用cookie和session实现自动登录

算是今天的学习笔记吧。。。
在点击登录输入用户名和密码后，当验证用户名和密码都正确且有正确返回值时，在LoginSvl中创建一个cookie保存此用户名和密码：

String unamepwd = user.getUname()+","+user.getPwd();
Cookie cookie=new Cookie("unamepwd",unamepwd);
cookie.setMaxAge(60*60*24*7);
response.addCookie(cookie);

创建一个过滤器，在下次登录时，当session中的user为空，则从cookie中获取上次保存的用户名密码，调用biz,通过biz调dao,验证cookie中保存的信息是否是否适用于此次登录，即验证数据库中密码或用户名是否改变，若改变，则清除此cookie。若没改变，则自动登录。
LoginFilter中的代码：

    public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain chain) throws IOException, ServletException {
		
		HttpServletRequest request=(HttpServletRequest) req;
		HttpServletResponse response=(HttpServletResponse) resp;
		if(request.getSession().getAttribute("user") == null){
			Cookie loginCookie=getLoginCookie(request, "unamepwd");
			if(loginCookie != null){
				String[] unamepwds=loginCookie.getValue().split(",");
				UserBiz bbiz =new UserBiz();
				User uuser=bbiz.login(unamepwds[0], unamepwds[1]);
				if(uuser != null){
					request.getSession().setAttribute("user", uuser);
				}else{
					Cookie cookie=new Cookie(loginCookie.getName(),null);
					cookie.setMaxAge(0);
					response.addCookie(cookie);
				}
			}
			
		}
		chain.doFilter(request, response);
	}
	
	private Cookie getLoginCookie(HttpServletRequest request,String cookieName){
		Cookie strRet = null;
		if(request.getCookies() != null){
			Cookie[] cookies = request.getCookies();                             
			for(int i=0;i<cookies.length;i++){
				Cookie cookie = cookies[i];
				String cm = cookie.getName();			
				if(cm.equals(cookieName)){	
					strRet = cookie;	
					break;
				}				
			}
		}
		return strRet;
	}

注：filter需要在web.xml中做响应配置。其中<url-pattern></url-pattern>中只能写/*,否则不能自动登录。
最后要在点击退出按钮时，清除cookie，以免其他用户无法登录：
LoginOutSvl中代码:

public void service(HttpServletRequest request,HttpServletResponse response)
    throws ServletException,IOException{
		
		request.getSession().invalidate();
		Cookie loginCookie = getLoginCookie(request, "unamepwd"); 
		Cookie cookie=new Cookie(loginCookie.getName(),null);
		cookie.setMaxAge(0);   
		response.addCookie(cookie);
		request.getRequestDispatcher("MainSvl").forward(request,response);
	
	}
	
	private Cookie getLoginCookie(HttpServletRequest request,String cookieName){
		Cookie strRet = null;
		if(request.getCookies() != null){
			Cookie[] cookies = request.getCookies();                             
			for(int i=0;i<cookies.length;i++){
				Cookie cookie = cookies[i];
				String cm = cookie.getName();			
				if(cm.equals(cookieName)){	
					strRet = cookie;	
					break;
				}				
			}
		}
		
		return strRet;
	}