高性能WEB开发之疯狂的HTML压缩

发布时间:2020-11-23编辑:脚本学堂
本文是 高性能WEB开发的第十篇,介绍HTML压缩的相关内容,供大家学习参考。

    本文是 高性能WEB开发的第十篇,介绍HTML压缩的相关内容,供大家学习参考。

    前言:    
    网友 skyaspnet 问我如何压缩HTML,当时回答是推荐他使用gzip,后来想想,要是能把所有的html,jsp(aspx)在运行前都压缩成1行未免不是一件好事啊。一般我们启动gzip都比较少对html启动gzip,因为现在的html都是动态的,不会使用浏览器缓存,而启用gzip的话每次请求都需要压缩,会比较消耗服务器资源,对js,css启动gzip比较好是因为js,css都会使用缓存。我个人觉得的压缩html的最大好处就是一本万利,只要写好了一次,以后所有程序都可以使用,不会增加任何额外的开发工作。

   在“JS、CSS的合并、压缩、缓存管理”一文中说到自己写过的1个自动合并、压缩JS,CSS,并添加版本号的组件。这次把压缩html的功能也加入到该组件中,流程很简单,就是在程序启动(contextInitialized or Application_Start)的时候扫描所有html,jsp(aspx)进行压缩。

压缩的注意事项
实现的方式主要是用正则表达式去查找,替换。在html压缩的时候,主要要注意下面几点:
1. pre,textarea 标签里面的内容格式需要保留,不能压缩。
2. 去掉html注释的时候,有些注释是不能去掉的,比如:<!--[if IE 6]> ..... <![endif]-->
3. 压缩嵌入式js中的注释要注意,因为可能注释符号会出现在字符串中,比如: var url = "http://www.cnblogs.com";    // 前面的//不是注释
   去掉JS换行符的时候,不能直接跟一下行动内容,需要有空格,考虑下面的代码:
   else
        return;
   如果不带空格,则变成elsereturn。
4. jsp(aspx) 中很有可能会使用<% %>嵌入一些服务器代码,这个时候也需要单独处理,里面注释的处理方法跟js的一样。

源代码:

下面是java实现的源代码,也可以点这里下载该代码,相信大家都看的懂,也很容易改成net代码:
 

复制代码 代码如下:
 import java.io.StringReader;
 import java.io.StringWriter;
 import java.util.*;
 import java.util.regex.*;
 
  /*******************************************
   * 压缩jsp,html中的代码,去掉所有空白符、换行符
   * @author  bearrui(ak-47)
   * @version 0.1
   * @date     2010-5-13
   *******************************************/
  public class HtmlCompressor {
      private static String tempPreBlock = "%%%HTMLCOMPRESS~PRE&&&";
      private static String tempTextAreaBlock = "%%%HTMLCOMPRESS~TEXTAREA&&&";
      private static String tempScriptBlock = "%%%HTMLCOMPRESS~SCRIPT&&&";
      private static String tempStyleBlock = "%%%HTMLCOMPRESS~STYLE&&&";
      private static String tempJspBlock = "%%%HTMLCOMPRESS~JSP&&&";
     
      private static Pattern commentPattern = Pattern.compile("<!--s*[^[].*?-->", Pattern.DOTALL | Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
      private static Pattern itsPattern = Pattern.compile(">s+?<", Pattern.DOTALL | Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
      private static Pattern prePattern = Pattern.compile("<pre[^>]*?>.*?</pre>", Pattern.DOTALL | Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
      private static Pattern taPattern = Pattern.compile("<textarea[^>]*?>.*?</textarea>", Pattern.DOTALL | Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
      private static Pattern jspPattern = Pattern.compile("<%([^-@][wW]*?)%>", Pattern.DOTALL | Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
      // <script></script>
      private static Pattern scriptPattern = Pattern.compile("(?:<scripts*>|<script type=['"]text/javascript['"]s*>)(.*?)</script>", Pattern.DOTALL | Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
      private static Pattern stylePattern = Pattern.compile("<style[^>()]*?>(.+)</style>", Pattern.DOTALL | Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
 
      // 单行注释,
      private static Pattern signleCommentPattern = Pattern.compile("//.*");
      // 字符串匹配
      private static Pattern stringPattern = Pattern.compile("("[^"n]*?"|'[^'n]*?')");
      // trim去空格和换行符
      private static Pattern trimPattern = Pattern.compile("ns*",Pattern.MULTILINE);
      private static Pattern trimPattern2 = Pattern.compile("s*r",Pattern.MULTILINE);
      // 多行注释
      private static Pattern multiCommentPattern = Pattern.compile("/*.*?*/", Pattern.DOTALL | Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
 
      private static String tempSingleCommentBlock = "%%%HTMLCOMPRESS~SINGLECOMMENT&&&";  // //占位符
      private static String tempMulitCommentBlock1 = "%%%HTMLCOMPRESS~MULITCOMMENT1&&&";  // /*占位符
      private static String tempMulitCommentBlock2 = "%%%HTMLCOMPRESS~MULITCOMMENT2&&&";  // */占位符
   
      public static String compress(String html) throws Exception {
          if(html == null || html.length() == 0) {
              return html;
          }
         
          List<String> preBlocks = new ArrayList<String>();
          List<String> taBlocks = new ArrayList<String>();
          List<String> scriptBlocks = new ArrayList<String>();
          List<String> styleBlocks = new ArrayList<String>();
          List<String> jspBlocks = new ArrayList<String>();
         
          String result = html;
         
          //preserve inline java code
          Matcher jspMatcher = jspPattern.matcher(result);
          while(jspMatcher.find()) {
              jspBlocks.add(jspMatcher.group(0));
          }
          result = jspMatcher.replaceAll(tempJspBlock);
         
          //preserve PRE tags
          Matcher preMatcher = prePattern.matcher(result);
          while(preMatcher.find()) {
              preBlocks.add(preMatcher.group(0));
          }
          result = preMatcher.replaceAll(tempPreBlock);
         
          //preserve TEXTAREA tags
          Matcher taMatcher = taPattern.matcher(result);
          while(taMatcher.find()) {
              taBlocks.add(taMatcher.group(0));
          }
          result = taMatcher.replaceAll(tempTextAreaBlock);
         
          //preserve SCRIPT tags
          Matcher scriptMatcher = scriptPattern.matcher(result);
          while(scriptMatcher.find()) {
              scriptBlocks.add(scriptMatcher.group(0));
          }
          result = scriptMatcher.replaceAll(tempScriptBlock);
         
          // don't process inline css
          Matcher styleMatcher = stylePattern.matcher(result);
          while(styleMatcher.find()) {
              styleBlocks.add(styleMatcher.group(0));
          }
          result = styleMatcher.replaceAll(tempStyleBlock);
         
          //process pure html
          result = processHtml(result);
         
          //process preserved blocks
          result = processPreBlocks(result, preBlocks);
          result = processTextareaBlocks(result, taBlocks);
          result = processScriptBlocks(result, scriptBlocks);
          result = processStyleBlocks(result, styleBlocks);
          result = processJspBlocks(result, jspBlocks);
        
         preBlocks = taBlocks = scriptBlocks = styleBlocks = jspBlocks = null;
        
         return result.trim();
     }
    
     private static String processHtml(String html) {
         String result = html;
        
         //remove comments
 //        if(removeComments) {
             result = commentPattern.matcher(result).replaceAll("");
//        }
        
        //remove inter-tag spaces
 //        if(removeIntertagSpaces) {
             result = itsPattern.matcher(result).replaceAll("><");
 //        }
        
         //remove multi whitespace characters
 //        if(removeMultiSpaces) {
             result = result.replaceAll("s{2,}"," ");
 //        }
                
         return result;
     }
    
     private static String processJspBlocks(String html, List<String> blocks){
         String result = html;
         for(int i = 0; i < blocks.size(); i++) {
             blocks.set(i, compressJsp(blocks.get(i)));
         }
         //put preserved blocks back
         while(result.contains(tempJspBlock)) {
             result = result.replaceFirst(tempJspBlock, Matcher.quoteReplacement(blocks.remove(0)));
         }
        
         return result;
     }
     private static String processPreBlocks(String html, List<String> blocks) throws Exception {
         String result = html;
        
         //put preserved blocks back
         while(result.contains(tempPreBlock)) {
             result = result.replaceFirst(tempPreBlock, Matcher.quoteReplacement(blocks.remove(0)));
         }
        
         return result;
     }
    
     private static String processTextareaBlocks(String html, List<String> blocks) throws Exception {
         String result = html;
        
         //put preserved blocks back
         while(result.contains(tempTextAreaBlock)) {
             result = result.replaceFirst(tempTextAreaBlock, Matcher.quoteReplacement(blocks.remove(0)));
         }
        
         return result;
     }
    
     private static String processScriptBlocks(String html, List<String> blocks) throws Exception {
         String result = html;
        
 //        if(compressJavaScript) {
             for(int i = 0; i < blocks.size(); i++) {
                 blocks.set(i, compressJavaScript(blocks.get(i)));
             }
 //        }
        
         //put preserved blocks back
         while(result.contains(tempScriptBlock)) {
             result = result.replaceFirst(tempScriptBlock, Matcher.quoteReplacement(blocks.remove(0)));
         }
        
         return result;
     }
    
     private static String processStyleBlocks(String html, List<String> blocks) throws Exception {
         String result = html;
        
 //        if(compressCss) {
             for(int i = 0; i < blocks.size(); i++) {
                 blocks.set(i, compressCssStyles(blocks.get(i)));
             }
 //        }
        
         //put preserved blocks back
         while(result.contains(tempStyleBlock)) {
             result = result.replaceFirst(tempStyleBlock, Matcher.quoteReplacement(blocks.remove(0)));
         }
        
         return result;
     }
    
     private static String compressJsp(String source)  {
         //check if block is not empty
         Matcher jspMatcher = jspPattern.matcher(source);
         if(jspMatcher.find()) {
             String result = compressJspJs(jspMatcher.group(1));
             return (new StringBuilder(source.substring(0, jspMatcher.start(1))).append(result).append(source.substring(jspMatcher.end(1)))).toString();
         } else {
             return source;
         }
     }   
     private static String compressJavaScript(String source)  {
         //check if block is not empty
         Matcher scriptMatcher = scriptPattern.matcher(source);
         if(scriptMatcher.find()) {
             String result = compressJspJs(scriptMatcher.group(1));
             return (new StringBuilder(source.substring(0, scriptMatcher.start(1))).append(result).append(source.substring(scriptMatcher.end(1)))).toString();
         } else {
             return source;
         }
     }
        
     private static String compressCssStyles(String source)  {
         //check if block is not empty
         Matcher styleMatcher = stylePattern.matcher(source);
         if(styleMatcher.find()) {
             // 去掉注释,换行
             String result= multiCommentPattern.matcher(styleMatcher.group(1)).replaceAll("");
             result = trimPattern.matcher(result).replaceAll("");
             result = trimPattern2.matcher(result).replaceAll("");
             return (new StringBuilder(source.substring(0, styleMatcher.start(1))).append(result).append(source.substring(styleMatcher.end(1)))).toString();
         } else {
             return source;
         }
     }
    
     private static String compressJspJs(String source){
         String result = source;
         // 因注释符合有可能出现在字符串中,所以要先把字符串中的特殊符好去掉
         Matcher stringMatcher = stringPattern.matcher(result);
         while(stringMatcher.find()){
             String tmpStr = stringMatcher.group(0);
            
             if(tmpStr.indexOf("//") != -1 || tmpStr.indexOf("/*") != -1 || tmpStr.indexOf("*/") != -1){
                 String blockStr = tmpStr.replaceAll("//", tempSingleCommentBlock).replaceAll("/*", tempMulitCommentBlock1)
                                 .replaceAll("*/", tempMulitCommentBlock2);
                 result = result.replace(tmpStr, blockStr);
             }
         }
         // 去掉注释
         result = signleCommentPattern.matcher(result).replaceAll("");
         result = multiCommentPattern.matcher(result).replaceAll("");
         result = trimPattern2.matcher(result).replaceAll("");
         result = trimPattern.matcher(result).replaceAll(" ");
         // 恢复替换掉的字符串
         result = result.replaceAll(tempSingleCommentBlock, "//").replaceAll(tempMulitCommentBlock1, "/*")
                 .replaceAll(tempMulitCommentBlock2, "*/");
        
         return result;
     }
 }

    使用注意事项
    使用了上面方法后,再运行程序,是不是发现每个页面查看源代码的时候都变成1行啦,还不错吧,但是在使用的时候还是要注意一些问题:
    1. 嵌入js本来想调用yuicompressor来压缩,yuicompressor压缩JS前,会先编译js是否合法,因我们嵌入的js中可能很多会用到一些服务器端代码,比如 var now = <%=DateTime.now %> ,这样的代码会编译不通过,所以无法使用yuicompressor。

    最后只能自己写压缩JS代码,自己写的比较粗燥,所以有个问题还解决,就是如果开发人员在一句js代码后面没有加分号的话,压缩成1行就很有可能出问题。所以使用这个需要保证每条语句结束后都必须带分号。

   2. 因为是在程序启动的时候压缩所有jsp(aspx),所以如果是用户请求的时候动态产生的html就无法压缩。