javax.servlet.Filter过滤器用法

第一步：写过滤器类，实现Filter接口

public class MyFilter implements Filter{//销毁时执行public void destroy() {System.out.println("MyFilter销毁了");}//每请求一次执行一次,过滤所有请求public void doFilter(ServletRequest arg0, ServletResponse arg1,FilterChain arg2) throws IOException, ServletException {System.out.println("转到下一个Filter前");arg2.doFilter(arg0, arg1);System.out.println("转到下一个Filter后");}//服务器启动时执行一次public void init(FilterConfig arg0) throws ServletException {System.out.println("MyFilter开始了");}}

第二步：配置web.xml文件

  <filter>  <filter-name>he</filter-name>  <filter-class>com.he.util.MyFilter</filter-class>  </filter>  <filter-mapping>  <filter-name>he</filter-name>  <url-pattern>/*</url-pattern>  </filter-mapping>