struts2配置文件加载流程分析

首先org.apache.struts2.dispatcher. FilterDispatcher.java 中的init（）方法，
 

public void init(FilterConfig filterConfig) throws ServletException { this.filterConfig = filterConfig; String param = filterConfig.getInitParameter("packages");//由此可以看出可以增加参数packages String packages = "org.apache.struts2.static template org.apache.struts2.interceptor.debugging" ; if (param != null ) { packages = param + " " + packages; } this.pathPrefixes = parse(packages); dispatcher = new Dispatcher(filterConfig.getServletContext()); }

org.apache.struts2.dispatcher. Dispatcher.java
首先执行静态代码块：

static { ObjectFactory.setObjectFactory(new StrutsObjectFactory()); ActionProxyFactory.setFactory(new StrutsActionProxyFactory()); }

 
执行构造方法
   public Dispatcher(ServletContext servletContext) {
       init(servletContext);
}
然后执行init()方法：

boolean reloadi18n = Boolean.valueOf(
(String) Settings.get(StrutsConstants.STRUTS_I18N_RELOAD)).booleanValue();
上面的语句读取了properties文件。


读取properties文件的流程：
首先执行Org.apache.struts2.dispatcher.Dispatcher.java 类的方法init()中的语句
       boolean reloadi18n = Boolean.valueOf((String)
Settings.get(StrutsConstants.STRUTS_I18N_RELOAD)).booleanValue();

然后执行了org.apacher.struts2.config.Setting.java类中的方法
   public static String get(String name) throws IllegalArgumentException {
       String val = getInstance().getImpl(name);
       return val;
   }
然后执行了
   public static Settings getInstance() {
       return (settingsImpl == null) ? getDefaultInstance() : settingsImpl;
}
然后执行了

private static Settings getDefaultInstance() { if (defaultImpl == null ) { // Create bootstrap implementation defaultImpl = new DefaultSettings(); // 产生了一个DefaultSettings对象 // Create default implementation try { String className = get (StrutsConstants.STRUTS_CONFIGURATION); if (! className.equals(defaultImpl.getClass().getName())) { try { // singleton instances shouldn't be built accessing request or session-specific context data defaultImpl = (Settings) ObjectFactory.getObjectFactory().buildBean(Thread.currentThread().getContextClassLoader().loadClass(className), null ); } catch (Exception e) { LOG.error("Could not instantiate settings" , e); } } } catch (IllegalArgumentException ex) { // ignore } } return defaultImpl; }

然后首先执行了语句defaultImpl = new DefaultSettings();

public DefaultSettings() { // Create default implementations // Use default properties and struts.properties ArrayList list = new ArrayList(); try { list.add(new PropertiesSettings("struts"));//从这里加载struts.properties文件 } catch (Exception e) { log.warn("Could not find or error in struts.properties" , e); } try { list.add(new PropertiesSettings("org/apache/struts2/default")); //加载默认的defualt.properties文件 } catch (Exception e) { log.error("Could not find org/apache/struts2/default.properties" , e); } Settings[] configList = new Settings[list.size()];//定义了Settings对象数组 config = new DelegatingSettings((Settings[]) list.toArray(configList)); // Add list of additional properties settingss try { StringTokenizer configFiles = new StringTokenizer((String) config.getImpl(StrutsConstants.STRUTS_CUSTOM_PROPERTIES), "," ); 加载了用户自己定义的properties文件。 while (configFiles.hasMoreTokens()) { String name = configFiles.nextToken(); try { list.add(new PropertiesSettings(name)); } catch (Exception e) { log.error("Could not find " + name + ".properties. Skipping" ); } } configList = new Settings[list.size()]; config = new DelegatingSettings((Settings[]) list.toArray(configList)); } catch (IllegalArgumentException e) { // thrown when Settings is unable to find a certain property // eg. struts.custom.properties in default.properties which is commented // out } // Add additional list of i18n global resource bundles try { LocalizedTextUtil.addDefaultResourceBundle("org/apache/struts2/struts-messages" ); StringTokenizer bundleFiles = new StringTokenizer((String) config.getImpl(StrutsConstants.STRUTS_CUSTOM_I18N_RESOURCES), ", " ); while (bundleFiles.hasMoreTokens()) { String name = bundleFiles.nextToken(); try { log.info("Loading global messages from " + name); LocalizedTextUtil.addDefaultResourceBundle(name); } catch (Exception e) { log.error("Could not find " + name + ".properties. Skipping" ); } } } catch (IllegalArgumentException e) { // struts.custom.i18n.resources wasn't provided } }

看看org.apache.struts2.config.DelegatingSettings.java下面的方法。

/* * * Gets the specified property - calls getImpl(String) method on config objects in config list * until successful. * * @see #get(String) */ public String getImpl(String name) throws IllegalArgumentException { // Delegate to the other settings IllegalArgumentException e = null ; for (int i = 0; i < configList.length; i++ ) { try { return configList[i].getImpl(name); } catch (IllegalArgumentException ex) { e = ex; // Try next config } } throw e; }

小结：
    通过上面的代码分析，大家就可以明白为什么struts.properties中的配置项会自动覆盖default.properties中的属性，而不会配用户自定义的配置文件覆盖。

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