上篇讲了Tomcat实例化一个单例的ActionServlet。依据web.xml配置文件做好对应的初始化工作。
这时client产生一个.do结尾的request请求，採用get/post方式提交之后。不论哪种方式提交，都会进入到process核心方法中。
public void <strong>doGet</strong>(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
<strong>process</strong>(request, response);
}
public void <strong>doPost</strong>(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
<strong>process</strong>(request, response);
}
protected void process(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
ModuleUtils.getInstance().selectModule(request, getServletContext());
ModuleConfig config = getModuleConfig(request);
RequestProcessor processor = getProcessorForModule(config);
if (processor == null) {
processor = getRequestProcessor(config);
}
processor.process(request, response);
}
首先调用org.apache.struts.util.ModuleUtils类的selectModule()方法。这种方法依据请求对象和servletContext选择负责处理当前请求所属的模块。然后把与该模块相关的ModuleConfig和MessageResources对象存储倒request范围中，这使得框架的其余组件能够方便地从request范围中读取这些对象，从而获取应用配置信息和消息资源。
其次， 实例化RequestProcessor类。然后调用RequestProcessor类的process()方法，来完毕十几的预处理请求操作。
public void process(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
// Wrap multipart requests with a special wrapper
request = processMultipart(request);
// Identify the path component we will use to select a mapping
String path = processPath(request, response);
if (path == null) {
return;
}
if (log.isDebugEnabled()) {
log.debug("Processing a '" + request.getMethod() +
"' for path '" + path + "'");
}
// Select a Locale for the current user if requested
processLocale(request, response);
// Set the content type and no-caching headers if requested
processContent(request, response);
processNoCache(request, response);
// General purpose preprocessing hook
if (!processPreprocess(request, response)) {
return;
}
this.processCachedMessages(request, response);
// Identify the mapping for this request
ActionMapping mapping = processMapping(request, response, path);
if (mapping == null) {
return;
}
// Check for any role required to perform this action
if (!processRoles(request, response, mapping)) {
return;
}
// Process any ActionForm bean related to this request
ActionForm form = processActionForm(request, response, mapping);
processPopulate(request, response, form, mapping);
// 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;
}
// Process a forward or include specified by this mapping
if (!processForward(request, response, mapping)) {
return;
}
if (!processInclude(request, response, mapping)) {
return;
}
// Create or acquire the Action instance to process this request
Action action = processActionCreate(request, response, mapping);
if (action == null) {
return;
}
// Call the Action instance itself
ActionForward forward =
processActionPerform(request, response,
action, form, mapping);
// Process the returned ActionForward instance
processForwardConfig(request, response, forward);
}
依照process（）方法的运行流程，
if (!"POST".equalsIgnoreCase(request.getMethod())) {
return (request);
}
2、获取request对象的ContentType，假设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);
}
String path = processPath(request, response);
if (path == null) {
return;
}
if (log.isDebugEnabled()) {
log.debug("Processing a '" + request.getMethod() +
"' for path '" + path + "'");
}
通过调用processPath方法。获得訪问的详细action的名字
protected void processLocale(HttpServletRequest request,HttpServletResponse response) {
// Are we configured to select the Locale automatically?
if (!moduleConfig.getControllerConfig().getLocale()) {
return;
}
// Has a Locale already been selected?
HttpSession session = request.getSession();
if (session.getAttribute(Globals.LOCALE_KEY) != null) {
return;
}
// Use the Locale returned by the servlet container (if any)
Locale locale = request.getLocale();
if (locale != null) {
if (log.isDebugEnabled()) {
log.debug(" Setting user locale '" + locale + "'");
}
session.setAttribute(Globals.LOCALE_KEY, locale);
}
}
是本地服务还是国际化服务，这是依据浏览器的设置的（确切的说是依据操作系统设置的）
当中processContent用来确定内容类型和编码类型
processNoCache依据配置文件里的配置属性来确定某些内容是否进行缓存
依据request。response和action的名字去Struts.config.xml中获取相应的actionmapping，也就是将我们配置好的request要请求的action放入到ActionMapping对象中去。
1、首先去配置文件中找对应的配置信息
// Is there a mapping for this path?ActionMapping mapping = (ActionMapping) moduleConfig.findActionConfig(path);
2、假设有配置则把它放入request。并返回。
// 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（假设有的话）”。相同找到了就放到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、假设还是没有找到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;此时。ActionMapping元素包括了如Action类的名称及在请求中用到的ActionForm的信息，另外还有配置在当前ActionMapping的里的ActionForwards信息。
protected ActionForm processActionForm(HttpServletRequest request,
HttpServletResponse response,
ActionMapping mapping) {
// Create (if necessary) a form bean to use
ActionForm instance = RequestUtils.createActionForm
(request, mapping, moduleConfig, servlet);
if (instance == null) {
return (null);
}
// Store the new instance in the appropriate scope
if (log.isDebugEnabled()) {
log.debug(" Storing ActionForm bean instance in scope '" +
mapping.getScope() + "' under attribute key '" +
mapping.getAttribute() + "'");
}
if ("request".equals(mapping.getScope())) {
request.setAttribute(mapping.getAttribute(), instance);
} else {
HttpSession session = request.getSession();
session.setAttribute(mapping.getAttribute(), instance);
}
return (instance);
}
protected void processPopulate(HttpServletRequest request,
HttpServletResponse response,
ActionForm form,
ActionMapping mapping)
throws ServletException {
if (form == null) {
return;
}
// Populate the bean properties of this ActionForm instance
if (log.isDebugEnabled()) {
log.debug(" Populating bean properties from this request");
}
form.setServlet(this.servlet);
form.reset(mapping, request);
if (mapping.getMultipartClass() != null) {
request.setAttribute(Globals.MULTIPART_KEY,
mapping.getMultipartClass());
}
RequestUtils.populate(form, mapping.getPrefix(), mapping.getSuffix(),
request);
// Set the cancellation request attribute if appropriate
if ((request.getParameter(Constants.CANCEL_PROPERTY) != null) ||
(request.getParameter(Constants.CANCEL_PROPERTY_X) != null)) {
request.setAttribute(Globals.CANCEL_KEY, Boolean.TRUE);
}
}
验证表单数据合法性，这个可用可不用的。假设使用了Struts的验证，这里会自己主动的运行该方法进行验证。
处理mapping指定的forward 和 include，Struts检查<action>元素的forward和include属性的值。假如有配置。则把forward和include 请求放在配置的页面内，之后转发到详细的ActionServlet中进行详细业务逻辑的处理。
至此，RequestProcessor的核心方法process运行完成。之后会到详细的Ａction中运行业务相关的操作。
纵观整个运行流程，其基本的方法无外乎两个，一个是AcionServlet中的process方法，还有一个是RequestProcessor的process()方法，至于其它的截取请求路径，填充actionForm。国际化等方法也都被用于外观模式封装在了process方法中。
SSH框架之Struts（3）——Struts的执行流程之核心方法
原文：http://www.cnblogs.com/cynchanpin/p/7130344.html