This Blog entry is part two of the series; writing JBoss Customer Services. This Blog  assumes that you have completed
all the coding tasks detailed in the previous blog entry. To review the previous Blog entry; we set-up an Eclipse development project and coded an MBean interface and ServiceMBeanSupport class. Next, we created and modified the jboss-service.xml file for our BlogExampleService. An Ant build.xml file was used to compile, assemble, and deploy the SAR File. Once the SAR File was deployed, the JBoss JMX-Console was used to access our service and invoke lifecycle methods. Now we are ready to extend the JBoss service to utilize other JBoss’s Scheduling services.

JBoss Scheduling Service
The JBoss documentation describes the JBoss scheduler service as follows:

Java includes a simple timer-based capability through the java.util.Timer and java.util.TimerTask utility classes. JMX also includes a mechanism for scheduling JMX notifications at a given time with an optional repeat interval as the java.management.timer.TimerMBean agent service.

JBoss includes two variations of the JMX timer service in the org.jboss.varia.
scheduler.Scheduler and org.jboss.varia.scheduler.ScheduleManager MBeans. In essence, the Scheduler Instance runs a scheduling service for any Schedulable instances. For more information on the Scheduling service please refer to the JBoss documentation.

Implement Schedulable Interface
In order to create a schedulable implementation, the ServiceMBeanSupport class (BlogExampleService) needs to implement the  org.jboss.varia.scheduler.Schedulable class.

Modify the BlogExampleService java program to implement the Schedulable interface:

public class BlogExampleService extends ServiceMBeanSupport
implements BlogExampleServiceMBean, Schedulable {

Eclipse will help to organize your class by importing org.jboss.varia.
scheduler.Schedulable from the scheduler-plugin.jar (part of the projects build path). You will need to override the abstract perform method and add a logging entry:

    public void perform(Date inDate, long repetitionCountdown) {
            _log.info("perform() date: " + inDate +
                           “Repetition Countdown " + repetitionCountdown);
  
   }

Add the following Scheduler MBean configuration details to the jboss-service.xml file (insert this text after the BlogExampleService configuration):

 <mbean code="org.jboss.varia.scheduler.Scheduler"
  name="blog.example:service=BlogExampleScheduler">
  <attribute name="StartAtStartup">false</attribute>
  <attribute name="SchedulableClass">
   blog.example.services.BlogExampleService
  </attribute>
  <attribute name="SchedulableArguments">
  </attribute>
  <attribute name="SchedulableArgumentTypes">
  </attribute>
  <attribute name="InitialStartDate">NOW</attribute>
  <attribute name="SchedulePeriod">60000</attribute>
  <attribute name="InitialRepetitions">3</attribute>
  <depends>blog.example:service=BlogExampleService</depends>
 </mbean>

Jboss-service.xml Scheduler MBean Attributes:

The Scheduler MBean is named BlogExampleScheduler under the blog.example domain. The MBean has the following attributes:
• Start scheduler on startup = No
• Class to call = blog.example.services.BlogExampleService
• Constructor argument = None
• Constructor argument types = None
• When to start Scheduler – Now ( this translates into one second after startup)
• Interval period between scheduled call = 60,000 milliseconds (1 minute)
• Number of times the scheduler will invoke the target callback (BlogExampleService.perform()) = 3 times
• The BlogExampleScheduler depends on the creation of the BlogExampleService.

Deploy the BlogExampleScheduler Service
As we discussed in Part I, JBoss services are deployed as a SAR Files. To compile, assemble, and deploy the SAR File, run the deploy target of the build.xml file. The JBoss console output should look like this:

Buildfile: C:\psBlogs\blog-example\build.xml
compile:
    [javac] Compiling 1 source file to C:\psBlogs\blog-example\build
dist:
     [copy] Copying 1 file to C:\psBlogs\blog-example\build
      [jar] Building jar: C:\psBlogs\blog-example\dist\blog_example.sar
deploy:
     [copy] Copying 1 file to C:\jboss-4.0.3SP1\server\default\deploy
BUILD SUCCESSFUL
Total time: 5 seconds

Start the JBoss Console
Enter http://localhost:8080/ in your browser. Next, select the jmx-console hyperlink under the JBoss Management category. The JMX Agent View page will display the registered service domains; including the blog.example domain.

Start the Scheduler
Since the BlogExampleScheduler’s StartAtStartup attribute is set to false, the scheduler must be started manually using the JBoss JMX-Console.

1. Select the service=BlogExampleScheduler link under the blog.example domain.
2. Scroll down to the BlogExampleScheduler operations.
3. Press the Invoke Button under the startScheduler() operation.

JBoss console output
As the scheduler runs, the JBoss output will capture the following log entries:
 [BlogExampleService] perform() date: Fri Apr 14 07:27:10 EDT 2006 Repetition Countdown 2
[BlogExampleService] perform() date Fri Apr 14 07:27:10 EDT 2006 Repetition Countdown 1
[BlogExampleService] perform() date: Fri Apr 14 07:27:10 EDT 2006 Repetition Countdown 0

Notice that the Repetition Countdown is decrementing each time the perform method is called.

Dealing with Constructor Parameters
To simulate a service constructor that has parameters, we will add a parameterized constructor to the BlogExampleService class.
 
Modify BlogExampleService.java as follows:

1. Add two private class variables:

private String firstName;
private int value;

2. Add assessors and mutators for the new variables (e.g. getFirstName(), etc)

3. Create a parameterized constructor for the BlogExampleService java program:

// add parameterized constructor
public BlogExampleService(String firstName, int value) {
      this. firstName = firstName;
      this.value = value;
}

4. Since you have created a parameterized constructor, you will also need to create an empty constructor.

// add empty constructor
public BlogExampleService() {

}

Next edit the jboss-service.xml file to implement the new parameterized constructor. Modify the SchedulableArguments and SchedulableArgumentTypes attributes as follows:

  <attribute name="SchedulableArguments">
      firstName, value
  </attribute>
  <attribute name="SchedulableArgumentTypes">
      java.lang.String, int
  </attribute>

The SchedulableArguments attribute defines the constructor arguments. This comma separated list must map to the parameter list of the constructor. The SchedulableArgumentTypes attribute defines the argument type for the list of parameters detailed in the SchedulableArguments. Since firstName is of type String and value is of type int, the SchedulableArgumentTypes list is java.lang.String, int.

To validate that the parameter list is implemented, modify the perform method in BlogExampleService.java program as follows:

_log.info("perform() date: " + inDate + " Repetition Countdown " + repetitionCountdown + " name= " + getFirstName() + " value = " + getValue());

Deploy the BlogExampleScheduler Service
Run the deploy target of the build.xml file to compile, assemble, and deploy the SAR File.

Start the JBoss Console
Enter http://localhost:8080/ in the browser. Select the jmx-console hyperlink under the JBoss Management category. The JMX Agent View page will display the registered service domains; including the blog.example domain. You will now see two services:

• service=BlogExampleScheduler
• service=BlogExampleService

Enter the Constructor Parameters
Select the service=BlogExampleScheduler link under the blog.example domain. Under the List of MBean Attributes, enter a string and an integer in the SchedulableArguments Value textbox (remember the comma). As an example:
  

BlogExample, 100

Press the Apply Changes button to commit the changes.

Start the Scheduler
Start the Scheduler Service from the JBoss JMX-Console.

1. Select the service=BlogExampleScheduler link under the blog.example domain.
2. Scroll down to the BlogExampleScheduler operations.
3. Press the Invoke Button under the startScheduler() operation.

JBoss console output
As the scheduler runs, the JBoss output will capture the following log entries:

[BlogExampleService] perform() date: Fri Apr 14 07:47:10 EDT 2006 Repetition Countdown 2 firstName= BlogExample value = 100
[BlogExampleService] perform() date: Fri Apr 14 07:48:10 EDT 2006 Repetition Countdown 1 firstName= BlogExample value = 100
[BlogExampleService] perform() date: Fri Apr 14 07:49:10 EDT 2006 Repetition Countdown 0 firstName= BlogExample value = 100

Notice that the string and int value that were entered in the SchedulableArguments Value textbox are displayed in the output.

Exception
Return to the JBoss JMX-Console and select the service=BlogExampleScheduler link. Enter BlogExample, hundred in the SchedulableArguments Value textbox. Press the Apply Changes button to commit the changes. Now start the scheduler by pressing the invoke button for the startSchedule method. Since the parameter values are invalid (hundred is not and int), the scheduler fails. Here is a selection from the stack trace:

ERROR [Scheduler] Could not load or create constructor argument
java.lang.NumberFormatException: For input string: "hundred"
 at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
 at java.lang.Integer.parseInt(Integer.java:447)
 at java.lang.Integer.<init>(Integer.java:620)

Be sure to correct the error; remember to select the Apply Changes button to commit the changes.

Using other Core JBoss Services
This section of the blog provides some simple code for using other JBoss Core Services; JBossMQ, and Java Mail.

JBossMQ Server (JMS)

The org.jboss.mq.server.jmx.Queue is used to define a JMS Queue Destination on the JBossMQ server. The “name” attribute of the JMX object name of this MBean is used to determine the destination name.

Add the MBean definition to the jboss-service.xml:

<mbean code="org.jboss.mq.server.jmx.Queue"
name="jboss.mq.destination:service=Queue,name=BlogExampleQueue">
 <depends optional-attribute-name="DestinationManager">
  jboss.mq:service=DestinationManager
 </depends>
</mbean>

The following code example shows how to use the BlogExampleQueue:

public static void sendMessage(String inMessage)  throws NamingException, JMSException {
        _log.info("sendMessage().");

        String msgText;
        Properties properties = new Properties();
        properties.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory");
        properties.put(Context.PROVIDER_URL, "jnp://localhost:1099");
        properties.put("java.naming.factory.url.pkgs","org.jboss.naming:org.jnp.interfaces");
        properties.put("jnp.disableDiscovery", "true");

        InitialContext ctx = new InitialContext(properties);
        Queue queue = (Queue) ctx.lookup("queue/BlogExampleQueue");
        QueueConnectionFactory qcf = (QueueConnectionFactory) ctx.lookup("QueueConnectionFactory");

        QueueConnection qc = qcf.createQueueConnection();

        try {
            QueueSession qs = qc.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
            QueueSender sender = qs.createSender(queue);
            TextMessage message = qs.createTextMessage(inMessage);
            sender.send(message);
            qc.start();
        } finally {
            qc.close();
        }
    }

JBOSS Mail Server

JBoss has a built-in implementation of the JavaMail API.

Add the following MBean definition to the jboss-service.xml:

<mbean code="blog.example.services.BlogExampleService"
  name="blog.example:service=BlogExampleService">  <depends>jboss:service=Mail</depends>
</mbean>

The following code example shows how to use the JBoss Mail Service. The perform method is called by the JBoss Scheduler. The perform method calls the processInbox method to read inbox messages from a pop3 mail server.

     // ServiceBean callback method
    public void perform(Date now, long repetitions) {
        _log.info("BlogExampleService ============= perform");
        this.processInbox();
    }

    // working method to process messages from the INBOX
    public void processInbox() {
        _log.info("BlogExampleService ======== processInbox ");

        Message[] messages = null;
        String[]emaildata = null;
        Folder inboxFolder = null;

        Store store;    // email store

        try {
            Properties properties = new Properties();
            properties.put(Context.INITIAL_CONTEXT_FACTORY,
                "org.jnp.interfaces.NamingContextFactory");
            properties.put(Context.PROVIDER_URL, "jnp://localhost:1099");
            properties.put("java.naming.factory.url.pkgs",
                "org.jboss.naming:org.jnp.interfaces");
            properties.put("jnp.disableDiscovery", "true");

            ctx = new InitialContext(properties);
            // JBoss Email Service
            ctx = (Context) ctx.lookup("java:");
            mailSession = (Session) ctx.lookup("Mail");

            // -- Get hold of a POP3 message store, and connect to it --
            if (null != mailSession) {
                store = mailSession.getStore("pop3");
                store.connect(null, "", "");

                // -- Try to get hold of the default folder --
                inboxFolder = store.getDefaultFolder();

                // -- ...and its INBOX --
                inboxFolder = inboxFolder.getFolder("INBOX");

                // -- Open the folder for read write --
                inboxFolder.open(Folder.READ_WRITE);

                // retrieve all the messages from the inbox
                messages = inboxFolder.getMessages();

                for (int x= 0; x< messages.length; x++) {                           
                // delete the email from the inbox                        

               messages[x].setFlag(Flags.Flag.DELETED, true);
                }
                   
                // create the array from the email message.
                emaildata = processMessage(messages[x]);                   
                }

                inboxFolder.close(true);
                store.close();
            } else {
                _log.warn("No Mail Session");
            }
        } catch (NoSuchProviderException e) {
            e.printStackTrace();
        } catch (MessagingException e) {
            e.printStackTrace();
        } catch (NamingException e) {
            e.printStackTrace();
        }
    }

   private String[] processMessage(Message message) {
        String[] stringMessages = new String[100];
        int index = 0;

        try {
            // -- Get the message part (i.e. the message itself) --
            Part messagePart = message;
            Object content = messagePart.getContent();

            // -- or its first body part if it is a multipart message --
            if (content instanceof Multipart) {
                messagePart = ((Multipart) content).getBodyPart(0);
            }

            // -- Get the content type --
            String contentType = messagePart.getContentType();

            if (contentType.startsWith("text/plain") ||
                    contentType.startsWith("text/html")) {
                InputStream is = messagePart.getInputStream();

                BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                String thisLine = reader.readLine();

                while (thisLine != null) {
                     thisLine = reader.readLine();
                     stringMessages[index++] = thisLine;  
                }
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }

        return stringMessages;
    }

The blog entries detailed writing JBoss Custom Service services and using some JBoss core services including; the Scheduler, JBossMQ (JMS), and Mail services. All JBoss services are accessible via the JBoss JMX-Console. The JBoss Services expose lifecycle methods and attributes which can be modified or executed from the console. A major benefit of using a JBoss Service is that you can stop, reconfigure, and restart the service without restarting the JBoss Application Server. Please refer to the JBoss website for more details.