静态元素过期时间

当用户访问网站的时候一些图片会自动缓存在电脑浏览器缓存中，当下一次访问的时候就不必要再次加载了。当超时或更新时，会重新请求加载。

[root@chy logs]# !vim
vim /usr/local/apache2.4/conf/extra/httpd-vhosts.con(配置如下)
 
    ExpiresActive on
    ExpiresByType image/gif  "access plus 1 days"
    ExpiresByType image/jpeg "access plus 24 hours"
    ExpiresByType image/png "access plus 24 hours"
    ExpiresByType text/css "now plus 2 hour"
    ExpiresByType application/x-javascript "now plus 2 hours"
    ExpiresByType application/javascript "now plus 2 hours"
    ExpiresByType application/x-shockwave-flash "now plus 2 hours"
    ExpiresDefault "now plus 0 min"

以上为增加的内容，如下为配置的详解

    ExpiresActive on  //打开该功能的开关
    ExpiresByType image/gif  "access plus 1 days" （定义gif的失效时间）
    ExpiresByType image/jpeg "access plus 24 hours"（定义jpeg的失效时间）
    ExpiresByType image/png "access plus 24 hours"
    ExpiresByType text/css "now plus 2 hour"
    ExpiresByType application/x-javascript "now plus 2 hours"
    ExpiresByType application/javascript "now plus 2 hours"
    ExpiresByType application/x-shockwave-flash "now plus 2 hours"
    ExpiresDefault "now plus 0 min"

测试并查看增加模块

[root@chy ~]# /usr/local/apache2.4/bin/apachectl -M |grep expire
(模块并么有打开)
[root@chy ~]# vim /usr/local/apache2.4/conf/httpd.conf
（编辑主配置文件）
#LoadModule expires_module modules/mod_expires.so
（找到expires并把它的注释去掉：LoadModule expires_module modules/mod_expires.so
）
[root@chy ~]# /usr/local/apache2.4/bin/apachectl graceful
(加载一下配置文件)
[root@chy ~]# /usr/local/apache2.4/bin/apachectl -M |grep expire
 expires_module (shared)
（然后查看此模块是否存在）
测试：
[root@chy 111.com]# curl -x127.0.0.1:80 www.111.com/lf.png -I
HTTP/1.1 200 OK
Date: Thu, 03 Aug 2017 00:00:31 GMT
Server: Apache/2.4.27 (Unix) PHP/5.6.30
Last-Modified: Wed, 19 Oct 2016 08:52:35 GMT
ETag: "1bca7-53f33ee277ac0"
Accept-Ranges: bytes
Content-Length: 113831
Cache-Control: max-age=86400
Expires: Fri, 04 Aug 2017 00:00:31 GMT
Content-Type: image/png