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我在让示例 EJB 程序工作时遇到问题。它来自“从新手到专业人士的 J2EE 1.4 入门”的第 11 章 该示例包括一个消息驱动 Bean，但我似乎无法让定时会话 Bean 工作。我在 GlassFish 3 中不断收到以下错误消息。

WARNING: Local Exception Stack: 
Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.0.1.v20100213-r6600): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'BLOB, SCHEDULE, INTERVALDURATION, OWNERID, STATE, LASTEXPIRATIONRAW, PKHASHCODE,' at line 1
Error Code: 1064
Call: SELECT TIMERID, INITIALEXPIRATIONRAW, BLOB, SCHEDULE, INTERVALDURATION, OWNERID, STATE, LASTEXPIRATIONRAW, PKHASHCODE, CREATIONTIMERAW, CONTAINERID FROM EJB__TIMER__TBL WHERE (((CONTAINERID = ?) AND (OWNERID = ?)) AND (STATE = ?))
    bind => [89237833827221504, server, 0]
Query: ReadAllQuery(name="findTimersByContainerAndOwnerAndState" referenceClass=TimerState sql="SELECT TIMERID, INITIALEXPIRATIONRAW, BLOB, SCHEDULE, INTERVALDURATION, OWNERID, STATE, LASTEXPIRATIONRAW, PKHASHCODE, CREATIONTIMERAW, CONTAINERID FROM EJB__TIMER__TBL WHERE (((CONTAINERID = ?) AND (OWNERID = ?)) AND (STATE = ?))")
    at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:333)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:687)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:530)
    at org.eclipse.persistence.sessions.server.ServerSession.executeCall(ServerSession.java:529)
    at 
    ...

这是代码：

-- TimeIt.java --

package timer;

import java.rmi.RemoteException;
import javax.ejb.EJBObject;

public interface TimeIt extends EJBObject {
  // the public business method on the timer bean
  public void startTimer() throws RemoteException;
}

-- TimeItHome.java --

package timer;

import java.rmi.RemoteException;
import javax.ejb.EJBHome;
import javax.ejb.CreateException;

public interface TimeItHome extends EJBHome {
  // the create method for the timer bean.
  public TimeIt create() throws CreateException, RemoteException;
}

-- TimeItBean.java --

package timer;

import java.rmi.RemoteException;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.ejb.EJBException;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
import javax.ejb.TimedObject;
import javax.ejb.Timer;
import javax.ejb.TimerService;
import javax.jms.JMSException;
import javax.jms.Queue;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;
import javax.jms.QueueSender;
import javax.jms.QueueSession;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class TimeItBean implements SessionBean, TimedObject {

  // save a reference to the context
  private SessionContext context;

  // public business method to start the timer
  public void startTimer() {
    TimerService timerService = context.getTimerService();
    // after initial five seconds, then every ten seconds
    Timer timer = timerService.createTimer(5000, 10000, "timer");
  }

  public void ejbCreate() {
  }

  // *** TimedObject interface

  // timer ejb method - timer expires - send message to queue
  @Override
  public void ejbTimeout(Timer timer) {
    QueueConnection connection = null;

    try {
      // Obtain a JNDI connection using the jndi.properties file
      Context context = new InitialContext();

      // Look up a JMS Connection Factory
      QueueConnectionFactory connectionFactory = (QueueConnectionFactory) context.lookup("jms/ConnectionFactory");

      // Create a JMS Connection
      connection = connectionFactory.createQueueConnection();

      // Create the JMS Session
      boolean transacted = false;
      int acknowledgeMode = Session.AUTO_ACKNOWLEDGE;

      QueueSession session = connection.createQueueSession(transacted, acknowledgeMode);

      // lookup the queue (destination)
      Queue queue = (Queue) context.lookup("jms/Queue");

      // Create a sender for the session to the queue
      QueueSender sender = session.createSender(queue);

      // Create the message - a string to print on the other side
      SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy.MM.dd 'at' HH:mm:ss.SSS");

      // Create a text message
      TextMessage textMessage = session.createTextMessage();

      // set the text of the message
      textMessage.setText("log entry, the time is: " + dateFormat.format(new Date()));

      // send the message
      sender.send(textMessage);

    }
    catch(NamingException naming) {
      naming.printStackTrace();
    }
    catch(JMSException jms) {
      jms.printStackTrace();
    }
    finally {
      if (connection != null) {
        try {
          connection.close();
        }
        catch (JMSException jms) {
        }
      }
    }    
  }

  // *** SessionBean interface

  @Override
  public void ejbActivate() throws EJBException, RemoteException {
    // TODO Auto-generated method stub
  }

  @Override
  public void ejbPassivate() throws EJBException, RemoteException {
    // TODO Auto-generated method stub    
  }

  @Override
  public void ejbRemove() throws EJBException, RemoteException {
    // TODO Auto-generated method stub    
  }

  @Override
  public void setSessionContext(SessionContext context) throws EJBException, RemoteException {
    this.context = context;
  }  
}

这是我的 ejb-jar.xml 文件：

<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar 
  id="ejb-jar_ID" 
  version="2.1"
  xmlns="http://java.sun.com/xml/ns/j2ee" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/ejb-jar_2_1.xsd">

  <display-name>MDB-Timer</display-name>
  <enterprise-beans>
    <session>
      <ejb-name>TimeItBean</ejb-name>
      <home>timer.TimeItHome</home>
      <remote>timer.TimeIt</remote>
      <ejb-class>timer.TimeItBean</ejb-class>
      <session-type>Stateless</session-type>
      <transaction-type>Container</transaction-type>
    </session>
  </enterprise-beans>
</ejb-jar>
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