四个有用的Java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;   
   }*/   
}    
}