SpringMVC配置session过期拦截器，返回登录页面

spring-mvc.xml配置

<mvc:interceptors>
　　<!-- session失效拦截器 -->
    <mvc:interceptor>
    <!-- 匹配的是url路径， 如果不配置或/**,将拦截所有的Controller -->
    　　<mvc:mapping path="${frontPath}/**" />
        <!-- 不需要拦截的地址 -->
        <mvc:exclude-mapping path="${frontPath}"/>
        <mvc:exclude-mapping path="${frontPath}/"/>
        <mvc:exclude-mapping path="${frontPath}/login"/>
        <bean class="com.jeeplus.modules.sys.interceptor.SystemSessionInterceptor"></bean>
    </mvc:interceptor>
</mvc:interceptors>

拦截器类：

public class SystemSessionInterceptor implements HandlerInterceptor {
    @Override
    public void postHandle(HttpServletRequest request,
        HttpServletResponse response, Object handler,
        ModelAndView modelAndView) throws Exception {
    } 

    @Override
    public void afterCompletion(HttpServletRequest request,
        HttpServletResponse response, Object handler, Exception ex)
        throws Exception {
    } 

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
        Object handler) throws Exception {
        Principal principal = UserUtils.getPrincipal();
        if (principal == null) {
            response.setContentType("text/html");
            response.setCharacterEncoding("utf-8");
            PrintWriter out = response.getWriter();
            StringBuilder builder = new StringBuilder();
            builder.append("<script type=\"text/javascript\" charset=\"UTF-8\">");
            builder.append("alert(\"登录已过期，请重新登录！\");");
            builder.append("parent.window.location.href='"+request.getContextPath()+"/f/login';");
            builder.append("</script>");
            out.print(builder.toString());
            out.close();
            return false;
        }
        return true;
    }
}