拦截器实现对用户是否登录及登陆超时的验证

本文以spring为例，其他的框架原理相同，请自己查找

Spring3中通过mvc:interceptors标签配置拦截器

这个标签用于注册一个自定义拦截器或者是WebRequestInterceptors.

可以通过定义URL来进行路径请求拦截，可以做到较为细粒度的拦截控制。

例如在配置文件加入

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:mvc="http://www.springframework.org/schema/mvc"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="

http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-3.0.xsd

http://www.springframework.org/schema/mvc

http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

<mvc:interceptors>

</mvc:interceptors>

<mvc:interceptors>

<mvc:interceptor>

<mvc:mapping path="/secure/*"/>

</mvc:interceptor>

<mvc:interceptor>

<mvc:mapping path="/admin/*.do"/>

</mvc:interceptor>

</mvc:interceptors>

</beans>

定义的拦截器只需要实现

@Override

public boolean preHandle(HttpServletRequest req,HttpServletResponse res, Object handler)

举一个实际的例子进行说明：

1、spring-mvc.xml配置文件中

<mvc:interceptors>
        <bean class="com.shxt.framework.utils.LoggedInterceptor"></bean>
    </mvc:interceptors>

2、对应的拦截器类：

@Repository
public class LoggedInterceptor extends HandlerInterceptorAdapter {

    /**
    * action之前执行
    */
    @Override
    public boolean preHandle(HttpServletRequest request,
            HttpServletResponse response, Object handler) throws Exception {

        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        // 后台session控制
        String[] noFilters = new String[] { "login", "handle" };    //url中如果有login和handle不拦截
        String uri = request.getRequestURI();

        if (uri.indexOf("common") != -1) {
            boolean beFilter = true;
            for (String s : noFilters) {
                if (uri.indexOf(s) != -1) {
                    beFilter = false;
                    break;
                }
            }
            if (beFilter) {
                Object obj = request.getSession().getAttribute(SystemConstants.LOGINED);
                if (null == obj) {
                    // 未登录
                    PrintWriter out = response.getWriter();
                    StringBuilder builder = new StringBuilder();
                    builder.append("<script type=\"text/javascript\" charset=\"UTF-8\">");
                    builder.append("alert(\"页面过期，请重新登录\");");
                    builder.append("window.top.location.href=\"");
                    builder.append(SystemConstants.BASEPATH); //这里是http://ip:port/项目名
                    builder.append("/common/user/login\";</script>"); //这里是重新登录的页面url
                    out.print(builder.toString());
                    out.close();
                    return false;
                }
            }
        }
        return super.preHandle(request, response, handler);
    }

    /**
    * 生成视图之前执行
    */
    @Override
    public void postHandle(HttpServletRequest request,
            HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
    }

    /**
    * 最后执行，可用于释放资源
    */
    @Override
    public void afterCompletion(HttpServletRequest request,
            HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
    }
}

3、配置session的有效期

在web.xml中添加

<session-config>
<session-timeout>30</session-timeout>
</session-config>

在30分钟之内session有效，在测试的时候可以讲其改为1，一分钟之后再访问，就会弹出提示“重新登录”的窗口