Struts2.0配置文件的加载分析

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。