/*
* Copyright 2002-2012 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springmodules.validation.valang.web.servlet.mvc;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.springframework.validation.BindException;
import org.springframework.validation.Errors;
import org.springframework.web.HttpSessionRequiredException;
import org.springframework.web.bind.ServletRequestDataBinder;
import org.springframework.web.servlet.ModelAndView;
import org.springmodules.validation.web.servlet.mvc.BaseCommandController;
/**
* <p>Form controller that auto-populates a form bean from the request.
* This, either using a new bean instance per request, or using the same bean
* when the {@code sessionForm} property has been set to {@code true}.</p>
*
* <p>This class is the base class for both framework subclasses such as
* {@link SimpleFormController} and {@link AbstractWizardFormController}
* and custom form controllers that you may provide yourself.</p>
*
* <p>A form-input view and an after-submission view have to be provided
* programmatically. To provide those views using configuration properties,
* use the {@link SimpleFormController}.</p>
*
* <p>Subclasses need to override {@code showForm} to prepare the form view,
* and {@code processFormSubmission} to handle submit requests. For the latter,
* binding errors like type mismatches will be reported via the given "errors" holder.
* For additional custom form validation, a validator (property inherited from
* BaseCommandController) can be used, reporting via the same "errors" instance.</p>
*
* <p>Comparing this Controller to the Struts notion of the {@code Action}
* shows us that with Spring, you can use any ordinary JavaBeans or database-
* backed JavaBeans without having to implement a framework-specific class
* (like Struts' {@code ActionForm}). More complex properties of JavaBeans
* (Dates, Locales, but also your own application-specific or compound types)
* can be represented and submitted to the controller, by using the notion of
* a {@code java.beans.PropertyEditor}. For more information on that
* subject, see the workflow of this controller and the explanation of the
* {@link BaseCommandController}.</p>
*
* <p><b><a name="workflow">Workflow
* (<a href="BaseCommandController.html#workflow">and that defined by superclass</a>):</b><br>
* <ol>
* <li><b>The controller receives a request for a new form (typically a GET).</b></li>
* <li>Call to {@link #formBackingObject formBackingObject()} which by default,
* returns an instance of the commandClass that has been configured
* (see the properties the superclass exposes), but can also be overridden
* to e.g. retrieve an object from the database (that needs to be modified
* using the form).</li>
* <li>Call to {@link #initBinder initBinder()} which allows you to register
* custom editors for certain fields (often properties of non-primitive
* or non-String types) of the command class. This will render appropriate
* Strings for those property values, e.g. locale-specific date strings.</li>
* <li><em>Only if {@code bindOnNewForm} is set to {@code true}</em>, then
* {@link org.springframework.web.bind.ServletRequestDataBinder ServletRequestDataBinder}
* gets applied to populate the new form object with initial request parameters and the
* {@link #onBindOnNewForm(HttpServletRequest, Object, BindException)} callback method is
* called. <em>Note:</em> any defined Validators are not applied at this point, to allow
* partial binding. However be aware that any Binder customizations applied via
* initBinder() (such as
* {@link org.springframework.validation.DataBinder#setRequiredFields(String[])} will
* still apply. As such, if using bindOnNewForm=true and initBinder() customizations are
* used to validate fields instead of using Validators, in the case that only some fields
* will be populated for the new form, there will potentially be some bind errors for
* missing fields in the errors object. Any view (JSP, etc.) that displays binder errors
* needs to be intelligent and for this case take into account whether it is displaying the
* initial form view or subsequent post results, skipping error display for the former.</li>
* <li>Call to {@link #showForm(HttpServletRequest, HttpServletResponse, BindException) showForm()}
* to return a View that should be rendered (typically the view that renders
* the form). This method has to be implemented in subclasses.</li>
* <li>The showForm() implementation will call {@link #referenceData referenceData()},
* which you can implement to provide any relevant reference data you might need
* when editing a form (e.g. a List of Locale objects you're going to let the
* user select one from).</li>
* <li>Model gets exposed and view gets rendered, to let the user fill in the form.</li>
* <li><b>The controller receives a form submission (typically a POST).</b>
* To use a different way of detecting a form submission, override the
* {@link #isFormSubmission isFormSubmission} method.
* </li>
* <li>If {@code sessionForm} is not set, {@link #formBackingObject formBackingObject()}
* is called to retrieve a form object. Otherwise, the controller tries to
* find the command object which is already bound in the session. If it cannot
* find the object, it does a call to {@link #handleInvalidSubmit handleInvalidSubmit}
* which - by default - tries to create a new form object and resubmit the form.</li>
* <li>The {@link org.springframework.web.bind.ServletRequestDataBinder ServletRequestDataBinder}
* gets applied to populate the form object with current request parameters.
* <li>Call to {@link #onBind onBind(HttpServletRequest, Object, Errors)} which allows
* you to do custom processing after binding but before validation (e.g. to manually
* bind request parameters to bean properties, to be seen by the Validator).</li>
* <li>If {@code validateOnBinding} is set, a registered Validator will be invoked.
* The Validator will check the form object properties, and register corresponding
* errors via the given {@link org.springframework.validation.Errors Errors}</li> object.
* <li>Call to {@link #onBindAndValidate onBindAndValidate()} which allows you
* to do custom processing after binding and validation (e.g. to manually
* bind request parameters, and to validate them outside a Validator).</li>
* <li>Call {@link #processFormSubmission(HttpServletRequest, HttpServletResponse,
* Object, BindException) processFormSubmission()} to process the submission, with
* or without binding errors. This method has to be implemented in subclasses.</li>
* </ol>
* </p>
*
* <p>In session form mode, a submission without an existing form object in the
* session is considered invalid, like in case of a resubmit/reload by the browser.
* The {@link #handleInvalidSubmit handleInvalidSubmit} method is invoked then,
* by default trying to resubmit. It can be overridden in subclasses to show
* corresponding messages or to redirect to a new form, in order to avoid duplicate
* submissions. The form object in the session can be considered a transaction
* token in that case.</p>
*
* <p>Note that views should never retrieve form beans from the session but always
* from the request, as prepared by the form controller. Remember that some view
* technologies like Velocity cannot even access a HTTP session.</p>
*
* <p><b><a name="config">Exposed configuration properties</a>
* (<a href="BaseCommandController.html#config">and those defined by superclass</a>):</b><br>
* <table border="1">
* <tr>
* <td><b>name</b></td>
* <td><b>default</b></td>
* <td><b>description</b></td>
* </tr>
* <tr>
* <td>bindOnNewForm</td>
* <td>false</td>
* <td>Indicates whether to bind servlet request parameters when
* creating a new form. Otherwise, the parameters will only be
* bound on form submission attempts.</td>
* </tr>
* <tr>
* <td>sessionForm</td>
* <td>false</td>
* <td>Indicates whether the form object should be kept in the session
* when a user asks for a new form. This allows you e.g. to retrieve
* an object from the database, let the user edit it, and then persist
* it again. Otherwise, a new command object will be created for each
* request (even when showing the form again after validation errors).</td>
* </tr>
* </table>
* </p>
*
* <p><strong>Note</strong>: From Spring 3.2.3, was removed in Spring 4.0.</p>
*
* @author Rod Johnson
* @author Juergen Hoeller
* @author Alef Arendsen
* @author Rob Harrop
* @author Colin Sampaleanu
* @see #showForm(HttpServletRequest, HttpServletResponse, BindException)
* @see #processFormSubmission
* @see SimpleFormController
* @see AbstractWizardFormController
* @deprecated as of Spring 3.0, in favor of annotated controllers
*/
@Deprecated
public abstract class AbstractFormController extends BaseCommandController {
private boolean bindOnNewForm = false;
private boolean sessionForm = false;
/**
* Create a new AbstractFormController.
* <p>Subclasses should set the following properties, either in the constructor
* or via a BeanFactory: commandName, commandClass, bindOnNewForm, sessionForm.
* Note that "commandClass" doesn't need to be set when overriding
* {@link #formBackingObject}, since the latter determines the class anyway.
* <p>"cacheSeconds" is by default set to 0 (-> no caching for all form controllers).
* @see #setCommandName
* @see #setCommandClass
* @see #setBindOnNewForm
* @see #setSessionForm
* @see #formBackingObject
*/
public AbstractFormController() {
setCacheSeconds(0);
}
/**
* Set whether request parameters should be bound to the form object
* in case of a non-submitting request, that is, a new form.
*/
public final void setBindOnNewForm(boolean bindOnNewForm) {
this.bindOnNewForm = bindOnNewForm;
}
/**
* Return {@code true} if request parameters should be bound in case of a new form.
*/
public final boolean isBindOnNewForm() {
return this.bindOnNewForm;
}
/**
* Activate/deactivate session form mode. In session form mode,
* the form is stored in the session to keep the form object instance
* between requests, instead of creating a new one on each request.
* <p>This is necessary for either wizard-style controllers that populate a
* single form object from multiple pages, or forms that populate a persistent
* object that needs to be identical to allow for tracking changes.
* <p>Please note that the {@link AbstractFormController} class (and all
* subclasses of it unless stated to the contrary) do <i>not</i> support
* the notion of a conversation. This is important in the context of this
* property, because it means that there is only <i>one</i> form per session:
* this means that if session form mode is activated and a user opens up
* say two tabs in their browser and attempts to edit two distinct objects
* using the same form, then the <i>shared</i> session state can potentially
* (and most probably will) be overwritten by the last tab to be opened,
* which can lead to errors when either of the forms in each is finally
* submitted.
* <p>If you need to have per-form, per-session state management (that is,
* stateful web conversations), the recommendation is to use
* <a href="http://www.springframework.org/webflow">Spring WebFlow</a>,
* which has full support for conversations and has a much more flexible
* usage model overall.
* @param sessionForm {@code true} if session form mode is to be activated
*/
public final void setSessionForm(boolean sessionForm) {
this.sessionForm = sessionForm;
}
/**
* Return {@code true} if session form mode is activated.
*/
public final boolean isSessionForm() {
return this.sessionForm;
}
/**
* Handles two cases: form submissions and showing a new form.
* Delegates the decision between the two to {@link #isFormSubmission},
* always treating requests without existing form session attribute
* as new form when using session form mode.
* @see #isFormSubmission
* @see #showNewForm
* @see #processFormSubmission
*/
@Override
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);
}
}
/**
* Determine if the given request represents a form submission.
* <p>The default implementation treats a POST request as form submission.
* Note: If the form session attribute doesn't exist when using session form
* mode, the request is always treated as new form by handleRequestInternal.
* <p>Subclasses can override this to use a custom strategy, e.g. a specific
* request parameter (assumably a hidden field or submit button name).
* @param request current HTTP request
* @return if the request represents a form submission
*/
protected boolean isFormSubmission(HttpServletRequest request) {
return "POST".equals(request.getMethod());
}
/**
* Return the name of the HttpSession attribute that holds the form object
* for this form controller.
* <p>The default implementation delegates to the {@link #getFormSessionAttributeName()}
* variant without arguments.
* @param request current HTTP request
* @return the name of the form session attribute, or {@code null} if not in session form mode
* @see #getFormSessionAttributeName
* @see javax.servlet.http.HttpSession#getAttribute
*/
protected String getFormSessionAttributeName(HttpServletRequest request) {
return getFormSessionAttributeName();
}
/**
* Return the name of the HttpSession attribute that holds the form object
* for this form controller.
* <p>Default is an internal name, of no relevance to applications, as the form
* session attribute is not usually accessed directly. Can be overridden to use
* an application-specific attribute name, which allows other code to access
* the session attribute directly.
* @return the name of the form session attribute
* @see javax.servlet.http.HttpSession#getAttribute
*/
protected String getFormSessionAttributeName() {
return getClass().getName() + ".FORM." + getCommandName();
}
/**
* Show a new form. Prepares a backing object for the current form
* and the given request, including checking its validity.
* @param request current HTTP request
* @param response current HTTP response
* @return the prepared form view
* @throws Exception in case of an invalid new form object
* @see #getErrorsForNewForm
*/
protected final ModelAndView showNewForm(HttpServletRequest request, HttpServletResponse response)
throws Exception {
logger.debug("Displaying new form");
return showForm(request, response, getErrorsForNewForm(request));
}
/**
* Create a BindException instance for a new form.
* Called by {@link #showNewForm}.
* <p>Can be used directly when intending to show a new form but with
* special errors registered on it (for example, on invalid submit).
* Usually, the resulting BindException will be passed to
* {@link #showForm(HttpServletRequest, HttpServletResponse, BindException)},
* after registering the errors on it.
* @param request current HTTP request
* @return the BindException instance
* @throws Exception in case of an invalid new form object
* @see #showNewForm
* @see #showForm(HttpServletRequest, HttpServletResponse, BindException)
* @see #handleInvalidSubmit
*/
protected final BindException getErrorsForNewForm(HttpServletRequest request) throws Exception {
// Create form-backing object for new form.
Object command = formBackingObject(request);
if (command == null) {
throw new ServletException("Form object returned by formBackingObject() must not be null");
}
if (!checkCommand(command)) {
throw new ServletException("Form object returned by formBackingObject() must match commandClass");
}
// Bind without validation, to allow for prepopulating a form, and for
// convenient error evaluation in views (on both first attempt and resubmit).
ServletRequestDataBinder binder = createBinder(request, command);
BindException errors = new BindException(binder.getBindingResult());
if (isBindOnNewForm()) {
logger.debug("Binding to new form");
binder.bind(request);
onBindOnNewForm(request, command, errors);
}
// Return BindException object that resulted from binding.
return errors;
}
/**
* Callback for custom post-processing in terms of binding for a new form.
* Called when preparing a new form if {@code bindOnNewForm} is {@code true}.
* <p>The default implementation delegates to {@code onBindOnNewForm(request, command)}.
* @param request current HTTP request
* @param command the command object to perform further binding on
* @param errors validation errors holder, allowing for additional
* custom registration of binding errors
* @throws Exception in case of invalid state or arguments
* @see #onBindOnNewForm(javax.servlet.http.HttpServletRequest, Object)
* @see #setBindOnNewForm
*/
protected void onBindOnNewForm(HttpServletRequest request, Object command, BindException errors)
throws Exception {
onBindOnNewForm(request, command);
}
/**
* Callback for custom post-processing in terms of binding for a new form.
* <p>Called by the default implementation of the
* {@link #onBindOnNewForm(HttpServletRequest, Object, BindException)} variant
* with all parameters, after standard binding when displaying the form view.
* Only called if {@code bindOnNewForm} is set to {@code true}.
* <p>The default implementation is empty.
* @param request current HTTP request
* @param command the command object to perform further binding on
* @throws Exception in case of invalid state or arguments
* @see #onBindOnNewForm(HttpServletRequest, Object, BindException)
* @see #setBindOnNewForm(boolean)
*/
protected void onBindOnNewForm(HttpServletRequest request, Object command) throws Exception {
}
/**
* Return the form object for the given request.
* <p>Calls {@link #formBackingObject} if not in session form mode.
* Else, retrieves the form object from the session. Note that the form object
* gets removed from the session, but it will be re-added when showing the
* form for resubmission.
* @param request current HTTP request
* @return object form to bind onto
* @throws org.springframework.web.HttpSessionRequiredException
* if a session was expected but no active session (or session form object) found
* @throws Exception in case of invalid state or arguments
* @see #formBackingObject
*/
@Override
protected final Object getCommand(HttpServletRequest request) throws Exception {
// If not in session-form mode, create a new form-backing object.
if (!isSessionForm()) {
return formBackingObject(request);
}
// Session-form mode: retrieve form object from HTTP session attribute.
HttpSession session = request.getSession(false);
if (session == null) {
throw new HttpSessionRequiredException("Must have session when trying to bind (in session-form mode)");
}
String formAttrName = getFormSessionAttributeName(request);
Object sessionFormObject = session.getAttribute(formAttrName);
if (sessionFormObject == null) {
throw new HttpSessionRequiredException("Form object not found in session (in session-form mode)");
}
// Remove form object from HTTP session: we might finish the form workflow
// in this request. If it turns out that we need to show the form view again,
// we'll re-bind the form object to the HTTP session.
if (logger.isDebugEnabled()) {
logger.debug("Removing form session attribute [" + formAttrName + "]");
}
session.removeAttribute(formAttrName);
return currentFormObject(request, sessionFormObject);
}
/**
* Retrieve a backing object for the current form from the given request.
* <p>The properties of the form object will correspond to the form field values
* in your form view. This object will be exposed in the model under the specified
* command name, to be accessed under that name in the view: for example, with
* a "spring:bind" tag. The default command name is "command".
* <p>Note that you need to activate session form mode to reuse the form-backing
* object across the entire form workflow. Else, a new instance of the command
* class will be created for each submission attempt, just using this backing
* object as template for the initial form.
* <p>The default implementation calls {@link #createCommand()},
* creating a new empty instance of the specified command class.
* Subclasses can override this to provide a preinitialized backing object.
* @param request current HTTP request
* @return the backing object
* @throws Exception in case of invalid state or arguments
* @see #setCommandName
* @see #setCommandClass
* @see #createCommand
*/
protected Object formBackingObject(HttpServletRequest request) throws Exception {
return createCommand();
}
/**
* Return the current form object to use for binding and further processing,
* based on the passed-in form object as found in the HttpSession.
* <p>The default implementation simply returns the session form object as-is.
* Subclasses can override this to post-process the session form object,
* for example reattaching it to a persistence manager.
* @param sessionFormObject the form object retrieved from the HttpSession
* @return the form object to use for binding and further processing
* @throws Exception in case of invalid state or arguments
*/
protected Object currentFormObject(HttpServletRequest request, Object sessionFormObject) throws Exception {
return sessionFormObject;
}
/**
* Prepare the form model and view, including reference and error data.
* Can show a configured form page, or generate a form view programmatically.
* <p>A typical implementation will call
* {@code showForm(request, errors, "myView")}
* to prepare the form view for a specific view name, returning the
* ModelAndView provided there.
* <p>For building a custom ModelAndView, call {@code errors.getModel()}
* to populate the ModelAndView model with the command and the Errors instance,
* under the specified command name, as expected by the "spring:bind" tag.
* You also need to include the model returned by {@link #referenceData}.
* <p>Note: If you decide to have a "formView" property specifying the
* view name, consider using SimpleFormController.
* @param request current HTTP request
* @param response current HTTP response
* @param errors validation errors holder
* @return the prepared form view, or {@code null} if handled directly
* @throws Exception in case of invalid state or arguments
* @see #showForm(HttpServletRequest, BindException, String)
* @see org.springframework.validation.Errors
* @see org.springframework.validation.BindException#getModel
* @see #referenceData(HttpServletRequest, Object, Errors)
* @see SimpleFormController#setFormView
*/
protected abstract ModelAndView showForm(
HttpServletRequest request, HttpServletResponse response, BindException errors)
throws Exception;
/**
* Prepare model and view for the given form, including reference and errors.
* <p>In session form mode: Re-puts the form object in the session when
* returning to the form, as it has been removed by getCommand.
* <p>Can be used in subclasses to redirect back to a specific form page.
* @param request current HTTP request
* @param errors validation errors holder
* @param viewName name of the form view
* @return the prepared form view
* @throws Exception in case of invalid state or arguments
*/
protected final ModelAndView showForm(HttpServletRequest request, BindException errors, String viewName)
throws Exception {
return showForm(request, errors, viewName, null);
}
/**
* Prepare model and view for the given form, including reference and errors,
* adding a controller-specific control model.
* <p>In session form mode: Re-puts the form object in the session when returning
* to the form, as it has been removed by getCommand.
* <p>Can be used in subclasses to redirect back to a specific form page.
* @param request current HTTP request
* @param errors validation errors holder
* @param viewName name of the form view
* @param controlModel model map containing controller-specific control data
* (e.g. current page in wizard-style controllers or special error message)
* @return the prepared form view
* @throws Exception in case of invalid state or arguments
*/
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);
}
/**
* Create a reference data map for the given request, consisting of
* bean name/bean instance pairs as expected by ModelAndView.
* <p>The default implementation returns {@code null}.
* Subclasses can override this to set reference data used in the view.
* @param request current HTTP request
* @param command form object with request parameters bound onto it
* @param errors validation errors holder
* @return a Map with reference data entries, or {@code null} if none
* @throws Exception in case of invalid state or arguments
* @see ModelAndView
*/
protected Map referenceData(HttpServletRequest request, Object command, Errors errors) throws Exception {
return null;
}
/**
* Process form submission request. Called by {@link #handleRequestInternal}
* in case of a form submission, with or without binding errors. Implementations
* need to proceed properly, typically showing a form view in case of binding
* errors or performing a submit action else.
* <p>Subclasses can implement this to provide custom submission handling like
* triggering a custom action. They can also provide custom validation and call
* {@link #showForm(HttpServletRequest, HttpServletResponse, BindException)}
* or proceed with the submission accordingly.
* <p>For a success view, call {@code errors.getModel()} to populate the
* ModelAndView model with the command and the Errors instance, under the
* specified command name, as expected by the "spring:bind" tag. For a form view,
* simply return the ModelAndView object provided by
* {@link #showForm(HttpServletRequest, HttpServletResponse, BindException)}.
* @param request current servlet request
* @param response current servlet response
* @param command form object with request parameters bound onto it
* @param errors holder without errors (subclass can add errors if it wants to)
* @return the prepared model and view, or {@code null}
* @throws Exception in case of errors
* @see #handleRequestInternal
* @see #isFormSubmission
* @see #showForm(HttpServletRequest, HttpServletResponse, BindException)
* @see org.springframework.validation.Errors
* @see org.springframework.validation.BindException#getModel
*/
protected abstract ModelAndView processFormSubmission(
HttpServletRequest request, HttpServletResponse response, Object command, BindException errors)
throws Exception;
/**
* Handle an invalid submit request, e.g. when in session form mode but no form object
* was found in the session (like in case of an invalid resubmit by the browser).
* <p>The default implementation simply tries to resubmit the form with a new
* form object. This should also work if the user hit the back button, changed
* some form data, and resubmitted the form.
* <p>Note: To avoid duplicate submissions, you need to override this method.
* Either show some "invalid submit" message, or call {@link #showNewForm} for
* resetting the form (prepopulating it with the current values if "bindOnNewForm"
* is true). In this case, the form object in the session serves as transaction token.
* <pre>
* protected ModelAndView handleInvalidSubmit(HttpServletRequest request, HttpServletResponse response) throws Exception {
* return showNewForm(request, response);
* }</pre>
* You can also show a new form but with special errors registered on it:
* <pre class="code">
* protected ModelAndView handleInvalidSubmit(HttpServletRequest request, HttpServletResponse response) throws Exception {
* BindException errors = getErrorsForNewForm(request);
* errors.reject("duplicateFormSubmission", "Duplicate form submission");
* return showForm(request, response, errors);
* }</pre>
* @param request current HTTP request
* @param response current HTTP response
* @return a prepared view, or {@code null} if handled directly
* @throws Exception in case of errors
* @see #showNewForm
* @see #getErrorsForNewForm
* @see #showForm(HttpServletRequest, HttpServletResponse, BindException)
* @see #setBindOnNewForm
*/
protected ModelAndView handleInvalidSubmit(HttpServletRequest request, HttpServletResponse response)
throws Exception {
Object command = formBackingObject(request);
ServletRequestDataBinder binder = bindAndValidate(request, command);
BindException errors = new BindException(binder.getBindingResult());
return processFormSubmission(request, response, command, errors);
}
}