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一、配置方法
1 映射过滤应用程序中所有资源
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>/*</url-pattern> //访问当前主机，当前应用程序根下的所有文件包括多级子目录下的所有文件，注意这里*前有“/” </filter-mapping></div>
2 过滤指定的类型文件资源
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>*.html</url-pattern> //访问当前主机，当前应用程序根目录下的所有html文件，注意：*.html前没有“/”,否则错误 </filter-mapping></div>
其中*.html要过滤jsp那么就改*.html为*.jsp，但是注意没有“/”斜杠。如果要同时过滤多种类型资源：
方法1 url-pattern 分开写
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>*.html</url-pattern> </filter-mapping> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>*.jsp</url-pattern>//访问当前主机，当前应用程序根目录以所有及子目录下的所有jsp文件 </filter-mapping></div>
方法2 将url-pattern合并
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>*.html;*.jsp</url-pattern> </filter-mapping>//*.html;*.jsp两类型之间用分号;间隔</div>
3 过滤指定的目录下的所有文件
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>/folder_name/*</url-pattern>//访问当前主机，当前应用程序根目录下的folder_name子目录（可是多级子目录）下所有文件 </filter-mapping></div>
4 过滤指定的servlet
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <servlet-name>loggerservlet</servlet-name> </filter-mapping> <servlet> <servlet-name>loggerservlet</servlet-name> <servlet-class>myfilter.LoggerServlet</servlet-class> </servlet></div>
5 过滤指定文件（即单一文件）
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>/simplefilter.html</url-pattern> </filter-mapping></div>
6 过滤指定目录下的指定类型的所有文件
这种情况下在web.xml中无法一次性配置完成，需要结合filter的实现类
首先在web.xml中配置过滤指定目录下的所有文件
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>/dir_name/*</url-pattern> </filter-mapping></div>
然后在filter的实现类中的doFilter方法中获取请求的uri或者url，判断uri或者url中是否包含指定文件类型的字符串，决定是否过滤
//获得用户请求的uri
String uri = request.getRequestURI();
if(uri.contains(".jsp")||uri.contains(".html"))
System.out.println("开始过滤"+url);
</div>
7 过滤指定目录下指定类型的单一文件
<filter> <filter-name>loggerfilter</filter-name> <filter-class>myfilter.LoggerFilter</filter-class> </filter> <filter-mapping> <filter-name>loggerfilter</filter-name> <url-pattern>/dir_name/index.jsp</url-pattern> </filter-mapping></div>
以上都要注意是否有斜杠“/”
二、实例
不缓存文件
<filter>
<filter-name>NoCache</filter-name>
<filter-class>com.sys.common.Filters.ResponseHeaderFilter
</filter-class>
<init-param>
<param-name>Cache-Control</param-name>
<param-value>no-cache, must-revalidate</param-value>
</init-param>
</filter>
</div>
缓存文件一周
<filter>
<filter-name>CacheForWeek</filter-name>
<filter-class>com.sys.common.Filters.ResponseHeaderFilter
</filter-class>
<init-param>
<param-name>Cache-Control</param-name>
<param-value>max-age=604800, public</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CacheForWeek</filter-name>
<url-pattern>/images/*</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>CacheForWeek</filter-name>
<url-pattern>*.js</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>CacheForWeek</filter-name>
<url-pattern>*.css</url-pattern>
</filter-mapping>
</div>
自定义的filter：
public class ResponseHeaderFilter implements Filter {
FilterConfig fc;
public void doFilter(ServletRequest req, ServletResponse res,FilterChain chain) throws IOException, ServletException {
HttpServletResponse response = (HttpServletResponse) res;
for (Enumeration e = fc.getInitParameterNames(); e.hasMoreElements();) {
String headerName = (String) e.nextElement();
response.addHeader(headerName, fc.getInitParameter(headerName));
}
chain.doFilter(req, response);
}
public void init(FilterConfig filterConfig) {
this.fc = filterConfig;
}
public void destroy() {
this.fc = null;
}
}