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;   
 
 
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());  
     }  
    }  
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}  
}  
 
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");