Struts2.3.15.1源码浅析

Struts2.3.15.1源码浅析
Struts2 两大运行主线：
- 1.初始化主线：初始化主线主要是为Struts2创建运行环境(此处的环境与Struts2身处的Web环境是有区别的)，初始化入口StrutsPrepareAndExecuteFilter继承 Filter，遵循Filter规范，初始化只是在应用启动的时候运行一次，以后无论过来多少HttpServletRequest都不会再运行啦。
StrutsPrepareAndExecuteFilter.java
Java代码
1. public void init(FilterConfig filterConfig) throws ServletException {
2. InitOperations init = new InitOperations();//Http请求预处理工具类，ExecuteOperates Http请求逻辑处理类
3. Dispatcher dispatcher = null;
4. try {
5. FilterHostConfig config = new FilterHostConfig(filterConfig);
6. init.initLogging(config);
7. dispatcher = init.initDispatcher(config);//核心分发器Dispatcher初始化
8. //初始化静态资源加载器
9. init.initStaticContentLoader(config, dispatcher);
10. //初始化进行http预处理操作类
11. prepare = new PrepareOperations(filterConfig.getServletContext(), dispatcher);
12. //初始化进行http请求逻辑处理操作类
13. execute = new ExecuteOperations(filterConfig.getServletContext(), dispatcher);
14. this.excludedPatterns = init.buildExcludedPatternsList(dispatcher);
16. postInit(dispatcher, filterConfig);
17. } finally {
18. if (dispatcher != null) {
19. dispatcher.cleanUpAfterInit();
20. }
21. init.cleanup();//初始化清除工作
22. }
23. }
首先我们来看看，Struts2核心分发器初始化过程：

InitOperations.java
Java代码
1. /**
2. * Creates and initializes the dispatcher
3. */
4. public Dispatcher initDispatcher( HostConfig filterConfig ) {
5. Dispatcher dispatcher = createDispatcher(filterConfig);
6. dispatcher.init();
7. return dispatcher;
8. }
10. /**
11. * Create a {@link Dispatcher}
12. */
13. private Dispatcher createDispatcher( HostConfig filterConfig ) {
14. Map<String, String> params = new HashMap<String, String>();
15. for ( Iterator e = filterConfig.getInitParameterNames(); e.hasNext(); ) {
16. String name = (String) e.next();
17. String value = filterConfig.getInitParameter(name);
18. params.put(name, value);
19. }
20. return new Dispatcher(filterConfig.getServletContext(), params);
21. }
顺着流程，接着探索dispatcher.init()，这里是加载配置文件的地方

Dispatcher.java
Java代码
1. public void init() {
3. if (configurationManager == null) {
4. configurationManager = createConfigurationManager(BeanSelectionProvider.DEFAULT_BEAN_NAME);
5. }
7. try {
8. init_FileManager();
9. init_DefaultProperties(); // [1]加载default.properties org/apache/struts2/default.properties
10. init_TraditionalXmlConfigurations(); // [2]加载struts-default.xml,struts-plugin.xml,struts.xml
11. init_LegacyStrutsProperties(); // [3]
12. init_CustomConfigurationProviders(); // [5]初始化自定义的provider配置类全名和实现ConfigurationProvider接口，用逗号隔开即可
13. init_FilterInitParameters() ; // [6]
14. init_AliasStandardObjects() ; // [7]加载框架内部内置的对象struts-default.xml中<bean>节点
16. Container container = init_PreloadConfiguration();
17. container.inject(this);
18. init_CheckWebLogicWorkaround(container);
20. if (!dispatcherListeners.isEmpty()) {
21. for (DispatcherListener l : dispatcherListeners) {
22. l.dispatcherInitialized(this);
23. }
24. }
25. } catch (Exception ex) {
26. if (LOG.isErrorEnabled())
27. LOG.error("Dispatcher initialization failed", ex);
28. throw new StrutsException(ex);
29. }
30. }
让我们截取init_TraditionalXmlConfigurations();的加载过程来了解Struts2是如何来加载我们配置的配置文件的：
Java代码
1. private void init_TraditionalXmlConfigurations() {
2. //首先读取web.xml中的config初始参数如果不存在，默认加载加载struts-default.xml,struts-plugin.xml,struts.xml
3. //如果不想使用默认值，在web.xml中设置config参数即可
4. String configPaths = initParams.get("config");
5. if (configPaths == null) {
6. configPaths = DEFAULT_CONFIGURATION_PATHS;
7. }
8. String[] files = configPaths.split("\s*[,]\s*");
9. for (String file : files) {
10. if (file.endsWith(".xml")) {
11. if ("xwork.xml".equals(file)) {//xwork.xml文件单独解析
12. configurationManager.addContainerProvider(createXmlConfigurationProvider(file, false));
13. } else {
14. configurationManager.addContainerProvider(createStrutsXmlConfigurationProvider(file, false, servletContext));
15. }
16. } else {
17. throw new IllegalArgumentException("Invalid configuration file name");
18. }
19. }
20. }
createStrutsXmlConfigurationProvider方法创建StrutsXmlConfigurationProvider对象，其继承XmlConfigurationProvider对象，而XmlConfigurationProvider 实现了ConfigurationProvider接口，ConfigurationProvider使用java很少见到的多继承机制，继承了ContainerProvider和PackageProvider接口。 XmlConfigurationProvider负责读取和解析配置文件，
Java代码
1. /**
2. * Create a PackageConfig from an XML element representing it.
3. */
4. protected PackageConfig addPackage(Element packageElement) throws ConfigurationException {
5. String packageName = packageElement.getAttribute("name");
6. PackageConfig packageConfig = configuration.getPackageConfig(packageName);
7. if (packageConfig != null) {
8. if (LOG.isDebugEnabled()) {
9. LOG.debug("Package [#0] already loaded, skipping re-loading it and using existing PackageConfig [#1]", packageName, packageConfig);
10. }
11. return packageConfig;
12. }
13. PackageConfig.Builder newPackage = buildPackageContext(packageElement);
14. if (newPackage.isNeedsRefresh()) {
15. return newPackage.build();
16. }
17. if (LOG.isDebugEnabled()) {
18. LOG.debug("Loaded " + newPackage);
19. }
20. // add result types (and default result) to this package
21. addResultTypes(newPackage, packageElement);
22. // load the interceptors and interceptor stacks for this package
23. loadInterceptors(newPackage, packageElement);
24. // load the default interceptor reference for this package
25. loadDefaultInterceptorRef(newPackage, packageElement);
26. // load the default class ref for this package
27. loadDefaultClassRef(newPackage, packageElement);
28. // load the global result list for this package
29. loadGlobalResults(newPackage, packageElement);
30. // load the global exception handler list for this package
31. loadGobalExceptionMappings(newPackage, packageElement);
32. // get actions
33. NodeList actionList = packageElement.getElementsByTagName("action");
34. for (int i = 0; i < actionList.getLength(); i++) {
35. Element actionElement = (Element) actionList.item(i);
36. addAction(actionElement, newPackage);
37. }
38. // load the default action reference for this package
39. loadDefaultActionRef(newPackage, packageElement);
40. PackageConfig cfg = newPackage.build();
41. configuration.addPackageConfig(cfg.getName(), cfg);
42. return cfg;
43. }
其中
- addAction()方法负责读取节点，并将数据保存在ActionConfig中；
- addResultTypes()方法负责读取节点，并将数据保存在ResultTypeConfig中；ResultTypeConfig使用了构造器模式创建对象
- loadInterceptors()方法负责读取节点，并将数据保存在InterceptorConfig中；
- loadInterceptorStack()方法负责读取节点，并将数据保存在InterceptorStackConfig中；
- loadInterceptorStacks()方法负责读取节点，并将数据保存在InterceptorStackConfig中；
而以上这些方法都将会被addPackage()invoke，并将数据汇集到PackageConfig中。

配置文件实际的加载流程： DefaultConfiguration.reloadContainer()时调用了containerProvider.init(this);

XmlConfigurationProvider.java
Java代码
1. public void init(Configuration configuration) {
2. this.configuration = configuration;
3. this.includedFileNames = configuration.getLoadedFileNames();
4. loadDocuments(configFileName);
5. }
加载Documents:
Java代码
1. private void loadDocuments(String configFileName) {
2. try {
3. loadedFileUrls.clear();
4. documents = loadConfigurationFiles(configFileName, null);
5. } catch (ConfigurationException e) {
6. throw e;
7. } catch (Exception e) {
8. throw new ConfigurationException("Error loading configuration file " + configFileName, e);
9. }
10. }
13. private List<Document> loadConfigurationFiles(String fileName, Element includeElement) {
14. List<Document> docs = new ArrayList<Document>();
15. List<Document> finalDocs = new ArrayList<Document>();
16. if (!includedFileNames.contains(fileName)) {
17. if (LOG.isDebugEnabled()) {
18. LOG.debug("Loading action configurations from: " + fileName);
19. }
21. includedFileNames.add(fileName);
23. Iterator<URL> urls = null;
24. InputStream is = null;
26. IOException ioException = null;
27. try {
28. urls = getConfigurationUrls(fileName);
29. } catch (IOException ex) {
30. ioException = ex;
31. }
33. if (urls == null || !urls.hasNext()) {
34. if (errorIfMissing) {
35. throw new ConfigurationException("Could not open files of the name " + fileName, ioException);
36. } else {
37. if (LOG.isInfoEnabled()) {
38. LOG.info("Unable to locate configuration files of the name "
39. + fileName + ", skipping");
40. }
41. return docs;
42. }
43. }
45. URL url = null;
46. while (urls.hasNext()) {
47. try {
48. url = urls.next();
49. is = fileManager.loadFile(url);
51. InputSource in = new InputSource(is);
53. in.setSystemId(url.toString());
55. docs.add(DomHelper.parse(in, dtdMappings));
56. } catch (XWorkException e) {
57. if (includeElement != null) {
58. throw new ConfigurationException("Unable to load " + url, e, includeElement);
59. } else {
60. throw new ConfigurationException("Unable to load " + url, e);
61. }
62. } catch (Exception e) {
63. throw new ConfigurationException("Caught exception while loading file " + fileName, e, includeElement);
64. } finally {
65. if (is != null) {
66. try {
67. is.close();
68. } catch (IOException e) {
69. LOG.error("Unable to close input stream", e);
70. }
71. }
72. }
73. }
75. //sort the documents, according to the "order" attribute
76. Collections.sort(docs, new Comparator<Document>() {
77. public int compare(Document doc1, Document doc2) {
78. return XmlHelper.getLoadOrder(doc1).compareTo(XmlHelper.getLoadOrder(doc2));
79. }
80. });
82. for (Document doc : docs) {
83. Element rootElement = doc.getDocumentElement();
84. NodeList children = rootElement.getChildNodes();
85. int childSize = children.getLength();
87. for (int i = 0; i < childSize; i++) {
88. Node childNode = children.item(i);
90. if (childNode instanceof Element) {
91. Element child = (Element) childNode;
93. final String nodeName = child.getNodeName();
94. //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
95. //如Struts.xml中可配置成<include file="actions_*.xml"/>
96. if ("include".equals(nodeName)) {
97. String includeFileName = child.getAttribute("file");
98. if (includeFileName.indexOf('*') != -1) {
99. // handleWildCardIncludes(includeFileName, docs, child);
100. ClassPathFinder wildcardFinder = new ClassPathFinder();
101. wildcardFinder.setPattern(includeFileName);
102. Vector<String> wildcardMatches = wildcardFinder.findMatches();
103. for (String match : wildcardMatches) {
104. finalDocs.addAll(loadConfigurationFiles(match, child));
105. }
106. } else {
107. finalDocs.addAll(loadConfigurationFiles(includeFileName, child));
108. }
109. }
110. }
111. }
112. finalDocs.add(doc);
113. loadedFileUrls.add(url.toString());
114. }
116. if (LOG.isDebugEnabled()) {
117. LOG.debug("Loaded action configuration from: " + fileName);
118. }
119. }
120. return finalDocs;
121. }
init_CustomConfigurationProviders(); // [5]初始化自定义的provider配置类全名和实现ConfigurationProvider接口，用逗号隔开即可
Java代码
1. private void init_CustomConfigurationProviders() {
2. String configProvs = initParams.get("configProviders");
3. if (configProvs != null) {
4. String[] classes = configProvs.split("\s*[,]\s*");
5. for (String cname : classes) {
6. try {
7. Class cls = ClassLoaderUtil.loadClass(cname, this.getClass());
8. ConfigurationProvider prov = (ConfigurationProvider)cls.newInstance();
9. configurationManager.addContainerProvider(prov);
10. } catch (InstantiationException e) {
11. throw new ConfigurationException("Unable to instantiate provider: "+cname, e);
12. } catch (IllegalAccessException e) {
13. throw new ConfigurationException("Unable to access provider: "+cname, e);
14. } catch (ClassNotFoundException e) {
15. throw new ConfigurationException("Unable to locate provider class: "+cname, e);
16. }
17. }
18. }
19. }
接下来我们把目光放到Container container = init_PreloadConfiguration();上，从代码的表面意义上可以看出是对容器进行初始化
Java代码
1. private Container init_PreloadConfiguration() {
2. Configuration config = configurationManager.getConfiguration();
3. Container container = config.getContainer();
5. boolean reloadi18n = Boolean.valueOf(container.getInstance(String.class, StrutsConstants.STRUTS_I18N_RELOAD));
6. LocalizedTextUtil.setReloadBundles(reloadi18n);
8. ContainerHolder.store(container);
10. return container;
11. }
Configuration与ConfigurationManager作为Struts2初始化过程中的两大强力的辅助类，对于配置元素的管理启动了至关重要的作用。

Configuration，提供了框架所有配置元素访问的接口，而且对所有配置元素进行初始化调度，接下来我们就从 Configuration config = configurationManager.getConfiguration();一点一点地来揭示Configuration对配置元素初始化调度的本质。
Java代码
1. /**
2. * Get the current XWork configuration object. By default an instance of DefaultConfiguration will be returned
3. *
4. * @see com.opensymphony.xwork2.config.impl.DefaultConfiguration
5. */
6. public synchronized Configuration getConfiguration() {
7. if (configuration == null) {
8. setConfiguration(createConfiguration(defaultFrameworkBeanName));
9. try {
10. configuration.reloadContainer(getContainerProviders());
11. } catch (ConfigurationException e) {
12. setConfiguration(null);
13. throw new ConfigurationException("Unable to load configuration.", e);
14. }
15. } else {
16. conditionalReload();
17. }
19. return configuration;
20. }
关键在于configuration.reloadContainer(getContainerProviders());方法，我们接着看代码：
Java代码
1. /**
2. * Calls the ConfigurationProviderFactory.getConfig() to tell it to reload the configuration and then calls
3. * buildRuntimeConfiguration().
4. *
5. * @throws ConfigurationException
6. */
7. public synchronized List<PackageProvider> reloadContainer(List<ContainerProvider> providers) throws ConfigurationException {
8. packageContexts.clear();
9. loadedFileNames.clear();
10. List<PackageProvider> packageProviders = new ArrayList<PackageProvider>();
12. ContainerProperties props = new ContainerProperties();
13. ContainerBuilder builder = new ContainerBuilder();
14. Container bootstrap = createBootstrapContainer(providers);
15. for (final ContainerProvider containerProvider : providers)
16. {
17. bootstrap.inject(containerProvider);
18. containerProvider.init(this);
19. containerProvider.register(builder, props);
20. }
21. props.setConstants(builder);
23. builder.factory(Configuration.class, new Factory<Configuration>() {
24. public Configuration create(Context context) throws Exception {
25. return DefaultConfiguration.this;
26. }
27. });
29. ActionContext oldContext = ActionContext.getContext();
30. try {
31. // Set the bootstrap container for the purposes of factory creation
33. setContext(bootstrap);
34. container = builder.create(false);
35. setContext(container);
36. objectFactory = container.getInstance(ObjectFactory.class);
38. // Process the configuration providers first
39. for (final ContainerProvider containerProvider : providers)
40. {
41. if (containerProvider instanceof PackageProvider) {
42. container.inject(containerProvider);
43. ((PackageProvider)containerProvider).loadPackages();
44. packageProviders.add((PackageProvider)containerProvider);
45. }
46. }
48. // Then process any package providers from the plugins
49. Set<String> packageProviderNames = container.getInstanceNames(PackageProvider.class);
50. for (String name : packageProviderNames) {
51. PackageProvider provider = container.getInstance(PackageProvider.class, name);
52. provider.init(this);
53. provider.loadPackages();
54. packageProviders.add(provider);
55. }
57. rebuildRuntimeConfiguration();
58. } finally {
59. if (oldContext == null) {
60. ActionContext.setContext(null);
61. }
62. }
63. return packageProviders;
64. }
很显然我们在这个方法中看到，方法的参数即是一组配置元素的加载器(ConfigurationProvider) Struts2的初始换主线自此全部结束。

*****************************************华丽的分割线***************************************

下面我们再来看看Struts2的第二条主线：

######请求处理主线我们回到StrutsPrepareAndExecuteFilter来看看，Filter标准中的doFilter()方法：
Java代码
1. public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
3. HttpServletRequest request = (HttpServletRequest) req;
4. HttpServletResponse response = (HttpServletResponse) res;
6. try {
7. prepare.setEncodingAndLocale(request, response);
8. prepare.createActionContext(request, response);
9. prepare.assignDispatcherToThread();
10. if (excludedPatterns != null && prepare.isUrlExcluded(request, excludedPatterns)) {
11. chain.doFilter(request, response);
12. } else {
13. request = prepare.wrapRequest(request);
14. ActionMapping mapping = prepare.findActionMapping(request, response, true);
15. if (mapping == null) {
16. boolean handled = execute.executeStaticResourceRequest(request, response);
17. if (!handled) {
18. chain.doFilter(request, response);
19. }
20. } else {
21. execute.executeAction(request, response, mapping);
22. }
23. }
24. } finally {
25. prepare.cleanupRequest(request);
26. }
27. }
prepare.createActionContext(request, response);：创建上下文ActionContext并初始化其内部线程安全的ThreadLocal对象
Java代码
1. /**
2. * Creates the action context and initializes the thread local
3. */
4. public ActionContext createActionContext(HttpServletRequest request, HttpServletResponse response) {
5. ActionContext ctx;
6. Integer counter = 1;
7. Integer oldCounter = (Integer) request.getAttribute(CLEANUP_RECURSION_COUNTER);
8. if (oldCounter != null) {
9. counter = oldCounter + 1;
10. }
12. ActionContext oldContext = ActionContext.getContext();
13. if (oldContext != null) {
14. // detected existing context, so we are probably in a forward
15. ctx = new ActionContext(new HashMap<String, Object>(oldContext.getContextMap()));
16. } else {
17. ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();
18. stack.getContext().putAll(dispatcher.createContextMap(request, response, null, servletContext));
19. ctx = new ActionContext(stack.getContext());
20. }
21. request.setAttribute(CLEANUP_RECURSION_COUNTER, counter);
22. ActionContext.setContext(ctx);
23. return ctx;
24. }
prepare.assignDispatcherToThread();:将dispatcher对象绑定到Dispatcher内部线程安全的instance对象中

request = prepare.wrapRequest(request);:对HttpServletRequest进行封装，传统的Web容器元素的数据是通过HttpServletRequest 的接口实现访问，但是在Struts2中数据的储存位置发生了变化，它们不在适合于web对象绑定在一起，而是以ActionContext的形式存在于当前的线程中，故传统的访问方式无法访问到Struts2中的数据，因此Struts2针对这种情况作出了对HttpServletRequest装饰的扩展。

PrepareOperations.java
Java代码
1. /**
2. * Wraps the request with the Struts wrapper that handles multipart requests better
3. * @return The new request, if there is one
4. * @throws ServletException
5. */
6. public HttpServletRequest wrapRequest(HttpServletRequest oldRequest) throws ServletException {
7. HttpServletRequest request = oldRequest;
8. try {
9. // Wrap request first, just in case it is multipart/form-data
10. // parameters might not be accessible through before encoding (ww-1278)
11. request = dispatcher.wrapRequest(request, servletContext);
12. } catch (IOException e) {
13. throw new ServletException("Could not wrap servlet request with MultipartRequestWrapper!", e);
14. }
15. return request;
16. }
Dispatcher.java
Java代码
1. /**
2. * Wrap and return the given request or return the original request object.
3. * </p>
4. * This method transparently handles multipart data as a wrapped class around the given request.
5. * Override this method to handle multipart requests in a special way or to handle other types of requests.
6. * Note, {@link org.apache.struts2.dispatcher.multipart.MultiPartRequestWrapper} is
7. * flexible - look first to that object before overriding this method to handle multipart data.
8. *
9. * @param request the HttpServletRequest object.
10. * @param servletContext Our ServletContext object
11. * @return a wrapped request or original request.
12. * @see org.apache.struts2.dispatcher.multipart.MultiPartRequestWrapper
13. * @throws java.io.IOException on any error.
14. */
15. public HttpServletRequest wrapRequest(HttpServletRequest request, ServletContext servletContext) throws IOException {
16. // don't wrap more than once
17. if (request instanceof StrutsRequestWrapper) {
18. return request;
19. }
21. String content_type = request.getContentType();
22. if (content_type != null && content_type.contains("multipart/form-data")) {
23. MultiPartRequest mpr = getMultiPartRequest();
24. LocaleProvider provider = getContainer().getInstance(LocaleProvider.class);
25. request = new MultiPartRequestWrapper(mpr, request, getSaveDir(servletContext), provider);
26. } else {
27. request = new StrutsRequestWrapper(request, disableRequestAttributeValueStackLookup);
28. }
30. return request;
31. }
ActionMapping mapping = prepare.findActionMapping(request, response, true);ActionMapping是一个普通的java类，但是它将 URL形式的HTTP请求与Struts2中的Action建立起了联系。Struts2在进行Http请求处理时，由ActionMapper的实现类在运行期查找相应的事件映射关系并生成ActionMapping对象。
Java代码
1. /**
2. * Finds and optionally creates an {@link ActionMapping}. if forceLookup is false, it first looks in the current request to see if one
3. * has already been found, otherwise, it creates it and stores it in the request. No mapping will be created in the
4. * case of static resource requests or unidentifiable requests for other servlets, for example.
5. * @param forceLookup if true, the action mapping will be looked up from the ActionMapper instance, ignoring if there is one
6. * in the request or not
7. */
8. public ActionMapping findActionMapping(HttpServletRequest request, HttpServletResponse response, boolean forceLookup) {
9. ActionMapping mapping = (ActionMapping) request.getAttribute(STRUTS_ACTION_MAPPING_KEY);
10. if (mapping == null || forceLookup) {
11. try {
12. //ActionMapper类才是Struts2进行URL Mapping关系查找的核心类
13. mapping = dispatcher.getContainer().getInstance(ActionMapper.class).getMapping(request, dispatcher.getConfigurationManager());
14. if (mapping != null) {
15. request.setAttribute(STRUTS_ACTION_MAPPING_KEY, mapping);
16. }
17. } catch (Exception ex) {
18. dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
19. }
20. }
22. return mapping;
23. }
ActionMapper类具有多个默认的实现类，每个实现类具有不同的ActionMapping查找规则，所以这个地方给我们留下了无限的遐想，是个很好的扩展点。

execute.executeAction(request, response, mapping);:开始真正执行业务逻辑 ExecuteOperations.java
Java代码
1. /**
2. * Executes an action
3. * @throws ServletException
4. */
5. public void executeAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping) throws ServletException {
6. dispatcher.serviceAction(request, response, servletContext, mapping);
7. }
Dispatcher.java
Java代码
1. public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,
2. ActionMapping mapping) throws ServletException {
4. Map<String, Object> extraContext = createContextMap(request, response, mapping, context);
6. // If there was a previous value stack, then create a new copy and pass it in to be used by the new Action
7. ValueStack stack = (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);
8. boolean nullStack = stack == null;
9. if (nullStack) {
10. ActionContext ctx = ActionContext.getContext();
11. if (ctx != null) {
12. stack = ctx.getValueStack();
13. }
14. }
15. if (stack != null) {
16. extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack));
17. }
19. String timerKey = "Handling request from Dispatcher";
20. try {
21. UtilTimerStack.push(timerKey);
22. String namespace = mapping.getNamespace();
23. String name = mapping.getName();
24. String method = mapping.getMethod();
26. Configuration config = configurationManager.getConfiguration();
27. ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(
28. namespace, name, method, extraContext, true, false);
30. request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());
31. //如果ActionMapping对象中包含Result对象，则直接跳过Action而执行Result
32. // if the ActionMapping says to go straight to a result, do it!
33. if (mapping.getResult() != null) {
34. Result result = mapping.getResult();
35. result.execute(proxy.getInvocation());
36. } else {
37. proxy.execute();
38. }
40. // If there was a previous value stack then set it back onto the request
41. if (!nullStack) {
42. request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);
43. }
44. } catch (ConfigurationException e) {
45. // WW-2874 Only log error if in devMode
46. if (devMode) {
47. String reqStr = request.getRequestURI();
48. if (request.getQueryString() != null) {
49. reqStr = reqStr + "?" + request.getQueryString();
50. }
51. LOG.error("Could not find action or result " + reqStr, e);
52. } else {
53. if (LOG.isWarnEnabled()) {
54. LOG.warn("Could not find action or result", e);
55. }
56. }
57. sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);
58. } catch (Exception e) {
59. if (handleException || devMode) {
60. sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);
61. } else {
62. throw new ServletException(e);
63. }
64. } finally {
65. UtilTimerStack.pop(timerKey);
66. }
67. }
Map<String, Object> extraContext = createContextMap(request, response, mapping, context);: 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

Dispatcher.java
Java代码
1. /**
2. * Create a context map containing all the wrapped request objects
3. *
4. * @param request The servlet request
5. * @param response The servlet response
6. * @param mapping The action mapping
7. * @param context The servlet context
8. * @return A map of context objects
9. */
10. public Map<String,Object> createContextMap(HttpServletRequest request, HttpServletResponse response,
11. ActionMapping mapping, ServletContext context) {
13. // request map wrapping the http request objects
14. Map requestMap = new RequestMap(request);
16. // parameters map wrapping the http parameters. ActionMapping parameters are now handled and applied separately
17. Map params = new HashMap(request.getParameterMap());
19. // session map wrapping the http session
20. Map session = new SessionMap(request);
22. // application map wrapping the ServletContext
23. Map application = new ApplicationMap(context);
25. Map<String,Object> extraContext = createContextMap(requestMap, params, session, application, request, response, context);
27. if (mapping != null) {
28. extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);
29. }
30. return extraContext;
31. }
接下来调用Configuration对象的reloadContainer()利用ContainerBuilder对象生成Container对象，为生成ActionProxy对象做好准备，

ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy( namespace, name, method, extraContext, true, false);创建ActionProxyFacotry的过程也完成了ActionInvocation对象的创建：

DefaultActionProxyFactory.java----------createActionProxy()
Java代码
1. public ActionProxy createActionProxy(ActionInvocation inv, String namespace, String actionName, String methodName, boolean executeResult, boolean cleanupContext) {
2. DefaultActionProxy proxy = new DefaultActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);
3. container.inject(proxy);
4. proxy.prepare();//
5. return proxy;
6. }
DefaultActionProxy.java----------prepare()
Java代码
1. protected void prepare() {
2. String profileKey = "create DefaultActionProxy: ";
3. try {
4. UtilTimerStack.push(profileKey);
5. config = configuration.getRuntimeConfiguration().getActionConfig(namespace, actionName);
7. if (config == null && unknownHandlerManager.hasUnknownHandlers()) {
8. config = unknownHandlerManager.handleUnknownAction(namespace, actionName);
9. }
10. if (config == null) {
11. throw new ConfigurationException(getErrorMessage());
12. }
14. resolveMethod();
16. if (!config.isAllowedMethod(method)) {
17. throw new ConfigurationException("Invalid method: " + method + " for action " + actionName);
18. }
20. invocation.init(this);
22. } finally {
23. UtilTimerStack.pop(profileKey);
24. }
25. }
DefaultActionInvocation.java-------------init(ActionProxy proxy)
Java代码
1. public void init(ActionProxy proxy) {
2. this.proxy = proxy;
3. Map<String, Object> contextMap = createContextMap();
5. // Setting this so that other classes, like object factories, can use the ActionProxy and other
6. // contextual information to operate
7. ActionContext actionContext = ActionContext.getContext();
9. if (actionContext != null) {
10. actionContext.setActionInvocation(this);
11. }
13. createAction(contextMap);
15. if (pushAction) {
16. stack.push(action);//压入CompoundRoot 压栈操作
17. contextMap.put("action", action);
18. }
20. invocationContext = new ActionContext(contextMap);
21. invocationContext.setName(proxy.getActionName());
23. // get a new List so we don't get problems with the iterator if someone changes the list
24. List<InterceptorMapping> interceptorList = new ArrayList<InterceptorMapping>(proxy.getConfig().getInterceptors());
25. interceptors = interceptorList.iterator();
26. }
DefaultActionInvocation.java---createAction(contextMap);
Java代码
1. protected void createAction(Map<String, Object> contextMap) {
2. // load action
3. String timerKey = "actionCreate: " + proxy.getActionName();
4. try {
5. UtilTimerStack.push(timerKey);
6. action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);
7. } catch (InstantiationException e) {
8. throw new XWorkException("Unable to intantiate Action!", e, proxy.getConfig());
9. } catch (IllegalAccessException e) {
10. throw new XWorkException("Illegal access to constructor, is it public?", e, proxy.getConfig());
11. } catch (Exception e) {
12. String gripe;
14. if (proxy == null) {
15. gripe = "Whoa! No ActionProxy instance found in current ActionInvocation. This is bad ... very bad";
16. } else if (proxy.getConfig() == null) {
17. gripe = "Sheesh. Where'd that ActionProxy get to? I can't find it in the current ActionInvocation!?";
18. } else if (proxy.getConfig().getClassName() == null) {
19. gripe = "No Action defined for '" + proxy.getActionName() + "' in namespace '" + proxy.getNamespace() + "'";
20. } else {
21. gripe = "Unable to instantiate Action, " + proxy.getConfig().getClassName() + ", defined for '" + proxy.getActionName() + "' in namespace '" + proxy.getNamespace() + "'";
22. }
24. gripe += (((" -- " + e.getMessage()) != null) ? e.getMessage() : " [no message in exception]");
25. throw new XWorkException(gripe, e, proxy.getConfig());
26. } finally {
27. UtilTimerStack.pop(timerKey);
28. }
30. if (actionEventListener != null) {
31. action = actionEventListener.prepare(action, stack);
32. }
33. }
继续回到Dispatcher中的proxy.execute();继续执行业务逻辑 DefaultActionProxy.java-------------execute()
Java代码
1. public String execute() throws Exception {
2. ActionContext nestedContext = ActionContext.getContext();
3. ActionContext.setContext(invocation.getInvocationContext());
5. String retCode = null;
7. String profileKey = "execute: ";
8. try {
9. UtilTimerStack.push(profileKey);
11. retCode = invocation.invoke();
12. } finally {
13. if (cleanupContext) {
14. ActionContext.setContext(nestedContext);
15. }
16. UtilTimerStack.pop(profileKey);
17. }
19. return retCode;
20. }
DefaultActionInvocation.java---invoke()
Java代码
1. /**
2. * @throws ConfigurationException If no result can be found with the returned code
3. */
4. public String invoke() throws Exception {
5. String profileKey = "invoke: ";
6. try {
7. UtilTimerStack.push(profileKey);
9. if (executed) {
10. throw new IllegalStateException("Action has already executed");
11. }
13. if (interceptors.hasNext()) {
14. final InterceptorMapping interceptor = interceptors.next();
15. String interceptorMsg = "interceptor: " + interceptor.getName();
16. UtilTimerStack.push(interceptorMsg);
17. try {
18. resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);
19. }
20. finally {
21. UtilTimerStack.pop(interceptorMsg);
22. }
23. } else {
24. resultCode = invokeActionOnly();
25. }
27. // this is needed because the result will be executed, then control will return to the Interceptor, which will
28. // return above and flow through again
29. if (!executed) {
30. if (preResultListeners != null) {
31. for (Object preResultListener : preResultListeners) {
32. PreResultListener listener = (PreResultListener) preResultListener;
34. String _profileKey = "preResultListener: ";
35. try {
36. UtilTimerStack.push(_profileKey);
37. listener.beforeResult(this, resultCode);
38. }
39. finally {
40. UtilTimerStack.pop(_profileKey);
41. }
42. }
43. }
45. // now execute the result, if we're supposed to
46. if (proxy.getExecuteResult()) {
47. executeResult();
48. }
50. executed = true;
51. }
53. return resultCode;
54. }
55. finally {
56. UtilTimerStack.pop(profileKey);
57. }
58. }
resultCode = invokeActionOnly();:真正调用Action实际逻辑的地方

DefaultActionInvocation.java---invokeActionOnly()
Java代码
1. public String invokeActionOnly() throws Exception {
2. return invokeAction(getAction(), proxy.getConfig());
3. }
5. protected String invokeAction(Object action, ActionConfig actionConfig) throws Exception {
6. String methodName = proxy.getMethod();
8. if (LOG.isDebugEnabled()) {
9. LOG.debug("Executing action method = " + actionConfig.getMethodName());
10. }
12. String timerKey = "invokeAction: " + proxy.getActionName();
13. try {
14. UtilTimerStack.push(timerKey);
16. boolean methodCalled = false;
17. Object methodResult = null;
18. Method method = null;
19. try {
20. method = getAction().getClass().getMethod(methodName, EMPTY_CLASS_ARRAY);
21. } catch (NoSuchMethodException e) {
22. // hmm -- OK, try doXxx instead
23. try {
24. String altMethodName = "do" + methodName.substring(0, 1).toUpperCase() + methodName.substring(1);
25. method = getAction().getClass().getMethod(altMethodName, EMPTY_CLASS_ARRAY);
26. } catch (NoSuchMethodException e1) {
27. // well, give the unknown handler a shot
28. if (unknownHandlerManager.hasUnknownHandlers()) {
29. try {
30. methodResult = unknownHandlerManager.handleUnknownMethod(action, methodName);
31. methodCalled = true;
32. } catch (NoSuchMethodException e2) {
33. // throw the original one
34. throw e;
35. }
36. } else {
37. throw e;
38. }
39. }
40. }
42. if (!methodCalled) {
43. methodResult = method.invoke(action, EMPTY_OBJECT_ARRAY);
44. }
46. return saveResult(actionConfig, methodResult);
47. } catch (NoSuchMethodException e) {
48. throw new IllegalArgumentException("The " + methodName + "() is not defined in action " + getAction().getClass() + "");
49. } catch (InvocationTargetException e) {
50. // We try to return the source exception.
51. Throwable t = e.getTargetException();
53. if (actionEventListener != null) {
54. String result = actionEventListener.handleException(t, getStack());
55. if (result != null) {
56. return result;
57. }
58. }
59. if (t instanceof Exception) {
60. throw (Exception) t;
61. } else {
62. throw e;
63. }
64. } finally {
65. UtilTimerStack.pop(timerKey);
66. }
67. }
OK 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。
Java代码
1. // now execute the result, if we're supposed to
2. if (proxy.getExecuteResult()) {
3. executeResult();
4. }
DefaultActionInvocation.java---executeResult()
Java代码
1. /**
2. * Uses getResult to get the final Result and executes it
3. *
4. * @throws ConfigurationException If not result can be found with the returned code
5. */
6. private void executeResult() throws Exception {
7. result = createResult();
9. String timerKey = "executeResult: " + getResultCode();
10. try {
11. UtilTimerStack.push(timerKey);
12. if (result != null) {
13. result.execute(this);
14. } else if (resultCode != null && !Action.NONE.equals(resultCode)) {
15. throw new ConfigurationException("No result defined for action " + getAction().getClass().getName()
16. + " and result " + getResultCode(), proxy.getConfig());
17. } else {
18. if (LOG.isDebugEnabled()) {
19. LOG.debug("No result returned for action " + getAction().getClass().getName() + " at " + proxy.getConfig().getLocation());
20. }
21. }
22. } finally {
23. UtilTimerStack.pop(timerKey);
24. }
25. }
DefaultActionInvocation.java---createResult()
Java代码
1. public Result createResult() throws Exception {
3. if (explicitResult != null) {
4. Result ret = explicitResult;
5. explicitResult = null;
7. return ret;
8. }
9. ActionConfig config = proxy.getConfig();
10. Map<String, ResultConfig> results = config.getResults();
12. ResultConfig resultConfig = null;
14. try {
15. resultConfig = results.get(resultCode);
16. } catch (NullPointerException e) {
17. if (LOG.isDebugEnabled()) {
18. LOG.debug("Got NPE trying to read result configuration for resultCode [#0]", resultCode);
19. }
20. }
22. if (resultConfig == null) {
23. // If no result is found for the given resultCode, try to get a wildcard '*' match.
24. resultConfig = results.get("*");
25. }
27. if (resultConfig != null) {
28. try {
29. return objectFactory.buildResult(resultConfig, invocationContext.getContextMap());
30. } catch (Exception e) {
31. if (LOG.isErrorEnabled()) {
32. LOG.error("There was an exception while instantiating the result of type #0", e, resultConfig.getClassName());
33. }
34. throw new XWorkException(e, resultConfig);
35. }
36. } else if (resultCode != null && !Action.NONE.equals(resultCode) && unknownHandlerManager.hasUnknownHandlers()) {
37. return unknownHandlerManager.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);
38. }
39. return null;
40. }
具体result.execute(this);的实现可以参考一下各类中的具体代码：

时间匆忙，只是对整个执行流程做了代码层面的演示，待后续将详细说明附上 ^.^
相关阅读:
刷题柱 -- 暂封
 模板重搭建計劃
 思路与好题记录与小技巧
 错误记录
 随便记点东西……
图床
 杂碎的小技巧
 hnsdfz -- 6.21 -- day7
hsdf -- 6.21 -- day6
hnsdfz -- 6.20 -- day5
原文地址：https://www.cnblogs.com/SoniceryD/p/4208779.html

Struts2.3.15.1源码浅析

Struts2 两大运行主线：