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在FilterDispatcher中首先关注的方法是init()和doFilter()，两个有用的局部变量（或者状态）
private FilterConfig filterConfig;
protected Dispatcher dispatcher;filterConfig用来向filter传递信息，提供了四个方法：
public abstract java.lang.String getFilterName();
public abstract javax.servlet.ServletContext getServletContext();
public abstract java.lang.String getInitParameter(java.lang.String arg0);
public abstract java.util.Enumeration getInitParameterNames();dispatcher做了FilterDispatcher大部分的工作。
首先来看init方法：
public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig;
//把filterConfig中的parameters和servletContext传递给new Dispatcher(filterConfig.getServletContext(), params)
dispatcher = createDispatcher(filterConfig);
//加载各种配置
dispatcher.init();
String param = filterConfig.getInitParameter("packages");
String packages = DEFAULT_STATIC_PACKAGES;
if (param != null) {
packages = param + " " + packages;
}
this.pathPrefixes = parse(packages);
}
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) res;
ServletContext servletContext = getServletContext();
String timerKey = "FilterDispatcher_doFilter: ";
try {
UtilTimerStack.push(timerKey);
request = prepareDispatcherAndWrapRequest(request, response);
ActionMapping mapping;//ActionMapping有四个字段 method, name, namespace,params, result对应着XML配置文件
try {
//装配mappings
mapping = actionMapper.getMapping(request, dispatcher.getConfigurationManager());
} catch (Exception ex) {
LOG.error("error getting ActionMapping", ex);
dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
return;
}
// 如果mapping是空的，则去找static的内容
if (mapping == null) {
String resourcePath = RequestUtils.getServletPath(request);
if ("".equals(resourcePath) && null != request.getPathInfo()) {
resourcePath = request.getPathInfo();
}
if (serveStatic && resourcePath.startsWith("/struts")) {
findStaticResource(resourcePath, findAndCheckResources(resourcePath), request, response);
} else {
// this is a normal request, let it pass through
chain.doFilter(request, response);
}
// The framework did its job here
return;
}
//这个方法是关键
dispatcher.serviceAction(request, response, servletContext, mapping);
} finally {
try {
ActionContextCleanUp.cleanUp(req);
} finally {
UtilTimerStack.pop(timerKey);
}
}
}
我们再来查看Dispatcher中的serviceAction。
public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,
ActionMapping mapping) throws ServletException {
//创建上下文，extraContext中包括parameterMap, sessionMap, applicationMap, locale, request, response, servletContext等等
Map<String, Object> extraContext = createContextMap(request, response, mapping, context);
//如果request之前有value stack，则复制一个并把它放到上下文中。
ValueStack stack = (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);
if (stack != null) {
extraContext.put(ActionContext.VALUE_STACK, ValueStackFactory.getFactory().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();
//利用工厂方法新建一个ActionProxy，它提供诸多代理方法。
ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(
namespace, name, extraContext, true, false);
proxy.setMethod(method);
request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());
// 如果mapping中定义了Result，则运行这个Result。Result还是非常值得一讲的
if (mapping.getResult() != null) {
Result result = mapping.getResult();
result.execute(proxy.getInvocation());
} else {
//没有则运行execute，即调用Invocation.invoke()
proxy.execute();
}
// If there was a previous value stack then set it back onto the request
if (stack != null) {
request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);
}
} catch (ConfigurationException e) {
LOG.error("Could not find action or result", e);
sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);
} catch (Exception e) {
throw new ServletException(e);
} finally {
UtilTimerStack.pop(timerKey);
}
}
public interface ActionProxy {
/** 在所有的依赖都配置好调用，在DefaultActionProxyFactory.createActionProxy中使用 */
void prepare() throws Exception;
/** @return 返回所代理的对象 */
Object getAction();
/** @return 返回所代理的对象的名字 */
String getActionName();
/** @return ActionProxy产生所借助的ActionConfig */
ActionConfig getConfig();
/** 设置是否在运行完Action之后运行Action所返回的Result */
void setExecuteResult(boolean executeResult);
/** @return the status of whether the ActionProxy is set to execute the Result after the Action is executed
*/
boolean getExecuteResult();
/** @return the ActionInvocation：表示Action的运行状态，包括Interceptors和Action的实例 */
ActionInvocation getInvocation();
/**
* @return the namespace the ActionConfig for this ActionProxy is mapped to
*/
String getNamespace();
/**
* 运行ActionProxy. 把ActionContext 设置为 ActionInvocation中的 ActionContext
* 关键还是调用ActionInvocation.invoke()。
* DefaultActionProxy中的实现
*public String execute() throws Exception {
* ActionContext nestedContext = ActionContext.getContext();
* ActionContext.setContext(invocation.getInvocationContext());
* String retCode = null;
* String profileKey = "execute: ";
* try {
* UtilTimerStack.push(profileKey);
* retCode = invocation.invoke();
* } finally {
* if (cleanupContext) {
* ActionContext.setContext(nestedContext);
* }
* UtilTimerStack.pop(profileKey);
* }
* return retCode;
*}
*/
String execute() throws Exception;
/** 设置Invocation中的Method的，如果空的话就用execute。 */
void setMethod(String method);
/**
* Returns the method to execute, or null if no method has been specified (meaning "execute" will be invoked)
*/
String getMethod();
}
再来看一下ActionInvocation.invoke()的实现:
public String invoke() throws Exception {
String profileKey = "invoke: ";
try {
UtilTimerStack.push(profileKey);
//如果运行过了，就抛出异常
if (executed) {
throw new IllegalStateException("Action has already executed");
}
//运行Interceptor
if (interceptors.hasNext()) {
final InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();
//UtilTimerStack.profile()即
/*public static <T> T profile(String name, ProfilingBlock<T> block) throws Exception {
UtilTimerStack.push(name);
try {
return block.doProfiling();
}
finally {
UtilTimerStack.pop(name);
}
}*/
UtilTimerStack.profile("interceptor: "+interceptor.getName(),
new UtilTimerStack.ProfilingBlock<String>() {
public String doProfiling() throws Exception {
resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);
return null;
}
});
} else {
resultCode = invokeActionOnly();
}
// this is needed because the result will be executed, then control will return to the Interceptor, which will
// return above and flow through again
[color=red]没看懂，好像是由于在下面还要调用result.execute(ActionInvocation)，那么还是有可能再次调用这个地方？[/color]
if (!executed) {
if (preResultListeners != null) {
for (Iterator iterator = preResultListeners.iterator();
iterator.hasNext();) {
PreResultListener listener = (PreResultListener) iterator.next();
String _profileKey="preResultListener: ";
try {
UtilTimerStack.push(_profileKey);
listener.beforeResult(this, resultCode);
}
finally {
UtilTimerStack.pop(_profileKey);
}
}
}
// now execute the result, if we're supposed to
if (proxy.getExecuteResult()) {
//调用result.execute(ActionInvocation);
executeResult();
}
executed = true;
}
return resultCode;
}
finally {
UtilTimerStack.pop(profileKey);
}
}
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