一个简单的Filter

一个简单的Filter例子．

/**
 * Description: Filter.
 *
 * Created on:2007-9-25 上午8:41:23
 *
 * @author Lzs
 *
 * @version 1.0
 */
public class LzsFilter implements Filter {

 private FilterConfig fConfig;

 private String reidrect;

 private String enable;

 private String ignore;

 private String[] ign;

 public void destroy() {
  fConfig = null;
  reidrect = null;
  enable = null;
  ignore = null;
 }

 public void doFilter(ServletRequest arg0, ServletResponse arg1,
   FilterChain arg2) throws IOException, ServletException {

  HttpServletRequest request = (HttpServletRequest) arg0;
  User user = (User) request.getSession()
    .getAttribute(Constants.USER_KEY);
  boolean ttt=false;
  // 配置过滤器的有效性
  if ("true".equalsIgnoreCase(enable)) {
   if (user == null) {
    for (int i = 0; i < ign.length; i++) {
     if (ign[i].equalsIgnoreCase(request.getServletPath())) {
      arg2.doFilter(arg0, arg1);
        ttt=true;
      break;
     }
    }
    if(!ttt){
     RequestDispatcher rd=null;
     rd=request.getRequestDispatcher(reidrect);
     rd.forward(arg0, arg1);
    }else{
     arg2.doFilter(arg0, arg1);
    }
    
   } else {
    arg2.doFilter(arg0, arg1);
   }
  } else {
   arg2.doFilter(arg0, arg1);
  }

 }

 public void init(FilterConfig arg0) throws ServletException {

  fConfig = arg0;
  reidrect = fConfig.getInitParameter("redirect");
  enable = fConfig.getInitParameter("enable");
  ignore = fConfig.getInitParameter("ignore");
  StringTokenizer token = new StringTokenizer(ignore, ",");
  ign = new String[token.countTokens()];
  int i = 0;
  while (token.hasMoreElements()) {
   ign[i++] = (String)token.nextElement();
  }

 }

}

web.xml配置信息如下:

      <filter>
 <filter-name>LzsFilter</filter-name>
 <filter-class>com.nokia.smp.acms.web.filter.LzsFilter</filter-class>
 <init-param>
  <param-name>redirect</param-name>
  <param-value>/logon.jsp</param-value>
 </init-param>
 <init-param>
  <param-name>ignore</param-name>
  <param-value>/logon.jsp,/logon.do</param-value>
 </init-param>
 <init-param>
  <param-name>enable</param-name>
  <param-value>true</param-value>
 </init-param>
  </filter>
  <filter-mapping>
      <filter-name>LzsFilter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>