java版的YUI3 combine服务-Combo Handler

YUI3中，为了避免js文件过大，各个功能模块是拆分的。它有一个“种子”的概念：先下载一个小的核心的js文件到浏览器端，再通过这个小的js文件去加载其它所需的模块。

这种按需加载虽然解决了单个js过大的问题，但是随之带来另外一个问题：如果一个页面使用了YUI的a、b、c功能，那么浏览器就要向服务器请求a.js、b.js、c.js三个文件，这样增加了浏览器向服务器的沟通次数。

为了解决后面的问题，YUI3又有一个combine的概念，预先下载的那个核心的js，把页面上需要的a、b、c模块合并成一个请求发给服务器，类似这样：http://mydomain.com/conbine?a.js&b.js&c.js。

这要求服务器接收到http://mydomain.com/conbine请求后，将参数取出来，找到对应的a、b、c的js文件，合并成一个js文件，返回给客户端。Combo Handler是Yahoo!开发的一个Apache模块,专门来干这个事情的。

如果只用java的web容器，可以把这项工作委托给servlet:

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<servlet>     <servlet-name>yuicombo</servlet-name>     <servlet-class>org.siqisource.mozo.servlets.YuiCombineServlet</servlet-class> </servlet>

对应的YUI配置为：

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YUI.GlobalConfig = {     combine: true,     comboBase: '<mz:webRoot/>/yuicombo?',     root: 'uilibrary/yui/', };

在servlet代码中，我使用了YUI的yuicompressor来压缩js和css文件，下面是maven配置。

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<dependency>     <groupId>com.yahoo.platform.yui</groupId>     <artifactId>yuicompressor</artifactId>     <version>2.4.7</version> </dependency>

其中的Path类只是为了获得web应用物理路径，在是用的时候替换一下即可。

目前已知的缺陷：对于css的按需加载，浏览器会请求客户端两次，目前不清楚是不是YUI3(测试版本：3.7.2)的问题。

具体代码如下：

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package org.siqisource.mozo.servlets;   import java.io.File; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.io.Reader; import java.io.Writer; import java.util.HashMap; import java.util.Map; import java.util.UUID; import java.util.regex.Matcher; import java.util.regex.Pattern;   import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;   import org.apache.commons.io.FileDeleteStrategy; import org.apache.commons.io.FileUtils; import org.siqisource.mozo.context.Path;   import com.yahoo.platform.yui.compressor.CssCompressor; import com.yahoo.platform.yui.compressor.JavaScriptCompressor;   public class YuiCombineServlet extends HttpServlet {       private static Map<String, String> cachedResources = new HashMap<String, String>();       private String cacheContextPath = "uilibrary/yui/cache/";       private String cacheDir = Path.getPhysicalPath() + cacheContextPath;       int linebreakpos = -1;     boolean munge = true;     boolean verbose = false;     boolean preserveAllSemiColons = false;     boolean disableOptimizations = false;       @Override     public void init() throws ServletException {           // 重置缓存文件夹         File catchedDir = new File(cacheDir);           if (catchedDir.exists()) {             FileDeleteStrategy strategy = FileDeleteStrategy.FORCE;             try {                 strategy.delete(catchedDir);             } catch (IOException e) {                 // TODO Auto-generated catch block                 e.printStackTrace();             }         }         catchedDir.mkdirs();           super.init();     }       @Override     protected void doGet(HttpServletRequest request,             HttpServletResponse response) throws ServletException, IOException {           String queryString = request.getQueryString();         String resourcePath = cachedResources.get(queryString);         // 已缓存         if (resourcePath == null) {               String[] resources = queryString.split("&");             String firstResource = resources[0];               String fileName = UUID.randomUUID().toString();               if (firstResource.endsWith(".js")) {                   fileName += ".js";                 Writer writer = new FileWriter(cacheDir + fileName);                 for (String resource : resources) {                     Reader reader = new FileReader(Path.getPhysicalPath()                             + resource);                     JavaScriptCompressor compressor = new JavaScriptCompressor(                             reader, null);                     compressor.compress(writer, linebreakpos, munge, verbose,                             preserveAllSemiColons, disableOptimizations);                     reader.close();                 }                 writer.flush();                 writer.close();               } else if (resources[0].endsWith(".css")) {                 fileName += ".css";                 Writer writer = new FileWriter(cacheDir + fileName);                 for (String resource : resources) {                     Reader reader = new FileReader(replacedUrlFile(resource));                     CssCompressor compressor = new CssCompressor(reader);                     compressor.compress(writer, linebreakpos);                     reader.close();                 }                 writer.flush();                 writer.close();             }               resourcePath = cacheContextPath + fileName;             cachedResources.put(queryString, resourcePath);         }         request.getRequestDispatcher(resourcePath).forward(request, response);         return;     }           public String replacedUrlFile(String fileName) throws IOException {           String cssfilePath = Path.getPhysicalPath() + fileName;         File cssFile = new File(cssfilePath);           String tempCssFilePath = cacheDir + "tmp-css-" + cssFile.getName();         File tempCssFile = new File(tempCssFilePath);         if (tempCssFile.exists()) {             return tempCssFilePath;         }           // 判断是否需要替换         String css = FileUtils.readFileToString(cssFile);         int maxIndex = css.length() - 1;         int appendIndex = 0;         Pattern p = Pattern.compile("url\\(\\s*([\"']?)");         if (!p.matcher(css).find()) {             return cssfilePath;         }           // 真的需要替换         Matcher m = p.matcher(css);         String url = fileName.substring(0, fileName.lastIndexOf('/'));         url = Path.getContextPath() + "/" + url + "/";           StringBuffer replacedUrlCss = new StringBuffer();           while (m.find()) {             int startIndex = m.start() + 4; // "url(".length()             String terminator = m.group(1); // ', " or empty (not quoted)               if (terminator.length() == 0) {                 terminator = ")";             }               boolean foundTerminator = false;               int endIndex = m.end() - 1;             while (foundTerminator == false && endIndex + 1 <= maxIndex) {                 endIndex = css.indexOf(terminator, endIndex + 1);                   if ((endIndex > 0) && (css.charAt(endIndex - 1) != '\\')) {                     foundTerminator = true;                     if (!")".equals(terminator)) {                         endIndex = css.indexOf(")", endIndex);                     }                 }             }               // Enough searching, start moving stuff over to the buffer             replacedUrlCss.append(css.substring(appendIndex, m.start()));               if (foundTerminator) {                 String token = css.substring(startIndex, endIndex);                 token = token.replaceAll("\\s+", "");                 String preserver = "url('" + url + token + "')";                 replacedUrlCss.append(preserver);                   appendIndex = endIndex + 1;             } else {                 // No end terminator found, re-add the whole match. Should we                 // throw/warn here?                 replacedUrlCss.append(css.substring(m.start(), m.end()));                 appendIndex = m.end();             }         }         FileUtils.writeStringToFile(tempCssFile, replacedUrlCss.toString());         return tempCssFilePath;       } }