EJB
在EJB2.1的规范中需要实现ejbTimeout方法,当然还有ejbPassivate、ejbRemove等方法。在EJB3.0中,只有你想用它们的时候,你才必须创建它们,否则不必实现。
这个例子主要有5个文件,这个例子的Bean是一个无状态会话Bean:
NewsTimer.java:业务接口。
NewsTimer.java:业务实现类。将来我们开发的EJB也都是这样命名(在接口名上加上Bean)。
Client.java:测试EJB的客户端类。
jndi.properties:jndi属性文件,提供访问jdni的基本配置属性。
Build.xml:ant 配置文件,用以编译、发布、测试、清除EJB。
下面针对每个文件的内容做一个介绍。
NewsTimer.java
package com.kuaff.ejb3.schedule;
import javax.ejb.Remote;
@Remote
public interface NewsTimer
{
public void fiveNews();
}
这个接口定义了fiveNews方法,如果这个方法被调用,5分钟后将往控制台上输出一条新闻。
你不必配置它的JNDI名称,也不必写它的配置文件。在JBOSS实现的EJB3.0中,你不必写任何的EJB部署文件和jboss部署文件。JBOSS默认使用接口的全称作为它的JNDI名。在上面的例子中,它的全称可以通过NewsTimerclass.forName()得到。
NewsTimerBean.java
package com.kuaff.ejb3.schedule;
import java.util.Date;
import javax.ejb.Inject;
import javax.ejb.SessionContext;
import javax.ejb.Stateless;
import javax.ejb.Timer;
@Stateless
public class NewsTimerBean implements NewsTimer
{
private @Inject SessionContext ctx;
public void fiveNews()
{
ctx.getTimerService().createTimer(new Date(new Date().getTime() + 300000), "子虚乌有电视台5分钟新闻栏目:现在过5分钟,又到即时新闻节目的时间了。");
}
public void ejbTimeout(Timer timer)
{
System.out.printf("时间到:%n%s%n" , timer.getInfo());
timer.cancel();
}
}
Client.java
package com.kuaff.ejb3.schedule;
import javax.naming.InitialContext;
import javax.naming.NamingException;
public class Client
{
public static void main(String[] args) throws NamingException
{
InitialContext ctx = new InitialContext();
NewsTimer timer = (NewsTimer) ctx.lookup(NewsTimer.class.getName());
timer.fiveNews();
}
}
这个类用来测试我们发布的计数器EJB。首先通过
ctx = new InitialContext();
得到上下文,然后通过lookup查找NewsTimer,然后启动计时。。
请运行{$JBOSS_HOME}/bin目录下的run.bat: run

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