javax.servlet.Filter�q�用 (转蝲)

wangjc — Wed, 07 Jan 2009 00:41:00 GMT

Servlets Filter 是Servlet 2.3 规范中新增加的，它是截取用户从客��L��提交的请求，在还没有到达需要访问的资源时运行的一个类。它操纵来自客户端的��h��Q�在资源�q�没有初发送到客户端前截取响应�Q��ƈ处理�q�些�q�没有发送到客户端的响应�?br /> Filters 有许多的应用场合。Servlet 2.3 规范��如下的地方可以应用Filter�Q?br /> authentication filters
logging and auditing filters
image conversion filters
data compression filters
encryption filters
tokenizing filters
filters that trigger resource access events
XSL/T filters that transform XML content
MIME-type chain filters

package jasso.web.filter;

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 SetCharacterEncodingFilter implements Filter {
private String encoding;

public void destroy() {
}

    public void doFilter(ServletRequest request, ServletResponse response,
       FilterChain chain) throws IOException, ServletException {
       request.setCharacterEncoding(encoding);
       chain.doFilter(request, response);
    }

    public void init(FilterConfig config) throws ServletException {
       encoding = config.getInitParameter("encoding");
    }
}

web.xml部分

......

   encodingFilter
   my.web.filter.SetCharacterEncodingFilter

       encoding
       Shift_JIS


   encodingFilter
   action

   action
   org.apache.struts.action.ActionServlet

     config
     /WEB-INF/config/struts-config.xml,/WEB-INF/config/struts-config-contents.xml


     debug
     2


     detail
     2

   1

----------------------------------------------

javax.servlet.filter的用�?/font>

如何实现一个过滤器呢？
1.所在的�c�d��现Filter接口
　public interface Filter
public void init(FilterConfig filterConfig)throws ServletException
�q��o器初始化是在容器启动时自动初始化
public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain)throws IOException,ServletExcepton
在标准Servlet中的doGet或doPost �Ҏ��中，传递参��Cؓ�Q�HttpServletRequest、HttpServletResponse
�q��o器销�?
public void destroy()
package cn.mldn.lxh.filter
import java.io.*;
import javax.servlet.*;
public class FirstFilter implements Filter
{
    public void init(FilterConfig config)throws ServletException
    {
       System.out.println("�q��o器初始化");
    }
　　public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain) throws IOException,ServletException
    {
       System.out.println(�q��odoFilter);
     }
   public void destroy()
   {
       System.out.println(�q��o器销�?;
   }
}
web.xml文�g配置

first
cn.mldn.lxh.filter.FirstFilter

first
与servlet中的url-pattern不一��P��此处表示寚w��个页面进行过滤，如果全部都过滤，�?/*"
/*

如果�q��o器要��内容传递到目的圎ͼ�则需要FilterChain,��请求��l�向下�{�?
�q��o器也会执行两�ơ：FilterChain�q�前执行一�ơ，之后再执行一��?
1.�q��o非法文字�Q?
package cn.mldn.lxh.filter;
import java.io.*;
import javax.servlet.*;
public class CharFilter implements Filter
{
public void init(FilterConfig filterConfig)throws ServletException
{
     //System.out.println("init");
}
public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain)throws IOException,ServletException
{
String content=request.getParameter("content");
//如果indexOf�q�回-1则表�C�没有查到所要的内容
if(content!=null) {
   if(content.indexOf("AAA")==-1)
   {
    chain.doFilter(request,response);
   }
   else
   {
    System.out.println("有非法文�?);
   //如果需要的话，此处依然可以使用RequestDispatcher�q�行跌��{
   }
}else
   {
    chain.doFilter(request,response);
   }
}
public void destroy()
{
//System.out.println("�q��o器销�?);
}
}

char
cn.mldn.lxh.filter.CharFilter

char
/*

2.对内容进行统一的编�?
setCharacterEncoding("GB2312");
package cn.mldn.lxh.filter;
import java.io.*;
import javax.servlet.*;
public class EncodingFilter implements Filter
{
public void init(FilterConfig filterConfig)throws ServletException
{
    //System.out.println("�q��o器初始化");
}
public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain)throws IOException,ServletException
{
   try{
      request.setCharacterEncoding("GB2312");
   }
   catch(Exception e)
   {}
   chain.doFilter(request,response);
}
public void destroy()
{
   //System.out.println("销�?);
}

}

encoding

encoding
/*

3.登陆验证
package cn.mldn.lxh.filter;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class LoginFilter implements Filter
{
    public void init(FilterCoinfig filterConfig)throws ServletException
    {
    //System.out.println("�q��o器初始化");
    }
}
public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain)throws IOException,ServletException
{
//Session属于http范畴�Q�把以ServletRequest对象需要先转换成HttpServletRequest对象
HttpServletRequest req=(HttpServletRequest)request;
HttpSession session =req.getSession();
//如果session不�ؓ�I�，则可以浏览其它页�?
if(session.getAttribute("uname")!=null)
{
chain.doFilter(request,response);
}
else
{
//通过requestDispatcher跌��{到登陆面
request.getRequestDispatcher("login.jsp").forward(request,response);
}
}
public void destroy()
{
//System,out.println("销�?);
}
}

login
cn.mldn.lxh.filter.LoginFilter

   参数名称
   参数�?


login
/*

��d��web.xml中的参数的方法：
public void init(FilterConfig arg0) throws ServletException {
   String 参数�? arg0.getInitParameter("参数名称");
}

wangjc 2009-01-07 08:41 发表评论

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javax.servlet.Filter�q�用 (转蝲)

javax.servlet.filter的用�?/font>