WebSphere Application Server ND V7中如何处理容器管理的数据库事务中会话 Bean 的连接异常？

package WebSphereSamples.ConnPool;

import java.util.*;
import java.sql.*;
import javax.sql.*;
import javax.ejb.*;
import javax.naming.*;
import com.ibm.websphere.ce.cm.ConnectionWaitTimeoutException;
import com.ibm.websphere.rsadapter.WSCallHelper;

/*************************************************************************************
* This Bean is designed to demonstrate Database Connections in a                      
* Container Managed Transaction Session Bean.  Its transaction attribute               *
* should be set to TX_REQUIRED or TX_REQUIRES_NEW.                                     *
**************************************************************************************
*/
public class ShowEmployeesCMTBean implements SessionBean {
		 private javax.ejb.SessionContext mySessionCtx = null;
	final static long serialVersionUID = 3206093459760846163L;
		 
	private javax.sql.DataSource ds;

//************************************************************************************
//* ejbActivate calls the getDS method, which does the JNDI lookup for the DataSource.
//* Because the DataSource lookup is in a separate method, we can also invoke it from	
//* the getEmployees method in the case where the DataSource field is null.		
	 		 
//************************************************************************************
public void ejbActivate() throws java.rmi.EJBException {
getDS();
}
/**
 * ejbCreate method 
 * @exception javax.ejb.CreateException 
 * @exception java.rmi.EJBException
 */
public void ejbCreate() throws javax.ejb.CreateException, java.rmi.EJBException {}
/**
 * ejbPassivate method
 * @exception java.rmi.EJBException
 */
public void ejbPassivate() throws java.rmi.EJBException {}
/**
 * ejbRemove method
 * @exception java.rmi.EJBException
 */
public void ejbRemove() throws java.rmi.EJBException {}

//************************************************************************************
//* The getEmployees method runs the database query to retrieve the employees.	      
//* The getDS method is only called if the DataSource variable is null.			
//* Because this session Bean uses Container Managed Transactions, it cannot retry the	
//* transaction on a StaleConnectionException.  However, it can throw an exception to	
//* its client indicating that the operation is retriable.				//************************************************************************************

public Vector getEmployees() throws ConnectionWaitTimeoutException, SQLException,
       RetryableConnectionException
{
   Connection conn = null;
   Statement stmt = null;
   ResultSet rs = null;
   Vector employeeList = new Vector();

   if (ds == null) getDS();
   		 
   try
   {
      // Get a Connection object conn using the DataSource factory.       conn = ds.getConnection();
      // Run DB query using standard JDBC coding.
      stmt = conn.createStatement();
      String query   = "Select FirstNme, MidInit, LastName " + 
                       "from Employee ORDER BY LastName";
      rs   = stmt.executeQuery(query);
      while (rs.next()) {
employeeList.addElement(rs.getString(3) + ", " +                                                               rs.getString(1) + " " + rs.getString(2));
      }                           
   } 
   catch (SQLException sqlX)
   {
     // Determine if the connection is stale
     if (WSCallHelper.getDataStoreHelper(ds).isConnectionError(sqlX))
     {
       // This exception indicates that the connection to the database is no longer valid.
       // Roll back the transaction, and throw an exception to the client indicating they
       // can retry the transaction if desired.

       System.out.println("Connection is stale: " + sqlX.getMessage());
       System.out.println("Rolling back transaction and throwing  RetryableConnectionException");

       mySessionCtx.setRollbackOnly();
       throw new RetryableConnectionException(sqlX.toString());
     }
     // Determine if the connection request timed out.
     else if ( sqlX instanceof ConnectionWaitTimeoutException
            || sqlX instanceof SQLTransientConnectionException
               && sqlX.getCause() instanceof ConnectionWaitTimeoutException)
     {
       // This exception is thrown if a connection can not be obtained from the
       // pool within a configurable amount of time.  Frequent occurrences of
       // this exception indicate an incorrectly tuned connection pool

       System.out.println("Connection Wait Timeout Exception during get connection or process SQL: " +
       sqlX.getMessage());
       throw sqlX instanceof ConnectionWaitTimeoutException ?
             sqlX :
             (ConnectionWaitTimeoutException) sqlX.getCause();
     } 
     else
     {
       //Throwing a remote exception will automatically roll back the container managed //transaction
System.out.println("SQL Exception during get connection or process SQL: " +
		 		 		 		 sqlX.getMessage());
       throw sqlX;
     } 
   }
   finally
   {
     // Always close the connection in a finally statement to ensure proper
     // closure in all cases. Closing the connection does not close and 
     // actual connection, but releases it back to the pool for reuse.

     if (rs != null)
     {
       try
       {
         rs.close();
       } 
       catch (Exception e)
       {
         System.out.println("Close Resultset Exception: " + 
                       e.getMessage());                
       }
     }
     			if (stmt != null)
     {
       try
       {
         stmt.close();
       } 
       catch (Exception e)
       {
         System.out.println("Close Statement Exception: " + 
                       e.getMessage());                
       }
     }
     if (conn != null)
     {
       try
       {
         conn.close();
       } 
       catch (Exception e)
       {
         System.out.println("Close connection exception: " + e.getMessage());
       }
     }
   }
   return employeeList;
}

/**
 * getSessionContext method
 * @return javax.ejb.SessionContext
 */
public javax.ejb.SessionContext getSessionContext() {
	return mySessionCtx;
}
//************************************************************************************
//* The getDS method performs the JNDI lookup for the data source.	
//* This method is called from ejbActivate, and from getEmployees if the data source		 
//* object is null.									
//************************************************************************************

private void getDS() {
	 try {
Hashtable parms = new Hashtable();
		parms.put(Context.INITIAL_CONTEXT_FACTORY, 
				"com.ibm.websphere.naming.WsnInitialContextFactory");
		InitialContext ctx = new InitialContext(parms);
		// Perform a naming service lookup to get the DataSource object.
ds = (DataSource)ctx.lookup("java:comp/env/jdbc/SampleDB");
		 } 
       catch (Exception e) {
		System.out.println("Naming service exception: " + e.getMessage());
            e.printStackTrace();
		 }
}
/**
 * setSessionContext method
 * @param ctx javax.ejb.SessionContext
 * @exception java.rmi.EJBException
 */
public void setSessionContext(javax.ejb.SessionContext ctx) throws java.rmi.EJBException {
		mySessionCtx = ctx;
}
}

package WebSphereSamples.ConnPool;

/**
 * This is a Home interface for the Session Bean
 */
public interface ShowEmployeesCMTHome extends javax.ejb.EJBHome {

/**
 * create method for a session Bean * @return WebSphereSamples.ConnPool.ShowEmployeesCMT
 * @exception javax.ejb.CreateException 
 * @exception java.rmi.RemoteException 
 */
WebSphereSamples.ConnPool.ShowEmployeesCMT create() throws javax.ejb.CreateException,
   java.rmi.RemoteException;
}

package WebSphereSamples.ConnPool;

/**
 * This is an Enterprise Java Bean Remote Interface
 */
public interface ShowEmployeesCMT extends javax.ejb.EJBObject {

/**
 * 
 * @return java.util.Vector
 */
java.util.Vector getEmployees() throws java.sql.SQLException, java.rmi.RemoteException,
 ConnectionWaitTimeoutException, WebSphereSamples.ConnPool.RetryableConnectionException;
}

package WebSphereSamples.ConnPool;

/**
 * Exception indicating that the operation can be retried
 * Creation date: (4/2/2001 10:48:08 AM)
 * @author: Administrator
 */
public class RetryableConnectionException extends Exception {
/**
 * RetryableConnectionException constructor.
 */
public RetryableConnectionException() {
super();
}
/**
 * RetryableConnectionException constructor.
 * @param s java.lang.String
 */
public RetryableConnectionException(String s) {
	super(s);
}
}