web.xml配置五个有用的过滤器

一、使浏览器不缓存页面的过滤器  
Java代码

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  
Java代码

  
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  
Java代码

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  
 
  Java代码

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
Java代码
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")) {          
        }      
        //下面还可以添加其他的用户权限，省去。      
     
     }      
	 
	 public void init(FilterConfig arg0) throws ServletException {          
     }      
     
}  

Xml代码
<!-- 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>   

<!-- 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：
Xml代码
<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>   
<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。