几种实用的java过滤器

java 代码
一、使浏览器不缓存页面的过滤器    

   1. import javax.servlet.*;      
   2. import javax.servlet.http.HttpServletResponse;      
   3. import java.io.IOException;      
   4.      
   5. /**    
   6. * 用于的使 Browser 不缓存页面的过滤器    
   7. */     
   8. public class ForceNoCacheFilter implements Filter {      
   9.      
  10. public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException      
  11. {      
  12.     ((HttpServletResponse) response).setHeader("Cache-Control","no-cache");      
  13.     ((HttpServletResponse) response).setHeader("Pragma","no-cache");      
  14.     ((HttpServletResponse) response).setDateHeader ("Expires", -1);      
  15.     filterChain.doFilter(request, response);      
  16. }      
  17.      
  18. public void destroy()      
  19. {      
  20. }      
  21.      
  22.       public void init(FilterConfig filterConfig) throws ServletException      
  23. {      
  24. }      
  25. }   

 
 
二、检测用户是否登陆的过滤器   

   1. import javax.servlet.*;      
   2. import javax.servlet.http.HttpServletRequest;      
   3. import javax.servlet.http.HttpServletResponse;      
   4. import javax.servlet.http.HttpSession;      
   5. import java.util.List;      
   6. import java.util.ArrayList;      
   7. import java.util.StringTokenizer;      
   8. import java.io.IOException;      
   9.      
  10. /**    
  11. * 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     
  12.    
  13.    
  14. * 配置参数     
  15.    
  16.    
  17. * checkSessionKey 需检查的在 Session 中保存的关键字    
  18.    
  19. * redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath    
  20.    
  21. * notCheckURLList 不做检查的 URL列表，以分号分开，并且 URL 中不包括 ContextPath    
  22.    
  23. */     
  24. public class CheckLoginFilter      
  25. implements Filter      
  26. {      
  27.       protected FilterConfig filterConfig = null;      
  28.       private String redirectURL = null;      
  29.       private List notCheckURLList = new ArrayList();      
  30.       private String sessionKey = null;      
  31.      
  32. public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException      
  33. {      
  34.     HttpServletRequest request = (HttpServletRequest) servletRequest;      
  35.     HttpServletResponse response = (HttpServletResponse) servletResponse;      
  36.      
  37.      HttpSession session = request.getSession();      
  38.     if(sessionKey == null)      
  39.     {      
  40.      filterChain.doFilter(request, response);      
  41.      return;      
  42.     }      
  43.     if((!checkRequestURIIntNotFilterList(request)) && session.getAttribute(sessionKey) == null)      
  44.     {      
  45.      response.sendRedirect(request.getContextPath() + redirectURL);      
  46.      return;      
  47.     }      
  48.     filterChain.doFilter(servletRequest, servletResponse);      
  49. }      
  50.      
  51. public void destroy()      
  52. {      
  53.     notCheckURLList.clear();      
  54. }      
  55.      
  56. private boolean checkRequestURIIntNotFilterList(HttpServletRequest request)      
  57. {      
  58.     String uri = request.getServletPath() + (request.getPathInfo() == null ? "" : request.getPathInfo());      
  59.     return notCheckURLList.contains(uri);      
  60. }      
  61.      
  62. public void init(FilterConfig filterConfig) throws ServletException      
  63. {      
  64.     this.filterConfig = filterConfig;      
  65.     redirectURL = filterConfig.getInitParameter("redirectURL");      
  66.     sessionKey = filterConfig.getInitParameter("checkSessionKey");      
  67.      
  68.     String notCheckURLListStr = filterConfig.getInitParameter("notCheckURLList");      
  69.      
  70.     if(notCheckURLListStr != null)      
  71.     {      
  72.      StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";");      
  73.      notCheckURLList.clear();      
  74.      while(st.hasMoreTokens())      
  75.      {      
  76.       notCheckURLList.add(st.nextToken());      
  77.      }      
  78.     }      
  79. }      
  80. }     


 
三、字符编码的过滤器   

   1. import javax.servlet.*;      
   2. import java.io.IOException;      
   3.      
   4. /**    
   5. * 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    
   6. */     
   7. public class CharacterEncodingFilter      
   8. implements Filter      
   9. {      
  10. protected FilterConfig filterConfig = null;      
  11. protected String encoding = "";      
  12.      
  13. public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException      
  14. {      
  15.           if(encoding != null)      
  16.            servletRequest.setCharacterEncoding(encoding);      
  17.           filterChain.doFilter(servletRequest, servletResponse);      
  18. }      
  19.      
  20. public void destroy()      
  21. {      
  22.     filterConfig = null;      
  23.     encoding = null;      
  24. }      
  25.      
  26.       public void init(FilterConfig filterConfig) throws ServletException      
  27. {      
  28.            this.filterConfig = filterConfig;      
  29.           this.encoding = filterConfig.getInitParameter("encoding");      
  30.      
  31. }      
  32. }     


 
四、资源保护过滤器   

   1. package catalog.view.util;      
   2.      
   3. import javax.servlet.Filter;      
   4. import javax.servlet.FilterConfig;      
   5. import javax.servlet.ServletRequest;      
   6. import javax.servlet.ServletResponse;      
   7. import javax.servlet.FilterChain;      
   8. import javax.servlet.ServletException;      
   9. import javax.servlet.http.HttpServletRequest;      
  10. import java.io.IOException;      
  11. import java.util.Iterator;      
  12. import java.util.Set;      
  13. import java.util.HashSet;      
  14. //      
  15. import org.apache.commons.logging.Log;      
  16. import org.apache.commons.logging.LogFactory;      
  17.      
  18. /**    
  19. * This Filter class handle the security of the application.    
  20. *     
  21. * It should be configured inside the web.xml.    
  22. *     
  23. * @author Derek Y. Shen    
  24. */     
  25. public class SecurityFilter implements Filter {      
  26. //the login page uri      
  27. private static final String LOGIN_PAGE_URI = "login.jsf";      
  28.        
  29. //the logger object      
  30. private Log logger = LogFactory.getLog(this.getClass());      
  31.        
  32. //a set of restricted resources      
  33. private Set restrictedResources;      
  34.        
  35. /**    
  36.    * Initializes the Filter.    
  37.    */     
  38. public void init(FilterConfig filterConfig) throws ServletException {      
  39.    this.restrictedResources = new HashSet();      
  40.    this.restrictedResources.add("/createProduct.jsf");      
  41.    this.restrictedResources.add("/editProduct.jsf");      
  42.    this.restrictedResources.add("/productList.jsf");      
  43. }      
  44.        
  45. /**    
  46.    * Standard doFilter object.    
  47.    */     
  48. public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)      
  49.     throws IOException, ServletException {      
  50.    this.logger.debug("doFilter");      
  51.         
  52.    String contextPath = ((HttpServletRequest)req).getContextPath();      
  53.    String requestUri = ((HttpServletRequest)req).getRequestURI();      
  54.         
  55.    this.logger.debug("contextPath = " + contextPath);      
  56.    this.logger.debug("requestUri = " + requestUri);      
  57.         
  58.    if (this.contains(requestUri, contextPath) && !this.authorize((HttpServletRequest)req)) {      
  59.     this.logger.debug("authorization failed");      
  60.     ((HttpServletRequest)req).getRequestDispatcher(LOGIN_PAGE_URI).forward(req, res);      
  61.    }      
  62.    else {      
  63.     this.logger.debug("authorization succeeded");      
  64.     chain.doFilter(req, res);      
  65.    }      
  66. }      
  67.        
  68. public void destroy() {}       
  69.        
  70. private boolean contains(String value, String contextPath) {      
  71.    Iterator ite = this.restrictedResources.iterator();      
  72.         
  73.    while (ite.hasNext()) {      
  74.     String restrictedResource = (String)ite.next();      
  75.          
  76.     if ((contextPath + restrictedResource).equalsIgnoreCase(value)) {      
  77.      return true;      
  78.     }      
  79.    }      
  80.         
  81.    return false;      
  82. }      
  83.        
  84. private boolean authorize(HttpServletRequest req) {      
  85.      
  86.                //处理用户登录      
  87.         /* UserBean user = (UserBean)req.getSession().getAttribute(BeanNames.USER_BEAN);    
  88.       
  89.    if (user != null && user.getLoggedIn()) {    
  90.     //user logged in    
  91.     return true;    
  92.    }    
  93.    else {    
  94.     return false;    
  95.    }*/     
  96. }      
  97. }