这一篇文章主要是记录struts.xml的初始化，还原struts2.xml的初始化流程。源码依据struts2-2.3.16.3版本。
struts2初始化入口，位于web.xml中：
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>
调用StrutsPrepareAndExecuteFilterinit(FilterConfig filterConfig)方法，进行初始化：
public void init(FilterConfig filterConfig) throws ServletException {
InitOperations init = new InitOperations();
Dispatcher dispatcher = null;
try {
FilterHostConfig config = new FilterHostConfig(filterConfig);
init.initLogging(config);
dispatcher = init.initDispatcher(config);
init.initStaticContentLoader(config, dispatcher);
prepare = new PrepareOperations(filterConfig.getServletContext(), dispatcher);
execute = new ExecuteOperations(filterConfig.getServletContext(), dispatcher);
this.excludedPatterns = init.buildExcludedPatternsList(dispatcher);
postInit(dispatcher, filterConfig);
} finally {
if (dispatcher != null) {
dispatcher.cleanUpAfterInit();
}
init.cleanup();
}
}
InitOperations定义了初始化的实现，提供struts2初始化的各个部件的构建过程，包括：logger、dispatcher、static content loader 。我们这里只关心dispatcher的初始化流程。
dispather的init过程被分解了多个步骤：
init_FileManager();
init_DefaultProperties(); // [1]
init_TraditionalXmlConfigurations(); // [2]//初始化struts.xml
init_LegacyStrutsProperties(); // [3]
init_CustomConfigurationProviders(); // [5]
init_FilterInitParameters() ; // [6]
init_AliasStandardObjects() ; // [7]
其中第2个步骤：init_TraditionalXmlConfigurations();就是准备初始化xml文件的：
private void init_TraditionalXmlConfigurations() {
String configPaths = initParams.get("config");
if (configPaths == null) {
configPaths = DEFAULT_CONFIGURATION_PATHS;//DEFAULT_CONFIGURATION_PATHS = "struts-default.xml,struts-plugin.xml,struts.xml",即默认需要初始化这三个配置文件。
}
String[] files = configPaths.split("\\s*[,]\\s*");
for (String file : files) {
if (file.endsWith(".xml")) {
if ("xwork.xml".equals(file)) {
configurationManager.addContainerProvider(createXmlConfigurationProvider(file, false));
} else {
configurationManager.addContainerProvider(createStrutsXmlConfigurationProvider(file, false, servletContext));
}
} else {
throw new IllegalArgumentException("Invalid configuration file name");
}
}
}
默认根据struts-default.xml,struts-plugin.xml,struts.xml （可根据init-param:config 修改加载路径） 分别创建三个 org.apache.struts2.config. StrutsXmlConfigurationProvider，其中方法register实现默认会从相应配置文件读取props加载到setting 中，会将bean放入ContainerBuilder中，最后将三个containerProviders并加入containerProviders。
全部的providers准备好后，preLoad配置的时候就会把配置初始化出来：
Container container = init_PreloadConfiguration();
private Container init_PreloadConfiguration() {
Configuration config = configurationManager.getConfiguration();
Container container = config.getContainer();
boolean reloadi18n = Boolean.valueOf(container.getInstance(String.class, StrutsConstants.STRUTS_I18N_RELOAD));
LocalizedTextUtil.setReloadBundles(reloadi18n);
ContainerHolder.store(container);
return container;
}
configurationManager.getConfiguration()的作用是根据配置将configuration对象实例化，并根据当前的container将内容填充：
public synchronized Configuration getConfiguration() {
if (configuration == null) {
setConfiguration(createConfiguration(defaultFrameworkBeanName));
try {
configuration.reloadContainer(getContainerProviders());
} catch (ConfigurationException e) {
setConfiguration(null);
throw new ConfigurationException("Unable to load configuration.", e);
}
} else {
conditionalReload();
}
return configuration;
}
调用每个providers的register方法解析制定的xml，此处的providers即包含前面在init_TraditionalXmlConfigurations中初始化的struts-default.xml,struts-plugin.xml,struts.xml的三个providers。
public synchronized List<PackageProvider> reloadContainer(List<ContainerProvider> providers) throws ConfigurationException {
packageContexts.clear();
loadedFileNames.clear();
List<PackageProvider> packageProviders = new ArrayList<PackageProvider>();
ContainerProperties props = new ContainerProperties();
ContainerBuilder builder = new ContainerBuilder();
Container bootstrap = createBootstrapContainer(providers);
for (final ContainerProvider containerProvider : providers)
{
bootstrap.inject(containerProvider);
containerProvider.init(this);
containerProvider.register(builder, props);
}
继续向下看StrutsXmlConfigurationProvider.register方法，可以看到关键逻辑是在父类里面：
StrutsXmlConfigurationProvider.java
public void register(ContainerBuilder containerBuilder, LocatableProperties props) throws ConfigurationException {
if (servletContext != null && !containerBuilder.contains(ServletContext.class)) {
containerBuilder.factory(ServletContext.class, new Factory<ServletContext>() {
public ServletContext create(Context context) throws Exception {
return servletContext;
}
});
}
super.register(containerBuilder, props);
}
这里将在xml文件中定义的bean、contants、unknown-handler-stack 元素取出来并加载到容器中去。
for (Document doc : documents) {
Element rootElement = doc.getDocumentElement();
NodeList children = rootElement.getChildNodes();
int childSize = children.getLength();
for (int i = 0; i < childSize; i++) {
Node childNode = children.item(i);
if (childNode instanceof Element) {
Element child = (Element) childNode;
final String nodeName = child.getNodeName();
if ("bean".equals(nodeName)) {
} else if ("constant".equals(nodeName)) {
} else if (nodeName.equals("unknown-handler-stack")) {
}
}
}
}
loadPackages负责初始化struts2 pacakge定义
for (Document doc : documents) {
Element rootElement = doc.getDocumentElement();
NodeList children = rootElement.getChildNodes();
int childSize = children.getLength();
for (int i = 0; i < childSize; i++) {
Node childNode = children.item(i);
if (childNode instanceof Element) {
Element child = (Element) childNode;
final String nodeName = child.getNodeName();
if ("package".equals(nodeName)) {
PackageConfig cfg = addPackage(child);
if (cfg.isNeedsRefresh()) {
reloads.add(child);
}
}
}
}
loadExtraConfiguration(doc);
}