java code for Servlet: session attribute listener

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;

public class SessionAttribListen implements HttpSessionAttributeListener {

/** Creates new SessionAttribListen */
public SessionAttribListen() {

System.out.println(getClass().getName());
}

public void attributeAdded(HttpSessionBindingEvent se) {

HttpSession session = se.getSession();
String id = session.getId();
String name = se.getName();
String value = (String) se.getValue();
String source = se.getSource().getClass().getName();
String message = new StringBuffer("Attribute bound to session in ")
.append(source).append("\nThe attribute name: ").append(name)
.append("\n").append("The attribute value:").append(value)
.append("\n").append("The session ID: ").append(id).toString();
System.out.println(message);
}

public void attributeRemoved(HttpSessionBindingEvent se) {

HttpSession session = se.getSession();
String id = session.getId();
String name = se.getName();
if (name == null)
name = "Unknown";
String value = (String) se.getValue();
String source = se.getSource().getClass().getName();
String message = new StringBuffer("Attribute unbound from session in ")
.append(source).append("\nThe attribute name: ").append(name)
.append("\n").append("The attribute value: ").append(value)
.append("\n").append("The session ID: ").append(id).toString();
System.out.println(message);
}

public void attributeReplaced(HttpSessionBindingEvent se) {

String source = se.getSource().getClass().getName();
String message = new StringBuffer("Attribute replaced in session ")
.append(source).toString();
System.out.println(message);
}
}