1. Struts2架构图
请求首先通过Filter chain,Filter主要包括ActionContextCleanUp,它主要清理当前线程的ActionContext和Dispatcher;FilterDispatcher主要通过AcionMapper来决定需要调用哪个Action。
ActionMapper取得了ActionMapping后,在Dispatcher的serviceAction方法里创建ActionProxy,ActionProxy创建ActionInvocation,然后ActionInvocation调用Interceptors,执行Action本身,创建Result并返回,当然,如果要在返回之前做些什么,可以实现PreResultListener。
2. Struts2部分类介绍
这部分从Struts2参考文档中翻译就可以了。
ActionMapper
ActionMapper其实是HttpServletRequest和Action调用请求的一个映射,它屏蔽了Action对于Request等java Servlet类的依赖。Struts2中它的默认实现类是DefaultActionMapper,ActionMapper很大的用处可以根据自己的需要来设计url格式,它自己也有Restful的实现,具体可以参考文档的docs\actionmapper.html。
ActionProxy&ActionInvocation
Action的一个代理,由ActionProxyFactory创建,它本身不包括Action实例,默认实现DefaultActionProxy是由ActionInvocation持有Action实例。ActionProxy作用是如何取得Action,无论是本地还是远程。而ActionInvocation的作用是如何执行Action,拦截器的功能就是在ActionInvocation中实现的。
ConfigurationProvider&Configuration
ConfigurationProvider就是Struts2中配置文件的解析器,Struts2中的配置文件主要是尤其实现类XmlConfigurationProvider及其子类StrutsXmlConfigurationProvider来解析。
3. Struts2请求流程
1、客户端发送请求
2、请求先通过ActionContextCleanUp-->FilterDispatcher
3、FilterDispatcher通过ActionMapper来决定这个Request需要调用哪个Action
4、如果ActionMapper决定调用某个Action,FilterDispatcher把请求的处理交给ActionProxy,这儿已经转到它的Delegate--Dispatcher来执行
5、ActionProxy根据ActionMapping和ConfigurationManager找到需要调用的Action类
6、ActionProxy创建一个ActionInvocation的实例
7、ActionInvocation调用真正的Action,当然这涉及到相关拦截器的调用
8、Action执行完毕,ActionInvocation创建Result并返回,当然,如果要在返回之前做些什么,可以实现PreResultListener。添加PreResultListener可以在Interceptor中实现,不知道其它还有什么方式?
4. Struts2(2.1.2)部分源码阅读
从org.apache.struts2.dispatcher.FilterDispatcher开始
-
- public void init(FilterConfig filterConfig) throws ServletException {
- try {
- this.filterConfig = filterConfig;
-
- initLogging();
-
- dispatcher = createDispatcher(filterConfig);
- dispatcher.init();
- dispatcher.getContainer().inject(this);
-
- String param = filterConfig.getInitParameter("packages");
- String packages = "org.apache.struts2.static template org.apache.struts2.interceptor.debugging";
- if (param != null) {
- packages = param + " " + packages;
- }
- this.pathPrefixes = parse(packages);
- } finally {
- ActionContext.setContext(null);
- }
- }
顺着流程我们看Disptcher的init方法。init方法里就是初始读取一些配置文件等,先看init_DefaultProperties,主要是读取properties配置文件。
- private void init_DefaultProperties() {
- configurationManager.addConfigurationProvider(new DefaultPropertiesProvider());
- }
打开DefaultPropertiesProvider
- public void register(ContainerBuilder builder, LocatableProperties props)
- throws ConfigurationException {
-
- Settings defaultSettings = null;
- try {
- defaultSettings = new PropertiesSettings("org/apache/struts2/default");
- } catch (Exception e) {
- throw new ConfigurationException("Could not find or error in org/apache/struts2/default.properties", e);
- }
-
- loadSettings(props, defaultSettings);
- }
-
-
-
- public PropertiesSettings(String name) {
-
- URL settingsUrl = ClassLoaderUtils.getResource(name + ".properties", getClass());
-
- if (settingsUrl == null) {
- LOG.debug(name + ".properties missing");
- settings = new LocatableProperties();
- return;
- }
-
- settings = new LocatableProperties(new LocationImpl(null, settingsUrl.toString()));
-
-
- InputStream in = null;
- try {
- in = settingsUrl.openStream();
- settings.load(in);
- } catch (IOException e) {
- throw new StrutsException("Could not load " + name + ".properties:" + e, e);
- } finally {
- if(in != null) {
- try {
- in.close();
- } catch(IOException io) {
- LOG.warn("Unable to close input stream", io);
- }
- }
- }
- }
再来看init_TraditionalXmlConfigurations方法,这个是读取struts-default.xml和Struts.xml的方法。
- private void init_TraditionalXmlConfigurations() {
-
-
-
-
- String configPaths = initParams.get("config");
- if (configPaths == null) {
- configPaths = DEFAULT_CONFIGURATION_PATHS;
- }
- String[] files = configPaths.split("\\s*[,]\\s*");
-
- for (String file : files) {
- if (file.endsWith(".xml")) {
- if ("xwork.xml".equals(file)) {
- configurationManager.addConfigurationProvider(new XmlConfigurationProvider(file, false));
- } else {
- configurationManager.addConfigurationProvider(new StrutsXmlConfigurationProvider(file, false, servletContext));
- }
- } else {
- throw new IllegalArgumentException("Invalid configuration file name");
- }
- }
- }
对于其它配置文件只用StrutsXmlConfigurationProvider,此类继承XmlConfigurationProvider,而XmlConfigurationProvider又实现ConfigurationProvider接口。类XmlConfigurationProvider负责配置文件的读取和解析,addAction()方法负责读取<action>标签,并将数据保存在ActionConfig中;addResultTypes()方法负责将<result-type>标签转化为ResultTypeConfig对象;loadInterceptors()方法负责将<interceptor>标签转化为InterceptorConfi对象;loadInterceptorStack()方法负责将<interceptor-ref>标签转化为InterceptorStackConfig对象;loadInterceptorStacks()方法负责将<interceptor-stack>标签转化成InterceptorStackConfig对象。而上面的方法最终会被addPackage()方法调用,将所读取到的数据汇集到PackageConfig对象中。来看XmlConfigurationProvider的源代码,详细的我自己也就大体浏览了一下,各位可以自己研读。
- protected PackageConfig addPackage(Element packageElement) throws ConfigurationException {
- PackageConfig.Builder newPackage = buildPackageContext(packageElement);
-
- if (newPackage.isNeedsRefresh()) {
- return newPackage.build();
- }
- .
-
- addResultTypes(newPackage, packageElement);
- loadInterceptors(newPackage, packageElement);
- loadDefaultInterceptorRef(newPackage, packageElement);
- loadDefaultClassRef(newPackage, packageElement);
- loadGlobalResults(newPackage, packageElement);
- loadGobalExceptionMappings(newPackage, packageElement);
- NodeList actionList = packageElement.getElementsByTagName("action");
-
- for (int i = 0; i < actionList.getLength(); i++) {
- Element actionElement = (Element) actionList.item(i);
- addAction(actionElement, newPackage);
- }
- loadDefaultActionRef(newPackage, packageElement);
- PackageConfig cfg = newPackage.build();
- configuration.addPackageConfig(cfg.getName(), cfg);
- return cfg;
- }
这儿发现一个配置上的小技巧,我的xwork2.0.*是没有的,但是看源码是看到xwork2.1.*是可以的。继续看XmlConfigurationProvider的源代码:
- private List loadConfigurationFiles(String fileName, Element includeElement) {
- List<Document> docs = new ArrayList<Document>();
- if (!includedFileNames.contains(fileName)) {
-
- 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 (nodeName.equals("include")) {
- String includeFileName = child.getAttribute("file");
- if(includeFileName.indexOf('*') != -1 ) {
- ClassPathFinder wildcardFinder = new ClassPathFinder();
- wildcardFinder.setPattern(includeFileName);
- Vector<String> wildcardMatches = wildcardFinder.findMatches();
- for (String match : wildcardMatches) {
- docs.addAll(loadConfigurationFiles(match, child));
- }
- }
- else {
-
- docs.addAll(loadConfigurationFiles(includeFileName, child));
- }
- }
- }
- }
- docs.add(doc);
- loadedFileUrls.add(url.toString());
- }
- }
- return docs;
- }
init_CustomConfigurationProviders方式初始自定义的Provider,配置类全名和实现ConfigurationProvider接口,用逗号隔开即可。
- private void init_CustomConfigurationProviders() {
- String configProvs = initParams.get("configProviders");
- if (configProvs != null) {
- String[] classes = configProvs.split("\\s*[,]\\s*");
- for (String cname : classes) {
- try {
- Class cls = ClassLoaderUtils.loadClass(cname, this.getClass());
- ConfigurationProvider prov = (ConfigurationProvider)cls.newInstance();
- configurationManager.addConfigurationProvider(prov);
- }
-
- }
- }
- }
好了,现在再回到FilterDispatcher,每次发送一个Request,FilterDispatcher都会调用doFilter方法。
- 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 {
- ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();
- ActionContext ctx = new ActionContext(stack.getContext());
- ActionContext.setContext(ctx);
-
- UtilTimerStack.push(timerKey);
-
- request = prepareDispatcherAndWrapRequest(request, response);
- ActionMapping mapping;
- try {
-
- 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;
- }
-
-
- if (mapping == null) {
-
- String resourcePath = RequestUtils.getServletPath(request);
-
- if ("".equals(resourcePath) && null != request.getPathInfo()) {
- resourcePath = request.getPathInfo();
- }
-
- if (serveStatic && resourcePath.startsWith("/struts")) {
- String name = resourcePath.substring("/struts".length());
- findStaticResource(name, request, response);
- } else {
- chain.doFilter(request, response);
- }
- return;
- }
-
- dispatcher.serviceAction(request, response, servletContext, mapping);
-
- } finally {
- try {
- ActionContextCleanUp.cleanUp(req);
- } finally {
- UtilTimerStack.pop(timerKey);
- }
- }
- }
Dispatcher类的serviceAction方法:
- public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,ActionMapping mapping) throws ServletException {
-
- Map<String, Object> extraContext = createContextMap(request, response, mapping, context);
-
-
- ValueStack stack = (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);
- 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 (mapping.getResult() != null) {
- Result result = mapping.getResult();
- result.execute(proxy.getInvocation());
- } else {
- proxy.execute();
- }
-
-
- 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) {
- sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);
- } finally {
- UtilTimerStack.pop(timerKey);
- }
- }
第一句createContextMap()方法,该方法主要把Application、Session、Request的key value值拷贝到Map中,并放在HashMap<String,Object>中,可以参见createContextMap方法:
- public Map<String,Object> createContextMap(HttpServletRequest request, HttpServletResponse response,
- ActionMapping mapping, ServletContext context) {
-
-
- Map requestMap = new RequestMap(request);
-
- Map params = new HashMap(request.getParameterMap());
-
- Map session = new SessionMap(request);
-
- Map application = new ApplicationMap(context);
- Map<String,Object> extraContext = createContextMap(requestMap, params, session, application, request, response, context);
- extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);
- return extraContext;
- }
后面才是最主要的--ActionProxy,ActionInvocation。ActionProxy是Action的一个代理类,也就是说Action的调用是通过ActionProxy实现的,其实就是调用了ActionProxy.execute()方法,而该方法又调用了ActionInvocation.invoke()方法。归根到底,最后调用的是DefaultActionInvocation.invokeAction()方法。先看DefaultActionInvocation的init方法。
- public void init(ActionProxy proxy) {
- this.proxy = proxy;
- Map contextMap = createContextMap();
-
-
-
- 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());
-
-
- List interceptorList = new ArrayList(proxy.getConfig().getInterceptors());
- interceptors = interceptorList.iterator();
- }
-
- protected void createAction(Map contextMap) {
-
- String timerKey = "actionCreate: "+proxy.getActionName();
- try {
- UtilTimerStack.push(timerKey);
-
- action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);
- }
- ..
- } finally {
- UtilTimerStack.pop(timerKey);
- }
-
- if (actionEventListener != null) {
- action = actionEventListener.prepare(action, stack);
- }
- }
接下来看看DefaultActionInvocation 的invoke方法。
看程序中的if(interceptors.hasNext())语句,当然,interceptors里存储的是interceptorMapping列表(它包括一个Interceptor和一个name),所有的截拦器必须实现Interceptor的intercept方法,而该方法的参数恰恰又是ActionInvocation,在intercept方法中还是调用invocation.invoke(),从而实现了一个Interceptor链的调用。当所有的Interceptor执行完,最后调用invokeActionOnly方法来执行Action相应的方法。
- protected String invokeAction(Object action, ActionConfig actionConfig) throws Exception {
- String methodName = proxy.getMethod();
- String timerKey = "invokeAction: "+proxy.getActionName();
- try {
- UtilTimerStack.push(timerKey);
-
- boolean methodCalled = false;
- Object methodResult = null;
- Method method = null;
- try {
-
- method = getAction().getClass().getMethod(methodName, new Class[0]);
- } catch (NoSuchMethodException e) {
-
- try {
- String altMethodName = "do" + methodName.substring(0, 1).toUpperCase() + methodName.substring(1);
- method = getAction().getClass().getMethod(altMethodName, new Class[0]);
- } catch (NoSuchMethodException e1) {
-
- if (unknownHandler != null) {
- try {
- methodResult = unknownHandler.handleUnknownActionMethod(action, methodName);
- methodCalled = true;
- } catch (NoSuchMethodException e2) {
-
- throw e;
- }
- } else {
- throw e;
- }
- }
- }
-
- if (!methodCalled) {
- methodResult = method.invoke(action, new Object[0]);
- }
-
-
- if (methodResult instanceof Result) {
- this.explicitResult = (Result) methodResult;
- return null;
- } else {
- return (String) methodResult;
- }
- } catch (NoSuchMethodException e) {
- throw new IllegalArgumentException("The " + methodName + "() is not defined in action " + getAction().getClass() + "");
- } catch (InvocationTargetException e) {
-
- Throwable t = e.getTargetException();
-
- if (actionEventListener != null) {
- String result = actionEventListener.handleException(t, getStack());
- if (result != null) {
- return result;
- }
- }
- if (t instanceof Exception) {
- throw(Exception) t;
- } else {
- throw e;
- }
- } finally {
- UtilTimerStack.pop(timerKey);
- }
- }
好了,action执行完了,还要根据ResultConfig返回到view,也就是在invoke方法中调用executeResult方法。
- private void executeResult() throws Exception {
-
- result = createResult();
- String timerKey = "executeResult: "+getResultCode();
- try {
- UtilTimerStack.push(timerKey);
- if (result != null) {
-
-
- result.execute(this);
- } else if (resultCode != null && !Action.NONE.equals(resultCode)) {
- throw new ConfigurationException("No result defined for action " + getAction().getClass().getName()
- + " and result " + getResultCode(), proxy.getConfig());
- } else {
- if (LOG.isDebugEnabled()) {
- LOG.debug("No result returned for action "+getAction().getClass().getName()+" at "+proxy.getConfig().getLocation());
- }
- }
- } finally {
- UtilTimerStack.pop(timerKey);
- }
- }
- public Result createResult() throws Exception {
- if (explicitResult != null) {
- Result ret = explicitResult;
- explicitResult = null;;
- return ret;
- }
- ActionConfig config = proxy.getConfig();
- Map results = config.getResults();
- ResultConfig resultConfig = null;
- synchronized (config) {
- try {
-
- resultConfig = (ResultConfig) results.get(resultCode);
- } catch (NullPointerException e) {
- }
- if (resultConfig == null) {
-
- resultConfig = (ResultConfig) results.get("*");
- }
- }
- if (resultConfig != null) {
- try {
-
- Result result = objectFactory.buildResult(resultConfig, invocationContext.getContextMap());
- return result;
- } catch (Exception e) {
- LOG.error("There was an exception while instantiating the result of type " + resultConfig.getClassName(), e);
- throw new XWorkException(e, resultConfig);
- }
- } else if (resultCode != null && !Action.NONE.equals(resultCode) && unknownHandler != null) {
- return unknownHandler.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);
- }
- return null;
- }
-
- public Result buildResult(ResultConfig resultConfig, Map extraContext) throws Exception {
- String resultClassName = resultConfig.getClassName();
- if (resultClassName == null)
- return null;
-
- Object result = buildBean(resultClassName, extraContext);
-
-
-
-
- reflectionProvider.setProperties(resultConfig.getParams(), result, extraContext);
- if (result instanceof Result)
- return (Result) result;
- throw new ConfigurationException(result.getClass().getName() + " does not implement Result.");
- }