幾個有用的過濾器(java)

java 代碼一、使瀏覽器不快取頁面面的過濾器     
import javax.servlet.*;    
import javax.servlet.http.HttpServletResponse;    
import java.io.IOException;        
/**   
* 用於的使 Browser 不快取頁面面的過濾器   
*/   
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     {     }    
}        
二、檢測使用者是否登陸的過濾器        
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;        
/**   
* 用於檢測使用者是否登陸的過濾器，如果未登入，則重新導向到指的登入頁面          
* 配置參數          
* checkSessionKey 需檢查的在 Session 中儲存的關鍵字      
* redirectURL 如果使用者未登入，則重新導向到指定的頁面，URL不包括 ContextPath      
* notCheckURLList 不做檢查的URL列表，以分號分開，並且 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、字元編碼的過濾器        
import javax.servlet.*;    
import java.io.IOException;        
/**   
* 用於設定 HTTP 要求字元編碼的過濾器，通過過濾器參數encoding指明使用何種字元編碼,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");        
 }    
}         
四、資源保護過濾器            
package catalog.view.util;        
import javax.servlet.Filter;    
import javax.servlet.FilterConfig;    
import javax.servlet.ServletRequest;    
import javax.servlet.ServletResponse;    
import javax.servlet.FilterChain;    
import javax.servlet.ServletException;    
import javax.servlet.http.HttpServletRequest;    
import java.io.IOException;    
import java.util.Iterator;    
import java.util.Set;    
import java.util.HashSet;    
//    
import org.apache.commons.logging.Log;    
import org.apache.commons.logging.LogFactory;        
/**   
* This Filter class handle the security of the application.   
*    
* It should be configured inside the web.xml.   
*    
* @author Derek Y. Shen   
*/   
public class SecurityFilter implements Filter {    
 //the login page uri    
 private static final String LOGIN_PAGE_URI = "login.jsf";          
 //the logger object    
 private Log logger = LogFactory.getLog(this.getClass());          
 //a set of restricted resources    
 private Set restrictedResources;          
 /**      
 * Initializes the Filter.      
 */   
 public void init(FilterConfig filterConfig) throws ServletException {       
  this.restrictedResources = new HashSet();       
  this.restrictedResources.add("/createProduct.jsf");       
  this.restrictedResources.add("/editProduct.jsf");       
  this.restrictedResources.add("/productList.jsf");    
 }          
 /**      
 * Standard doFilter object.      
 */   
 public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException
 {       
  this.logger.debug("doFilter");              
  String contextPath = ((HttpServletRequest)req).getContextPath();       
  String requestUri = ((HttpServletRequest)req).getRequestURI();              
  this.logger.debug("contextPath = " + contextPath);       
  this.logger.debug("requestUri = " + requestUri);              
  if (this.contains(requestUri, contextPath) && !this.authorize((HttpServletRequest)req)) {        
   this.logger.debug("authorization failed");        
   ((HttpServletRequest)req).getRequestDispatcher(LOGIN_PAGE_URI).forward(req, res);       
  }       
  else {        
   this.logger.debug("authorization succeeded");        
   chain.doFilter(req, res);       
  }    
 }          
 public void destroy() {}           
 private boolean contains(String value, String contextPath) {       
  Iterator ite = this.restrictedResources.iterator();              
  while (ite.hasNext()) {        
   String restrictedResource = (String)ite.next();                
   if ((contextPath + restrictedResource).equalsIgnoreCase(value)) {         
    return true;        
   }       
  }              
  return false;    
 }          
 private boolean authorize(HttpServletRequest req) {                      
   //處理使用者登入            

   UserBean user = (UserBean)req.getSession().getAttribute(BeanNames.USER_BEAN);            
   if (user != null && user.getLoggedIn()) {       
    //user logged in       
    return true;      
   }      
   else {       
    return false;      
   }  
 }    
}