自动缓存js和css或者image等文件

第一步:写一个filter,可以根据路径的正则来判断该路径的请求是否需要设置max-age:

 public class CacheFilter implements Filter{          private static transient Log logger = LogFactory.getLog(CacheFilter.class);              private Integer cacheTime = 3600 * 24;       private List<Pattern> patternList = new ArrayList<Pattern>();              private static ResourceBundle rb = ResourceBundle.getBundle("cache-pattern");       public void destroy() {                  }          public void doFilter(ServletRequest rq, ServletResponse rqs,               FilterChain fc) throws IOException, ServletException {                      fc.doFilter(rq, rqs);           if (rq instanceof HttpServletRequest && rqs instanceof HttpServletResponse) {               HttpServletRequest request = (HttpServletRequest) rq;               HttpServletResponse response = (HttpServletResponse) rqs;                              if (matchPattern(request.getRequestURI())) {                   response.setHeader("Cache-Control", "max-age=" + cacheTime);                   if (logger.isDebugEnabled()) {                       StringBuilder sb = new StringBuilder();                       sb.append(" set cache control for uri = ").append(request.getRequestURI());                       sb.append(" and the cache time is ").append(cacheTime).append(" second");                       logger.debug(sb.toString());                   }               }                      } else {               if (logger.isWarnEnabled()) {                   logger.warn("---- the request instance is not instanceof HttpServletRequest ---");                   logger.warn("---- the response instance is not instanceof HttpServletResponse ---");               }           }                  }          public void init(FilterConfig arg0) throws ServletException {           Enumeration<String> keys = rb.getKeys();           while (keys.hasMoreElements()) {               String p = keys.nextElement();               String value = rb.getString(p);               patternList.add(Pattern.compile(value, Pattern.CASE_INSENSITIVE));                              if (logger.isInfoEnabled()) {                   logger.info(">>>>>>>>>>> init the cache pattern " + value);               }           }                      if (arg0 != null) {               String ct = arg0.getInitParameter("cache-time");               if (!"".equals(ct) && null != ct) {                   cacheTime = new Integer(ct);                   if (logger.isInfoEnabled()) {                       logger.info(">>>>>>>>>> the cache time is " + cacheTime);                   }               }           }       }              private boolean matchPattern(String url) {           for (Pattern pattern : patternList) {               if (pattern.matcher(url).matches()) {                   return true;               }           }                      return false;       }          public static void main(String [] args) throws ServletException {           CacheFilter cf = new CacheFilter();           cf.init(null);           System.out.println(cf.matchPattern("/css/prototype.CSS"));       }   }  

第二步:在classpath路径下创建一个cache-pattern.properties文件,内容如下:

1. 1 = .*ext-all.js  
2. 2 = .*prototype.js  
3. 3 = .*/css/.*\\.css  

1 = .*ext-all.js2 = .*prototype.js3 = .*/css/.*\\.css

在这个配置文件中,您可以根据js和css的路径来配置哪些目录,或者哪些文件需要设置max-age.

第三步:
在web.xml添加如下内容:

 <filter>            <filter-name>cache-filter</filter-name>            <filter-class>com.filter.CacheFilter</filter-class>            <init-param>               <param-name>cache-time</param-name>               <param-value>86000</param-value>           </init-param>       </filter>      <filter-mapping>           <filter-name>cache-filter</filter-name>           <url-pattern>*.js</url-pattern>       </filter-mapping>              <filter-mapping>           <filter-name>cache-filter</filter-name>           <url-pattern>*.css</url-pattern>   </filter-mapping>

如此3步,就可以将js和css文件缓存于无形.快哉.