java同一用户不能同时登陆问题

好用简单packagecom.jswf.modle.sysuser;importjava.util.ArrayList;importjava.util.Hashtable;importjava.util.Iterator;importjava.util.List;importjava.util.Map;importjavax.servlet.http.HttpSession;importjavax.servlet.http.HttpSessionEvent;importjavax.servlet.http.HttpSessionListener;importorg.apache.struts2.ServletAct