session 共享

** * 远程Session * 存放在Memcached缓存服务器里的Session * @author lx * */public class CacheSessionProvider implements SessionProvider {    @Autowired    private MemCachedClient  memCachedClient;    private final String SESSIONID="sessionId";    //设置数据保存在memcached的保存时间    private final Integer  expiry=30*60;    /**     * 将session的值通过sessionId值存入memcached中     */    public void setAttribute(HttpServletRequest request, String name, Serializable value,HttpServletResponse response) {        // TODO Auto-generated method stub        Map<String, Serializable> session=new HashMap<String, Serializable>();        session.put(name, value);        String sessionId=getSessionId(request, response);        memCachedClient.set(sessionId, session, expiry);    }/** * 通过用户本地的sessionId值到服务器获取session * 从缓存服务器memcached中获取sessionId值对应的session */    public Serializable getAttribute(HttpServletRequest request, String name,HttpServletResponse response) {        // TODO Auto-generated method stub        String sessionId=getSessionId(request, response);        Map<String, Serializable> session = (Map<String, Serializable>)memCachedClient.get(sessionId);        //返回保存在session中的用户数据        if(session!=null){            return session.get(name);        }        return null;    }    /**     *      * 删除缓存服务器memcached中中key=sessionId,这样用户即使     * 通过本地的sessionID也获取不到用户的数据     */    public void logout(HttpServletRequest request,HttpServletResponse response) {        // TODO Auto-generated method stub        //用户本地cookie        String sessionId=getSessionId(request, response);        if(memCachedClient.keyExists(sessionId)){            memCachedClient.delete(sessionId);        }    }/** * 获取sessionId，如果用户没有sessionId,则为用户创建一个sessionId */    public String getSessionId(HttpServletRequest request,HttpServletResponse response) {        //获取存储在cookie的sessionId           Cookie[] cookies = request.getCookies();           if(cookies!=null && cookies.length>0){               for (Cookie cookie : cookies) {                   if(SESSIONID.equals(cookie.getName())){                       return cookie.getValue();                   }            }           }           //如果没有sessionId，为用户创建一个           String sessionId=UUID.randomUUID().toString().replaceAll("-", "");           Cookie cookie=new Cookie(SESSIONID, sessionId);           cookie.setMaxAge(-1);// 默认-1，代表关闭浏览器就销毁cookie           cookie.setPath("/");           response.addCookie(cookie);        return sessionId;    }