web.xml配置五个有用的过滤器

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一、使浏览器不缓存页面的过滤器
Java代码

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
Java代码

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
Java代码

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
Java代码

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;            }      }        }

五利用Filter限制用户浏览权限
Java代码
在一个系统中通常有多个权限的用户。不同权限用户的可以浏览不同的页面。使用Filter进行判断不仅省下了代码量，而且如果要更改的话只需要在Filter文件里动下就可以。
以下是Filter文件代码：

import java.io.IOException;          import javax.servlet.Filter;        import javax.servlet.FilterChain;        import javax.servlet.FilterConfig;        import javax.servlet.ServletException;        import javax.servlet.ServletRequest;        import javax.servlet.ServletResponse;        import javax.servlet.http.HttpServletRequest;               public class RightFilter implements Filter {                   public void destroy() {            }                   public void doFilter(ServletRequest sreq, ServletResponse sres, FilterChain arg2) throws IOException, ServletException {                // 获取uri地址                HttpServletRequest request=(HttpServletRequest)sreq;                String uri = request.getRequestURI();                String ctx=request.getContextPath();                uri = uri.substring(ctx.length());                //判断admin级别网页的浏览权限                if(uri.startsWith("/admin")) {                    if(request.getSession().getAttribute("admin")==null) {                        request.setAttribute("message","您没有这个权限");                        request.getRequestDispatcher("/login.jsp").forward(sreq,sres);                        return;                    }                 }                //判断manage级别网页的浏览权限                if(uri.startsWith("/manage")) {                    }                //下面还可以添加其他的用户权限，省去。                    }                    public void init(FilterConfig arg0) throws ServletException {                 }               }

Xml代码

<filter>
     <filter-name>RightFilter</filter-name>
      <filter-class>cn.itkui.filter.RightFilter</filter-class>
</filter>
<filter-mapping>
      <filter-name>RightFilter</filter-name>
      <url-pattern>/admin/*</url-pattern>
</filter-mapping>
<filter-mapping>
      <filter-name>RightFilter</filter-name>
      <url-pattern>/manage/*</url-pattern>
</filter-mapping>


<filter>
<filter-name>RightFilter</filter-name>
<filter-class>cn.itkui.filter.RightFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>RightFilter</filter-name>
<url-pattern>/admin/*</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>RightFilter</filter-name>
<url-pattern>/manage/*</url-pattern>
</filter-mapping>

在web.xml中加入Filter的配置，如下：
Xml代码
<filter>
<filter-name>EncodingAndCacheflush</filter-name>
<filter-class>EncodingAndCacheflush</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
    </filter>
    <filter-mapping>
        <filter-name>EncodingAndCacheflush</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
<filter>
<filter-name>EncodingAndCacheflush</filter-name>
<filter-class>EncodingAndCacheflush</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>EncodingAndCacheflush</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

要传递参数的时候最好使用form进行传参，如果使用链接的话当中文字符的时候过滤器转码是不会起作用的，还有就是页面上

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