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1.浏览器不使用缓存设置过滤器

 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   
 {   
 }   
 }   

2.检测用户是否登录

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());   
      }   
     }   
 }   
 }   

3.编码过滤器

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");   
   
 }   
 }   

4.资源过滤器

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;  
    }*/  
 }   
 }