web常用的Filter业务功能

一、使浏览器不缓存页面的过滤器
import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
* 用于的使 Browser 不缓存页面的过滤器
*/
public class ForceNoCacheFilter implements Filter {

public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException,

ServletException
{
   ((HttpServletResponse) response).setHeader("Cache-Control","no-cache");
   ((HttpServletResponse) response).setHeader("Pragma","no-cache");
   ((HttpServletResponse) response).setDateHeader ("Expires", -1);
   filterChain.doFilter(request, response);
}

public void destroy()
{
}

     public void init(FilterConfig filterConfig) throws ServletException
{
}
}

二、检测用户是否登陆的过滤器

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.util.List;
import java.util.ArrayList;
import java.util.StringTokenizer;
import java.io.IOException;

/**
* 用于检测用户是否登陆的过滤器，如果未登录，则重定向到指的登录页面

* 配置参数

* checkSessionKey 需检查的在 Session 中保存的关键字

* redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath

* notCheckURLList 不做检查的URL列表，以分号分开，并且 URL 中不包括 ContextPath

*/
public class CheckLoginFilter
implements Filter
{
     protected FilterConfig filterConfig = null;
     private String redirectURL = null;
     private List notCheckURLList = new ArrayList();
     private String sessionKey = null;

public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws

IOException, ServletException
{
   HttpServletRequest request = (HttpServletRequest) servletRequest;
   HttpServletResponse response = (HttpServletResponse) servletResponse;

    HttpSession session = request.getSession();
   if(sessionKey == null)
   {
    filterChain.doFilter(request, response);
    return;
   }
   if((!checkRequestURIIntNotFilterList(request)) && session.getAttribute(sessionKey) == null)
   {
    response.sendRedirect(request.getContextPath() + redirectURL);
    return;
   }
   filterChain.doFilter(servletRequest, servletResponse);
}

public void destroy()
{
   notCheckURLList.clear();
}

private boolean checkRequestURIIntNotFilterList(HttpServletRequest request)
{
   String uri = request.getServletPath() + (request.getPathInfo() == null ? "" : request.getPathInfo());
   return notCheckURLList.contains(uri);
}

public void init(FilterConfig filterConfig) throws ServletException
{
   this.filterConfig = filterConfig;
   redirectURL = filterConfig.getInitParameter("redirectURL");
   sessionKey = filterConfig.getInitParameter("checkSessionKey");

   String notCheckURLListStr = filterConfig.getInitParameter("notCheckURLList");

   if(notCheckURLListStr != null)
   {
    StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";");
    notCheckURLList.clear();
    while(st.hasMoreTokens())
    {
     notCheckURLList.add(st.nextToken());
    }
   }
}
}

三、字符编码的过滤器

import javax.servlet.*;
import java.io.IOException;

/**
* 用于设置 HTTP 请求字符编码的过滤器，通过过滤器参数encoding指明使用何种字符编码,用于处理Html Form请求参数的中文问题

*/
public class Cha

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