几个有用的过滤器(java)

java 代码一、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 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、资源保护过滤器            
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) {                      
   //处理用户登录            

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

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