java幾個有用的Servlet過濾器

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 用於的使 Browser 不緩存頁面的過濾器
*/
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
{
}
}
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;
/**
* 用於檢測用戶是否登陸的過濾器，如果未登錄，則重定向到指的登錄頁面<p>
* 配置參數<p>
* checkSessionKey 需檢查的在 Session 中保存的關鍵字<br/>
* redirectURL 如果用戶未登錄，則重定向到指定的頁面，URL不包括 ContextPath<br/>
* notCheckURLList 不做檢查的URL列表，以分號分開，並且 URL 中不包括 ContextPath<br/>
*/
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());
　 }
}
}
}
import javax.servlet.*;
import java.io.IOException;
/**
* 用於設置 HTTP 請求字符編碼的過濾器，通過過濾器參數encoding指明使用何種字符編碼,用於處理Html Form請求參數的中文問題
*/
public class CharacterEncodingFilter
implements Filter
{
protected FilterConfig filterConfig = null;
protected String encoding = "";
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException
{
　　　　if(encoding != null)
　　　　 servletRequest.setCharacterEncoding(encoding);
filterChain.doFilter(servletRequest, servletResponse);
}
public void destroy()
{
filterConfig = null;
encoding = null;
}
　　public void init(FilterConfig filterConfig) throws ServletException
{
this.filterConfig = filterConfig;
　　　　this.encoding = filterConfig.getInitParameter("encoding");