session

web中每次登录或退出，session是怎么处理的？

一、首先，写一个监听器，监听用户请求和session的操作动作

public class AppRequestListener implements ServletRequestListener,
        HttpSessionAttributeListener {

    private final Log log = LogFactory.getLog(AppRequestListener.class);

    @Override
    public void attributeAdded(HttpSessionBindingEvent event) {//在session中添加对象时触发
        dealSessionErr(event, "add");

    }

    @Override
    public void attributeRemoved(HttpSessionBindingEvent event) {//移除session时触发
        dealSessionErr(event, "remove");

    }

    @Override
    public void attributeReplaced(HttpSessionBindingEvent event) {//替换session中对象时触发
        dealSessionErr(event, "replace");

    }

    @Override
    public void requestDestroyed(ServletRequestEvent event) {//用户请求结束时，触发该方法
        CtxSessionBag.clear();

    }

    @Override
    public void requestInitialized(ServletRequestEvent requestEvent) {//用户请求到达初始化时，触发该方法
        HttpServletRequest request = (HttpServletRequest) requestEvent
                .getServletRequest();
        String pin = LoginUtils.getPin(request);
        try {
            request.setCharacterEncoding("UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        SessionBagImpl sessionBag = null;
        if (pin == null) {
            return;
        }

        if (sessionBag == null) {
            sessionBag = new SessionBagImpl();
        }

        sessionBag.setIp(request.getRemoteAddr());
        sessionBag.setSessionNbr(request.getSession().getId());

        BackOperator bo = sessionBag.getBackOperator();
        if (bo == null) {
            bo = new BackOperator();
        }
        bo.setUserName(pin);
        sessionBag.setBackOperator(bo);
        CtxSessionBag.setSessionBag(sessionBag);

    }

}

二、在web.xml中添加监听器

<listener>
　　<listener-class>com.***.web.listener.AppRequestListener</listener-class>
</listener>

三、AppRequestListener 是监听器，每次请求的时候或session操作的时候，都会执行，所以在这个类里，

requestInitialized方法里，每次用户请求时，把用户信息封装到CtxSessionBag里

public class CtxSessionBag {
    private static final ThreadLocal<SessionBagImpl> sessionBagThread = new ThreadLocal<SessionBagImpl>();
    
    public static SessionBagImpl getSessionBag() {
        return sessionBagThread.get();
    }

    public static void setSessionBag(SessionBagImpl s){
        sessionBagThread.set(s);
    }
    
    public static void clear(){
        sessionBagThread.set(null);
    }
}

CtxSessionBag 把session信息存到ThreadLocal里，可以共享，每次从CtxSessionBag 类静态方法取