贏在執行

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
?* 用于的使 Browser 不緩存頁面的過濾器
?*/
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、檢測用戶是否登陸的過濾器

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;

/**
?* 用于檢測用戶是否登陸的過濾器，如果未登錄，則重定向到指的登錄頁面<p>
?* 配置參數<p>
?* checkSessionKey 需檢查的在 Session 中保存的關鍵字<br/>
?* redirectURL 如果用戶未登錄，則重定向到指定的頁面，URL不包括 ContextPath<br/>
?* notCheckURLList 不做檢查的URL列表，以分號分開，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、字符編碼的過濾器

import javax.servlet.*;
import java.io.IOException;

/**
?* 用于設置 HTTP 請求字符編碼的過濾器，通過過濾器參數encoding指明使用何種字符編碼,用于處理Html Form請求參數的中文問題
?*/
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、資源保護過濾器

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) {

             //處理用戶登錄
	     /*	UserBean user = (UserBean)req.getSession().getAttribute(BeanNames.USER_BEAN);

		if (user != null && user.getLoggedIn()) {
			//user logged in
			return true;
		}
		else {
			return false;
		}*/
	}
}