java 五个有用的过滤器

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 * 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       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;    }*/   }    }   五 利用Filter限制用户浏览权限 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")) {                //这里省去                 }             }            //下面还可以添加其他的用户权限,省去。            }           public void init(FilterConfig arg0) throws ServletException {                     }       } <!-- 判断页面的访问权限 -->     <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: <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 form的method也要设置为post,不然过滤器也起不了作用。 

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