和struts2启动一样，它也有一个入口，那就是org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter的doFilter方法。
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) res;
try {
prepare.setEncodingAndLocale(request, response);
prepare.createActionContext(request, response);
prepare.assignDispatcherToThread();
if ( excludedPatterns != null && prepare.isUrlExcluded(request, excludedPatterns)) {
chain.doFilter(request, response);
} else {
request = prepare.wrapRequest(request);
ActionMapping mapping = prepare.findActionMapping(request, response, true);
if (mapping == null) {
boolean handled = execute.executeStaticResourceRequest(request, response);
if (!handled) {
chain.doFilter(request, response);
}
} else {
execute.executeAction(request, response, mapping);
}
}
} finally {
prepare.cleanupRequest(request);
}
}
这部分包括设置编码，创建actioncontext，并把这个Distance变量设置到此线程的本地副本instance中
private static ThreadLocal<Dispatcher> instance = new ThreadLocal<Dispatcher>();
接下来是获得actionmapping。这个actionmapping是根据我们的request的uri来和配置文件中的设置匹配，得到相应的action。
public ActionMapping findActionMapping(HttpServletRequest request, HttpServletResponse response, boolean forceLookup) {
ActionMapping mapping = (ActionMapping) request.getAttribute(STRUTS_ACTION_MAPPING_KEY);
if (mapping == null || forceLookup) {
try {
mapping = dispatcher.getContainer().getInstance(ActionMapper.class).getMapping(request, dispatcher.getConfigurationManager());
if (mapping != null) {
request.setAttribute(STRUTS_ACTION_MAPPING_KEY, mapping);
}
} catch (Exception ex) {
dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
}
}
return mapping;
}
还记得dispatcher.getContainer().getInstance(ActionMapper.class)的原理吗？从我们上篇文章中，这个已经说过，在struts2的初始化中，container已经创建成功了，而且这个容器中有factories的这个map，每项都是一个name和type组成的Key和它对应的对象工厂的Value组成的。我们看看getMapping是怎么实现的。
public ActionMapping getMapping(HttpServletRequest request,
ConfigurationManager configManager) {
ActionMapping mapping = new ActionMapping();
String uri = getUri(request);
int indexOfSemicolon = uri.indexOf(";");
uri = (indexOfSemicolon > -1) ? uri.substring(0, indexOfSemicolon) : uri;
uri = dropExtension(uri, mapping);
if (uri == null) {
return null;
}
parseNameAndNamespace(uri, mapping, configManager);
handleSpecialParameters(request, mapping);
if (mapping.getName() == null) {
return null;
}
parseActionName(mapping);
return mapping;
}
protected ActionMapping parseActionName(ActionMapping mapping) {
if (mapping.getName() == null) {
return mapping;
}
if (allowDynamicMethodCalls) {
// handle "name!method" convention.
String name = mapping.getName();
int exclamation = name.lastIndexOf("!");
if (exclamation != -1) {
mapping.setName(name.substring(0, exclamation));
mapping.setMethod(name.substring(exclamation + 1));
}
}
return mapping;
}
protected void parseNameAndNamespace(String uri, ActionMapping mapping,
ConfigurationManager configManager) {
String namespace, name;
int lastSlash = uri.lastIndexOf("/");
if (lastSlash == -1) {
namespace = "";
name = uri;
} else if (lastSlash == 0) {
// ww-1046, assume it is the root namespace, it will fallback to
// default
// namespace anyway if not found in root namespace.
namespace = "/";
name = uri.substring(lastSlash + 1);
} else if (alwaysSelectFullNamespace) {
// Simply select the namespace as everything before the last slash
namespace = uri.substring(0, lastSlash);
name = uri.substring(lastSlash + 1);
} else {
// Try to find the namespace in those defined, defaulting to ""
Configuration config = configManager.getConfiguration();
String prefix = uri.substring(0, lastSlash);
namespace = "";
boolean rootAvailable = false;
// Find the longest matching namespace, defaulting to the default
for (Object cfg : config.getPackageConfigs().values()) {
String ns = ((PackageConfig) cfg).getNamespace();
if (ns != null && prefix.startsWith(ns) && (prefix.length() == ns.length() || prefix.charAt(ns.length()) == '/')) {
if (ns.length() > namespace.length()) {
namespace = ns;
}
}
if ("/".equals(ns)) {
rootAvailable = true;
}
}
name = uri.substring(namespace.length() + 1);
// Still none found, use root namespace if found
if (rootAvailable && "".equals(namespace)) {
namespace = "/";
}
}
if (!allowSlashesInActionNames && name != null) {
int pos = name.lastIndexOf('/');
if (pos > -1 && pos < name.length() - 1) {
name = name.substring(pos + 1);
}
}
mapping.setNamespace(namespace);
mapping.setName(name);
}
这段代码应该很简单吧。无非就是解析request的uri，获得它的namespace，name，method等，设置到actionmapping中。当获得了actionmapping后，就开始真正处理请求了。
execute.executeAction(request, response, mapping);
public void executeAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping) throws ServletException {
dispatcher.serviceAction(request, response, servletContext, mapping);
}
public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,
ActionMapping mapping) throws ServletException {
Map<String, Object> extraContext = createContextMap(request, response, mapping, context);
// If there was a previous value stack, then create a new copy and pass it in to be used by the new Action
ValueStack stack = (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);
boolean nullStack = stack == null;
if (nullStack) {
ActionContext ctx = ActionContext.getContext();
if (ctx != null) {
stack = ctx.getValueStack();
}
}
if (stack != null) {
extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack));
}
String timerKey = "Handling request from Dispatcher";
try {
UtilTimerStack.push(timerKey);
String namespace = mapping.getNamespace();
String name = mapping.getName();
String method = mapping.getMethod();
Configuration config = configurationManager.getConfiguration();
ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(
namespace, name, method, extraContext, true, false);
request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());
// if the ActionMapping says to go straight to a result, do it!
if (mapping.getResult() != null) {
Result result = mapping.getResult();
result.execute(proxy.getInvocation());
} else {
proxy.execute();
}
//................
}
前面一段是处理actioncontext和valuestack的内容。在createContextMap中根据原生的request，response等进行封装封装成map类型，再调用一个createContextMap的一个重载方法，把这些原生request,session等和封装后的map类型的request,session等放入到一个大的map中。如果你要在action中获得这些对象，也是可以的。
比如：Map<String, String> request=(Map<String, String>) ActionContext.getContext().get("request");对于Map类型的request用的字符串是"request"，如果你想获得原生request也是可以的，但是不是"request"，而是StrutsStatics.HTTP_REQUEST：
httprequest=(HttpServletRequest) ActionContext.getContext().get(StrutsStatics.HTTP_REQUEST);在map中就是以StrutsStatics.HTTP_REQUEST为键。
但是你可能会问：为什么session可以这样获得呢？Map<String, Object> session=ActionContext.getContext().getSession();而request却要通过get方法呢？
这是因为在ActionContext中并没有提供getRequest方法，也不知道为什么不提供，其实getSession()也是通过get方法实现的。
接下来是获得mapping的命名空间，action的名字，action的方法名。我们执行action,不就是要知道这些么。然后获得一个action的代理：ActionProxy proxy。
public ActionProxy createActionProxy(String namespace, String actionName, String methodName, Map<String, Object> extraContext, boolean executeResult, boolean cleanupContext) {
ActionInvocation inv = new DefaultActionInvocation(extraContext, true);
container.inject(inv);
return createActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);
}
创建actioninvocation。通过container的IOC机制进行注入。
public ActionProxy createActionProxy(ActionInvocation inv, String namespace, String actionName, String methodName, boolean executeResult, boolean cleanupContext) {
StrutsActionProxy proxy = new StrutsActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);
container.inject(proxy);
proxy.prepare();
return proxy;
}
此时才创建action的代理对象，以后就通过该代理对象去执行。
protected void prepare() {
String profileKey = "create DefaultActionProxy: ";
try {
UtilTimerStack.push(profileKey);
config = configuration.getRuntimeConfiguration().getActionConfig(namespace, actionName);
//.........
resolveMethod();
if (!config.isAllowedMethod(method)) {
throw new ConfigurationException("Invalid method: " + method + " for action " + actionName);
}
invocation.init(this);
}
//.........
}
public void init(ActionProxy proxy) {
this.proxy = proxy;
Map<String, Object> contextMap = createContextMap();
// Setting this so that other classes, like object factories, can use the ActionProxy and other
// contextual information to operate
ActionContext actionContext = ActionContext.getContext();
if (actionContext != null) {
actionContext.setActionInvocation(this);
}
createAction(contextMap);
if (pushAction) {
stack.push(action);
contextMap.put("action", action);
}
invocationContext = new ActionContext(contextMap);
invocationContext.setName(proxy.getActionName());
// get a new List so we don't get problems with the iterator if someone changes the list
List<InterceptorMapping> interceptorList = new ArrayList<InterceptorMapping>(proxy.getConfig().getInterceptors());
interceptors = interceptorList.iterator();
}
前面也是对context进行一些设置等，我就不分析了。
这里对actioninvocation进行了初始化操作，我们通过actioninvocation以后要执行一系列的interceptor和真正的action，所以这些东西都要在初始化中。
再回到serviceAction。因为我们已经得到了actionmapping和actionproxy。接下来就可以去执行拦截器interceptor和action了。
他们的执行就是如果还有interceptor就执行下一个interceptor，如果没有就执行真正的action了，采用一种责任链模式，这部分很简单，我也不分析。当action执行完后，又依次返回各个interceptor，再经过web服务器的各个容器中的各个valve（比如StandardContext容器的StandardContextValve）。这样就完成了整个的处理过程了。