四个有用的过虑器 Filter

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<p> * 配置参数<p> * checkSessionKey 需检查的在 Session 中保存的关键字<br/> * redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath<br/> * notCheckURLList 不做检查的URL列表，以分号分开，并且 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());   }  } }}

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; }*/ }}