Struts2架构图
请求首先通过Filter chainFilter主要包括ActionContextCleanUp它主要清理当前线程的ActionContext和DispatcherFilterDispatcher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ActionProxyActionProxy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。
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DefaultActionMapperActionMapper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。
ConfigurationProviderStruts2中的配置文件主要是尤其实现类XmlConfigurationProvider及其子类StrutsXmlConfigurationProvider来解析
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ActionFilterDispatcher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
Struts2(2.1.2)部分源码阅读
从org.apache.struts2.dispatcher.FilterDispatcher开始
//创建Dispatcher此类是一个Delegate它是真正完成根据url解析读取对应Action的地方 public void init(FilterConfig filterConfig) throws ServletException { try { this.filterConfig filterConfig; initLogging(); dispatcher createDispatcher(filterConfig); dispatcher.init(); dispatcher.getContainer().inject(this); //读取初始参数pakages调用parse()解析成类似/org/apache/struts2/static,/template的数组 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); } //PropertiesSettings //读取org/apache/struts2/default.properties的配置信息如果项目中需要覆盖可以在classpath里的struts.properties里覆写 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())); // Load settings 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() { //首先读取web.xml中的config初始参数值 //如果没有配置就使用默认的"struts-default.xml,struts-plugin.xml,struts.xml" //这儿就可以看出为什么默认的配置文件必须取名为这三个名称了 //如果不想使用默认的名称直接在web.xml中配置config初始参数即可 String configPaths initParams.get("config"); if (configPaths null) { configPaths DEFAULT_CONFIGURATION_PATHS; } String[] files configPaths.split("\\s*[,]\\s*"); //依次解析配置文件xwork.xml单独解析 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()方法负责读取标签并将数据保存在ActionConfig中addResultTypes()方法负责将标签转化为ResultTypeConfig对象loadInterceptors()方法负责将标签转化为InterceptorConfi对象loadInterceptorStack()方法负责将标签转化为InterceptorStackConfig对象loadInterceptorStacks()方法负责将标签转化成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 docs new ArrayList(); 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(); //解析每个action配置是对于include文件可以使用通配符*来进行配置 //如Struts.xml中可配置成 if (nodeName.equals("include")) { String includeFileName child.getAttribute("file"); if(includeFileName.indexOf(*) ! -1 ) { ClassPathFinder wildcardFinder new ClassPathFinder(); wildcardFinder.setPattern(includeFileName); Vector 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RequestFilterDispatcher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); //根据content type来使用不同的Request封装可以参见Dispatcher的wrapRequest request prepareDispatcherAndWrapRequest(request, response); ActionMapping mapping; try { //根据url取得对应的Action的配置信息--ActionMappingactionMapper是通过Container的inject注入的 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; } //如果找不到对应的action配置则直接返回。比如你输入***.jsp等等 //这儿有个例外就是如果path是以“/struts”开头则到初始参数packages配置的包路径去查找对应的静态资源并输出到页面流中当然.class文件除外。如果再没有则跳转到404 if (mapping null) { // there is no action in this request, should we look for a static resource? String resourcePath RequestUtils.getServletPath(request); if ("".equals(resourcePath) request.getPathInfo()) { resourcePath request.getPathInfo(); } if (serveStatic resourcePath.substring("/struts".length()); findStaticResource(name, request, response); } else { chain.doFilter(request, response); } return; } //正式开始Action的方法了 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 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); 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(); } // 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) { 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中可以参见createContextMap方法
public Map createContextMap(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping, ServletContext context) { // request map wrapping the http request objects Map requestMap new RequestMap(request); // parameters map wrapping the http parameters. ActionMapping parameters are now handled and applied separately Map params new HashMap(request.getParameterMap()); // session map wrapping the http session Map session new SessionMap(request); // application map wrapping the ServletContext Map application new ApplicationMap(context); Map 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--ActionProxyActionInvocation。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(); // 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); } //创建Action可Struts2里是每次请求都新建一个Action 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 dont get problems with the iterator if someone changes the list List interceptorList new ArrayList(proxy.getConfig().getInterceptors()); interceptors interceptorList.iterator(); } protected void createAction(Map contextMap) { // load action String timerKey "actionCreate: "proxy.getActionName(); try { UtilTimerStack.push(timerKey); //这儿默认建立Action是StrutsObjectFactory实际中我使用的时候都是使用Spring创建的Action这个时候使用的是SpringObjectFactory 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。
public String invoke() throws Exception { String profileKey "invoke: "; try { UtilTimerStack.push(profileKey); if (executed) { throw new IllegalStateException("Action has already executed"); } //先执行interceptors if (interceptors.hasNext()) { final InterceptorMapping interceptor (InterceptorMapping) interceptors.next(); UtilTimerStack.profile("interceptor: "interceptor.getName(), new UtilTimerStack.ProfilingBlock() { public String doProfiling() throws Exception { resultCode interceptor.getInterceptor().intercept(DefaultActionInvocation.this); return null; } }); } else { //interceptor执行完了之后执行action 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 if (!executed) { //在Result返回之前调用preResultListeners 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 were supposed to if (proxy.getExecuteResult()) { executeResult(); } executed true; } return resultCode; } finally { UtilTimerStack.pop(profileKey); } }
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 { //获得需要执行的方法 method getAction().getClass().getMethod(methodName, new Class[0]); } catch (NoSuchMethodException e) { //如果没有对应的方法则使用doXxxx来再次获得方法 try { String altMethodName "do" methodName.substring(0, 1).toUpperCase() methodName.substring(1); method getAction().getClass().getMethod(altMethodName, new Class[0]); } catch (NoSuchMethodException e1) { // well, give the unknown handler a shot if (unknownHandler ! null) { try { methodResult unknownHandler.handleUnknownActionMethod(action, methodName); methodCalled true; } catch (NoSuchMethodException e2) { // throw the original one throw e; } } else { throw e; } } } if (!methodCalled) { methodResult method.invoke(action, new Object[0]); } //根据不同的Result类型返回不同值 //如输出流Result 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) { // We try to return the source exception. 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 { //根据ResultConfig创建Result result createResult(); String timerKey "executeResult: "getResultCode(); try { UtilTimerStack.push(timerKey); if (result ! null) { //这儿正式执行:) //可以参考Result的实现如用了比较多的ServletDispatcherResult,ServletActionRedirectResult,ServletRedirectResult result.execute(this); } else if (resultCode ! null 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 { //根据result名称获得ResultConfigresultCode就是result的name resultConfig (ResultConfig) results.get(resultCode); } catch (NullPointerException e) { } if (resultConfig null) { //如果找不到对应name的ResultConfig则使用name为*的Result resultConfig (ResultConfig) results.get("*"); } } if (resultConfig ! null) { try { //参照StrutsObjectFactory的代码 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 null) { return unknownHandler.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode); } return null; } //StrutsObjectFactory public Result buildResult(ResultConfig resultConfig, Map extraContext) throws Exception { String resultClassName resultConfig.getClassName(); if (resultClassName null) return null; //创建Result因为Result是有状态的所以每次请求都新建一个 Object result buildBean(resultClassName, extraContext); //这句很重要后面将会谈到reflectionProvider参见OgnlReflectionProvider //resultConfig.getParams()就是result配置文件里所配置的参数 //setProperties方法最终调用的是Ognl类的setValue方法 //这句其实就是把param名值设置到根对象result上 reflectionProvider.setProperties(resultConfig.getParams(), result, extraContext); if (result instanceof Result) return (Result) result; throw new ConfigurationException(result.getClass().getName() " does not implement Result."); }
最后补充一下Struts2的查找值和设置值都是使用Ognl来实现的。关于Ognl的介绍可以到其官方网站查看http://www.ognl.org/我在网上也找到另外一篇http://www.javaeye.com/topic/254684和http://www.javaeye.com/topic/223612。完了来看下面这段小测试程序其它的Ognl的测试可以自己添加。
public class TestOgnl { private User user; private Map context; Before public void setUp() throws Exception { } Test public void ognlGetValue() throws Exception { reset(); Assert.assertEquals("myyate", Ognl.getValue("name", user)); Assert.assertEquals("cares", Ognl.getValue("dept.name", user)); Assert.assertEquals("myyate", Ognl.getValue("name", context, user)); Assert.assertEquals("contextmap", Ognl.getValue("#name", context, user)); Assert.assertEquals("parker", Ognl.getValue("#pen", context, user)); } Test public void ognlSetValue() throws Exception { reset(); Ognl.setValue("name", user, "myyateC"); Assert.assertEquals("myyateC", Ognl.getValue("name", user)); Ognl.setValue("dept.name", user, "caresC"); Assert.assertEquals("caresC", Ognl.getValue("dept.name", user)); Assert.assertEquals("contextmap", Ognl.getValue("#name", context, user)); Ognl.setValue("#name", context, user, "contextmapC"); Assert.assertEquals("contextmapC", Ognl.getValue("#name", context, user)); Assert.assertEquals("parker", Ognl.getValue("#pen", context, user)); Ognl.setValue("#name", context, user, "parkerC"); Assert.assertEquals("parkerC", Ognl.getValue("#name", context, user)); } public static void main(String[] args) throws Exception { JUnitCore.runClasses(TestOgnl.class); } private void reset() { user new User("myyate", new Dept("cares")); context new OgnlContext(); context.put("pen", "parker"); context.put("name", "contextmap"); } } class User { public User(String name, Dept dept) { this.name name; this.dept dept; } String name; private Dept dept; public Dept getDept() { return dept; } public String getName() { return name; } public void setDept(Dept dept) { this.dept dept; } public void setName(String name) { this.name name; } } class Dept { public Dept(String name) { this.name name; } private String name; public String getName() { return name; } public void setName(String name) { this.name name; } }