chain.doFilter(request,response)怎么用呀?

warword0 2008-06-24 10:43:51

1.先问个题外问题,在servlet标准类型里HttpServletRequest接口的对象request和在过滤器里的ServletRequest接口的对象request有什么区别呢?

2.我在听过滤器的视频时,对chain.doFilter(request,response)还是不太明白,视频说是为了把过滤向"下"继续传,请问这个"下"指的是哪里?
比如一个小例子



if(content != null) {



    if(content.indexOf("AAA") == -1) {

    

     chain.doFilter(request,response);

   } else {



     System.out.println("有非法文字");

   }



} else {



chain.doFilter(request,response);



}// chian.doFilter在这里是什么意思?

谢谢能给我讲讲!

...全文

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fang00y 2009-05-24

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原来如此啊~

TRMeister 2008-06-24

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"下"指的是哪里
值得是下一个filter，如果没有filter那就是你请求的资源。

一般filter都是一个链,web.xml 里面配置了几个就有几个。一个一个的连在一起

request -> filter1 -> filter2 ->filter3 -> .... -> request resource.

becloud 2008-06-24

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->do sth -> do sth ->如果是最后个filter,就访问真正的资源,结束后|
doFilter doFilter |
<-do sth <- do sth <- <-|

doFilter就是分界线

package com.wgh.filter; import java.io.IOException; import javax.servlet.*; public class CharacterEncodingFilter implements Filter{ protected String encoding = null; protected FilterConfig filterConfig = null; public void init(FilterConfig filterConfig) throws ServletException { this.filterConfig = filterConfig; this.encoding = filterConfig.getInitParameter("encoding"); } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { if (encoding != null) { request.setCharacterEncoding(encoding); response.setContentType("text/html; charset="+encoding); } chain.doFilter(request, response); } public void destroy() { this.encoding = null; this.filterConfig = null; } }

@Override public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) res; HttpSession session = request.getSession(); //是否登录 //开放注册页面 if(null==session.getAttribute("merchantInfo") &&request.getRequestURL().indexOf("regist/merchant/acount.jsp")==-1){ response.sendRedirect(request.getContextPath()); }else{ chain.doFilter(request, response); } } web.xml配置： <filter> <filter-name>accessFilterfilter-name> <filter-class>com.loginFilterfilter-class> filter> <filter-mapping> <filter-name>accessFilterfilter-name> /jsp/* filter-mapping>

/** * 作者: jilongliang * 当前类名:FilterChain.java * 项目名称:JavaStudy * 创建时间:2011-12-28 */ package org.java.com.design.filter; import java.util.ArrayList; import java.util.List; public class FilterChain implements Filter { List<Filter> filters = new ArrayList<Filter>(); int index = 0; public FilterChain addFilter(Filter f) { this.filters.add(f); return this;// 返回this可以连续添加. } @Override public void doFilter(Request request, Response response, FilterChain chain) { if (index == filters.size()) return; Filter filter = filters.get(index); index++; filter.doFilter(request, response, chain); } }

/** * 作者: jilongliang * 当前类名:FilterChain.java * 项目名称:JavaStudy * 创建时间:2011-12-28 */ package org.java.com.design.filter; import java.util.ArrayList; import java.util.List; public class FilterChain implements Filter { List<Filter> filters = new ArrayList<Filter>(); int index = 0; public FilterChain addFilter(Filter f) { this.filters.add(f); return this;// 返回this可以连续添加. } @Override public void doFilter(Request request, Response response, FilterChain chain) { if (index == filters.size()) return; Filter filter = filters.get(index); index++; filter.doFilter(request, response, chain); } }

请求到达servlet之前，拦截下来做预处理，处理之后便执行chain.doFilter(request, response)这个方法.chain.doFilter将请求转发给过滤器链下一个filter , 如果没有filter那就是你请求的资源

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