EJB - Timer Service

Timer Service is a mechanism by which scheduled application can be build. For example, salary slip generation on the 1st of every month. EJB 3.0 specification has specified @Timeout annotation, which helps in programming the EJB service in a stateless or message driven bean. EJB Container calls the method, which is annotated by @Timeout.
EJB Timer Service is a service provided by EJB container, which helps to create timer and to schedule callback when timer expires.
Inject SessionContext in bean using @Resource annotation −
@Stateless
public class TimerSessionBean {

   @Resource
   private SessionContext context;
   ...
}
Use SessionContext object to get TimerService and to create timer. Pass time in milliseconds and message.
public void createTimer(long duration) {
   context.getTimerService().createTimer(duration, "Hello World!");
}
Use @Timeout annotation to a method. Return type should be void and pass a parameter of type Timer. We are canceling the timer after first execution otherwise it will keep running after fix intervals.
@Timeout
public void timeOutHandler(Timer timer) {
   System.out.println("timeoutHandler : " + timer.getInfo());        
   timer.cancel();
}
Let us create a test EJB application to test Timer Service in EJB.
Create a project with a name EjbComponent under a package com.tutorialspoint.timer as explained in the EJB - Create Application chapter.
Create TimerSessionBean.java and TimerSessionBeanRemote as explained in the EJB - Create Application chapter. Keep rest of the files unchanged.
Clean and Build the application to make sure business logic is working as per the requirements.
Finally, deploy the application in the form of jar file on JBoss Application Server. JBoss Application server will get started automatically if it is not started yet.
Now create the EJB client, a console based application in the same way as explained in the EJB - Create Application chapter under topic Create Client to access EJB.
package com.tutorialspoint.timer;

import javax.annotation.Resource;
import javax.ejb.SessionContext;
import javax.ejb.Timer;
import javax.ejb.Stateless;
import javax.ejb.Timeout;

@Stateless
public class TimerSessionBean implements TimerSessionBeanRemote {

   @Resource
   private SessionContext context;

   public void createTimer(long duration) {
      context.getTimerService().createTimer(duration, "Hello World!");
   }

   @Timeout
   public void timeOutHandler(Timer timer) {
      System.out.println("timeoutHandler : " + timer.getInfo());        
      timer.cancel();
   }
}
package com.tutorialspoint.timer;

import javax.ejb.Remote;

@Remote
public interface TimerSessionBeanRemote {
   public void createTimer(long milliseconds);
}
As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.
As soon as you deploy the EjbComponent project on JBOSS, notice the jboss log.
JBoss has automatically created a JNDI entry for our session bean − TimerSessionBean/remote.
JBoss has automatically created a JNDI entry for our session bean − TimerSessionBean/remote.
We will using this lookup string to get remote business object of type −
 com.tutorialspoint.timer.TimerSessionBeanRemote  
We will using this lookup string to get remote business object of type −
 com.tutorialspoint.timer.TimerSessionBeanRemote  
...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   TimerSessionBean/remote - EJB3.x Default Remote Business Interface
   TimerSessionBean/remote-com.tutorialspoint.timer.TimerSessionBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=TimerSessionBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.timer.TimerSessionBeanRemote ejbName: TimerSessionBean
...   

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost
These properties are used to initialize the InitialContext object of java naming service.
These properties are used to initialize the InitialContext object of java naming service.
InitialContext object will be used to lookup stateless session bean.
InitialContext object will be used to lookup stateless session bean.
package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.TimerSessionBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class EJBTester {

   BufferedReader brConsoleReader = null; 
   Properties props;
   InitialContext ctx;
   {
      props = new Properties();
      try {
         props.load(new FileInputStream("jndi.properties"));
      } catch (IOException ex) {
         ex.printStackTrace();
      }
      try {
         ctx = new InitialContext(props);            
      } catch (NamingException ex) {
         ex.printStackTrace();
      }
      brConsoleReader = 
      new BufferedReader(new InputStreamReader(System.in));
   }
   
   public static void main(String[] args) {

      EJBTester ejbTester = new EJBTester();

      ejbTester.testTimerService();
   }
   
   private void showGUI() {
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options \n1. Add Book\n2. Exit \nEnter Choice: ");
   }
   
   private void testTimerService() {
      try {
         TimerSessionBeanRemote timerServiceBean = (TimerSessionBeanRemote)ctx.lookup("TimerSessionBean/remote");

         System.out.println("["+(new Date()).toString()+ "]" + "timer created.");
         timerServiceBean.createTimer(2000);            

      } catch (NamingException ex) {
         ex.printStackTrace();
      }
   }
}
EJBTester is doing the following tasks.
Load properties from jndi.properties and initialize the InitialContext object.
Load properties from jndi.properties and initialize the InitialContext object.
In testTimerService() method, jndi lookup is done with the name - "TimerSessionBean/remote" to obtain the remote business object (timer stateless EJB).
In testTimerService() method, jndi lookup is done with the name - "TimerSessionBean/remote" to obtain the remote business object (timer stateless EJB).
Then createTimer is invoked passing 2000 milliseconds as schedule time.
Then createTimer is invoked passing 2000 milliseconds as schedule time.
EJB Container calls the timeoutHandler method after 2 seconds.
EJB Container calls the timeoutHandler method after 2 seconds.
Locate EJBTester.java in project explorer. Right click on EJBTester class and select run file.
Verify the following output in Netbeans console.
run:
[Wed Jun 19 11:35:47 IST 2013]timer created.
BUILD SUCCESSFUL (total time: 0 seconds)

You can find the following callback entries in JBoss log
...
11:35:49,555 INFO  [STDOUT] timeoutHandler : Hello World!
...

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