在看完BaseCommandController和AbstractCommandController之后，我們再看BaseCommandController的另一個實現AbstractFormController，以及AbstractFormController的具體實現SimpleFormController。
先看看AbstractFormController對handleRequestInternal的實現：
protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response)
throws Exception {
// Form submission or new form to show?
if (isFormSubmission(request)) {
// Fetch form object from HTTP session, bind, validate, process submission.
try {
Object command = getCommand(request);
ServletRequestDataBinder binder = bindAndValidate(request, command);
BindException errors = new BindException(binder.getBindingResult());
return processFormSubmission(request, response, command, errors);
}
catch (HttpSessionRequiredException ex) {
// Cannot submit a session form if no form object is in the session.
if (logger.isDebugEnabled()) {
logger.debug("Invalid submit detected: " + ex.getMessage());
}
return handleInvalidSubmit(request, response);
}
}
else {
// New form to show: render form view.
return showNewForm(request, response);
}
}
這個方法，首先判斷是不是Form提交，判斷方法是：
protected boolean isFormSubmission(HttpServletRequest request) {
return "POST".equals(request.getMethod());
}
如果是form提交的話，系統首先創建一個Command，然后對數據進行綁定和驗證，之后調用processFormSubmission方法。showNewForm則調用showForm。
在AbstractFormController中里面有兩個抽象方法：
protected abstract ModelAndView processFormSubmission(
HttpServletRequest request, HttpServletResponse response, Object command, BindException errors)
throws Exception;
protected abstract ModelAndView showForm(
HttpServletRequest request, HttpServletResponse response, BindException errors)
throws Exception;
好了，看完AbstractFormController之后，再看看SimpleFormController是如何實現：
protected ModelAndView processFormSubmission(
HttpServletRequest request, HttpServletResponse response, Object command, BindException errors)
throws Exception {
if (errors.hasErrors()) {
if (logger.isDebugEnabled()) {
logger.debug("Data binding errors: " + errors.getErrorCount());
}
return showForm(request, response, errors);
}
else if (isFormChangeRequest(request, command)) {
logger.debug("Detected form change request -> routing request to onFormChange");
onFormChange(request, response, command, errors);
return showForm(request, response, errors);
}
else {
logger.debug("No errors -> processing submit");
return onSubmit(request, response, command, errors);
}
}
在上面的方法中，如果有錯誤，調用showForm，來顯示form。沒有錯誤的話，則調用onSubmit方法。
protected final ModelAndView showForm(
HttpServletRequest request, BindException errors, String viewName, Map controlModel)
throws Exception {
// In session form mode, re-expose form object as HTTP session attribute.
// Re-binding is necessary for proper state handling in a cluster,
// to notify other nodes of changes in the form object.
if (isSessionForm()) {
String formAttrName = getFormSessionAttributeName(request);
if (logger.isDebugEnabled()) {
logger.debug("Setting form session attribute [" + formAttrName + "] to: " + errors.getTarget());
}
request.getSession().setAttribute(formAttrName, errors.getTarget());
}
// Fetch errors model as starting point, containing form object under
// "commandName", and corresponding Errors instance under internal key.
Map model = errors.getModel();
// Merge reference data into model, if any.
Map referenceData = referenceData(request, errors.getTarget(), errors);
if (referenceData != null) {
model.putAll(referenceData);
}
// Merge control attributes into model, if any.
if (controlModel != null) {
model.putAll(controlModel);
}
// Trigger rendering of the specified view, using the final model.
return new ModelAndView(viewName, model);
}
在showForm中，設置屬性，放在model中，然后在viewName進行設置。
FormController就是上面的過程。具體的執行過程和詳細信息會在以后的博客中具體介紹。