大家都知道，在Web应用程序中，为了节省网络开销，往往吧多个小的js文件整合成一个大的js文件，吧多个小的css文件整合成一个大的js文件,这样原本N次小文件的请求就可以合并成单次的网络请求。最典型的做这件事情的工具是大名鼎鼎的yui-compressor.
其实在Liferay中，我们为了达到合并css,js的目的，用了不同于yui-compressor的方法，这就是我们的主角 MinifierFilter.
既然是Filter，那么它肯定有filter-mapping，我们轻易的在liferay-web.xml中找到了Filter的定义和Filter的mapping.
... <filter> <filter-name>Minifier Filter</filter-name> <filter-class>com.liferay.portal.servlet.filters.minifier.MinifierFilter</filter-class> </filter> <filter> <filter-name>Minifier Filter - JSP</filter-name> <filter-class>com.liferay.portal.servlet.filters.minifier.MinifierFilter</filter-class> <init-param> <param-name>url-regex-pattern</param-name> <param-value>.+/(aui_lang|barebone|css|everything|main)\.jsp</param-value> </init-param> </filter> ... <filter-mapping> <filter-name>Minifier Filter</filter-name> <url-pattern>*.css</url-pattern> </filter-mapping> <filter-mapping> <filter-name>Minifier Filter</filter-name> <url-pattern>*.js</url-pattern> </filter-mapping> <filter-mapping> <filter-name>Minifier Filter - JSP</filter-name> <url-pattern>*.jsp</url-pattern> </filter-mapping>...
所以，我们可以看到，当客户端对Liferay服务器上请求任意css或者javascript资源时候，都会被这个MinifierFilter所过滤，我们现在就来看下庐山真面目。
因为MinifierFilter最终实现了Filter接口，而doFilter方法在父类的父类BaseFilter中定义，这个doFilter仅仅是调用processFilter()方法，
public void doFilter( ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { try { HttpServletRequest request = (HttpServletRequest)servletRequest; HttpServletResponse response = (HttpServletResponse)servletResponse; processFilter(request, response, filterChain); } catch (IOException ioe) { throw ioe; } catch (ServletException se) { throw se; }所以这就是我们的入口：
protected void processFilter( HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws Exception { Object minifiedContent = getMinifiedContent( request, response, filterChain); if (minifiedContent == null) { minifiedContent = getMinifiedBundleContent(request, response); } if (minifiedContent == null) { processFilter(MinifierFilter.class, request, response, filterChain); } else { if (minifiedContent instanceof File) { ServletResponseUtil.write(response, (File)minifiedContent); } else if (minifiedContent instanceof String) { ServletResponseUtil.write(response, (String)minifiedContent); } } }首先，它会去执行06-07行的getMinifiedContent()方法,它会调用以下代码：
在getMinifiedContent()方法中，它会调用2个方法来分别最小化css和最小化js.
如下：
protected Object getMinifiedContent( HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws Exception { .. .. String minifiedContent = null; if (realPath.endsWith(_CSS_EXTENSION)) { if (_log.isInfoEnabled()) { _log.info("Minifying CSS " + file); } minifiedContent = minifyCss(request, response, file); response.setContentType(ContentTypes.TEXT_CSS); FileUtil.write(cacheContentTypeFile, ContentTypes.TEXT_CSS); } else if (realPath.endsWith(_JAVASCRIPT_EXTENSION)) { if (_log.isInfoEnabled()) { _log.info("Minifying JavaScript " + file); } minifiedContent = minifyJavaScript(file); response.setContentType(ContentTypes.TEXT_JAVASCRIPT); FileUtil.write(cacheContentTypeFile, ContentTypes.TEXT_JAVASCRIPT); } else if (realPath.endsWith(_JSP_EXTENSION)) { if (_log.isInfoEnabled()) { _log.info("Minifying JSP " + file); } StringServletResponse stringResponse = new StringServletResponse( response); processFilter( MinifierFilter.class, request, stringResponse, filterChain); CacheResponseUtil.setHeaders(response, stringResponse.getHeaders()); response.setContentType(stringResponse.getContentType()); minifiedContent = stringResponse.getString(); if (minifierType.equals("css")) { minifiedContent = minifyCss( request, response, realPath, minifiedContent); } else if (minifierType.equals("js")) { minifiedContent = minifyJavaScript(minifiedContent); } FileUtil.write( cacheContentTypeFile, stringResponse.getContentType()); } else { return null; } FileUtil.write(cacheDataFile, minifiedContent); return minifiedContent; }
minifyCSS:
从第12行可以看出，如果判断扩展名是.css，那么需要吧文件minify一下，并且设置content-type为text/css,最后把这个文件放入cacheContentTypeFile中。
我们来看下minifyCSS到底做了什么事情：
protected String minifyCss( HttpServletRequest request, HttpServletResponse response, File file) throws IOException { String content = FileUtil.read(file); content = aggregateCss(file.getParent(), content); return minifyCss(request, response, file.getAbsolutePath(), content); }从这里可以清楚的看出，
05行是先吧这个css文件的内容通过FileUtil读出来，其实这个FileUtil的读的方式会去除所有的换行，参见最终调用的FileImpl的read方法：
public String read(File file, boolean raw) throws IOException { byte[] bytes = getBytes(file); if (bytes == null) { return null; } String s = new String(bytes, StringPool.UTF8); if (raw) { return s; } else { return StringUtil.replace( s, StringPool.RETURN_NEW_LINE, StringPool.NEW_LINE); } }然后把去除了所有换行的css文件的内容存入到变量content中。
07行会调用aggregateCSS来对这个css文件的内容做进一步处理，如何处理呢，我们看代码：
public static String aggregateCss(String dir, String content) throws IOException { StringBuilder sb = new StringBuilder(content.length()); int pos = 0; while (true) { int commentX = content.indexOf(_CSS_COMMENT_BEGIN, pos); int commentY = content.indexOf( _CSS_COMMENT_END, commentX + _CSS_COMMENT_BEGIN.length()); int importX = content.indexOf(_CSS_IMPORT_BEGIN, pos); int importY = content.indexOf( _CSS_IMPORT_END, importX + _CSS_IMPORT_BEGIN.length()); if ((importX == -1) || (importY == -1)) { sb.append(content.substring(pos, content.length())); break; } else if ((commentX != -1) && (commentY != -1) && (commentX < importX) && (commentY > importX)) { commentY += _CSS_COMMENT_END.length(); sb.append(content.substring(pos, commentY)); pos = commentY; } else { sb.append(content.substring(pos, importX)); String importFileName = content.substring( importX + _CSS_IMPORT_BEGIN.length(), importY); String importFullFileName = dir.concat(StringPool.SLASH).concat( importFileName); String importContent = FileUtil.read(importFullFileName); if (importContent == null) { if (_log.isWarnEnabled()) { _log.warn( "File " + importFullFileName + " does not exist"); } importContent = StringPool.BLANK; } String importDir = StringPool.BLANK; int slashPos = importFileName.lastIndexOf(CharPool.SLASH); if (slashPos != -1) { importDir = StringPool.SLASH.concat( importFileName.substring(0, slashPos + 1)); } importContent = aggregateCss(dir + importDir, importContent); int importDepth = StringUtil.count( importFileName, StringPool.SLASH); // LEP-7540 String relativePath = StringPool.BLANK; for (int i = 0; i < importDepth; i++) { relativePath += "../"; } importContent = StringUtil.replace( importContent, new String[] { "url('" + relativePath, "url(\"" + relativePath, "url(" + relativePath }, new String[] { "url('[$TEMP_RELATIVE_PATH$]", "url(\"[$TEMP_RELATIVE_PATH$]", "url([$TEMP_RELATIVE_PATH$]" }); importContent = StringUtil.replace( importContent, "[$TEMP_RELATIVE_PATH$]", StringPool.BLANK); sb.append(importContent); pos = importY + _CSS_IMPORT_END.length(); } } return sb.toString(); }其实这段代码非常简单，它就是找出页面上所有的css注释 /* */，然后把这些注释去除，然后找出页面上@import(url=)的这种外部css文件，递归的调用aggregateCSS直到他们不含有外部引入标记，然后把这些文件的内容（已经被去除了注释，换行符等）插入到引入它们的css文件中。
minifyJavaScript:
从第23行可以看出，当遇到文件扩展名是.js时，它就会调用minifyJavaScript方法来最小化这个js文件，并且设置content-type为text/javascript,最后把minify之后的文件存入cacheContentTypeFile。
我们来看下minifyJavaScript到底做了什么事情：
protected String minifyJavaScript(File file) throws IOException { String content = FileUtil.read(file); return minifyJavaScript(content); }它首先还是利用FileUtil来去除换行（见minifyCSS部分对这个方法的讲解），然后对于已经没有换行符的js文件继续调用minifyJavaScript()：
protected String minifyJavaScript(String content) { return MinifierUtil.minifyJavaScript(content); }它又去调用MinifierUtil工具类方法来完成任务，最终执行任务的是MinifierUtil的_minifyJavaScript方法：
private String _minifyJavaScript(String content) { UnsyncStringWriter unsyncStringWriter = new UnsyncStringWriter(); try { JavaScriptCompressor javaScriptCompressor = new JavaScriptCompressor( new UnsyncStringReader(content), new JavaScriptErrorReporter()); javaScriptCompressor.compress( unsyncStringWriter, _JS_LINE_BREAK, _JS_MUNGE, _JS_VERBOSE, _JS_PRESERVE_ALL_SEMICOLONS, _JS_DISABLE_OPTIMIZATIONS); } catch (Exception e) { _log.error("JavaScript Minifier failed for\n" + content); unsyncStringWriter.append(content); } return unsyncStringWriter.toString(); }它会先创建一个JavaScriptCompressor对象，然后用它来压缩没有换行符的js文件，采用的方式是和yahoo的yui-compressor一样的方式,算法很复杂，没必要一行行看了。
minifyJSP:
从34行可以看到，它会先判断是jsp扩展名，当然了， 它也不会对所有的jsp都生效，它生效的jsp文件都在liferay-web.xml中的这个filter的<init-param>中，具体的就是
barebone.jsp,everything.jsp等因为满足init-param的正则表达式的pattern,所以会通过这个过滤器。从第47-56行可以看出他会吧原来cache的所有被minify处理过的css或者js内容再minify一下然后写入String变量，然后第59-60行利用FileUtil进一步去除换行符，然后把cacheContentFile的内容以最终请求的MIME格式来复写一遍。
当我们在文章一开始的MinifierFilter的processFilter()方法中执行了所有的getMinifiedContent调用后：
Object minifiedContent = getMinifiedContent( request, response, filterChain);
此时，这个Object minifiedContent的内容就不是null了。
现在我们来执行MinifierFilter的最后2个语句，它可以判断这个minifiedContent是个文件还是字符串，从而让其写入ServletResponse对象中并且返回给客户端，写入的方式是调用ServletResponseUtil工具类：
else { if (minifiedContent instanceof File) { ServletResponseUtil.write(response, (File)minifiedContent); } else if (minifiedContent instanceof String) { ServletResponseUtil.write(response, (String)minifiedContent); } }
由此大功告成，我们所有的css,js资源文件都得到了最小化，然后整合成单个文件.
高级话题：barebone.jsp和everything.jsp
事实上，Liferay启用了2个配置，一个只引入最少最需要的js文件，最终组合为barebone.jsp，一个是引入所有的js文件，最终组合为everything.jsp,他们可以自由切换，切换代码在top_js.jspf中：
<c:choose> <c:when test="<%= themeDisplay.isThemeJsFastLoad() %>"> <c:choose> <c:when test="<%= themeDisplay.isThemeJsBarebone() %>"> <script src="<%= HtmlUtil.escape(PortalUtil.getStaticResourceURL(request, themeDisplay.getPathJavaScript() + "/barebone.jsp", "minifierBundleId=javascript.barebone.files", javaScriptLastModified)) %>" type="text/javascript"></script> </c:when> <c:otherwise> <script src="<%= HtmlUtil.escape(PortalUtil.getStaticResourceURL(request, themeDisplay.getPathJavaScript() + "/everything.jsp", "minifierBundleId=javascript.everything.files", javaScriptLastModified)) %>" type="text/javascript"></script> </c:otherwise> </c:choose> </c:when> <c:otherwise>
这里可以看出来，切换主要去判断themeDisplay.isThemeJSBarebone，而这个配置在portal.properties中，比如我们服务器设置了javascript.barebone.enabled=true，则开启了barebone,则最后看情况可以有barebone.jsp可以有everything.jsp:
# # Set this property to false to always load JavaScript files listed in the # property "javascript.everything.files". Set this to true to sometimes # load "javascript.barebone.files" and sometimes load # "javascript.everything.files". # # The default logic is coded in com.liferay.portal.events.ServicePreAction # in such a way that unauthenticated users get the list of barebone # JavaScript files whereas authenticated users get both the list of barebone # JavaScript files and the list of everything JavaScript files. # javascript.barebone.enabled=true
无论是barebone.jsp还是everything.jsp，他们的bundleId和读取目录都是预先是定好的：
# # Input a list of comma delimited properties that are valid bundle ids for # the JavaScript minifier. # javascript.bundle.ids=\ javascript.barebone.files,\ javascript.everything.files # # Define a bundle directory for each property listed in # "javascript.bundle.ids". # javascript.bundle.dir[javascript.barebone.files]=/html/js javascript.bundle.dir[javascript.everything.files]=/html/js #
只不过barebone.jsp合并的js文件少，而everything.jsp文件合并全部的js文件：
barebone.jsp合并并且最小化哪些js文件呢?这也可以从portal.properties文件中找到答案：
javascript.barebone.files=\ \ # # YUI core # \ aui/yui/yui.js,\ \ # # YUI modules # \ aui/anim-base/anim-base.js,\ aui/anim-color/anim-color.js,\ aui/anim-curve/anim-curve.js,\ ...
而everything.jsp合并并且最小化哪些js文件呢？它是由javascript.barebone.files 包含的所有js文件，外加如下列表的不在barebone中的文件：
# # Specify the list of everything files (everything else not already in the # list of barebone files). # javascript.everything.files=\ \ # # YUI modules # \ aui/async-queue/async-queue.js,\ aui/cookie/cookie.js,\ aui/event-touch/event-touch.js,\ aui/querystring-stringify/querystring-stringify.js,\ \ # # Alloy modules # \ aui/aui-io/aui-io-plugin.js,\ aui/aui-io/aui-io-request.js,\ aui/aui-loading-mask/aui-loading-mask.js,\ aui/aui-parse-content/aui-parse-content.js,\ \ # # Liferay modules # \ liferay/address.js,\ liferay/dockbar.js,\ liferay/layout_configuration.js,\ liferay/layout_exporter.js,\ liferay/session.js,\ \ # # Deprecated JS # \ liferay/deprecated.js
这样一分析下来，整个Liferay框架的静态资源加载文件就非常清晰了。
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