Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## Sending and Receiving Messages Using a Simple Web Application

Web applications can use the JMS API to send and receive messages, as noted in Using Java EE Components to Produce and to Synchronously Receive Messages. This section describes the components of a very simple web application that uses the JMS API.

This section assumes that you are familiar with the basics of JavaServer Faces technology, described in Part IX, "The Web Tier."

The example, `websimplemessage`, is under the `_tut-install_/jms/examples/` directory. It uses sending and receiving Facelets pages as well as corresponding backing beans. When a user enters a message in the text field of the sending page and clicks a button, the backing bean for the page sends the message to a queue and displays it on the page. When the user goes to the receiving page and clicks another button, the backing bean for that page receives the message synchronously and displays it.

Figure 49-2 The websimplemessage Application

### The websimplemessage Facelets Pages

The Facelets pages for the example are as follows.

- `sender.xhtml`, which provides a labeled `h:InputText` tag where the user enters the message, along with two command buttons. When the user clicks the Send Message button, the `senderBean.sendMessage` method is called to send the message to the queue and display its contents. When the user clicks the Go to Receive Page button, the `receiver.xhtml` page appears.

- `receiver.xhtml`, which also provides two command buttons. When the user clicks the Receive Message button, the `receiverBean.getMessage` method is called to fetch the message from the queue and display its contents. When the user clicks the Send Another Message button, the sender.xhtml page appears again.

### The websimplemessage Managed Beans

The two managed beans for the example are as follows.

- `SenderBean.java`, a CDI managed bean with one property, `messageText`, and one business method, `sendMessage`. The class is annotated with `@JMSDestinationDefinition` to create a component-private queue:

      @JMSDestinationDefinition(
              name = "java:comp/jms/webappQueue",
              interfaceName = "javax.jms.Queue",
              destinationName = "PhysicalWebappQueue")
      @Named
      @RequestScoped
      public class SenderBean {

  The `sendMessage` method injects a `JMSContext` (using the default connection factory) and the queue, creates a producer, sends the message the user typed on the Facelets page, and creates a `FacesMessage` to display on the Facelets page:

      @Inject
      private JMSContext context;
      @Resource(lookup = "java:comp/jms/webappQueue")
      private Queue queue;
      private String messageText;
      ...
      public void sendMessage() {
          try {
              String text = "Message from producer: " + messageText;
              context.createProducer().send(queue, text);

              FacesMessage facesMessage =
                      new FacesMessage("Sent message: " + text);
              FacesContext.getCurrentInstance().addMessage(null, facesMessage);
          } catch (Throwable t) {
              logger.log(Level.SEVERE,
                      "SenderBean.sendMessage: Exception: {0}",
                      t.toString());
          }
      }

- `ReceiverBean.java`, a CDI managed bean with one business method, `getMessage`. The method injects a `JMSContext` (using the default connection factory) and the queue that was defined in `SenderBean`, creates a consumer, receives the message, and creates a `FacesMessage` to display on the Facelets page:

      @Inject
      private JMSContext context;
      @Resource(lookup = "java:comp/jms/webappQueue")
      private Queue queue;
      ...
      public void getMessage() {
          try {
              JMSConsumer receiver = context.createConsumer(queue);
              String text = receiver.receiveBody(String.class);

              if (text != null) {
                  FacesMessage facesMessage =
                          new FacesMessage("Reading message: " + text);
                  FacesContext.getCurrentInstance().addMessage(null, facesMessage);
              } else {
                  FacesMessage facesMessage =
                          new FacesMessage("No message received after 1 second");
                  FacesContext.getCurrentInstance().addMessage(null, facesMessage);
              }
          } catch (Throwable t) {
              logger.log(Level.SEVERE,
                      "ReceiverBean.getMessage: Exception: {0}",
                      t.toString());
          }
      }

### Running the websimplemessage Example

You can use either NetBeans IDE or Maven to build, package, deploy, and run the `websimplemessage` application.

The following topics are addressed here:

- Creating Resources for the websimplemessage Example

- To Package and Deploy websimplemessage Using NetBeans IDE

- To Package and Deploy websimplemessage Using Maven

- To Run the websimplemessage Example

#### Creating Resources for the websimplemessage Example

This example uses an annotation-defined queue and the preconfigured default connection factory `java:comp/DefaultJMSConnectionFactory`.

#### To Package and Deploy websimplemessage Using NetBeans IDE

1. Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).

2. From the File menu, choose Open Project.

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

       tut-install/examples/jms

4. Select the `websimplemessage` folder.

5. Click Open Project.

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

   This command builds and deploys the project.

#### To Package and Deploy websimplemessage Using Maven

1. Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).

2. In a terminal window, go to:

       tut-install/examples/jms/websimplemessage/

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

       mvn install

#### To Run the websimplemessage Example

1. In a web browser, enter the following URL:

       http://localhost:8080/websimplemessage

2. Enter a message in the text field and click Send Message.

   If, for example, you enter "Hello, Duke", the following appears below the buttons:

       Sent message: Message from producer: Hello, Duke

3. Click Go to Receive Page.

4. Click Receive Message.

   The following appears below the buttons:

       Reading message: Message from producer: Hello, Duke

5. Click Send Another Message to return to the sending page.

6. After you have finished running the application, undeploy it using either the Services tab of NetBeans IDE or the `mvn cargo:undeploy` command.

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