java过滤器四个实例

java 代码

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;   

   }*/   

}    

}