四个有用的过虑器

 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 uriprivate static final String LOGIN_PAGE_URI = "login.jsf";//the logger objectprivate Log logger = LogFactory.getLog(this.getClass());//a set of restricted resourcesprivate 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 inreturn true;}else {return false;}*/}}