struts2配置文件加载流程分析

一个0后IT之路 2010-04-29

转自:http://tech.it168.com/j/2007-09-21/200709211302700.shtml

感谢作者wmj2003

struts2配置文件加载流程分析[收藏此页][打印]

作者:wmj20032007-09-21网友评论1条内容导航:struts2配置文件加载流程分析第1页:struts2配置文件加载流程分析

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

publicvoidinit(FilterConfigfilterConfig)throwsServletException{

this.filterConfig=filterConfig;

Stringparam=filterConfig.getInitParameter("packages");//由此可以看出可以增加参数packages

Stringpackages="org.apache.struts2.statictemplateorg.apache.struts2.interceptor.debugging";

if(param!=null){

packages=param+""+packages;

}

this.pathPrefixes=parse(packages);

dispatcher=newDispatcher(filterConfig.getServletContext());

}

org.apache.struts2.dispatcher.Dispatcher.java

首先执行静态代码块:

static{

ObjectFactory.setObjectFactory(newStrutsObjectFactory());

ActionProxyFactory.setFactory(newStrutsActionProxyFactory());

}

执行构造方法

publicDispatcher(ServletContextservletContext){

init(servletContext);

}

然后执行init()方法:

booleanreloadi18n=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

booleanreloadi18n=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

publicstaticStringget(Stringname)throwsIllegalArgumentException{

Stringval=getInstance().getImpl(name);

returnval;

}

然后执行了

publicstaticSettingsgetInstance(){

return(settingsImpl==null)?getDefaultInstance():settingsImpl;

}

然后执行了

privatestaticSettingsgetDefaultInstance(){

if(defaultImpl==null){

//Createbootstrapimplementation

defaultImpl=newDefaultSettings();//产生了一个DefaultSettings对象

//Createdefaultimplementation

try{

StringclassName=get(StrutsConstants.STRUTS_CONFIGURATION);

if(!className.equals(defaultImpl.getClass().getName())){

try{

//singletoninstancesshouldn'tbebuiltaccessingrequestorsession-specificcontextdata

defaultImpl=(Settings)ObjectFactory.getObjectFactory().buildBean(Thread.currentThread().getContextClassLoader().loadClass(className),null);

}catch(Exceptione){

LOG.error("Couldnotinstantiatesettings",e);

}

}

}catch(IllegalArgumentExceptionex){

//ignore

}

}

returndefaultImpl;

}

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

publicDefaultSettings(){

//Createdefaultimplementations

//Usedefaultpropertiesandstruts.properties

ArrayListlist=newArrayList();

try{

list.add(newPropertiesSettings("struts"));//从这里加载struts.properties文件

}catch(Exceptione){

log.warn("Couldnotfindorerrorinstruts.properties",e);

}

try{

list.add(newPropertiesSettings("org/apache/struts2/default"));//加载默认的defualt.properties文件

}catch(Exceptione){

log.error("Couldnotfindorg/apache/struts2/default.properties",e);

}

Settings[]configList=newSettings[list.size()];//定义了Settings对象数组

config=newDelegatingSettings((Settings[])list.toArray(configList));

//Addlistofadditionalpropertiessettingss

try{

StringTokenizerconfigFiles=newStringTokenizer((String)config.getImpl(StrutsConstants.STRUTS_CUSTOM_PROPERTIES),",");

加载了用户自己定义的properties文件。

while(configFiles.hasMoreTokens()){

Stringname=configFiles.nextToken();

try{

list.add(newPropertiesSettings(name));

}catch(Exceptione){

log.error("Couldnotfind"+name+".properties.Skipping");

}

}

configList=newSettings[list.size()];

config=newDelegatingSettings((Settings[])list.toArray(configList));

}catch(IllegalArgumentExceptione){

//thrownwhenSettingsisunabletofindacertainproperty

//eg.struts.custom.propertiesindefault.propertieswhichiscommented

//out

}

//Addadditionallistofi18nglobalresourcebundles

try{

LocalizedTextUtil.addDefaultResourceBundle("org/apache/struts2/struts-messages");

StringTokenizerbundleFiles=newStringTokenizer((String)config.getImpl(StrutsConstants.STRUTS_CUSTOM_I18N_RESOURCES),",");

while(bundleFiles.hasMoreTokens()){

Stringname=bundleFiles.nextToken();

try{

log.info("Loadingglobalmessagesfrom"+name);

LocalizedTextUtil.addDefaultResourceBundle(name);

}catch(Exceptione){

log.error("Couldnotfind"+name+".properties.Skipping");

}

}

}catch(IllegalArgumentExceptione){

//struts.custom.i18n.resourceswasn'tprovided

}

}

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

/**

*Getsthespecifiedproperty-callsgetImpl(String)methodonconfigobjectsinconfiglist

*untilsuccessful.

*

*@see#get(String)

*/

publicStringgetImpl(Stringname)throwsIllegalArgumentException{

//Delegatetotheothersettings

IllegalArgumentExceptione=null;

for(inti=0;i<configList.length;i++){

try{

returnconfigList[i].getImpl(name);

}catch(IllegalArgumentExceptionex){

e=ex;

//Trynextconfig

}

}

throwe;

}

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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