMsgBean processed message: text: id=7 to local
 app server
Sent message: text: id=8 to remote app server
ReplyListener: Received message: id=8, text=ReplyMsgBean processed message: text: id=8 to remote
 app server
Sent message: text: id=9 to local app server
ReplyListener: Received message: id=9, text=ReplyMsgBean processed message: text: id=9 to local
 app server
Sent message: text: id=10 to remote app server
ReplyListener: Received message: id=10, text=ReplyMsgBean processed message: text: id=10 to remote
 app server
Waiting for 0 message(s) from local app server
Waiting for 0 message(s) from remote app server
Finished
Closing connection 1
Closing connection 2

On the local system, where the message-driven bean receives the odd-numbered messages, the output in the server log looks like this (wrapped in logging information):

ReplyMsgBean: Received message: text: id=1 to local app server
ReplyMsgBean: Received message: text: id=3 to local app server
ReplyMsgBean: Received message: text: id=5 to local app server
ReplyMsgBean: Received message: text: id=7 to local app server
ReplyMsgBean: Received message: text: id=9 to local app server

On the remote system, where the bean receives the even-numbered messages, the output in the server log looks like this (wrapped in logging information):

ReplyMsgBean: Received message: text: id=2 to remote app server
ReplyMsgBean: Received message: text: id=4 to remote app server
ReplyMsgBean: Received message: text: id=6 to remote app server
ReplyMsgBean: Received message: text: id=8 to remote app server
ReplyMsgBean: Received message: text: id=10 to remote app server

Undeploy the modules after you finish running the client. To undeploy the multiclient module, perform these steps:

Verify that you are still in the directory multiclient.
Type the following command:
ant undeploy

To undeploy the replybean module, perform these steps:

Change to the directory replybean:
cd ../replybean
Type the following command:
ant undeploy
Type the following command:
ant undeploy-remote -Dsys=remote-system-name
Replace remote-system-name with the actual name of the remote system.

To remove the generated files, use the following command in both the replybean and multiclient directories:

ant clean

An Application Example That Deploys a Message-Driven Bean on Two Servers

Overview of the sendremote Example Modules

Figure 32–4 A Java EE Application That Sends Messages to Two Servers

Writing the Module Components for the sendremote Example

Coding the Application Client: MultiAppServerClient.java

Coding the Message-Driven Bean: ReplyMsgBean.java

Creating Resources for the sendremote Example

Using Two Application Servers for the sendremote Example

Building, Deploying, and Running the sendremote Modules Using NetBeans IDE

Building, Deploying, and Running the sendremote Modules Using Ant