package demo;
import java.io.ioexception;
import javax.servlet.filter;
import javax.servlet.filterchain;
import javax.servlet.filterconfig;
import javax.servlet.servletexception;
import javax.servlet.servletrequest;
import javax.servlet.servletresponse;
public class demofilter implements filter
{
  private string name=null;
  @override
  public void destroy()
  {
  }
  @override
  public void dofilter(servletrequest arg0, servletresponse arg1,
      filterchain arg2) throws ioexception, servletexception
  {
    arg0.setattribute("name", "init text string : " + name);
    arg2.dofilter(arg0, arg1);
  }
  @override
  public void init(filterconfig arg0) throws servletexception
  {
    //獲得web.xml中filter init-param 中的配置
    name = arg0.getinitparameter("name");
  }
}

  <!--聲明一個(gè)filter-->
  <filter>
  <!--filter的名稱(chēng)-->
    <filter-name>demofilter</filter-name>
  <!--filter 類(lèi)-->
    <filter-class>demo.demofilter</filter-class>
  <!--該filter類(lèi)需要的配置-->
    <init-param>
      <param-name>name</param-name>
      <param-value>my name is tanyong</param-value>
    </init-param>
  </filter>

  <!--為url-pattern 中相匹配的url鏈接 映射至相應(yīng)的filter filter 通過(guò) filter-name來(lái)識(shí)別-->
  <filter-mapping>
    <filter-name>demofilter</filter-name>
    <!--匹配映射規(guī)則，我這里用的是所有請(qǐng)求都要在demofilter filter 里面去兜晃一圈-->
    <url-pattern>/*</url-pattern>
  </filter-mapping>