public String execute() throws Exception{
		//MD5 加密部分
		userpasswd = EncoderPwdByMd5(userpasswd);
			try{
				user = this.userDao.queryUser(username, userpasswd);
				if(user.equals(null)){
					this.getRequest().put("userinfo", "false");
				}
			}catch (Exception e) {
				System.out.println(e.getMessage());
				this.getRequest().put("login_info", "false");
				return "exception";
			}
			if(user.getUserright().equals("1")) {
				//系统管理员	
				this.getSession().put("user", this.user);
				return "backindex";
			}else if(user.getUserright().equals("2")) {
				//版主			
				this.getSession().put("user", this.user);
				return "user_plate";
			}else if(user.getUserright().equals("3")) {
				//普通用户
				this.getSession().put("user", this.user);
				return "user_info";
			}else {
				//出现异常
				return "error";
			}
	}