/* * JBoss, the OpenSource J2EE webOS * * Distributable under LGPL license. * See terms of license at gnu.org. */package test.session;import java.rmi.RemoteException;import java.sql.Connection;import java.sql.Statement;import java.sql.ResultSet;import java.sql.SQLException;import javax.ejb.CreateException;import javax.ejb.EJBException;import javax.ejb.SessionBean;import javax.ejb.SessionContext;import javax.naming.Context;import javax.naming.InitialContext;import javax.naming.NamingException;import javax.sql.DataSource;import test.interfaces.ServiceUnavailableException;/** * Encapsulates the retrival of DB data * * @author Andreas Schaefer * @version $Revision: 1.1 $ * * @ejb:bean name="test/SequenceGenerator" *           display-name="Generates unique Identifier for an Entity" *           type="Stateless" *           jndi-name="ejb/test/SequenceGenerator" * @ejb:env-entry name="DataSource_Name" *                value="DefaultDS" * @ejb:resource_ref res-name="jdbc/DefaultDS"*/public class SequenceGeneratorBean   implements SessionBean{   // -------------------------------------------------------------------------   // Static   // -------------------------------------------------------------------------   // -------------------------------------------------------------------------   // Members    // -------------------------------------------------------------------------   private SessionContext mContext;   // Only for test purposes   private int mNextNumber = 0;   // -------------------------------------------------------------------------   // Methods   // -------------------------------------------------------------------------     /**    * Delivers the next sequence number from the given Sequence Name    *    * @param pSequenceName Name of the Sequence Generator    *    * @return Next sequence number    *    * @throws RemoteException     *    * @ejb:interface-method view-type="remote"    * @ejb:transaction type="Mandatory"    **/   public int getNextNumber( String pSequenceName )      throws         ServiceUnavailableException,         RemoteException   {      Connection aConnection = null;      Statement aStatement = null;      try      {/* This normally works for DBs like PostgreSQL, Oracle and others         // Get the Home Interface         Context aJNDIContext = new InitialContext();         String lDataSourceName = (String) aJNDIContext.lookup(             "java:comp/env/DataSource_Name"          );         // Get the Datasource         DataSource aSource = (DataSource) aJNDIContext.lookup( "java:/" + lDataSourceName );         // Get JDBC Connection, create statement and get the result to return         aConnection = aSource.getConnection();         aStatement = aConnection.createStatement();         String aSql = "SELECT Nextval( '" + pSequenceName + "' ) ";         if( Debug.LEVEL >= Debug.REGULAR ) System.err.println( "Sql Statement: " + aSql );         ResultSet aResult = aStatement.executeQuery( aSql );         if( aResult.next() )         {            return aResult.getInt( 1 );         }         else         {            return -1;         }*/// Hypersonic does not provide a feature like Sequences therefore// we just use the highest ID and add 1 to it. Because this method// requireds a transaction this method will block any call from other// Beans until the transaction is finished.// ATTENTION: this works fine as long as all EJBs get their new unique// ID from there and nobody adds a new record to the DB other than through// this application server.         // Get the Home Interface         Context aJNDIContext = new InitialContext();         // Get the Datasource         DataSource aSource = (DataSource) aJNDIContext.lookup( "java:/DefaultDS" );         // Get JDBC Connection, create statement and get the result to return         aConnection = aSource.getConnection();         aStatement = aConnection.createStatement();         //AS This is only working for a demo because two threads could get the same         //AS Sequence Number because of multi threading         String aSql = "SELECT MAX( id ) FROM " + pSequenceName;         ResultSet aResult = aStatement.executeQuery( aSql );         int lResult = -1;         if( aResult.next() ) {            lResult = aResult.getInt( 1 );            if( lResult <= 0 ) {               lResult = 1;            }         }         return lResult + 1;      }      catch( SQLException se ) {         throw new ServiceUnavailableException ( "Sequence number is broken" );      }      catch( NamingException ne ) {         throw new ServiceUnavailableException ( "JNDI Lookup broken" );      }      finally {         try {            if( aStatement != null ) {               aStatement.close();            }         }         catch( Exception e ) {         }         try {            if( aConnection != null ) {               aConnection.close();            }         }         catch( Exception e ) {         }      }   }   /**    * Create the Session Bean    *    * @throws CreateException     *    * @ejb:create-method view-type="remote"    **/   public void ejbCreate()      throws         CreateException   {   }   /**    * Describes the instance and its content for debugging purpose    *    * @return Debugging information about the instance and its content    **/   public String toString()   {      return "SequenceGeneratorBean [ " + " ]";   }   // -------------------------------------------------------------------------   // Framework Callbacks   // -------------------------------------------------------------------------      public void setSessionContext( SessionContext aContext )      throws EJBException   {      mContext = aContext;   }      public void ejbActivate()      throws EJBException   {   }      public void ejbPassivate()      throws EJBException   {   }   public void ejbRemove()      throws EJBException   {   }}