struts2请求的执行顺序

来看看struts2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);        }    }

在分析之前先看一下prepare.findActionMapping(）方法

 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;    }

如果从请求中获取不到ActionMapping，则从新生成
看这条代码
mapping = dispatcher.getContainer().getInstance(ActionMapper.class).getMapping(request, dispatcher.getConfigurationManager());

   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);        return parseActionName(mapping);    }

从里就是从uri中取数据从而为mapping赋值。

下面我们继续开始doFilter()中方法的讲解。
来看一下execute.executeAction(request, response, mapping);这个方法

  public void executeAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping) throws ServletException {        dispatcher.serviceAction(request, response, servletContext, mapping);    }

继续跟

 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();            }            // If there was a previous value stack then set it back onto the request            if (!nullStack) {                request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);            }        } catch (ConfigurationException e) {            // WW-2874 Only log error if in devMode            if (devMode) {                String reqStr = request.getRequestURI();                if (request.getQueryString() != null) {                    reqStr = reqStr + "?" + request.getQueryString();                }                LOG.error("Could not find action or result\n" + reqStr, e);            } else {                if (LOG.isWarnEnabled()) {                    LOG.warn("Could not find action or result", e);                }            }            sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);        } catch (Exception e) {            if (handleException || devMode) {                sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);            } else {                throw new ServletException(e);            }        } finally {            UtilTimerStack.pop(timerKey);        }    }

String namespace = mapping.getNamespace();String name = mapping.getName(); String method = mapping.getMethod();这里三条代码就用到最一开始的mapping，就是从uri中获取的数据。紧接着是创建ActionProxy，然后proxy.execute()方法。这里先去看看创建ActionProxy的过程。

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);    }

跟createActionProxy
创建DefaultActionInvocation将extraContext赋值给成员变量extraContext

public ActionProxy createActionProxy(ActionInvocation inv, String namespace, String actionName, String methodName, boolean executeResult, boolean cleanupContext) {        DefaultActionProxy proxy = new DefaultActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);        container.inject(proxy);        proxy.prepare();        return proxy;    }

创建DefaultActionProxy对象，将invocaiton，namespace,actionName,methodName,executeResult,cleanupContext，赋值给proxy ，然后我们去查看一下proxy.prepare()方法

protected void prepare() {        String profileKey = "create DefaultActionProxy: ";        try {            UtilTimerStack.push(profileKey);            config = configuration.getRuntimeConfiguration().getActionConfig(namespace, actionName);            if (config == null && unknownHandlerManager.hasUnknownHandlers()) {                config = unknownHandlerManager.handleUnknownAction(namespace, actionName);            }            if (config == null) {                throw new ConfigurationException(getErrorMessage());            }            resolveMethod();            if (!config.isAllowedMethod(method)) {                throw new ConfigurationException("Invalid method: " + method + " for action " + actionName);            }            invocation.init(this);        } finally {            UtilTimerStack.pop(profileKey);        }    }

在这个方法对config成员变量实例化了，ActionConfig
先来看一下configuration.getRuntimeConfiguration()

protected synchronized RuntimeConfiguration buildRuntimeConfiguration() throws ConfigurationException {        Map<String, Map<String, ActionConfig>> namespaceActionConfigs = new LinkedHashMap<String, Map<String, ActionConfig>>();        Map<String, String> namespaceConfigs = new LinkedHashMap<String, String>();        for (PackageConfig packageConfig : packageContexts.values()) {            if (!packageConfig.isAbstract()) {                String namespace = packageConfig.getNamespace();                Map<String, ActionConfig> configs = namespaceActionConfigs.get(namespace);                if (configs == null) {                    configs = new LinkedHashMap<String, ActionConfig>();                }                Map<String, ActionConfig> actionConfigs = packageConfig.getAllActionConfigs();                for (Object o : actionConfigs.keySet()) {                    String actionName = (String) o;                    ActionConfig baseConfig = actionConfigs.get(actionName);                    configs.put(actionName, buildFullActionConfig(packageConfig, baseConfig));                }                namespaceActionConfigs.put(namespace, configs);                if (packageConfig.getFullDefaultActionRef() != null) {                    namespaceConfigs.put(namespace, packageConfig.getFullDefaultActionRef());                }            }        }        PatternMatcher<int[]> matcher = container.getInstance(PatternMatcher.class);        return new RuntimeConfigurationImpl(Collections.unmodifiableMap(namespaceActionConfigs),                Collections.unmodifiableMap(namespaceConfigs), matcher);    }

将从packageConfig中获取actionConfigs,然后将actionconfig放入到namespaceConfigs中。
接下来看一下getActionConfig（）方法

 public ActionConfig getActionConfig(String namespace, String name) {            ActionConfig config = findActionConfigInNamespace(namespace, name);            // try wildcarded namespaces            if (config == null) {                NamespaceMatch match = namespaceMatcher.match(namespace);                if (match != null) {                    config = findActionConfigInNamespace(match.getPattern(), name);                    // If config found, place all the matches found in the namespace processing in the action's parameters                    if (config != null) {                        config = new ActionConfig.Builder(config)                                .addParams(match.getVariables())                                .build();                    }                }            }            // fail over to empty namespace            if ((config == null) && (namespace != null) && (!"".equals(namespace.trim()))) {                config = findActionConfigInNamespace("", name);            }            return config;        }

在加載配置信息的時候，就把配置文件中信息加載到InterceptorStackConfig，resultTypeConfig等等中最終是放到PackageConfig对象中了，这个PackageConfig对象被放到DefaultConfiguration的packageContexts中。而findActionConfigInNamespace是DefaultConfiguration类中内部类的方法

 private ActionConfig findActionConfigInNamespace(String namespace, String name) {            ActionConfig config = null;            if (namespace == null) {                namespace = "";            }            Map<String, ActionConfig> actions = namespaceActionConfigs.get(namespace);            if (actions != null) {                config = actions.get(name);                // Check wildcards                if (config == null) {                    config = namespaceActionConfigMatchers.get(namespace).match(name);                    // fail over to default action                    if (config == null) {                        String defaultActionRef = namespaceConfigs.get(namespace);                        if (defaultActionRef != null) {                            config = actions.get(defaultActionRef);                        }                    }                }            }            return config;        }

这里的namespaceActionConfigs其实是configuration.getRuntimeConfiguration()这个方法调用创建一个RuntimeConfiguration对象，传递进来，也就是说，这里的findActionConfigInNamespace也就在在PackageConfig中寻找。
看一下 prepare方法中的invocation.init(this);方法

 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();    }

this.proxy = proxy;这一条代码是将代理对象赋值给invocation对象。然后方法中创建action，并且将action放入根栈中最后。最后为拦截器映射得迭代器对象。
proxy.getConfig()里面就是配置信息里面的数据，所以这里可以拿到interceptorsmappings。

下面讲解一下proxy.execute()方法

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;    }

执行到invocation.invoke()方法

public String invoke() throws Exception {        String profileKey = "invoke: ";        try {            UtilTimerStack.push(profileKey);            if (executed) {                throw new IllegalStateException("Action has already executed");            }            if (interceptors.hasNext()) {                final InterceptorMapping interceptor = interceptors.next();                String interceptorMsg = "interceptor: " + interceptor.getName();                UtilTimerStack.push(interceptorMsg);                try {                                resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);                            }                finally {                    UtilTimerStack.pop(interceptorMsg);                }            } 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            if (!executed) {                if (preResultListeners != null) {                    for (Object preResultListener : preResultListeners) {                        PreResultListener listener = (PreResultListener) preResultListener;                        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()) {                    executeResult();                }                executed = true;            }            return resultCode;        }        finally {            UtilTimerStack.pop(profileKey);        }    }

在这个方法中拦截器会执行intercept方法，当然拦截器执行过程中会调用invocation.invoke()方法，从而形成拦截器链，当然当拦截器遍历完毕时就会执行到action的动作方法，然后action会返回，执行result结果集，第一次执行标识为true,执行玩改变标识，以后不再执行，执行完结果集返回，然后回到最后一个拦截器执行剩下的代码，然后一次往上执行拦截器剩下的代码。

到此完毕