Filter小例子

原創文章,鼓勵轉載請務必注明出處,作者:李佳

最近項目中需要轉換路徑,把通路/m ,/m/,/m/* 的連接配接分發到三種不同類型的手機中,解決方法是使用Filter,在進入Servlet之前進行攔截,之後改變顯示路徑相關代碼如下:

package common.util.mobile;

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;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import common.init.InitParam;

public class MoblieFilter implements Filter{

 protected FilterConfig filterConfig;

 public void destroy() {

 }

 public void doFilter(ServletRequest request, ServletResponse response,

            FilterChain chain) throws IOException, ServletException {

  try{

  HttpServletRequest httpRequest = (HttpServletRequest)request;

  HttpServletResponse httpResponse = (HttpServletResponse)response;

  String requestURL = httpRequest.getRequestURI();

  InitParam.DebugLog("[doFilter:] Coming URL:" + requestURL);

  String replacement = "/i/";

  if(requestURL.equals("/m/") ||requestURL.equals("/m")){

   httpRequest.getRequestDispatcher(httpResponse.encodeURL("/m/index.servlet?moblie=true")).forward(request, response);

   //httpResponse.sendRedirect(httpResponse.encodeRedirectURL("/m/index.servlet?moblie=true"));

  } else

  {

   int mobiletype = Carrier.recognize(httpRequest);

   if(mobiletype == Carrier.IMODE){

    replacement = "/i/";      

   }else if(mobiletype == Carrier.JSKY){

    replacement = "/j/";      

   }else if(mobiletype == Carrier.EZWEB){

    replacement = "/e/";      

   }

   InitParam.DebugLog("[doFilter:] Final URL:" + requestURL.replaceFirst("/m/",replacement));

   httpRequest.getRequestDispatcher(requestURL.replaceFirst("/m/",replacement)+"?moblie=true").forward(request, response);

   //httpResponse.sendRedirect(httpResponse.encodeRedirectURL(requestURL.replaceFirst("/m/",replacement)+"?moblie=true"));

  }

  chain.doFilter(request, response);

  }catch (Exception e) {

  }

 }

 public void init(FilterConfig filterConfig) throws ServletException {

     this.filterConfig = filterConfig;

 }

}

在web.xml中加入如下配置:

<filter>

  <filter-name>mobilefilter</filter-name>

  <filter-class>common.util.mobile.MoblieFilter</filter-class>

 </filter>

 <filter-mapping>

  <filter-name>mobilefilter</filter-name>

  <url-pattern>/m/</url-pattern>

 </filter-mapping>

 <filter-mapping>

  <filter-name>mobilefilter</filter-name>

  <url-pattern>/m</url-pattern>

 </filter-mapping>

 <filter-mapping>

  <filter-name>mobilefilter</filter-name>

  <url-pattern>/m/*</url-pattern>

 </filter-mapping>