Java四个有用的过滤器Filter

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;   
  
  
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;   
  
  
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;   
  
  
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;   
  
  
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;   
    
   
 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");   
 }   
    
   
 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   
         
 }   
}