Web开发5个有用的过滤器（转）

声明：本文所有代码纯属转载，原文请参考：http://wwwdd2315.blog.163.com/blog/static/66661889201110150206606/

一、使浏览器不缓存页面的过滤器  
Java代码

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

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

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

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：  
 

Java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