过虑器基础三—页面缓存和生成验证码(49)

设置某些页面缓存或是不缓存

要想让所有浏览器不缓存页面：

    <%

        response.setHeader("expires","-1");

        response.setHeader("pragma","no-cache");

        response.setHeader("cache-control","no-cache");

    %>

分析：通过一个过虑器，对所有*.jsp过虑，设置三个头，全部不缓存。

第一步：实现过虑器接口

public void doFilter(ServletRequest request, ServletResponse response,

           FilterChain chain) throws IOException, ServletException {

       //转换

       HttpServletResponse resp = (HttpServletResponse) response;

       resp.setHeader("expires","-1");

        resp.setHeader("pragma","no-cache");

        resp.setHeader("cache-control","no-cache");

       //都放行

       chain.doFilter(request, response);

    }

第二步：配置过虑器，url-pattern=*.jsp

<!-- 配置控制缓存的filter -->

    <filter>

       <filter-name>cache</filter-name>

       <filter-class>cn.itcast.filter.CacheFilter</filter-class>

    </filter>

    <filter-mapping>

       <filter-name>cache</filter-name>

       <url-pattern>*.jsp</url-pattern>

    </filter-mapping>

第三步：设置对某些页面缓存N天

       HttpServletResponse resp = (HttpServletResponse) response;

       //计算2天以后的毫秒值

       //日历

       Calendar cl = Calendar.getInstance();

       //日历上加2天

       cl.add(Calendar.DATE, 2);

       long time = cl.getTimeInMillis();

       resp.setDateHeader("expires", time);[W2] 

       //resp.setHeader("expires",""+time);

//         resp.setHeader("pragma","no-cache");

//         resp.setHeader("cache-control","no-cache");

       //都放行

       chain.doFilter(request,resp);