EJB定时器服务 - EJB

定时器服务使用计划应用程序可以建立一个机制。例如,每月1日的工资单生成。 EJB3.0规范指定超时注释,这有助于编程一个无状态或消息驱动Bean的EJB服务。 EJB容器调用的方法,这是注释@Timeout.

EJB计时器服务是有助于创造的定时器,并安排回调计时器到期时由EJB容器提供的服务。

创建定时器的步骤

使用@ Resource注解注入SessionContext的bean

@Stateless
public class TimerSessionBean {

   @Resource
   private SessionContext context;
   ...
}

使用SessionContext对象TimerService创造定时器的。传递时间(以毫秒为单位)和消息。

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

使用定时器的步骤

使用@Timeout批注的方法。返回类型必须为void,并传递一个参数类型的定时器。我们取消计时器后第一次执行,否则将继续运行,修正后的时间间隔。

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

示例应用程序

让我们创建一个测试测试计时器服务在EJB的EJB应用程序中。

Step 描述
1 Create a project with a name EjbComponent under a package com.tutorialspoint.timer as explained in the EJB - Create Application chapter.
2 Create TimerSessionBean.java and TimerSessionBeanRemote as explained in the EJB - Create Application chapter. Keep rest of the files unchanged.
3 Clean and Build the application to make sure business logic is working as per the requirements.
4 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.
5 Now create the ejb client, a console based application in the same way as explained in theEJB - Create Application chapter under topic Create Client to access EJB.

EJBComponent (EJB Module)

TimerSessionBean.java

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();
   }
}

TimerSessionBeanRemote.java

package com.tutorialspoint.timer;

import javax.ejb.Remote;

@Remote
public interface TimerSessionBeanRemote {
   public void createTimer(long milliseconds);
}
  • 一旦你在Jboss应用服务器部署EjbComponent项目,发现jboss日志。

  • JBoss已经自动为我们的会话bean创建一个JNDI条目 -TimerSessionBean/remote.

  • 我们将使用这个查询字符串来获得远程类型的业务对象 -com.tutorialspoint.timer.TimerSessionBeanRemote

JBoss应用服务器的日志输出

...
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
...

EJBTester (EJB Client)

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost
  • 这些属性是用来初始化InitialContext对象的Java命名服务

  • InitialContext对象将被用于查找无状态会话bean

EJBTester.java

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 
1\. Add Book
2\. Exit 
Enter 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做以下任务。

  • jndi.properties中加载和初始化的InitialContext对象。

  • 在testTimerService()方法,名字完成JNDI查找 - “TimerSessionBean/remote”,以获得远程业务对象(定时器无状态EJB)。

  • 然后的调用createTimer通过预定时间为2000毫秒。

  • 2秒后EJB容器调用timeoutHandler,方法。

运行客户端访问EJB

在项目资源管理器中找到EJBTester.java。右键点击上EJBTester类,并选择run file.

在Netbeans控制台验证以下输出。

run:
[Wed Jun 19 11:35:47 IST 2013]timer created.
BUILD SUCCESSFUL (total time: 0 seconds)

JBoss应用服务器的日志输出

你可以找到以下的回调在JBoss日志项

...
11:35:49,555 INFO  [STDOUT] timeoutHandler : Hello World!
...