设置常用过滤器-站点黑名单、内容压缩

设置站点黑名单的过滤器

功能描述

        不允许从禁用的站点（IP）访问当前应用，也不允许从禁用的站点链接到当前应用。
        为了简单起见，设置禁用站点时，暂不支持使用通配符。只是抛砖引玉了。
        比如：禁止其他的网站引用本站的图片资源，只需在此基础上稍作修改即可。

使用方法

        在 java web 项目的 web.xml 文件中添加如下代码。

<!--设置站点黑名单的过滤器配置  开始 -->
<filter> 
 <filter-name>BannedAccessFilter</filter-name> 
 <filter-class>com.hmw.filter.BannedAccessFilter</filter-class> 
 <init-param> 
     <description>需要禁用的站点，一个站点占用一行</description> 
     <param-name>bannedSites</param-name> 
     <param-value> 
         192.168.1.101 
         192.168.1.102 
         www.csdn.net 
     </param-value> 
 </init-param> 
</filter> 
  
<filter-mapping> 
 <filter-name>BannedAccessFilter</filter-name> 
 <url-pattern>／*</url-pattern> 
</filter-mapping> 
<!--设置站点黑名单的过滤器配置  结束 --> 

过滤器源码

package com.hmw.filter; 
  
import java.io.IOException; 
import java.io.PrintWriter; 
import java.net.MalformedURLException; 
import java.net.URL; 
import java.util.HashSet; 
import java.util.StringTokenizer; 
  
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; 
  
import org.apache.commons.lang3.StringUtils; 
import org.apache.log4j.Logger; 
  
/** 
 * 设置禁用站点（黑名单）的过滤器 
*/
public class BannedAccessFilter implements Filter { 
    static final Logger logger = Logger.getLogger(BannedAccessFilter.class); 
      
    private HashSet bannedSiteTable; 
      
    /** 
     * 将配置的禁用站点列表初始化到一个 HashSet 中 
     */
    @Override
    public void init(FilterConfig config) throws ServletException { 
        bannedSiteTable = new HashSet(); 
        String bannedSites = config.getInitParameter("bannedSites"); 
        // Default token set: white space. 
        StringTokenizer tok = new StringTokenizer(bannedSites); 
        while (tok.hasMoreTokens()) { 
            String bannedSite = tok.nextToken(); 
            bannedSiteTable.add(bannedSite); 
            logger.info("Banned " + bannedSite); 
        } 
    } 
      
    /** 
     * 如果请求来自被禁用的站点，或是从被禁用的站点链接过来的，则拒绝访问。 
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException { 
        logger.debug("BannedAccessFilter: Filtering the Request..."); 
          
        HttpServletRequest req = (HttpServletRequest) request; 
        String requestingHost = req.getRemoteHost(); 
        String referringHost = getReferringHost(req.getHeader("Referer")); 
          
        String bannedSite = null; 
        boolean isBanned = false; 
        if (bannedSiteTable.contains(requestingHost)) { 
            bannedSite = requestingHost; 
            isBanned = true; 
        } else if (bannedSiteTable.contains(referringHost)) { 
            bannedSite = referringHost; 
            isBanned = true; 
        } 
          
        if (isBanned) { 
            showWarning(response, bannedSite); 
        } else { 
            chain.doFilter(request, response); 
        } 
          
        logger.debug("BannedAccessFilter: Filtering the Response..."); 
    } 
  
    @Override
    public void destroy() { 
    } 
  
    /** 
     * 根据 URL 链接地址，取得该链接地址所在的站点 
     * @param refererringURLString URL链接地址 
     * @return 该 URL 链接地址所在的站点，如果传入的参数不是一个符合URL规范的字符串，则返回 <CODE>null</CODE> 
     */
    private String getReferringHost(String refererringURLString) { 
        if(StringUtils.isBlank(refererringURLString)) 
            return null; 
          
        try { 
            URL referringURL = new URL(refererringURLString); 
            return referringURL.getHost(); 
        } catch (MalformedURLException mue) { // Malformed 
            return null; 
        } 
    } 
  
    /** 
     * 如果用户是从禁用站点访问的该应用，或是从禁用站点链接过来的，则调用此方法将警告信息展现给用户。 
     * @param response HTTP请求响应对象 
     * @param bannedSite 禁止的站点 
     * @throws ServletException 
     * @throws IOException 
     * @author <A href="mailto:hemw@mochasoft.com.cn">何明旺</A> 
     */
    private void showWarning(ServletResponse response, String bannedSite) throws ServletException, IOException { 
        String htmlCode  = ""; 
        htmlCode += "<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">"; 
        htmlCode += "<html xmlns="http://www.w3.org/1999/xhtml">"; 
        htmlCode += "  <head>"; 
        htmlCode += "      <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />"; 
        htmlCode += "      <title>禁止访问</title>"; 
        htmlCode += "  </head>"; 
        htmlCode += "  <body>"; 
        htmlCode += "      <h1>禁止访问</h1>"; 
        htmlCode += "      <p>对不起，您无法访问该资源，因为您的站点已经被列入我们的黑名单！</p>"; 
        htmlCode += "      <p>您的站点是：<strong>" + bannedSite + "</strong></p>"; 
        htmlCode += "  </body>"; 
        htmlCode += "</html>"; 
  
        response.setContentType("text/html"); 
        PrintWriter out = null; 
        try{ 
            out = response.getWriter(); 
            out.println(htmlCode); 
        }finally{ 
              if(out != null){ 
                out.flush(); 
                out.close(); 
              } 
        } 
          
        /* 
         * 也可以使用下面的方法直接转发或重定向到指定的警告页面 
         * 转发： 
         *     ((HttpServletRequest)request).getRequestDispatcher("/warn.html").forward(request, response); 
         * 重定向： 
         *     ((HttpServletResponse)response).sendRedirect("webAppContext/warn.html"); 
         */
    } 
} 

 将响应数据进行压缩处理的过滤器

功能描述

        如果浏览器支持 gzip 压缩格式的数据，则将响应的数据使用 gzip 压缩后再输出。

使用方法

        在 java web 项目的 web.xml 文件中添加如下代码。

<!--压缩过滤器的配置  开始 -->
 <filter> 
 <filter-name>CompressionFilter</filter-name> 
 <filter-class>com.hmw.filter.CompressionFilter</filter-class> 
 </filter> 
   
 <filter-mapping> 
 <filter-name>CompressionFilter</filter-name> 
   <servlet-name>/LongServlet</servlet-name> 
 </filter-mapping> 
<!--压缩过滤器的配置  结束 --> 

过滤器源码

CompressionFilter.java
?package com.hmw.filter; 
  
import java.io.ByteArrayOutputStream; 
import java.io.IOException; 
import java.io.OutputStream; 
import java.io.OutputStreamWriter; 
import java.util.zip.GZIPOutputStream; 
  
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; 
import javax.servlet.http.HttpServletResponse; 
  
/** 
 * 压缩过滤器 <BR> 
 * 如果浏览器支持 gzip 压缩格式的数据，则将响应的数据使用 gzip 压缩后再输出。 
 *  */
public class CompressionFilter implements Filter { 
  
    @Override
    public void init(FilterConfig config) throws ServletException { 
    } 
  
    /** 
     * 如果浏览器不支持 gzip 压缩，则不做直接放行（不做压缩处理）<BR> 
     * 反之，将HTTP响应头的编码设置为 <CODE>gzip</CODE>，然后将响应数据使用 gzip 进行压缩处理。 
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, 
            FilterChain chain) throws ServletException, IOException { 
        HttpServletRequest req = (HttpServletRequest) request; 
        HttpServletResponse res = (HttpServletResponse) response; 
  
        if (!isGzipSupported(req)) { // Invoke resource normally. 
            chain.doFilter(req, res); 
            return; 
        } 
  
        // 将响应头信息中的内容编码设置为 gzip 
        res.setHeader("Content-Encoding", "gzip"); 
          
        // 调用资源，使用 CharArrayWrapper 包装输出 
        CharArrayWrapper responseWrapper = new CharArrayWrapper(res); 
        chain.doFilter(req, responseWrapper); 
        // 取得存放输出数据的 char 型数组 
        char[] responseChars = responseWrapper.toCharArray(); 
          
        // 将响应数据压缩后存入一个 byte 型的数组，然后输出到 
        ByteArrayOutputStream byteStream = new ByteArrayOutputStream(); 
        GZIPOutputStream zipOut = new GZIPOutputStream(byteStream); 
        OutputStreamWriter tempOut = new OutputStreamWriter(zipOut); 
        // 将原来的响应数据压缩后写入二字节输出流 
        tempOut.write(responseChars); 
        // 关闭输出流 
        tempOut.close(); 
  
        // 更新响应头信息中 Content-Length 的值。 
        res.setContentLength(byteStream.size()); 
        // 将压缩后的数据发送至客户端 
        OutputStream realOut = res.getOutputStream(); 
        byteStream.writeTo(realOut); 
    } 
  
    @Override
    public void destroy() { 
    } 
  
    /** 
     * 检测浏览器是否支持 Gzip 压缩 
     *  
     * @param req HTTP 请求对象 
     * @return 如果浏览器支持 Gzip 压缩，则返回 true，反之，则返回 false 
     */
    private boolean isGzipSupported(HttpServletRequest req) { 
        String browserEncodings = req.getHeader("Accept-Encoding"); 
        return ((browserEncodings != null) && (browserEncodings.indexOf("gzip") != -1)); 
    } 
} 
CharArrayWrapper.java
?package com.hmw.filter; 
  
import java.io.CharArrayWriter; 
import java.io.PrintWriter; 
  
import javax.servlet.http.HttpServletResponse; 
import javax.servlet.http.HttpServletResponseWrapper; 
  
/** 
 * A response wrapper that takes everything the client would normally output and 
 * saves it in one big character array. 
 */
public class CharArrayWrapper extends HttpServletResponseWrapper { 
    private CharArrayWriter charWriter; 
  
    /** 
     * Initializes wrapper. 
     * <P> 
     * First, this constructor calls the parent constructor. That call is 
     * crucial so that the response is stored and thus setHeader, *setStatus, 
     * addCookie, and so forth work normally. 
     * <P> 
     * Second, this constructor creates a CharArrayWriter that will be used to 
     * accumulate the response. 
     */
    public CharArrayWrapper(HttpServletResponse response) { 
        super(response); 
        charWriter = new CharArrayWriter(); 
    } 
  
    /** 
     * When servlets or JSP pages ask for the Writer, don't give them the real 
     * one. Instead, give them a version that writes into the character array. 
     * The filter needs to send the contents of the array to the client (perhaps 
     * after modifying it). 
     */
    @Override
    public PrintWriter getWriter() { 
        return new PrintWriter(charWriter); 
    } 
  
    /** 
     * Get a String representation of the entire buffer. 
     * <P> 
     * Be sure <B>not</B> to call this method multiple times on the same 
     * wrapper. The API for CharArrayWriter does not guarantee that it 
     * "remembers" the previous value, so the call is likely to make a new 
     * String every time. 
     */
    @Override
    public String toString() { 
        return charWriter.toString(); 
    } 
  
    /** Get the underlying character array. */
    public char[] toCharArray() { 
        return charWriter.toCharArray(); 
    } 
} 

 替换禁用语（指定关键字）

功能描述

        将请求响应中所有的禁用关键字替换掉之后再输出。

使用方法

        在 java web 项目的 web.xml 文件中添加如下代码。

<!--替换关键字的过滤器配置  开始 -->
 <filter> 
 <filter-name>StopWordsFilter</filter-name> 
 <filter-class>com.hmw.filter.StopWordsFilter</filter-class> 
 <init-param> 
     <description>需要禁用的关键字，一个关键字占一行</description> 
     <param-name>keys</param-name> 
     <param-value> 
       QQ 
       百度 
       七一五 
     </param-value> 
 </init-param> 
 </filter> 
   
 <filter-mapping> 
 <filter-name>StopWordsFilter</filter-name> 
   <servlet-name>*.jsp</servlet-name> 
 </filter-mapping> 
<!--替换关键字的过滤器  结束 --> 

过滤器源码

ReplaceKeyWordFilter.java
?package com.hmw.filter; 
  
import java.io.IOException; 
import java.io.PrintWriter; 
import java.util.HashSet; 
import java.util.Iterator; 
import java.util.Set; 
import java.util.StringTokenizer; 
  
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.HttpServletResponse; 
  
/** 
 * 替换关键字的滤器 <BR> 
 *  */
public class StopWordsFilter implements Filter { 
    private Set keyWords = new HashSet(); 
  
    /** 
     * 将需要进行替换的关键字添加到一个定义好的 Set 中 
     */
    @Override
    public void init(FilterConfig config) throws ServletException { 
        String keys =  config.getInitParameter("keys"); 
        StringTokenizer tokenizer = new StringTokenizer(keys); 
        String token = null; 
        while (tokenizer.hasMoreTokens()) { 
            token = tokenizer.nextToken(); 
            if(token != null && token.length() > 0){ 
                keyWords.add(tokenizer.nextToken()); 
            } 
        } 
    } 
  
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, 
            FilterChain chain) throws ServletException, IOException { 
        CharArrayWrapper responseWrapper = new CharArrayWrapper( 
                (HttpServletResponse) response); 
        // 调用请求资源（使用自己包装的 responseWrapper） 
        chain.doFilter(request, responseWrapper); 
        // 取得响应字符串 
        String responseString = responseWrapper.toString(); 
        // 将需要替换的关键字用“**”替换掉 
        Iterator iter = keyWords.iterator(); 
        while (iter.hasNext()) { 
            responseString = replace(responseString, iter.next(), "**"); 
        } 
          
        // 修改响应头信息中的 Content-Length 
        response.setContentLength(responseString.length()); 
        PrintWriter out = response.getWriter(); 
        out.write(responseString); 
    } 
  
    @Override
    public void destroy() { 
    } 
  
    /** 
     * 将字符串中的所有的指定子字符串替换掉 
     * @param mainString 需要进行替换的字符串 
     * @param orig 需要被替换的子串 
     * @param replacement 替换后的新串 
     * @return 返回替换后的字符串 
     */
    public static String replace(String mainString, String orig, String replacement) { 
        String result = ""; 
        int oldIndex = 0; 
        int index = 0; 
        int origLength = orig.length(); 
        while ((index = mainString.indexOf(orig, oldIndex)) != -1) { 
            result = result + mainString.substring(oldIndex, index) + replacement; 
            oldIndex = index + origLength; 
        } 
        result = result + mainString.substring(oldIndex); 
        return result; 
    } 
} 
CharArrayWrapper.java
?package com.hmw.filter; 
  
import java.io.CharArrayWriter; 
import java.io.PrintWriter; 
  
import javax.servlet.http.HttpServletResponse; 
import javax.servlet.http.HttpServletResponseWrapper; 
  
/** 
 * A response wrapper that takes everything the client would normally output and 
 * saves it in one big character array. 
 */
public class CharArrayWrapper extends HttpServletResponseWrapper { 
    private CharArrayWriter charWriter; 
  
    /** 
     * Initializes wrapper. 
     * <P> 
     * First, this constructor calls the parent constructor. That call is 
     * crucial so that the response is stored and thus setHeader, *setStatus, 
     * addCookie, and so forth work normally. 
     * <P> 
     * Second, this constructor creates a CharArrayWriter that will be used to 
     * accumulate the response. 
     */
    public CharArrayWrapper(HttpServletResponse response) { 
        super(response); 
        charWriter = new CharArrayWriter(); 
    } 
  
    /** 
     * When servlets or JSP pages ask for the Writer, don't give them the real 
     * one. Instead, give them a version that writes into the character array. 
     * The filter needs to send the contents of the array to the client (perhaps 
     * after modifying it). 
     */
    @Override
    public PrintWriter getWriter() { 
        return new PrintWriter(charWriter); 
    } 
  
    /** 
     * Get a String representation of the entire buffer. 
     * <P> 
     * Be sure <B>not</B> to call this method multiple times on the same 
     * wrapper. The API for CharArrayWriter does not guarantee that it 
     * "remembers" the previous value, so the call is likely to make a new 
     * String every time. 
     */
    @Override
    public String toString() { 
        return charWriter.toString(); 
    } 
  
    /** Get the underlying character array. */
    public char[] toCharArray() { 
        return charWriter.toCharArray(); 
    } 
}