Openjpa customize @SequenceGenerator for @id

MyFilelog.java

package my.database;

import java.sql.Timestamp;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
@Table(name="MY_FILELOG")
@SequenceGenerator(name="MYSQ",sequenceName="my.database.MyLogSeq(Sequence=DISTRIBUTE_SEQ)")
public class MyFilelog {
	
	public static char SUCCESS = 'S';
	public static char FAIL = 'F';
	
	@Id
	@GeneratedValue(strategy=GenerationType.SEQUENCE,generator="MYSQ")
	@Column(name="LOG_ID")
	private Long pk;
	
	@Column(name="PACKAGE_ID")
	private String packageId;
	
	@Column(name="STORE_ID")
	private String storeId;
	
	@Column(name="TERMINAL_ID")
	private int terminalId;
	
	@Column(name="FILE_NAME")
	private String fileName;
	
	@Column(name="FILE_STATUS")
	private char fileStatus;
	
	@Column(name="FILE_TIMESTAMP")
	@Temporal(TemporalType.TIMESTAMP)
	private Timestamp fileTimestamp;
	
	@Column(name="DESC")
	private String desc;

	//getter and setter
}

MyLogSeq.java

package my.database;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.apache.openjpa.jdbc.conf.JDBCConfiguration;
import org.apache.openjpa.jdbc.kernel.AbstractJDBCSeq;
import org.apache.openjpa.jdbc.kernel.JDBCStore;
import org.apache.openjpa.jdbc.meta.ClassMapping;
import org.apache.openjpa.jdbc.sql.DBDictionary;
import org.apache.openjpa.lib.conf.Configurable;
import org.apache.openjpa.lib.conf.Configuration;
import org.apache.openjpa.lib.util.Localizer;
import org.apache.openjpa.util.UserException;

public class MyLogSeq extends AbstractJDBCSeq implements Configurable {
	
	private JDBCConfiguration _conf = null;
	private static Localizer _loc = Localizer.forPackage(MyLogSeq.class);
	private String _select = null;
	private String _format = null;
	private String _seqName = "OPENJPA_SEQUENCE";
	private String _schema = "";
	
	
	public String getSequence(){
		return this._seqName;
	}
	
	// set sequence
	public void setSequence(String seqName){
		this._seqName= seqName;
	}
	
	@Override
	public JDBCConfiguration getConfiguration() {
		return _conf;
	}

	@Override
	protected Object nextInternal(JDBCStore store, ClassMapping mapping)
			throws Exception {
		 System.out.println("Hello nextInternal");
		 Connection conn = getConnection(store);
	        try {
	       	/* Customize ID here.
	       	*  example
	       	*  return "ABC"+getSequence(conn);
	       	*/
	            return getSequence(conn);
	        } finally {
	            closeConnection(conn);
	        }
	}
	
    /**
     * Return the next sequence value.
     */
    private long getSequence(Connection conn)
        throws SQLException {
        DBDictionary dict = _conf.getDBDictionaryInstance();
        PreparedStatement stmnt = null;
        ResultSet rs = null;
        try {
            stmnt = conn.prepareStatement(_select);
            dict.setTimeouts(stmnt, _conf, false);
            synchronized(this) {
                rs = stmnt.executeQuery();
            }
            if (rs.next())
                return rs.getLong(1);

            // no row !?
            throw new UserException(_loc.get("invalid-seq-sql", _select));
        } finally {
            // clean up our resources
            if (rs != null)
                try { rs.close(); } catch (SQLException se) {}
            if (stmnt != null)
                try { stmnt.close(); } catch (SQLException se) {}
        }
    }

	@Override
	public void endConfiguration() {
		DBDictionary dict = _conf.getDBDictionaryInstance();
		if(_format==null){
			_format = dict.nextSequenceQuery;
		}
		_schema = _conf.getSchema(); //get schema from persistence.xml
		this._select = "SELECT nextval for "+_schema+"."+_seqName+" FROM SYSIBM.SYSDUMMY1";
	}

	@Override
	public void setConfiguration(Configuration arg0) {
		_conf = (JDBCConfiguration)arg0;
		
	}

	@Override
	public void startConfiguration() {
		//
	}

}