java过滤器学习2(例子)

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        * 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());         }        }    }    } 

三、字符编码的过滤器

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

mport 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;      }*/   }    }