利用spring mvc 的拦截器做登录

思路:配置拦截规则,哪些需要拦截(需要登录才能访问的页面或者用到用户id的都要拦截),在拦截器中获取session,判断session中有没有user对象.有则放行,没有则表示没有登录,进行页面跳转,哪些不需要拦截的页面,如登录页面,主页等

//spring mvc的拦截器 实现HandlerInterceptor类,重写三个方法
public class LoginInterceptor implements 
		                      HandlerInterceptor{
    
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {
		
		//1.获取session
		HttpSession session = request.getSession();
		//2.从session中获取user;返回Object obj
		Object obj = session.getAttribute("user");
		//3.obj==null,表示没有登录则 重定向到  showLogin.do;return false
		if(obj==null){
			String path = request.getContextPath()+"/user/showLogin.do";
			response.sendRedirect(path);
			return false;
		}
		//4.obj!=null,表示已登录则放行请求return true;
		return true;
	}

	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
			ModelAndView modelAndView) throws Exception {
		// TODO Auto-generated method stub
		
	}

	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
			throws Exception {
		// TODO Auto-generated method stub
		
	}

}

xml里配置拦截规则

<mvc:interceptors>
		<mvc:interceptor>
            <!--需要拦截的请求路径-->
			<mvc:mapping path="/user/*"/>
			<mvc:mapping path="/address/*"/>
			<mvc:mapping path="/cart/*"/>
             <!--不需要拦截的请求-->
			<mvc:exclude-mapping path="/user/register.do"/>
			<mvc:exclude-mapping path="/user/login.do"/>
			<bean class="cn.hu.interceptor.LoginInterceptor"/>
		</mvc:interceptor>
</mvc:interceptors>

控制层获取session(便于使用登录用户的id)

//需要用到userid的控制层,直接继承此类就可以,方便减少重复代码

public class SessionController {
	public Integer getId(HttpSession session){
		User user = (User)session.getAttribute("user");
		if(user!=null){
			return user.getId();
		}else{
			return null;
		}
	}

}