4）HttpSessionAttributeListener：

HttpSessionAttributeListener能監測到有人正在往HttpSession裡新增屬性。你可以採取相應的措施。

例 2.2.4.1

package com;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
public class MyHttpSessionAttributeListener implements HttpSessionAttributeListener  {
    public void attributeAdded(HttpSessionBindingEvent arg0) {
        System.out.println("增加了" + arg0.getName() + " " +
                arg0.getValue() );       
    }
    public void attributeRemoved(HttpSessionBindingEvent arg0) {
        System.out.println("去除了" + arg0.getName() + " " +
                arg0.getValue() );
    }
    public void attributeReplaced(HttpSessionBindingEvent arg0) {
        System.out.println("取代了" + arg0.getName() + " " +
                arg0.getValue()+"現在的新值是"+arg0.getSession().getAttribute(arg0.getName()) );
    }
}
詳情請見：