轉載：javaweb學習總結(四十三)——Filter高級開發

時間 2019-11-30

標籤轉載 javaweb 學習總結四十三 filter 高級開發欄目 Java 简体版

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javaweb學習總結(四十三)——Filter高級開發

轉自：http://www.cnblogs.com/xdp-gacl/p/3952405.htmljavascript

　　在filter中能夠獲得表明用戶請求和響應的request、response對象，所以在編程中可使用Decorator(裝飾器)模式對request、response對象進行包裝，再把包裝對象傳給目標資源，從而實現一些特殊需求。css

1、Decorator設計模式

1.一、Decorator設計模式介紹

　　當某個對象的方法不適應業務需求時，一般有2種方式能夠對方法進行加強：html

編寫子類，覆蓋需加強的方法。
使用Decorator設計模式對方法進行加強。

　　在閻宏博士的《JAVA與模式》一書中開頭是這樣描述裝飾（Decorator）模式的：裝飾模式又名包裝(Wrapper)模式。裝飾模式以對客戶端透明的方式擴展對象的功能，是繼承關係的一個替代方案。裝飾模式是在沒必要改變原類文件和使用繼承的狀況下，動態的擴展一個對象的功能。它是經過建立一個包裝對象，也就是裝飾來包裹真實的對象。java

　　那麼在實際應用中遇到需加強對象的方法時，到底選用哪一種方式比較好呢？這個沒有具體的定式，只能是根據具體的需求來採用具體的方式，不過有一種狀況下，必須使用Decorator設計模式：即被加強的對象，開發人員只能獲得它的對象，沒法獲得它的class文件。好比request、response對象，開發人員之因此在servlet中能經過sun公司定義的HttpServletRequest\response接口去操做這些對象，是由於Tomcat服務器廠商編寫了request、response接口的實現類。web服務器在調用servlet時，會用這些接口的實現類建立出對象，而後傳遞給servlet程序。此種狀況下，因爲開發人員根本不知道服務器廠商編寫的request、response接口的實現類是哪一個？在程序中只能拿到服務器廠商提供的對象，所以就只能採用Decorator設計模式對這些對象進行加強。web

1.二、Decorator設計模式的實現

　　1.首先看須要被加強對象繼承了什麼接口或父類，編寫一個類也去繼承這些接口或父類。
　　2.在類中定義一個變量，變量類型即需加強對象的類型。
　　3.在類中定義一個構造函數，接收需加強的對象。
　　4.覆蓋需加強的方法，編寫加強的代碼。數據庫

2、使用Decorator設計模式加強request對象

　　Servlet API 中提供了一個request對象的Decorator設計模式的默認實現類HttpServletRequestWrapper，HttpServletRequestWrapper 類實現了request 接口中的全部方法，但這些方法的內部實現都是僅僅調用了一下所包裝的的 request 對象的對應方法，以免用戶在對request對象進行加強時須要實現request接口中的全部方法。編程

2.一、使用Decorator模式包裝request對象解決get和post請求方式下的中文亂碼問題

　　編寫一個用於處理中文亂碼的過濾器CharacterEncodingFilter，代碼以下：設計模式

  1 package me.gacl.web.filter;  2  3 import java.io.IOException;  4  5 import javax.servlet.Filter;  6 import javax.servlet.FilterChain;  7 import javax.servlet.FilterConfig;  8 import javax.servlet.ServletException;  9 import javax.servlet.ServletRequest;  10 import javax.servlet.ServletResponse;  11 import javax.servlet.http.HttpServletRequest;  12 import javax.servlet.http.HttpServletRequestWrapper;  13 import javax.servlet.http.HttpServletResponse;  14  15 /**  16 * @ClassName: CharacterEncodingFilter  17 * @Description: 此過濾器用來解決解決get、post請求方式下的中文亂碼問題  18 * @author: 孤傲蒼狼  19 * @date: 2014-8-31 下午11:09:37  20 *  21 */  22 public class CharacterEncodingFilter implements Filter {  23  24 private FilterConfig filterConfig = null;  25 //設置默認的字符編碼  26 private String defaultCharset = "UTF-8";  27  28 public void doFilter(ServletRequest req, ServletResponse resp,  29 FilterChain chain) throws IOException, ServletException {  30  31 HttpServletRequest request = (HttpServletRequest) req;  32 HttpServletResponse response = (HttpServletResponse) resp;  33 //獲得在web.xml中配置的字符編碼  34 String charset = filterConfig.getInitParameter("charset");  35 if(charset==null){  36 charset = defaultCharset;  37  }  38  request.setCharacterEncoding(charset);  39  response.setCharacterEncoding(charset);  40 response.setContentType("text/html;charset="+charset);  41  42 MyCharacterEncodingRequest requestWrapper = new MyCharacterEncodingRequest(request);  43  chain.doFilter(requestWrapper, response);  44  }  45  46 public void init(FilterConfig filterConfig) throws ServletException {  47 //獲得過濾器的初始化配置信息  48 this.filterConfig = filterConfig;  49  }  50  51 public void destroy() {  52  53  }  54 }  55  56 /**  57 * @ClassName: MyCharacterEncodingRequest  58 * @Description: Servlet API中提供了一個request對象的Decorator設計模式的默認實現類HttpServletRequestWrapper,  59 * (HttpServletRequestWrapper類實現了request接口中的全部方法，但這些方法的內部實現都是僅僅調用了一下所包裝的的 request對象的對應方法)  60 * 以免用戶在對request對象進行加強時須要實現request接口中的全部方法。  61 * 因此當須要加強request對象時，只須要寫一個類繼承HttpServletRequestWrapper類，而後在重寫須要加強的方法便可  62 * @author: 孤傲蒼狼  63 * @date: 2014-9-2 下午10:42:57  64 * 1.實現與被加強對象相同的接口  65  二、定義一個變量記住被加強對象  66  三、定義一個構造函數，接收被加強對象  67  四、覆蓋須要加強的方法  68  五、對於不想加強的方法，直接調用被加強對象（目標對象）的方法  69 */  70 class MyCharacterEncodingRequest extends HttpServletRequestWrapper{  71 //定義一個變量記住被加強對象(request對象是須要被加強的對象)  72 private HttpServletRequest request;  73 //定義一個構造函數，接收被加強對象  74 public MyCharacterEncodingRequest(HttpServletRequest request) {  75 super(request);  76 this.request = request;  77  }  78 /* 覆蓋須要加強的getParameter方法  79  * @see javax.servlet.ServletRequestWrapper#getParameter(java.lang.String)  80 */  81  @Override  82 public String getParameter(String name) { 83 try{ 84 //獲取參數的值 85 String value= this.request.getParameter(name); 86 if(value==null){ 87 return null; 88 } 89 //若是不是以get方式提交數據的，就直接返回獲取到的值 90 if(!this.request.getMethod().equalsIgnoreCase("get")) { 91 return value; 92 }else{ 93 //若是是以get方式提交數據的，就對獲取到的值進行轉碼處理 94 value = new String(value.getBytes("ISO8859-1"),this.request.getCharacterEncoding()); 95 return value; 96 } 97 }catch (Exception e) { 98 throw new RuntimeException(e); 99 } 100 } 101 }

　　在web.xml文件中配置CharacterEncodingFilter數組

 1 <!--配置字符過濾器，解決get、post請求方式下的中文亂碼問題-->  2 <filter>  3 <filter-name>CharacterEncodingFilter</filter-name>  4 <filter-class>me.gacl.web.filter.CharacterEncodingFilter</filter-class>  5 </filter>  6  7 <filter-mapping>  8 <filter-name>CharacterEncodingFilter</filter-name>  9 <url-pattern>/*</url-pattern> 10 </filter-mapping>

　　編寫jsp測試頁面，以下：瀏覽器

 1 <%@ page language="java" pageEncoding="UTF-8"%>  2 <%--引入jstl標籤庫 --%>  3 <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>  4 <!DOCTYPE HTML>  5 <html>  6 <head>  7 <title>使用字符過濾器解決解決get、post請求方式下的中文亂碼問題</title>  8 </head>  9 10 <body> 11 <%--使用c:url標籤構建url，構建好的url存儲在servletDemo1變量中--%> 12 <c:url value="/servlet/ServletDemo1" scope="page" var="servletDemo1"> 13 <%--構建的url的附帶的中文參數 ，參數名是：username，值是：孤傲蒼狼--%> 14 <c:param name="username" value="孤傲蒼狼"></c:param> 15 </c:url> 16 <%--使用get的方式訪問 --%> 17 <a href="${servletDemo1}">超連接(get方式請求)</a> 18 <hr/> 19 <%--使用post方式提交表單 --%> 20 <form action="${pageContext.request.contextPath}/servlet/ServletDemo1" method="post"> 21 用戶名：<input type="text" name="username" value="孤傲蒼狼" /> 22 <input type="submit" value="post方式提交"> 23 </form> 24 25 </body> 26 </html>

　　編寫處理用戶請求的ServletDemo1

 1 package me.gacl.web.controller;  2  3 import java.io.IOException;  4 import java.io.PrintWriter;  5  6 import javax.servlet.ServletException;  7 import javax.servlet.http.HttpServlet;  8 import javax.servlet.http.HttpServletRequest;  9 import javax.servlet.http.HttpServletResponse; 10 11 public class ServletDemo1 extends HttpServlet { 12 13 public void doGet(HttpServletRequest request, HttpServletResponse response) 14 throws ServletException, IOException { 15 //接收參數 16 String username = request.getParameter("username"); 17 //獲取請求方式 18 String method = request.getMethod(); 19 //獲取輸出流 20 PrintWriter out = response.getWriter(); 21 out.write("請求的方式："+method); 22 out.write("<br/>"); 23 out.write("接收到的參數："+username); 24  } 25 26 public void doPost(HttpServletRequest request, HttpServletResponse response) 27 throws ServletException, IOException { 28  doGet(request, response); 29  } 30 31 }

　　測試結果以下：

　　從運行結果中能夠看到，不管是get請求方式仍是post請求方式，中文亂碼問題均可以完美解決了。

2.二、使用Decorator模式包裝request對象實現html標籤轉義功能

　　編寫一個html轉義過濾器，代碼以下：

  1 package me.gacl.web.filter;  2  3 import java.io.IOException;  4  5 import javax.servlet.Filter;  6 import javax.servlet.FilterChain;  7 import javax.servlet.FilterConfig;  8 import javax.servlet.ServletException;  9 import javax.servlet.ServletRequest;  10 import javax.servlet.ServletResponse;  11 import javax.servlet.http.HttpServletRequest;  12 import javax.servlet.http.HttpServletRequestWrapper;  13 import javax.servlet.http.HttpServletResponse;  14  15 /**  16 * @ClassName: HtmlFilter  17 * @Description: html轉義過濾器  18 * @author: 孤傲蒼狼  19 * @date: 2014-9-2 下午11:28:41  20 *  21 */  22 public class HtmlFilter implements Filter {  23  24 public void doFilter(ServletRequest req, ServletResponse resp,  25 FilterChain chain) throws IOException, ServletException {  26  27 HttpServletRequest request = (HttpServletRequest) req;  28 HttpServletResponse response = (HttpServletResponse) resp;  29  30 MyHtmlRequest myrequest = new MyHtmlRequest(request);  31  chain.doFilter(myrequest, response);  32  33  }  34  35  36 public void destroy() {  37  38  }  39  40  41 public void init(FilterConfig filterConfig) throws ServletException {  42  43  }  44 }  45  46 /**  47 * @ClassName: MyHtmlRequest  48 * @Description: 使用Decorator模式包裝request對象，實現html標籤轉義功能  49 * @author: 孤傲蒼狼  50 * @date: 2014-9-2 下午11:29:09  51 *  52 */  53 class MyHtmlRequest extends HttpServletRequestWrapper {  54  55 private HttpServletRequest request;  56  57 public MyHtmlRequest(HttpServletRequest request) {  58 super(request);  59 this.request = request;  60  }  61  62 /* 覆蓋須要加強的getParameter方法  63  * @see javax.servlet.ServletRequestWrapper#getParameter(java.lang.String)  64 */  65  @Override  66 public String getParameter(String name) {  67 String value = this.request.getParameter(name);  68 if (value == null) {  69 return null;  70  }  71 //調用filter轉義value中的html標籤  72 return filter(value);  73  }  74  75 /**  76  * @Method: filter  77  * @Description: 過濾內容中的html標籤  78  * @Anthor:孤傲蒼狼  79  * @param message  80  * @return  81 */  82 public String filter(String message) {  83 if (message == null){  84 return null; 85 } 86 char content[] = new char[message.length()]; 87 message.getChars(0, message.length(), content, 0); 88 StringBuffer result = new StringBuffer(content.length + 50); 89 for (int i = 0; i < content.length; i++) { 90 switch (content[i]) { 91 case '<': 92 result.append("&lt;"); 93 break; 94 case '>': 95 result.append("&gt;"); 96 break; 97 case '&': 98 result.append("&amp;"); 99 break; 100 case '"': 101 result.append("&quot;"); 102 break; 103 default: 104 result.append(content[i]); 105 } 106 } 107 return result.toString(); 108 } 109 }

　　在web.xml文件中配置HtmlFilter

 1 <!--配置Html過濾器，轉義內容中的html標籤-->  2 <filter>  3 <filter-name>HtmlFilter</filter-name>  4 <filter-class>me.gacl.web.filter.HtmlFilter</filter-class>  5 </filter>  6  7 <filter-mapping>  8 <filter-name>HtmlFilter</filter-name>  9 <url-pattern>/*</url-pattern> 10 </filter-mapping>

　　編寫jsp測試頁面，以下：

 1 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>  2 <!DOCTYPE HTML>  3 <html>  4 <head>  5 <title>html過濾器測試</title>  6 </head>  7  8 <body>  9 <form action="${pageContext.request.contextPath}/servlet/ServletDemo2" method="post"> 10  留言: 11 <textarea rows="8" cols="70" name="message"> 12 <script type="text/javascript"> 13 while(true){ 14  alert("死循環了，我會不停地彈出了"); 15  } 16 </script> 17 <a href="http://www.cnblogs.com">訪問博客園</a> 18 </textarea> 19 <input type="submit" value="發表"> 20 </form> 21 </body> 22 </html>

　　編寫處理用戶請求的ServletDemo2

 1 package me.gacl.web.controller;  2  3 import java.io.IOException;  4  5 import javax.servlet.ServletException;  6 import javax.servlet.http.HttpServlet;  7 import javax.servlet.http.HttpServletRequest;  8 import javax.servlet.http.HttpServletResponse;  9 10 public class ServletDemo2 extends HttpServlet { 11 12 public void doGet(HttpServletRequest request, HttpServletResponse response) 13 throws ServletException, IOException { 14 //獲取用戶輸入的內容 15 String message = request.getParameter("message"); 16 response.getWriter().write("您上次的留言是：<br/>" + message); 17  } 18 19 public void doPost(HttpServletRequest request, HttpServletResponse response) 20 throws ServletException, IOException { 21  doGet(request, response); 22  } 23 }

測試結果以下：

　　從運行結果中能夠看到，全部的html標籤都被轉義輸出了。

2.三、使用Decorator模式包裝request對象實現敏感字符過濾功能

　　編寫一個敏感字符過濾器，代碼以下：

  1 package me.gacl.web.filter;  2  3 import java.io.BufferedReader;  4 import java.io.IOException;  5 import java.io.InputStream;  6 import java.io.InputStreamReader;  7 import java.io.UnsupportedEncodingException;  8 import java.util.ArrayList;  9 import java.util.List;  10 import javax.servlet.Filter;  11 import javax.servlet.FilterChain;  12 import javax.servlet.FilterConfig;  13 import javax.servlet.ServletException;  14 import javax.servlet.ServletRequest;  15 import javax.servlet.ServletResponse;  16 import javax.servlet.http.HttpServletRequest;  17 import javax.servlet.http.HttpServletRequestWrapper;  18 import javax.servlet.http.HttpServletResponse;  19  20 /**  21 * @ClassName: DirtyFilter  22 * @Description: 敏感詞過濾器  23 * @author: 孤傲蒼狼  24 * @date: 2014-9-6 上午10:43:11  25 *  26 */  27 public class DirtyFilter implements Filter {  28  29 private FilterConfig config = null;  30  31  @Override  32 public void init(FilterConfig filterConfig) throws ServletException {  33 this.config = filterConfig;  34  }  35  36  @Override  37 public void doFilter(ServletRequest req, ServletResponse resp,  38 FilterChain chain) throws IOException, ServletException {  39  40 HttpServletRequest request = (HttpServletRequest) req;  41 HttpServletResponse response = (HttpServletResponse) resp;  42 DirtyRequest dirtyrequest = new DirtyRequest(request);  43  44  chain.doFilter(dirtyrequest, response);  45  }  46  47  @Override  48 public void destroy() {  49  50  }  51  52 /**  53  * @Method: getDirtyWords  54  * @Description: 獲取敏感字符  55  * @Anthor:孤傲蒼狼  56  *  57  * @return  58 */  59 private List<String> getDirtyWords(){  60 List<String> dirtyWords = new ArrayList<String>();  61 String dirtyWordPath = config.getInitParameter("dirtyWord");  62 InputStream inputStream = config.getServletContext().getResourceAsStream(dirtyWordPath);  63 InputStreamReader is = null;  64 try {  65 is = new InputStreamReader(inputStream,"UTF-8");  66 } catch (UnsupportedEncodingException e2) {  67  e2.printStackTrace();  68  }  69 BufferedReader reader = new BufferedReader(is);  70  String line;  71 try {  72 while ((line = reader.readLine())!= null) {//若是 line爲空說明讀完了  73  dirtyWords.add(line);  74  }  75 } catch (IOException e) {  76  e.printStackTrace();  77  }  78 return dirtyWords;  79  }  80  81 /** 82 * @ClassName: DirtyRequest 83 * @Description: 使用Decorator模式包裝request對象，實現敏感字符過濾功能 84 * @author: 孤傲蒼狼 85 * @date: 2014-9-6 上午11:56:35 86 * 87 */ 88 class DirtyRequest extends HttpServletRequestWrapper{ 89 90 private List<String> dirtyWords = getDirtyWords(); 91 private HttpServletRequest request; 92 public DirtyRequest(HttpServletRequest request) { 93 super(request); 94 this.request = request; 95 } 96 /* 重寫getParameter方法，實現對敏感字符的過濾 97 * @see javax.servlet.ServletRequestWrapper#getParameter(java.lang.String) 98 */ 99 @Override 100 public String getParameter(String name) { 101 102 String value = this.request.getParameter(name); 103 if(value==null){ 104 return null; 105 } 106 107 for(String dirtyWord : dirtyWords){ 108 if(value.contains(dirtyWord)){ 109 System.out.println("內容中包含敏感詞："+dirtyWord+"，將會被替換成****"); 110 //替換敏感字符 111 value = value.replace(dirtyWord, "****"); 112 } 113 } 114 return value; 115 } 116 } 117 }

　　在web.xml文件中配置DirtyFilter

 1  <!--配置敏感字符過濾器-->  2 <filter>  3 <filter-name>DirtyFilter</filter-name>  4 <filter-class>me.gacl.web.filter.DirtyFilter</filter-class>  5 <!-- 配置要過濾的敏感字符文件 -->  6 <init-param>  7 <param-name>dirtyWord</param-name>  8 <param-value>/WEB-INF/DirtyWord.txt</param-value>  9 </init-param> 10 </filter> 11 12 <filter-mapping> 13 <filter-name>DirtyFilter</filter-name> 14 <url-pattern>/*</url-pattern> 15 </filter-mapping>

　　當用戶填寫的內容包含一些敏感字符時，在DirtyFilter過濾器中就會將這些敏感字符替換掉。

　　咱們若是將上述的CharacterEncodingFilter、HtmlFilter、DirtyFilter這三個過濾器聯合起來使用，那麼就至關因而把request對象包裝了3次，request對象的getParameter方法通過3次重寫，使得getParameter方法的功能大大加強，能夠同時解決中文亂碼，html標籤轉義，敏感字符過濾這些需求。

　　在實際開發中徹底能夠將上述的三個過濾器合併成一個，讓合併後的過濾器具備解決中文亂碼，html標籤轉義，敏感字符過濾這些功能，例如：

  1 package me.gacl.web.filter;  2  3 import java.io.BufferedReader;  4 import java.io.IOException;  5 import java.io.InputStream;  6 import java.io.InputStreamReader;  7 import java.io.UnsupportedEncodingException;  8 import java.util.ArrayList;  9 import java.util.List;  10  11 import javax.servlet.Filter;  12 import javax.servlet.FilterChain;  13 import javax.servlet.FilterConfig;  14 import javax.servlet.ServletException;  15 import javax.servlet.ServletRequest;  16 import javax.servlet.ServletResponse;  17 import javax.servlet.http.HttpServletRequest;  18 import javax.servlet.http.HttpServletRequestWrapper;  19 import javax.servlet.http.HttpServletResponse;  20  21 /**  22 * @ClassName: AdvancedFilter  23 * @Description: 這個過濾器是用來解決中文亂碼，轉義內容中的html標籤，過濾內容中的敏感字符的  24 * @author: 孤傲蒼狼  25 * @date: 2014-9-6 下午6:17:37  26 *  27 */  28 public class AdvancedFilter implements Filter {  29  30 private FilterConfig filterConfig = null;  31 //設置默認的字符編碼  32 private String defaultCharset = "UTF-8";  33  34  @Override  35 public void init(FilterConfig filterConfig) throws ServletException {  36 //獲得過濾器的初始化配置信息  37 this.filterConfig = filterConfig;  38  }  39  40  @Override  41 public void doFilter(ServletRequest req, ServletResponse resp,  42 FilterChain chain) throws IOException, ServletException {  43 HttpServletRequest request = (HttpServletRequest) req;  44 HttpServletResponse response = (HttpServletResponse) resp;  45 //獲得在web.xml中配置的字符編碼  46 String charset = filterConfig.getInitParameter("charset");  47 if(charset==null){  48 charset = defaultCharset;  49  }  50  request.setCharacterEncoding(charset);  51  response.setCharacterEncoding(charset);  52 response.setContentType("text/html;charset="+charset);  53  54 AdvancedRequest requestWrapper = new AdvancedRequest(request);  55  chain.doFilter(requestWrapper, response);  56  }  57  58  @Override  59 public void destroy() {  60  61  }  62  63 class AdvancedRequest extends HttpServletRequestWrapper{  64  65 private List<String> dirtyWords = getDirtyWords();  66  67 //定義一個變量記住被加強對象(request對象是須要被加強的對象)  68 private HttpServletRequest request;  69 //定義一個構造函數，接收被加強對象  70 public AdvancedRequest(HttpServletRequest request) {  71 super(request);  72 this.request = request;  73  }  74 /* 覆蓋須要加強的getParameter方法  75  * @see javax.servlet.ServletRequestWrapper#getParameter(java.lang.String)  76 */  77  @Override  78 public String getParameter(String name) {  79 try{ 80 //獲取參數的值 81 String value= this.request.getParameter(name); 82 if(value==null){ 83 return null; 84 } 85 //若是不是以get方式提交數據的，就直接返回獲取到的值 86 if(!this.request.getMethod().equalsIgnoreCase("get")) { 87 //調用filter轉義value中的html標籤 88 value= filter(value); 89 }else{ 90 //若是是以get方式提交數據的，就對獲取到的值進行轉碼處理 91 value = new String(value.getBytes("ISO8859-1"),this.request.getCharacterEncoding()); 92 //調用filter轉義value中的html標籤 93 value= filter(value); 94 } 95 96 for(String dirtyWord : dirtyWords){ 97 if(value.contains(dirtyWord)){ 98 System.out.println("內容中包含敏感詞："+dirtyWord+"，將會被替換成****"); 99 //替換敏感字符 100 value = value.replace(dirtyWord, "****"); 101 } 102 } 103 return value; 104 }catch (Exception e) { 105 throw new RuntimeException(e); 106 } 107 } 108 } 109 110 /** 111 * @Method: filter 112 * @Description: 過濾內容中的html標籤 113 * @Anthor:孤傲蒼狼 114 * @param value 115 * @return 116 */ 117 public String filter(String value) { 118 if (value == null){ 119 return null; 120 } 121 char content[] = new char[value.length()]; 122 value.getChars(0, value.length(), content, 0); 123 StringBuffer result = new StringBuffer(content.length + 50); 124 for (int i = 0; i < content.length; i++) { 125 switch (content[i]) { 126 case '<': 127 result.append("&lt;"); 128 break; 129 case '>': 130 result.append("&gt;"); 131 break; 132 case '&': 133 result.append("&amp;"); 134 break; 135 case '"': 136 result.append("&quot;"); 137 break; 138 default: 139 result.append(content[i]); 140 } 141 } 142 return (result.toString()); 143 } 144 145 /** 146 * @Method: getDirtyWords 147 * @Description: 獲取敏感字符 148 * @Anthor:孤傲蒼狼 149 * 150 * @return 151 */ 152 private List<String> getDirtyWords(){ 153 List<String> dirtyWords = new ArrayList<String>(); 154 String dirtyWordPath = filterConfig.getInitParameter("dirtyWord"); 155 InputStream inputStream = filterConfig.getServletContext().getResourceAsStream(dirtyWordPath); 156 InputStreamReader is = null; 157 try { 158 is = new InputStreamReader(inputStream,defaultCharset); 159 } catch (UnsupportedEncodingException e2) { 160 e2.printStackTrace(); 161 } 162 BufferedReader reader = new BufferedReader(is); 163 String line; 164 try { 165 while ((line = reader.readLine())!= null) {//若是 line爲空說明讀完了 166 dirtyWords.add(line); 167 } 168 } catch (IOException e) { 169 e.printStackTrace(); 170 } 171 return dirtyWords; 172 } 173 }

　　在web.xml文件中配置AdvancedFilter

 1   <filter>  2 <filter-name>AdvancedFilter</filter-name>  3 <filter-class>me.gacl.web.filter.AdvancedFilter</filter-class>  4 <init-param>  5 <param-name>charset</param-name>  6 <param-value>UTF-8</param-value>  7 </init-param>  8 <init-param>  9 <param-name>dirtyWord</param-name> 10 <param-value>/WEB-INF/DirtyWord.txt</param-value> 11 </init-param> 12 </filter> 13 14 <filter-mapping> 15 <filter-name>AdvancedFilter</filter-name> 16 <url-pattern>/*</url-pattern> 17 </filter-mapping>

　　AdvancedFilter過濾器同時具備解決中文亂碼，轉義內容中的html標籤，過濾內容中的敏感字符這些功能。

3、使用Decorator設計模式加強response對象

　　Servlet API 中提供了response對象的Decorator設計模式的默認實現類HttpServletResponseWrapper ，HttpServletResponseWrapper類實現了response接口中的全部方法，但這些方法的內部實現都是僅僅調用了一下所包裝的的 response對象的對應方法，以免用戶在對response對象進行加強時須要實現response接口中的全部方法。

3.一、response加強案例——壓縮響應正文內容

　　應用HttpServletResponseWrapper對象，壓縮響應正文內容。

　　具體思路:經過filter向目標頁面傳遞一個自定義的response對象。在自定義的response對象中，重寫getOutputStream方法和getWriter方法，使目標資源調用此方法輸出頁面內容時，得到的是咱們自定義的ServletOutputStream對象。在咱們自定義的ServletOuputStream對象中，重寫write方法，使寫出的數據寫出到一個buffer中。當頁面完成輸出後，在filter中就可獲得頁面寫出的數據，從而咱們能夠調用GzipOuputStream對數據進行壓縮後再寫出給瀏覽器，以此完成響應正文件壓縮功能。

　　編寫壓縮過濾器，代碼以下：

  1 package me.gacl.web.filter;  2  3 import java.io.ByteArrayOutputStream;  4 import java.io.IOException;  5 import java.io.OutputStreamWriter;  6 import java.io.PrintWriter;  7 import java.util.zip.GZIPOutputStream;  8  9 import javax.servlet.Filter;  10 import javax.servlet.FilterChain;  11 import javax.servlet.FilterConfig;  12 import javax.servlet.ServletException;  13 import javax.servlet.ServletOutputStream;  14 import javax.servlet.ServletRequest;  15 import javax.servlet.ServletResponse;  16 import javax.servlet.http.HttpServletRequest;  17 import javax.servlet.http.HttpServletResponse;  18 import javax.servlet.http.HttpServletResponseWrapper;  19  20 /**  21 * @ClassName: GzipFilter  22 * @Description: 壓縮過濾器，將web應用中的文本都通過壓縮後再輸出到瀏覽器  23 * @author: 孤傲蒼狼  24 * @date: 2014-9-7 上午10:52:42  25 *  26 */  27 public class GzipFilter implements Filter {  28  29 public void doFilter(ServletRequest req, ServletResponse resp,  30 FilterChain chain) throws IOException, ServletException {  31  32 HttpServletRequest request = (HttpServletRequest) req;  33 HttpServletResponse response = (HttpServletResponse) resp;  34  35 BufferResponse myresponse = new BufferResponse(response);  36  chain.doFilter(request, myresponse);  37 //拿出緩存中的數據，壓縮後再打給瀏覽器  38 byte out[] = myresponse.getBuffer();  39 System.out.println("原始大小:" + out.length);  40  41 ByteArrayOutputStream bout = new ByteArrayOutputStream();  42 //壓縮輸出流中的數據  43 GZIPOutputStream gout = new GZIPOutputStream(bout);  44  gout.write(out);  45  gout.close();  46  47 byte gzip[] = bout.toByteArray();  48 System.out.println("壓縮後的大小:" + gzip.length);  49  50 response.setHeader("content-encoding", "gzip");  51  response.setContentLength(gzip.length);  52  response.getOutputStream().write(gzip);  53  }  54  55 public void destroy() {  56  57  }  58  59 public void init(FilterConfig filterConfig) throws ServletException {  60  61  }  62 }  63  64 class BufferResponse extends HttpServletResponseWrapper{  65  66 private ByteArrayOutputStream bout = new ByteArrayOutputStream();  67 private PrintWriter pw;  68 private HttpServletResponse response;  69 public BufferResponse(HttpServletResponse response) {  70 super(response);  71 this.response = response;  72  }  73  @Override  74 public ServletOutputStream getOutputStream() throws IOException {  75 return new MyServletOutputStream(bout);  76  }  77  @Override  78 public PrintWriter getWriter() throws IOException {  79 pw = new PrintWriter(new OutputStreamWriter(bout,this.response.getCharacterEncoding()));  80 return pw; 81 } 82 83 public byte[] getBuffer(){ 84 try{ 85 if(pw!=null){ 86 pw.close(); 87 } 88 if(bout!=null){ 89 bout.flush(); 90 return bout.toByteArray(); 91 } 92 93 94 return null; 95 }catch (Exception e) { 96 throw new RuntimeException(e); 97 } 98 } 99 } 100 101 class MyServletOutputStream extends ServletOutputStream{ 102 103 private ByteArrayOutputStream bout; 104 public MyServletOutputStream(ByteArrayOutputStream bout){ 105 this.bout = bout; 106 } 107 108 @Override 109 public void write(int b) throws IOException { 110 this.bout.write(b); 111 } 112 }

　　在web.xml中配置壓縮過濾器

 1  <filter>  2 <description>配置壓縮過濾器</description>  3 <filter-name>GzipFilter</filter-name>  4 <filter-class>me.gacl.web.filter.GzipFilter</filter-class>  5 </filter>  6  7 <!--jsp文件的輸出的內容都通過壓縮過濾器壓縮後才輸出 -->  8 <filter-mapping>  9 <filter-name>GzipFilter</filter-name> 10 <url-pattern>*.jsp</url-pattern> 11 <!-- 配置過濾器的攔截方式--> 12 <!-- 對於在Servlet中經過 13  request.getRequestDispatcher("jsp頁面路徑").forward(request, response) 14  方式訪問的Jsp頁面的要進行攔截 --> 15 <dispatcher>FORWARD</dispatcher> 16 <!--對於直接以URL方式訪問的jsp頁面進行攔截，過濾器的攔截方式默認就是 REQUEST--> 17 <dispatcher>REQUEST</dispatcher> 18 </filter-mapping> 19 <!--js文件的輸出的內容都通過壓縮過濾器壓縮後才輸出 --> 20 <filter-mapping> 21 <filter-name>GzipFilter</filter-name> 22 <url-pattern>*.js</url-pattern> 23 </filter-mapping> 24 <!--css文件的輸出的內容都通過壓縮過濾器壓縮後才輸出 --> 25 <filter-mapping> 26 <filter-name>GzipFilter</filter-name> 27 <url-pattern>*.css</url-pattern> 28 </filter-mapping> 29 <!--html文件的輸出的內容都通過壓縮過濾器壓縮後才輸出 --> 30 <filter-mapping> 31 <filter-name>GzipFilter</filter-name> 32 <url-pattern>*.html</url-pattern> 33 </filter-mapping>

3.二、response加強案例——緩存數據到內存

　　對於頁面中不多更新的數據，例如商品分類，爲避免每次都要從數據庫查詢分類數據，所以可把分類數據緩存在內存或文件中，以此來減輕數據庫壓力，提升系統響應速度。

　　編寫緩存數據的過濾器，代碼以下：

  1 package me.gacl.web.filter;  2  3 import java.io.ByteArrayOutputStream;  4 import java.io.IOException;  5 import java.io.OutputStreamWriter;  6 import java.io.PrintWriter;  7 import java.util.HashMap;  8 import java.util.Map;  9  10 import javax.servlet.Filter;  11 import javax.servlet.FilterChain;  12 import javax.servlet.FilterConfig;  13 import javax.servlet.ServletException;  14 import javax.servlet.ServletOutputStream;  15 import javax.servlet.ServletRequest;  16 import javax.servlet.ServletResponse;  17 import javax.servlet.http.HttpServletRequest;  18 import javax.servlet.http.HttpServletResponse;  19 import javax.servlet.http.HttpServletResponseWrapper;  20  21 /**  22 * @ClassName: WebResourceCachedFilter  23 * @Description: Web資源緩存過濾器  24 * @author: 孤傲蒼狼  25 * @date: 2014-9-8 上午12:20:16  26 *  27 */  28 public class WebResourceCachedFilter implements Filter {  29 /**  30  * @Field: map  31  * 緩存Web資源的Map容器  32 */  33 private Map<String,byte[]> map = new HashMap<String,byte[]>();  34  35  @Override  36 public void init(FilterConfig filterConfig) throws ServletException {  37  38  }  39  40  @Override  41 public void doFilter(ServletRequest req, ServletResponse resp,  42 FilterChain chain) throws IOException, ServletException {  43 HttpServletRequest request = (HttpServletRequest) req;  44 HttpServletResponse response = (HttpServletResponse) resp;  45 //1.獲得用戶請求的uri  46 String uri = request.getRequestURI();  47 //2.看緩存中有沒有uri對應的數據  48 byte b[] = map.get(uri);  49 //3.若是緩存中有，直接拿緩存的數據打給瀏覽器，程序返回  50 if(b!=null){  51 //根據字節數組和指定的字符編碼構建字符串  52 String webResourceHtmlStr = new String(b,response.getCharacterEncoding());  53  System.out.println(webResourceHtmlStr);  54  response.getOutputStream().write(b);  55 return;  56  }  57 //4.若是緩存沒有，讓目標資源執行，並捕獲目標資源的輸出  58 BufferResponse myresponse = new BufferResponse(response);  59  chain.doFilter(request, myresponse);  60 //獲取緩衝流中的內容的字節數組  61 byte out[] = myresponse.getBuffer();  62 //5.把資源的數據以用戶請求的uri爲關鍵字保存到緩存中  63  map.put(uri, out);  64 //6.把數據打給瀏覽器  65  response.getOutputStream().write(out);  66  }  67  68  @Override  69 public void destroy() {  70  71  }  72  73 class BufferResponse extends HttpServletResponseWrapper{  74 private ByteArrayOutputStream bout = new ByteArrayOutputStream(); //捕獲輸出的緩存  75 private PrintWriter pw;  76 private HttpServletResponse response; 77 public BufferResponse(HttpServletResponse response) { 78 super(response); 79 this.response = response; 80 } 81 @Override 82 public ServletOutputStream getOutputStream() throws IOException { 83 return new MyServletOutputStream(bout); 84 } 85 @Override 86 public PrintWriter getWriter() throws IOException { 87 pw = new PrintWriter(new OutputStreamWriter(bout,this.response.getCharacterEncoding())); 88 return pw; 89 } 90 91 public byte[] getBuffer(){ 92 try{ 93 if(pw!=null){ 94 pw.close(); 95 } 96 return bout.toByteArray(); 97 }catch (Exception e) { 98 throw new RuntimeException(e); 99 } 100 } 101 } 102 103 class MyServletOutputStream extends ServletOutputStream{ 104 private ByteArrayOutputStream bout; 105 public MyServletOutputStream(ByteArrayOutputStream bout){ //接收數據寫到哪裏 106 this.bout = bout; 107 } 108 @Override 109 public void write(int b) throws IOException { 110 bout.write(b); 111 } 112 } 113 }

　　在web.xml中配置Web資源緩存過濾器

 1   <filter>  2 <description>Web資源緩存過濾器</description>  3 <filter-name>WebResourceCachedFilter</filter-name>  4 <filter-class>me.gacl.web.filter.WebResourceCachedFilter</filter-class>  5 </filter>  6  7 <filter-mapping>  8 <filter-name>WebResourceCachedFilter</filter-name>  9 <!-- 映射須要緩存輸出的JSP頁面，這幾個頁面都只是單純做爲輸入UI，不會有太多的變化，所以能夠緩存輸出 --> 10 <url-pattern>/login.jsp</url-pattern> 11 <url-pattern>/test.jsp</url-pattern> 12 <url-pattern>/test2.jsp</url-pattern> 13 </filter-mapping>

javaweb學習總結(四十三)——Filter高級開發

　　在filter中能夠獲得表明用戶請求和響應的request、response對象，所以在編程中可使用Decorator(裝飾器)模式對request、response對象進行包裝，再把包裝對象傳給目標資源，從而實現一些特殊需求。

1、Decorator設計模式

1.一、Decorator設計模式介紹

　　當某個對象的方法不適應業務需求時，一般有2種方式能夠對方法進行加強：

編寫子類，覆蓋需加強的方法。
使用Decorator設計模式對方法進行加強。

1.二、Decorator設計模式的實現

　　1.首先看須要被加強對象繼承了什麼接口或父類，編寫一個類也去繼承這些接口或父類。
　　2.在類中定義一個變量，變量類型即需加強對象的類型。
　　3.在類中定義一個構造函數，接收需加強的對象。
　　4.覆蓋需加強的方法，編寫加強的代碼。

2、使用Decorator設計模式加強request對象

2.一、使用Decorator模式包裝request對象解決get和post請求方式下的中文亂碼問題

　　編寫一個用於處理中文亂碼的過濾器CharacterEncodingFilter，代碼以下：

  1 package me.gacl.web.filter;
  2 
  3 import java.io.IOException;
  4 
  5 import javax.servlet.Filter;
  6 import javax.servlet.FilterChain;
  7 import javax.servlet.FilterConfig;
  8 import javax.servlet.ServletException;
  9 import javax.servlet.ServletRequest;
 10 import javax.servlet.ServletResponse;
 11 import javax.servlet.http.HttpServletRequest;
 12 import javax.servlet.http.HttpServletRequestWrapper;
 13 import javax.servlet.http.HttpServletResponse;
 14 
 15 /**
 16 * @ClassName: CharacterEncodingFilter
 17 * @Description: 此過濾器用來解決解決get、post請求方式下的中文亂碼問題
 18 * @author: 孤傲蒼狼
 19 * @date: 2014-8-31 下午11:09:37
 20 *
 21 */ 
 22 public class CharacterEncodingFilter implements Filter {
 23 
 24     private FilterConfig filterConfig = null;
 25     //設置默認的字符編碼
 26     private String defaultCharset = "UTF-8";
 27 
 28     public void doFilter(ServletRequest req, ServletResponse resp,
 29             FilterChain chain) throws IOException, ServletException {
 30         
 31         HttpServletRequest request = (HttpServletRequest) req;
 32         HttpServletResponse response = (HttpServletResponse) resp;
 33         //獲得在web.xml中配置的字符編碼
 34         String charset = filterConfig.getInitParameter("charset");
 35         if(charset==null){
 36             charset = defaultCharset;
 37         }
 38         request.setCharacterEncoding(charset);
 39         response.setCharacterEncoding(charset);
 40         response.setContentType("text/html;charset="+charset);
 41         
 42         MyCharacterEncodingRequest requestWrapper = new MyCharacterEncodingRequest(request);
 43         chain.doFilter(requestWrapper, response);
 44     }
 45 
 46     public void init(FilterConfig filterConfig) throws ServletException {
 47         //獲得過濾器的初始化配置信息
 48         this.filterConfig = filterConfig;
 49     }
 50     
 51     public void destroy() {
 52 
 53     }
 54 }
 55 
 56 /**
 57 * @ClassName: MyCharacterEncodingRequest
 58 * @Description: Servlet API中提供了一個request對象的Decorator設計模式的默認實現類HttpServletRequestWrapper,
 59 * (HttpServletRequestWrapper類實現了request接口中的全部方法，但這些方法的內部實現都是僅僅調用了一下所包裝的的 request對象的對應方法)
 60 * 以免用戶在對request對象進行加強時須要實現request接口中的全部方法。
 61 * 因此當須要加強request對象時，只須要寫一個類繼承HttpServletRequestWrapper類，而後在重寫須要加強的方法便可
 62 * @author: 孤傲蒼狼
 63 * @date: 2014-9-2 下午10:42:57
 64 *     1.實現與被加強對象相同的接口 
 65     二、定義一個變量記住被加強對象
 66     三、定義一個構造函數，接收被加強對象
 67     四、覆蓋須要加強的方法
 68     五、對於不想加強的方法，直接調用被加強對象（目標對象）的方法
 69 */ 
 70 class MyCharacterEncodingRequest extends HttpServletRequestWrapper{
 71     //定義一個變量記住被加強對象(request對象是須要被加強的對象)
 72     private HttpServletRequest request;
 73     //定義一個構造函數，接收被加強對象
 74     public MyCharacterEncodingRequest(HttpServletRequest request) {
 75         super(request);
 76         this.request = request;
 77     }
 78     /* 覆蓋須要加強的getParameter方法
 79      * @see javax.servlet.ServletRequestWrapper#getParameter(java.lang.String)
 80      */
 81     @Override
 82     public String getParameter(String name) {
 83         try{
 84             //獲取參數的值
 85             String value= this.request.getParameter(name);
 86             if(value==null){
 87                 return null;
 88             }
 89             //若是不是以get方式提交數據的，就直接返回獲取到的值
 90             if(!this.request.getMethod().equalsIgnoreCase("get")) {
 91                 return value;
 92             }else{
 93                 //若是是以get方式提交數據的，就對獲取到的值進行轉碼處理
 94                 value = new String(value.getBytes("ISO8859-1"),this.request.getCharacterEncoding());
 95                 return value;
 96             }
 97         }catch (Exception e) {
 98             throw new RuntimeException(e);
 99         }
100     }
101 }

　　在web.xml文件中配置CharacterEncodingFilter

 1 <!--配置字符過濾器，解決get、post請求方式下的中文亂碼問題-->
 2   <filter>
 3       <filter-name>CharacterEncodingFilter</filter-name>
 4       <filter-class>me.gacl.web.filter.CharacterEncodingFilter</filter-class>
 5   </filter>
 6   
 7   <filter-mapping>
 8       <filter-name>CharacterEncodingFilter</filter-name>
 9       <url-pattern>/*</url-pattern>
10   </filter-mapping>

　　編寫jsp測試頁面，以下：

 1 <%@ page language="java" pageEncoding="UTF-8"%>
 2 <%--引入jstl標籤庫 --%>
 3 <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
 4 <!DOCTYPE HTML>
 5 <html>
 6   <head>
 7     <title>使用字符過濾器解決解決get、post請求方式下的中文亂碼問題</title>
 8   </head>
 9   
10   <body>
11        <%--使用c:url標籤構建url，構建好的url存儲在servletDemo1變量中--%>
12        <c:url value="/servlet/ServletDemo1" scope="page" var="servletDemo1">
13            <%--構建的url的附帶的中文參數 ，參數名是：username，值是：孤傲蒼狼--%>
14            <c:param name="username" value="孤傲蒼狼"></c:param>
15        </c:url>
16       <%--使用get的方式訪問 --%>
17        <a href="${servletDemo1}">超連接(get方式請求)</a>
18        <hr/>
19        <%--使用post方式提交表單 --%>
20        <form action="${pageContext.request.contextPath}/servlet/ServletDemo1" method="post">
21            用戶名：<input type="text" name="username" value="孤傲蒼狼" />
22            <input type="submit" value="post方式提交">
23        </form>
24        
25   </body>
26 </html>

　　編寫處理用戶請求的ServletDemo1

 1 package me.gacl.web.controller;
 2 
 3 import java.io.IOException;
 4 import java.io.PrintWriter;
 5 
 6 import javax.servlet.ServletException;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 
11 public class ServletDemo1 extends HttpServlet {
12 
13     public void doGet(HttpServletRequest request, HttpServletResponse response)
14             throws ServletException, IOException {
15         //接收參數
16         String username = request.getParameter("username");
17         //獲取請求方式
18         String method = request.getMethod();
19         //獲取輸出流
20         PrintWriter out = response.getWriter();
21         out.write("請求的方式："+method);
22         out.write("<br/>");
23         out.write("接收到的參數："+username);
24     }
25 
26     public void doPost(HttpServletRequest request, HttpServletResponse response)
27             throws ServletException, IOException {
28         doGet(request, response);
29     }
30 
31 }

　　測試結果以下：

　　從運行結果中能夠看到，不管是get請求方式仍是post請求方式，中文亂碼問題均可以完美解決了。

2.二、使用Decorator模式包裝request對象實現html標籤轉義功能

　　編寫一個html轉義過濾器，代碼以下：

  1 package me.gacl.web.filter;
  2 
  3 import java.io.IOException;
  4 
  5 import javax.servlet.Filter;
  6 import javax.servlet.FilterChain;
  7 import javax.servlet.FilterConfig;
  8 import javax.servlet.ServletException;
  9 import javax.servlet.ServletRequest;
 10 import javax.servlet.ServletResponse;
 11 import javax.servlet.http.HttpServletRequest;
 12 import javax.servlet.http.HttpServletRequestWrapper;
 13 import javax.servlet.http.HttpServletResponse;
 14 
 15 /**
 16 * @ClassName: HtmlFilter
 17 * @Description: html轉義過濾器
 18 * @author: 孤傲蒼狼
 19 * @date: 2014-9-2 下午11:28:41
 20 *
 21 */ 
 22 public class HtmlFilter implements Filter {
 23 
 24     public void doFilter(ServletRequest req, ServletResponse resp,
 25             FilterChain chain) throws IOException, ServletException {
 26         
 27         HttpServletRequest request = (HttpServletRequest) req;
 28         HttpServletResponse response = (HttpServletResponse) resp;
 29 
 30         MyHtmlRequest myrequest = new MyHtmlRequest(request);
 31         chain.doFilter(myrequest, response);
 32         
 33     }
 34 
 35     
 36     public void destroy() {
 37         
 38     }
 39 
 40     
 41     public void init(FilterConfig filterConfig) throws ServletException {
 42         
 43     }
 44 }
 45 
 46 /**
 47 * @ClassName: MyHtmlRequest
 48 * @Description: 使用Decorator模式包裝request對象，實現html標籤轉義功能
 49 * @author: 孤傲蒼狼
 50 * @date: 2014-9-2 下午11:29:09
 51 *
 52 */ 
 53 class MyHtmlRequest extends HttpServletRequestWrapper {
 54 
 55     private HttpServletRequest request;
 56 
 57     public MyHtmlRequest(HttpServletRequest request) {
 58         super(request);
 59         this.request = request;
 60     }
 61 
 62     /* 覆蓋須要加強的getParameter方法
 63      * @see javax.servlet.ServletRequestWrapper#getParameter(java.lang.String)
 64      */
 65     @Override
 66     public String getParameter(String name) {
 67         String value = this.request.getParameter(name);
 68         if (value == null) {
 69             return null;
 70         }
 71         //調用filter轉義value中的html標籤
 72         return filter(value);
 73     }
 74 
 75     /**
 76     * @Method: filter
 77     * @Description: 過濾內容中的html標籤
 78     * @Anthor:孤傲蒼狼
 79     * @param message
 80     * @return
 81     */ 
 82     public String filter(String message) {
 83         if (message == null){
 84             return null;
 85         }
 86         char content[] = new char[message.length()];
 87         message.getChars(0, message.length(), content, 0);
 88         StringBuffer result = new StringBuffer(content.length + 50);
 89         for (int i = 0; i < content.length; i++) {
 90             switch (content[i]) {
 91             case '<':
 92                 result.append("&lt;");
 93                 break;
 94             case '>':
 95                 result.append("&gt;");
 96                 break;
 97             case '&':
 98                 result.append("&amp;");
 99                 break;
100             case '"':
101                 result.append("&quot;");
102                 break;
103             default:
104                 result.append(content[i]);
105             }
106         }
107         return result.toString();
108     }
109 }

　　在web.xml文件中配置HtmlFilter

 1 <!--配置Html過濾器，轉義內容中的html標籤-->
 2   <filter>
 3       <filter-name>HtmlFilter</filter-name>
 4       <filter-class>me.gacl.web.filter.HtmlFilter</filter-class>
 5   </filter>
 6   
 7   <filter-mapping>
 8       <filter-name>HtmlFilter</filter-name>
 9       <url-pattern>/*</url-pattern>
10   </filter-mapping>

　　編寫jsp測試頁面，以下：

 1 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
 2 <!DOCTYPE HTML>
 3 <html>
 4   <head>
 5     <title>html過濾器測試</title>
 6   </head>
 7   
 8   <body>
 9        <form action="${pageContext.request.contextPath}/servlet/ServletDemo2" method="post">
10            留言:
11            <textarea rows="8" cols="70" name="message">
12            <script type="text/javascript">
13            while(true){
14                alert("死循環了，我會不停地彈出了");
15            }
16            </script>
17         <a href="http://www.cnblogs.com">訪問博客園</a>
18            </textarea>
19            <input type="submit" value="發表">
20        </form>
21   </body>
22 </html>

　　編寫處理用戶請求的ServletDemo2

 1 package me.gacl.web.controller;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.ServletException;
 6 import javax.servlet.http.HttpServlet;
 7 import javax.servlet.http.HttpServletRequest;
 8 import javax.servlet.http.HttpServletResponse;
 9 
10 public class ServletDemo2 extends HttpServlet {
11 
12     public void doGet(HttpServletRequest request, HttpServletResponse response)
13             throws ServletException, IOException {
14         //獲取用戶輸入的內容
15         String message = request.getParameter("message");
16         response.getWriter().write("您上次的留言是：<br/>" + message);
17     }
18 
19     public void doPost(HttpServletRequest request, HttpServletResponse response)
20             throws ServletException, IOException {
21         doGet(request, response);
22     }
23 }

測試結果以下：

　　從運行結果中能夠看到，全部的html標籤都被轉義輸出了。

2.三、使用Decorator模式包裝request對象實現敏感字符過濾功能

　　編寫一個敏感字符過濾器，代碼以下：

  1 package me.gacl.web.filter;
  2 
  3 import java.io.BufferedReader;
  4 import java.io.IOException;
  5 import java.io.InputStream;
  6 import java.io.InputStreamReader;
  7 import java.io.UnsupportedEncodingException;
  8 import java.util.ArrayList;
  9 import java.util.List;
 10 import javax.servlet.Filter;
 11 import javax.servlet.FilterChain;
 12 import javax.servlet.FilterConfig;
 13 import javax.servlet.ServletException;
 14 import javax.servlet.ServletRequest;
 15 import javax.servlet.ServletResponse;
 16 import javax.servlet.http.HttpServletRequest;
 17 import javax.servlet.http.HttpServletRequestWrapper;
 18 import javax.servlet.http.HttpServletResponse;
 19 
 20 /**
 21 * @ClassName: DirtyFilter
 22 * @Description: 敏感詞過濾器
 23 * @author: 孤傲蒼狼
 24 * @date: 2014-9-6 上午10:43:11
 25 *
 26 */ 
 27 public class DirtyFilter implements Filter {
 28 
 29     private FilterConfig config = null;
 30     
 31     @Override
 32     public void init(FilterConfig filterConfig) throws ServletException {
 33         this.config = filterConfig;
 34     }
 35 
 36     @Override
 37     public void doFilter(ServletRequest req, ServletResponse resp,
 38             FilterChain chain) throws IOException, ServletException {
 39         
 40         HttpServletRequest request = (HttpServletRequest) req;
 41         HttpServletResponse response = (HttpServletResponse) resp;
 42         DirtyRequest dirtyrequest = new DirtyRequest(request);
 43         
 44         chain.doFilter(dirtyrequest, response);
 45     }
 46 
 47     @Override
 48     public void destroy() {
 49 
 50     }
 51     
 52     /**
 53     * @Method: getDirtyWords
 54     * @Description: 獲取敏感字符
 55     * @Anthor:孤傲蒼狼
 56     *
 57     * @return
 58     */ 
 59     private List<String> getDirtyWords(){
 60         List<String> dirtyWords = new ArrayList<String>();
 61         String dirtyWordPath = config.getInitParameter("dirtyWord");
 62         InputStream inputStream = config.getServletContext().getResourceAsStream(dirtyWordPath);
 63         InputStreamReader is = null;
 64         try {
 65             is = new InputStreamReader(inputStream,"UTF-8");
 66         } catch (UnsupportedEncodingException e2) {
 67             e2.printStackTrace();
 68         }
 69         BufferedReader reader = new BufferedReader(is);
 70         String line;
 71         try {
 72             while ((line = reader.readLine())!= null) {//若是 line爲空說明讀完了
 73                 dirtyWords.add(line);
 74             }
 75         } catch (IOException e) {
 76             e.printStackTrace();
 77         } 
 78         return dirtyWords;
 79     }
 80     
 81     /**
 82     * @ClassName: DirtyRequest
 83     * @Description: 使用Decorator模式包裝request對象，實現敏感字符過濾功能
 84     * @author: 孤傲蒼狼
 85     * @date: 2014-9-6 上午11:56:35
 86     *
 87     */ 
 88     class DirtyRequest extends HttpServletRequestWrapper{
 89 
 90         private List<String> dirtyWords = getDirtyWords();
 91         private HttpServletRequest request;
 92         public DirtyRequest(HttpServletRequest request) {
 93             super(request);
 94             this.request = request;
 95         }
 96         /* 重寫getParameter方法，實現對敏感字符的過濾
 97          * @see javax.servlet.ServletRequestWrapper#getParameter(java.lang.String)
 98          */
 99         @Override
100         public String getParameter(String name) {
101             
102             String value = this.request.getParameter(name);
103             if(value==null){
104                 return null;
105             }
106             
107             for(String dirtyWord : dirtyWords){
108                 if(value.contains(dirtyWord)){
109                     System.out.println("內容中包含敏感詞："+dirtyWord+"，將會被替換成****");
110                     //替換敏感字符
111                     value = value.replace(dirtyWord, "****");
112                 }
113             }
114             return value;
115         }
116     }
117 }

　　在web.xml文件中配置DirtyFilter

 1  <!--配置敏感字符過濾器-->
 2   <filter>
 3       <filter-name>DirtyFilter</filter-name>
 4       <filter-class>me.gacl.web.filter.DirtyFilter</filter-class>
 5       <!-- 配置要過濾的敏感字符文件 -->
 6       <init-param>
 7          <param-name>dirtyWord</param-name>    
 8          <param-value>/WEB-INF/DirtyWord.txt</param-value>
 9     </init-param>
10   </filter>
11   
12   <filter-mapping>
13       <filter-name>DirtyFilter</filter-name>
14       <url-pattern>/*</url-pattern>
15   </filter-mapping>

　　當用戶填寫的內容包含一些敏感字符時，在DirtyFilter過濾器中就會將這些敏感字符替換掉。

　　在實際開發中徹底能夠將上述的三個過濾器合併成一個，讓合併後的過濾器具備解決中文亂碼，html標籤轉義，敏感字符過濾這些功能，例如：

  1 package me.gacl.web.filter;
  2 
  3 import java.io.BufferedReader;
  4 import java.io.IOException;
  5 import java.io.InputStream;
  6 import java.io.InputStreamReader;
  7 import java.io.UnsupportedEncodingException;
  8 import java.util.ArrayList;
  9 import java.util.List;
 10 
 11 import javax.servlet.Filter;
 12 import javax.servlet.FilterChain;
 13 import javax.servlet.FilterConfig;
 14 import javax.servlet.ServletException;
 15 import javax.servlet.ServletRequest;
 16 import javax.servlet.ServletResponse;
 17 import javax.servlet.http.HttpServletRequest;
 18 import javax.servlet.http.HttpServletRequestWrapper;
 19 import javax.servlet.http.HttpServletResponse;
 20 
 21 /**
 22 * @ClassName: AdvancedFilter
 23 * @Description: 這個過濾器是用來解決中文亂碼，轉義內容中的html標籤，過濾內容中的敏感字符的
 24 * @author: 孤傲蒼狼
 25 * @date: 2014-9-6 下午6:17:37
 26 *
 27 */ 
 28 public class AdvancedFilter implements Filter {
 29 
 30     private FilterConfig filterConfig = null;
 31     //設置默認的字符編碼
 32     private String defaultCharset = "UTF-8";
 33     
 34     @Override
 35     public void init(FilterConfig filterConfig) throws ServletException {
 36         //獲得過濾器的初始化配置信息
 37         this.filterConfig = filterConfig;
 38     }
 39 
 40     @Override
 41     public void doFilter(ServletRequest req, ServletResponse resp,
 42             FilterChain chain) throws IOException, ServletException {
 43         HttpServletRequest request = (HttpServletRequest) req;
 44         HttpServletResponse response = (HttpServletResponse) resp;
 45         //獲得在web.xml中配置的字符編碼
 46         String charset = filterConfig.getInitParameter("charset");
 47         if(charset==null){
 48             charset = defaultCharset;
 49         }
 50         request.setCharacterEncoding(charset);
 51         response.setCharacterEncoding(charset);
 52         response.setContentType("text/html;charset="+charset);
 53         
 54         AdvancedRequest requestWrapper = new AdvancedRequest(request);
 55         chain.doFilter(requestWrapper, response);
 56     }
 57 
 58     @Override
 59     public void destroy() {
 60 
 61     }
 62 
 63     class AdvancedRequest extends HttpServletRequestWrapper{
 64         
 65         private List<String> dirtyWords = getDirtyWords();
 66         
 67         //定義一個變量記住被加強對象(request對象是須要被加強的對象)
 68         private HttpServletRequest request;
 69         //定義一個構造函數，接收被加強對象
 70         public AdvancedRequest(HttpServletRequest request) {
 71             super(request);
 72             this.request = request;
 73         }
 74         /* 覆蓋須要加強的getParameter方法
 75          * @see javax.servlet.ServletRequestWrapper#getParameter(java.lang.String)
 76          */
 77         @Override
 78         public String getParameter(String name) {
 79             try{
 80                 //獲取參數的值
 81                 String value= this.request.getParameter(name);
 82                 if(value==null){
 83                     return null;
 84                 }
 85                 //若是不是以get方式提交數據的，就直接返回獲取到的值
 86                 if(!this.request.getMethod().equalsIgnoreCase("get")) {
 87                     //調用filter轉義value中的html標籤
 88                     value= filter(value);
 89                 }else{
 90                     //若是是以get方式提交數據的，就對獲取到的值進行轉碼處理
 91                     value = new String(value.getBytes("ISO8859-1"),this.request.getCharacterEncoding());
 92                     //調用filter轉義value中的html標籤
 93                     value= filter(value);
 94                 }
 95                 
 96                 for(String dirtyWord : dirtyWords){
 97                     if(value.contains(dirtyWord)){
 98                         System.out.println("內容中包含敏感詞："+dirtyWord+"，將會被替換成****");
 99                         //替換敏感字符
100                         value = value.replace(dirtyWord, "****");
101                     }
102                 }
103                 return value;
104             }catch (Exception e) {
105                 throw new RuntimeException(e);
106             }
107         }
108     }
109 
110     /**
111     * @Method: filter
112     * @Description: 過濾內容中的html標籤
113     * @Anthor:孤傲蒼狼
114     * @param value
115     * @return
116     */ 
117     public String filter(String value) {
118         if (value == null){
119             return null;
120         }
121         char content[] = new char[value.length()];
122         value.getChars(0, value.length(), content, 0);
123         StringBuffer result = new StringBuffer(content.length + 50);
124         for (int i = 0; i < content.length; i++) {
125             switch (content[i]) {
126             case '<':
127                 result.append("&lt;");
128                 break;
129             case '>':
130                 result.append("&gt;");
131                 break;
132             case '&':
133                 result.append("&amp;");
134                 break;
135             case '"':
136                 result.append("&quot;");
137                 break;
138             default:
139                 result.append(content[i]);
140             }
141         }
142         return (result.toString());
143     }
144     
145     /**
146     * @Method: getDirtyWords
147     * @Description: 獲取敏感字符
148     * @Anthor:孤傲蒼狼
149     *
150     * @return
151     */ 
152     private List<String> getDirtyWords(){
153         List<String> dirtyWords = new ArrayList<String>();
154         String dirtyWordPath = filterConfig.getInitParameter("dirtyWord");
155         InputStream inputStream = filterConfig.getServletContext().getResourceAsStream(dirtyWordPath);
156         InputStreamReader is = null;
157         try {
158             is = new InputStreamReader(inputStream,defaultCharset);
159         } catch (UnsupportedEncodingException e2) {
160             e2.printStackTrace();
161         }
162         BufferedReader reader = new BufferedReader(is);
163         String line;
164         try {
165             while ((line = reader.readLine())!= null) {//若是 line爲空說明讀完了
166                 dirtyWords.add(line);
167             }
168         } catch (IOException e) {
169             e.printStackTrace();
170         } 
171         return dirtyWords;
172     }
173 }

　　在web.xml文件中配置AdvancedFilter

 1   <filter>
 2       <filter-name>AdvancedFilter</filter-name>
 3       <filter-class>me.gacl.web.filter.AdvancedFilter</filter-class>
 4       <init-param>
 5          <param-name>charset</param-name>    
 6          <param-value>UTF-8</param-value>
 7     </init-param>
 8       <init-param>
 9          <param-name>dirtyWord</param-name>    
10          <param-value>/WEB-INF/DirtyWord.txt</param-value>
11     </init-param>
12   </filter>
13   
14   <filter-mapping>
15       <filter-name>AdvancedFilter</filter-name>
16       <url-pattern>/*</url-pattern>
17   </filter-mapping>

　　AdvancedFilter過濾器同時具備解決中文亂碼，轉義內容中的html標籤，過濾內容中的敏感字符這些功能。

3、使用Decorator設計模式加強response對象

3.一、response加強案例——壓縮響應正文內容

　　應用HttpServletResponseWrapper對象，壓縮響應正文內容。

　　編寫壓縮過濾器，代碼以下：

  1 package me.gacl.web.filter;
  2 
  3 import java.io.ByteArrayOutputStream;
  4 import java.io.IOException;
  5 import java.io.OutputStreamWriter;
  6 import java.io.PrintWriter;
  7 import java.util.zip.GZIPOutputStream;
  8 
  9 import javax.servlet.Filter;
 10 import javax.servlet.FilterChain;
 11 import javax.servlet.FilterConfig;
 12 import javax.servlet.ServletException;
 13 import javax.servlet.ServletOutputStream;
 14 import javax.servlet.ServletRequest;
 15 import javax.servlet.ServletResponse;
 16 import javax.servlet.http.HttpServletRequest;
 17 import javax.servlet.http.HttpServletResponse;
 18 import javax.servlet.http.HttpServletResponseWrapper;
 19 
 20 /**
 21 * @ClassName: GzipFilter
 22 * @Description: 壓縮過濾器，將web應用中的文本都通過壓縮後再輸出到瀏覽器
 23 * @author: 孤傲蒼狼
 24 * @date: 2014-9-7 上午10:52:42
 25 *
 26 */ 
 27 public class GzipFilter implements Filter {
 28 
 29     public void doFilter(ServletRequest req, ServletResponse resp,
 30             FilterChain chain) throws IOException, ServletException {
 31         
 32         HttpServletRequest request = (HttpServletRequest) req;
 33         HttpServletResponse response = (HttpServletResponse) resp;
 34         
 35         BufferResponse myresponse = new BufferResponse(response);
 36         chain.doFilter(request, myresponse);
 37         //拿出緩存中的數據，壓縮後再打給瀏覽器
 38         byte out[] = myresponse.getBuffer();
 39         System.out.println("原始大小:" + out.length);
 40         
 41         ByteArrayOutputStream bout = new ByteArrayOutputStream();
 42         //壓縮輸出流中的數據
 43         GZIPOutputStream gout = new GZIPOutputStream(bout);
 44         gout.write(out);
 45         gout.close();
 46         
 47         byte gzip[] = bout.toByteArray();
 48         System.out.println("壓縮後的大小:" + gzip.length);
 49         
 50         response.setHeader("content-encoding", "gzip");
 51         response.setContentLength(gzip.length);
 52         response.getOutputStream().write(gzip);
 53     }
 54     
 55     public void destroy() {
 56         
 57     }
 58 
 59     public void init(FilterConfig filterConfig) throws ServletException {
 60         
 61     }
 62 }
 63 
 64 class BufferResponse extends HttpServletResponseWrapper{
 65 
 66     private ByteArrayOutputStream bout = new ByteArrayOutputStream();
 67     private PrintWriter pw;
 68     private HttpServletResponse response;
 69     public BufferResponse(HttpServletResponse response) {
 70         super(response);
 71         this.response = response;
 72     }
 73     @Override
 74     public ServletOutputStream getOutputStream() throws IOException {
 75         return new MyServletOutputStream(bout);
 76     }
 77     @Override
 78     public PrintWriter getWriter() throws IOException {
 79         pw = new PrintWriter(new OutputStreamWriter(bout,this.response.getCharacterEncoding()));
 80         return pw;
 81     }
 82     
 83     public byte[] getBuffer(){
 84         try{
 85             if(pw!=null){
 86                 pw.close();
 87             }
 88             if(bout!=null){
 89                 bout.flush();
 90                 return bout.toByteArray();
 91             }
 92             
 93             
 94             return null;
 95         }catch (Exception e) {
 96             throw new RuntimeException(e);
 97         }
 98     }
 99 }
100 
101 class MyServletOutputStream extends ServletOutputStream{
102 
103     private ByteArrayOutputStream bout;
104     public MyServletOutputStream(ByteArrayOutputStream bout){
105         this.bout = bout;
106     }
107     
108     @Override
109     public void write(int b) throws IOException {
110         this.bout.write(b);
111     }
112 }

　　在web.xml中配置壓縮過濾器

 1  <filter>
 2       <description>配置壓縮過濾器</description>
 3       <filter-name>GzipFilter</filter-name>
 4       <filter-class>me.gacl.web.filter.GzipFilter</filter-class>
 5   </filter>
 6   
 7   <!--jsp文件的輸出的內容都通過壓縮過濾器壓縮後才輸出 -->
 8   <filter-mapping>
 9       <filter-name>GzipFilter</filter-name>
10       <url-pattern>*.jsp</url-pattern>
11       <!-- 配置過濾器的攔截方式-->
12       <!-- 對於在Servlet中經過
13           request.getRequestDispatcher("jsp頁面路徑").forward(request, response) 
14       方式訪問的Jsp頁面的要進行攔截 -->
15       <dispatcher>FORWARD</dispatcher>
16       <!--對於直接以URL方式訪問的jsp頁面進行攔截，過濾器的攔截方式默認就是 REQUEST-->
17       <dispatcher>REQUEST</dispatcher>
18   </filter-mapping>
19   <!--js文件的輸出的內容都通過壓縮過濾器壓縮後才輸出 -->
20   <filter-mapping>
21       <filter-name>GzipFilter</filter-name>
22       <url-pattern>*.js</url-pattern>
23   </filter-mapping>
24   <!--css文件的輸出的內容都通過壓縮過濾器壓縮後才輸出 -->
25   <filter-mapping>
26       <filter-name>GzipFilter</filter-name>
27       <url-pattern>*.css</url-pattern>
28   </filter-mapping>
29   <!--html文件的輸出的內容都通過壓縮過濾器壓縮後才輸出 -->
30   <filter-mapping>
31       <filter-name>GzipFilter</filter-name>
32       <url-pattern>*.html</url-pattern>
33   </filter-mapping>

3.二、response加強案例——緩存數據到內存

　　編寫緩存數據的過濾器，代碼以下：

  1 package me.gacl.web.filter;
  2 
  3 import java.io.ByteArrayOutputStream;
  4 import java.io.IOException;
  5 import java.io.OutputStreamWriter;
  6 import java.io.PrintWriter;
  7 import java.util.HashMap;
  8 import java.util.Map;
  9 
 10 import javax.servlet.Filter;
 11 import javax.servlet.FilterChain;
 12 import javax.servlet.FilterConfig;
 13 import javax.servlet.ServletException;
 14 import javax.servlet.ServletOutputStream;
 15 import javax.servlet.ServletRequest;
 16 import javax.servlet.ServletResponse;
 17 import javax.servlet.http.HttpServletRequest;
 18 import javax.servlet.http.HttpServletResponse;
 19 import javax.servlet.http.HttpServletResponseWrapper;
 20 
 21 /**
 22 * @ClassName: WebResourceCachedFilter
 23 * @Description: Web資源緩存過濾器
 24 * @author: 孤傲蒼狼
 25 * @date: 2014-9-8 上午12:20:16
 26 *
 27 */ 
 28 public class WebResourceCachedFilter implements Filter {
 29     /**
 30     * @Field: map
 31     *          緩存Web資源的Map容器
 32     */ 
 33     private Map<String,byte[]> map = new HashMap<String,byte[]>();
 34     
 35     @Override
 36     public void init(FilterConfig filterConfig) throws ServletException {
 37 
 38     }
 39 
 40     @Override
 41     public void doFilter(ServletRequest req, ServletResponse resp,
 42             FilterChain chain) throws IOException, ServletException {
 43         HttpServletRequest request = (HttpServletRequest) req;
 44         HttpServletResponse response = (HttpServletResponse) resp;
 45         //1.獲得用戶請求的uri
 46         String uri = request.getRequestURI();
 47         //2.看緩存中有沒有uri對應的數據
 48         byte b[] = map.get(uri);
 49         //3.若是緩存中有，直接拿緩存的數據打給瀏覽器，程序返回
 50         if(b!=null){
 51             //根據字節數組和指定的字符編碼構建字符串
 52             String webResourceHtmlStr = new String(b,response.getCharacterEncoding());
 53             System.out.println(webResourceHtmlStr);
 54             response.getOutputStream().write(b);
 55             return;
 56         }
 57         //4.若是緩存沒有，讓目標資源執行，並捕獲目標資源的輸出
 58         BufferResponse myresponse = new BufferResponse(response);
 59         chain.doFilter(request, myresponse);
 60         //獲取緩衝流中的內容的字節數組
 61         byte out[] = myresponse.getBuffer();
 62         //5.把資源的數據以用戶請求的uri爲關鍵字保存到緩存中
 63         map.put(uri, out);
 64         //6.把數據打給瀏覽器
 65         response.getOutputStream().write(out);
 66     }
 67 
 68     @Override
 69     public void destroy() {
 70 
 71     }
 72 
 73     class BufferResponse extends HttpServletResponseWrapper{
 74         private ByteArrayOutputStream bout = new ByteArrayOutputStream();  //捕獲輸出的緩存
 75         private PrintWriter pw;
 76         private HttpServletResponse response;
 77         public BufferResponse(HttpServletResponse response) {
 78             super(response);
 79             this.response = response;
 80         }
 81         @Override
 82         public ServletOutputStream getOutputStream() throws IOException {
 83             return new MyServletOutputStream(bout);
 84         }
 85         @Override
 86         public PrintWriter getWriter() throws IOException {
 87             pw = new PrintWriter(new OutputStreamWriter(bout,this.response.getCharacterEncoding()));
 88             return pw;
 89         }
 90         
 91         public byte[] getBuffer(){
 92             try{
 93                 if(pw!=null){
 94                     pw.close();
 95                 }
 96                 return bout.toByteArray();
 97             }catch (Exception e) {
 98                 throw new RuntimeException(e);
 99             }
100         }
101     }
102 
103     class MyServletOutputStream extends ServletOutputStream{
104         private ByteArrayOutputStream bout;
105         public MyServletOutputStream(ByteArrayOutputStream bout){  //接收數據寫到哪裏
106             this.bout = bout;
107         }
108         @Override
109         public void write(int b) throws IOException {
110             bout.write(b);
111         }
112     }
113 }

　　在web.xml中配置Web資源緩存過濾器

 1   <filter>
 2        <description>Web資源緩存過濾器</description>
 3       <filter-name>WebResourceCachedFilter</filter-name>
 4       <filter-class>me.gacl.web.filter.WebResourceCachedFilter</filter-class>
 5   </filter>
 6   
 7   <filter-mapping>
 8       <filter-name>WebResourceCachedFilter</filter-name>
 9       <!-- 映射須要緩存輸出的JSP頁面，這幾個頁面都只是單純做爲輸入UI，不會有太多的變化，所以能夠緩存輸出 -->
10       <url-pattern>/login.jsp</url-pattern>
11       <url-pattern>/test.jsp</url-pattern>
12       <url-pattern>/test2.jsp</url-pattern>
13   </filter-mapping>