Struts1.3.x中ActionServlet源码分析之执行
执行流程：
1、ActionServlet处理.do的请求 不管是get还是post方式都将转到
??? protected void process(HttpServletRequest request, HttpServletResponse response) 方法。
???
2、根据请求对象和servletContext对象选择请求所隶属的模块
??? ModuleUtils.getInstance().selectModule(request, getServletContext());
???
3、加载模块配置对象 ModuleConfig config = getModuleConfig(request);
4、加载请求处理对象
??? RequestProcessor processor = getProcessorForModule(config);
??????? if (processor == null) {
??????????? processor = getRequestProcessor(config);
??????? }
???????
5、调用请求对象（processor）对象的
??? public void process(HttpServletRequest request, HttpServletResponse response)
??????? throws IOException, ServletException
??? 方法处理请求。
???
6、对mutipart请求（上传）进行特殊包装 request = processMultipart(request);
??? 1、首先判断是否为post方式，如果不是post方式，则肯定不是上传请求，则直接返回request对象
??????? if (!"POST".equalsIgnoreCase(request.getMethod())) {
??????????? return (request);
??????? }
???????
??? 2、获取request对象的ContentType，如果ContentType为multipart/form-datade 话则 new 一个 MultipartRequestWrapper 对象返回。否则直接返回request。
??????? String contentType = request.getContentType();
??????? if ((contentType != null)
??????????? && contentType.startsWith("multipart/form-data")) {
??????????? return (new MultipartRequestWrapper(request));
??????? } else {
??????????? return (request);
??????? }
???????
??????? 1、MultipartRequestWrapper继承于HttpServletRequestWrapper。下面是包装代码
??????????? public MultipartRequestWrapper(HttpServletRequest request) {
??????????????? super(request);
??????????????? this.parameters = new HashMap();
??????????? }
???????????
7、处理请求路径
??? String path = processPath(request, response); 返回的是访问的action的名字
???
8、如果返回值是空， 则方法直接return，结束。
??? if (path == null) {
??????? return;
??? }
???
9、把请求的方式（post/get）和action名字记入日志
??? if (log.isDebugEnabled()) {
??????? log.debug("Processing a '" + request.getMethod() + "' for path '"
??????????? + path + "'");
??? }
???
10、为当前的用户请求选择对应的local（区域和语言），这是根据浏览器的设置的。涉及到国际化问题。
??? // Select a Locale for the current user if requested
??? processLocale(request, response);
11、为response对象设置ContentType和no-cache的header信息。
??? // Set the content type and no-caching headers if requested
??? processContent(request, response);
??? processNoCache(request, response);
12、留了一个可以预处理请求的扩展接口。
??? // General purpose preprocessing hook
??? if (!processPreprocess(request, response)) {
??????? return;
??? }????? 这里processPreprocess方法只有一句话：return（true）；其实是为了可以扩展，如果要对请求预处理，可以继承这个类，然后重写这个
??? protected boolean processPreprocess(HttpServletRequest request,HttpServletResponse response) {
??????? return (true);
??? }
方法。
13、处理以前缓存的信息
??? this.processCachedMessages(request, response);
??? 其实就是清空session里如果存在的struts定义的提示信息和错误信息。???
14、根据request，response，和path（action的名字）返回actionMapping对象。
??? // Identify the mapping for this request
??? ActionMapping mapping = processMapping(request, response, path);
??? if (mapping == null) {
??????? return;
??? }
???
??? 1、首先去配置文件里找相应的配置信息
??????? // Is there a mapping for this path?
??????? ActionMapping mapping = (ActionMapping) moduleConfig.findActionConfig(path);
???
??? 2、如果有配置则把它放入request，并返回他。
??????? // If a mapping is found, put it in the request and return it
??????? if (mapping != null) {
??????????? request.setAttribute(Globals.MAPPING_KEY, mapping);
??????????? return (mapping);
??????? }
???????
??? 3、找到“未知的映射路径（如果有的话）”。同样找到了就放到request里并返回他。
??????? // Locate the mapping for unknown paths (if any)
??????? ActionConfig[] configs = moduleConfig.findActionConfigs();
??????? for (int i = 0; i < configs.length; i++) {
??????????? if (configs[i].getUnknown()) {
??????????????? mapping = (ActionMapping) configs[i];
??????????????? request.setAttribute(Globals.MAPPING_KEY, mapping);
??????????????? return (mapping);
??????????? }
??????? }
???
??? 4、如果还是没有找到mapping信息则发送错误消息，并返回null
??????? // No mapping can be found to process this request
??????? String msg = getInternal().getMessage("processInvalid");
??????? log.error(msg + " " + path);
??????? response.sendError(HttpServletResponse.SC_NOT_FOUND, msg);
??????? return null;
15、检查执行这个action所要的所有角色（是否有权访问）
??? // Check for any role required to perform this action
??? if (!processRoles(request, response, mapping)) {
??????? return;
??? }
???
??? 1、从actionMapping（mapping）对想里取得角色名称的数组。
??????? // Is this action protected by role requirements?
??????? String[] roles = mapping.getRoleNames();
???????
??? 2、如果mapping里没有角色信息（没有配置），就不做处理，直接返回true
??????? if ((roles == null) || (roles.length < 1)) {
??????????? return (true);
??????? }
???????
??? 3、依次取出配置了的角色 ，如果用户在角色中 （配置了的所有角色中的任意一个） ，则把用户名和角色名记 录到log里。并返回true。
??????? // Check the current user against the list of required roles
??????? for (int i = 0; i < roles.length; i++) {
??????????? if (request.isUserInRole(roles[i])) {
??????????????? if (log.isDebugEnabled()) {
??????????????????? log.debug(" User '" + request.getRemoteUser()
??????????????????????? + "' has role '" + roles[i] + "', granting access");
??????????????? }
??????????????? return (true);
??????????? }
??????? }
???????
??? 4、如果仍没找到用户所对应的角色，则说明这个用户是非法访问的。则把这个用户名记录到log里，发送错误信息，并返回false。
??????? // The current user is not authorized for this action
??????? if (log.isDebugEnabled()) {
??????????? log.debug(" User '" + request.getRemoteUser()
??????????????? + "' does not have any required role, denying access");
??????? }
??????? response.sendError(HttpServletResponse.SC_FORBIDDEN,
??????????? getInternal().getMessage("notAuthorized", mapping.getPath()));
??????? return (false);
16、处理与这个请求有关的所有actionForm。（调用processActionForm（）方法返回ActionForm对象）
??? // Process any ActionForm bean related to this request
??? ActionForm form = processActionForm(request, response, mapping);
???
??? 1、如果有需要就新建一个ActionForm来供使用。
??????? // Create (if necessary) a form bean to use
??????? ActionForm instance = RequestUtils.createActionForm(request, mapping, moduleConfig, servlet);
???????
??????? 1、查看mapping里是否配置name属性或attribute属性来指定ActionForm，如果都没有则返回null
??????????? // Is there a form bean associated with this mapping?
??????????? String attribute = mapping.getAttribute();
??????????? if (attribute == null) {
??????????????? return (null);
??????????? }
???????
??????? 2、通过name属性拿到ActionForm的配置信息
??????????? // Look up the form bean configuration information to use
??????????? String name = mapping.getName();
??????????? FormBeanConfig config = moduleConfig.findFormBeanConfig(name);
???????
??????? 3、如果没有与name属性相对应的<form-bean>配置，则在log里记录：没有配置与name对应的formBean，并返回null；
??????????? if (config == null) {
??????????????? log.warn("No FormBeanConfig found under '" + name + "'");
??????????????? return (null);
??????????? }
???????????
??????? 4、根据拿到的<form-bean>配置，在相应的范围里（request,session）找ActionForm的实例
??????????? ActionForm instance = lookupActionForm(request, attribute, mapping.getScope());
???????
??????? 5、如果找到，并被判定为可用，则返回找到的实例。
??????????? // Can we recycle the existing form bean instance (if there is one)?
??????????? if ((instance != null) && config.canReuse(instance)) {
??????????????? return (instance);
??????????? }
???????
??????? 6、如果没找到，（前面已经确定配置了formBean）。则新建一个ActionForm对象出来并返回他。
??????????? return createActionForm(config, servlet);
???????????
??????????? 1、首先判断传入的config，如果config为null，则直接返回null
??????????????? if (config == null) {
??????????????????? return (null);
??????????????? }
???????????
??????????? 2、创建并返回一个新的ActionForm对象。这里调用了config对象的createActionForm方法。该方法里肯定用到了反射机制。另外把创建的ActionForm或动态ActionForm的信息存到log里。同样，如果过程中出错，错误信息业将被保存到日志里。
??????????????? ActionForm instance = null;
??????????????? // Create and return a new form bean instance
??????????????? try {
??????????????????? instance = config.createActionForm(servlet);
??????????????????? if (log.isDebugEnabled()) {
??????????????????????? log.debug(" Creating new "
??????????????????????????? + (config.getDynamic() ? "DynaActionForm" : "ActionForm")
??????????????????????????? + " instance of type '" + config.getType() + "'");
??????????????????????? log.trace(" --> " + instance);
??????????????????? }
??????????????? } catch (Throwable t) {
??????????????????? log.error(servlet.getInternal().getMessage("formBean",
??????????????????????????? config.getType()), t);
??????????????? }
??????????????? return (instance);
???????????????
17、为ActionForm填充数据。
??? processPopulate(request, response, form, mapping);
???
??? 1、首先判断form是否为null，如果是则直接return。
??????? if (form == null) {
??????????? return;
??????? }
???
??? 2、往log里写入一句话提示从这里开始填充formBean
??????? if (log.isDebugEnabled()) {
??????????? log.debug(" Populating bean properties from this request");
??????? }
???
??? 3、设置Servlet。
??????? form.setServlet(this.servlet);
??????? （不知道具体作用）
???????
??? 4、执行reset方法重置表单。默认reset方法不做任何事情。这个方法是为了方便扩展。可以继承ActionForm类重写reset方法，这个方法可以用来做设置一些默认值等工作。
??????? form.reset(mapping, request);
???????
??? 5、如果是上传表单，则获取上传类。（不甚了解）
??????? if (mapping.getMultipartClass() != null) {
??????????? request.setAttribute(Globals.MULTIPART_KEY,
??????????????? mapping.getMultipartClass());
??????? }
???
??? 6、填充form
??????? RequestUtils.populate(form, mapping.getPrefix(), mapping.getSuffix(), request);
???????
??????? 1、建立一个HashMap 用于存放属性
??????????? // Build a list of relevant request parameters from this request
??????????? HashMap properties = new HashMap();
???????????
??????? 2、建立一个Enumeration用于存放参数名
??????????? // Iterator of parameter names
??????????? Enumeration names = null;
???????
??????? 3、建立一个Map来存放multipart参数
??????????? // Map for multipart parameters
??????????? Map multipartParameters = null;
???????
??????? 4、获取请求的ContentType和Method。并设置multipart表示为false。
??????????? String contentType = request.getContentType();
??????????? String method = request.getMethod();
??????????? boolean isMultipart = false;
???????????
??????? 5、如果是multipart表单则做上传处理（不甚了解）
??????????? if (bean instanceof ActionForm) {
??????????????? ((ActionForm) bean).setMultipartRequestHandler(null);
??????????? }
??????????? MultipartRequestHandler multipartHandler = null;
??????????? if ((contentType != null)
??????????????? && (contentType.startsWith("multipart/form-data"))
??????????????? && (method.equalsIgnoreCase("POST"))) {
??????????????? // Get the ActionServletWrapper from the form bean
??????????????? ActionServletWrapper servlet;
??????????????? if (bean instanceof ActionForm) {
??????????????????? servlet = ((ActionForm) bean).getServletWrapper();
??????????????? } else {
??????????????????? throw new ServletException("bean that's supposed to be "
??????????????????????? + "populated from a multipart request is not of type "
??????????????????????? + ""org.apache.struts.action.ActionForm", but type "
??????????????????????? + """ + bean.getClass().getName() + """);
??????????????? }
??????????????? // Obtain a MultipartRequestHandler
??????????????? multipartHandler = getMultipartHandler(request);
??????????????? if (multipartHandler != null) {
??????????????????? isMultipart = true;
??????????????????? // Set servlet and mapping info
??????????????????? servlet.setServletFor(multipartHandler);
??????????????????? multipartHandler.setMapping((ActionMapping) request
??????????????????????? .getAttribute(Globals.MAPPING_KEY));
??????????????????? // Initialize multipart request class handler
??????????????????? multipartHandler.handleRequest(request);
??????????????????? //stop here if the maximum length has been exceeded
??????????????????? Boolean maxLengthExceeded =
??????????????????????? (Boolean) request.getAttribute(MultipartRequestHandler.ATTRIBUTE_MAX_LENGTH_EXCEEDED);
??????????????????? if ((maxLengthExceeded != null)
??????????????????????? && (maxLengthExceeded.booleanValue())) {
??????????????????????? ((ActionForm) bean).setMultipartRequestHandler(multipartHandler);
??????????????????????? return;
??????????????????? }
??????????????????? //retrieve form values and put into properties
??????????????????? multipartParameters =
??????????????????????? getAllParametersForMultipartRequest(request,
??????????????????????????? multipartHandler);
??????????????????? names = Collections.enumeration(multipartParameters.keySet());
??????????????? }
??????????? }
???????????
??????? 6、如果不是上传，则把参数名存到names枚举里面。
??????????? if (!isMultipart) {
??????????????? names = request.getParameterNames();
??????????? }
???????
??????? 7、遍历这个枚举
??????????? while (names.hasMoreElements())
???????????
??????????? 1、把名字拿出来存到name和stripped变量里
??????????????? String name = (String) names.nextElement();
??????????????? String stripped = name;
???????????????
??????????? 2、去掉name的前缀和后缀（如果有的话（配置文件里可以配置））
??????????????? if (prefix != null) {
??????????????????? if (!stripped.startsWith(prefix)) {
??????????????????????? continue;
??????????????????? }
??????????????????? stripped = stripped.substring(prefix.length());
??????????????? }
??????????????? if (suffix != null) {
??????????????????? if (!stripped.endsWith(suffix)) {
??????????????????????? continue;
??????????????????? }
??????????????????? stripped =
??????????????????????? stripped.substring(0, stripped.length() - suffix.length());
??????????????? }
???????????????
??????????? 3、获取参数值，分上传和非上传两种方式
??????????????? Object parameterValue = null;
??????????????? if (isMultipart) {
??????????????????? parameterValue = multipartParameters.get(name);
??????????????????? parameterValue = rationalizeMultipleFileProperty(bean, name, parameterValue);
??????????????? } else {
??????????????????? parameterValue = request.getParameterValues(name);
??????????????? }
???????????????
??????????? 4、如果参数名去掉了前后缀后不是一org.Apache.struts开头则把参数存到定义好的HashMap里
??????????????? // Populate parameters, except "standard" struts attributes
??????????????? // such as 'org.apache.struts.action.CANCEL'
??????????????? if (!(stripped.startsWith("org.apache.struts."))) {
??????????????????? properties.put(stripped, parameterValue);
??????????????? }
???????????????
??????? 8、调用BeanUtils的方法把formBean的属性填充进去（异常处理那块不是很明白）
??????????? // Set the corresponding properties of our bean
??????????? try {
??????????????? BeanUtils.populate(bean, properties);
??????????? } catch (Exception e) {
??????????????? throw new ServletException("BeanUtils.populate", e);
??????????? } finally {
??????????????? if (multipartHandler != null) {
??????????????????? // Set the multipart request handler for our ActionForm.
??????????????????? // If the bean isn't an ActionForm, an exception would have been
??????????????????? // thrown earlier, so it's safe to assume that our bean is
??????????????????? // in fact an ActionForm.
??????????????????? ((ActionForm) bean).setMultipartRequestHandler(multipartHandler);
??????????????? }
??????????? }
???????????
??? 7、加入合适的话就把退出属性设置到request里；（还是不了解）
??????? // Set the cancellation request attribute if appropriate
??????? if ((request.getParameter(Globals.CANCEL_PROPERTY) != null)
??????????? || (request.getParameter(Globals.CANCEL_PROPERTY_X) != null)) {
??????????? request.setAttribute(Globals.CANCEL_KEY, Boolean.TRUE);
??????? }
???????
18、验证表单输入的合法性。如果有不合法的则return。（一般不用struts的表单级验证）
??? // Validate any fields of the ActionForm bean, if applicable
??? try {
??????? if (!processValidate(request, response, form, mapping)) {
??????????? return;
??????? }
??? } catch (InvalidCancelException e) {
??????? ActionForward forward = processException(request, response, e, form, mapping);
??????? processForwardConfig(request, response, forward);
??????? return;
??? } catch (IOException e) {
??????? throw e;
??? } catch (ServletException e) {
??????? throw e;
??? }
???
19、处理mapping指定的forward 和 include
??? // Process a forward or include specified by this mapping
??? if (!processForward(request, response, mapping)) {
??????? return;
??? }
??? if (!processInclude(request, response, mapping)) {
??????? return;
??? }
???
20、创建或者获取一个Action的实例来处理请求。
??? // Create or acquire the Action instance to process this request
??? Action action = processActionCreate(request, response, mapping);
???
??? 1、从mapping里取出配置的Action类名
??????? // Acquire the Action instance we will be using (if there is one)
??????? String className = mapping.getType();
???
??? 2、把查找Action实例的动作记入到日志里
??????? if (log.isDebugEnabled()) {
??????????? log.debug(" Looking for Action instance for class " + className);
??????? }
??? 3、在拿到Action实例之前先线程同步synchronized (actions) ，保证只有一个Action实例
???
??? 4、从map里取出Action返回，（如果有的话），并把结果写入日志
??????? nstance = (Action) actions.get(className);
??????? if (instance != null) {
??????????? if (log.isTraceEnabled()) {
??????????????? log.trace("? Returning existing Action instance");
??????????? }
??????????? return (instance);
??????? }
???
??? 5、如果上面的操作没进行，那说明要新建一个Action实例，把新建实例的动作记录到日志里
??????? if (log.isTraceEnabled()) {
??????????? log.trace("? Creating new Action instance");
??????? }
???????
??? 6、创建出Action实例，吧实例放到map里并返回实例
??????? try {
??????????????? instance = (Action) RequestUtils.applicationInstance(className);
??????????????? // Maybe we should propagate this exception
??????????????? // instead of returning null.
??????????? } catch (Exception e) {
??????????????? log.error(getInternal().getMessage("actionCreate",
??????????????????????? mapping.getPath()), e);
??????????????? response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
??????????????????? getInternal().getMessage("actionCreate", mapping.getPath()));
??????????????? return (null);
??????????? }
??????????? actions.put(className, instance);
??????????? if (instance.getServlet() == null) {
??????????????? instance.setServlet(this.servlet);
??????????? }
??????? }
??????? return (instance);
???????
21、再次判断Action是否创建成功，如果没有则方法直接return
??????? if (action == null) {
??????????? return;
??????? }
???????
22、执行Action的excute方法，获得ActionForward
??????? // Call the Action instance itself
??????? ActionForward forward = processActionPerform(request, response, action, form, mapping);
??????? 其中processActionPerform方法调用了action的excute方法：
??????? protected ActionForward processActionPerform(HttpServletRequest request,
??????????? HttpServletResponse response, Action action, ActionForm form,
??????????? ActionMapping mapping)
??????????? throws IOException, ServletException {
??????????? try {
??????????????? return (action.execute(mapping, form, request, response));
??????????? } catch (Exception e) {
??????????????? return (processException(request, response, e, form, mapping));
??????????? }
??????? }
??? 这里也做了一个处理，如果要在执行excute方法之前做一些操作，就可以覆盖processActionPerform方法。
???
23、更具Actionforward进行转发
??????? // Process the returned ActionForward instance
??????? processForwardConfig(request, response, forward);
???
??????? 1、如果ActionForward为空，则方法直接返回
??????????? if (forward == null) {
??????????????? return;
??????????? }
???????????
??????? 2、把接下来处理forward的操作记录到日志里
??????????? if (log.isDebugEnabled()) {
??????????????? log.debug("processForwardConfig(" + forward + ")");
??????????? }
???????
??????? 3、从mapping里获取forward对应的url，默认用forward的方式转发，如果配了redirect，则用redirect重定向
??????????? String forwardPath = forward.getPath();
??????????? String uri;
??????????? // If the forward can be unaliased into an action, then use the path of the action
??????????? String actionIdPath = RequestUtils.actionIdURL(forward, request, servlet);
??????????? if (actionIdPath != null) {
??????????????? forwardPath = actionIdPath;
??????????????? ForwardConfig actionIdForward = new ForwardConfig(forward);
??????????????? actionIdForward.setPath(actionIdPath);
??????????????? forward = actionIdForward;
??????????? }
??????????? // paths not starting with / should be passed through without any
??????????? // processing (ie. they're absolute)
??????????? if (forwardPath.startsWith("/")) {
??????????????? // get module relative uri
??????????????? uri = RequestUtils.forwardURL(request, forward, null);
??????????? } else {
??????????????? uri = forwardPath;
??????????? }
??????????? if (forward.getRedirect()) {
??????????????? // only prepend context path for relative uri
??????????????? if (uri.startsWith("/")) {
??????????????????? uri = request.getContextPath() + uri;
??????????????? }
??????????????? response.sendRedirect(response.encodeRedirectURL(uri));
??????????? } else {
??????????????? doForward(uri, request, response);
??????????? }
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