Custom Log4j appender to log messages into database via Hibernate

HibernateAppender.java

package org.aps.webprowo.hibernate;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.Vector;

import org.apache.log4j.Appender;
import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.spi.LoggingEvent;
import org.aps.eop.dao.DataAccessUtils;
import org.aps.eop.hibernate.TransactionUtil.TransactionHolder;
import org.aps.eop.hibernate.springtx.TxCallback;
import org.aps.eop.hibernate.springtx.TxTemplate;
import org.hibernate.Transaction;

/**
 * Log4J appender that uses Hibernate to store log messages in a database. 
 * 
 * <p>
 * 
 * This implementation assumes that the log message itself is a persistent
 * entity. Logging messages will be accumulated in a buffer of size
 * <i>bufferSize</i> and saved to the database when the buffer is full.
 * 
 * @author Lenny Marks (lenny@aps.org)
 * 
 */
public class HibernateAppender extends AppenderSkeleton implements Appender {
    
    private Vector buffer = new Vector();
    private int bufferSize = 20;
    private TxTemplate txTemplate;
    private DataAccessUtils daoUtils;
    
    public HibernateAppender(TxTemplate txTemplate, DataAccessUtils daoUtils) {
        this.txTemplate = txTemplate;
        this.daoUtils = daoUtils;
    }
    
    public void setBufferSize(int size)    {
        this.bufferSize = size;
    }
    
    /*
     * (non-Javadoc)
     * 
     * @see org.apache.log4j.AppenderSkeleton#append(org.apache.log4j.spi.LoggingEvent)
     */
    protected void append(LoggingEvent loggingEvent) {
        buffer.add(loggingEvent);
        
        synchronized (buffer) {
            if(buffer.size() >= bufferSize) {
                try {
                    persistEvents(new ArrayList(buffer));
                } catch(Exception e) {
                    System.err.println("Failed to write audit logs");
                    e.printStackTrace();
                } finally {
                	buffer.clear();
                }
            }
           
        }
       
    }

    private void persistEvents(final ArrayList logEvents) {
        txTemplate.execute(new TxCallback() {

            public Object execute(TransactionHolder tx) throws Exception {
                for(Iterator i = logEvents.iterator(); i.hasNext();) {
                    LoggingEvent logEvent = (LoggingEvent)i.next();
                    
                    daoUtils.saveObject(logEvent.getMessage());
                }
                
                return null;
            }
            
            
        });
        
    }

    public void close() {
        
    }

    public boolean requiresLayout() {
        return false;
    }

    
}