Hi all,
yatesco's SessionCleaningView inspired me to write a RedirectAfterPostView.
This view checks if the HTTP method was POST. After such a POST request, the view stores the model into the session and delegates to a redirect view. After a GET request - on the other hand - it restores any previously stored model from the session and delegates to an other view.
/**
* The RedirectAfterPostView is intended to be used with form controllers to
* avoid known issues with the usage of browser back buttons or reload buttons.
* It can be used to redirect to a view after a POST request instead of to
* directly present the result in the same request. <br/>
*
* @author Christof Laenzlinger
* @version $Id$
*/
public class RedirectAfterPostView implements View {
protected static Log log = LogFactory.getLog(RedirectAfterPostView.class);
private View delegatingView_;
private RedirectView redirectView_;
private List namesToStore_;
public void render(Map model, HttpServletRequest request,
HttpServletResponse response) throws Exception {
if (shouldRedirect(model, request)) {
storeModel(model, request);
redirectView_.render(model, request, response);
} else {
model = restoreModel(model, request);
delegatingView_.render(model, request, response);
}
}
/**
* @return true if the view should redirect.
* The default implementation will redirect after a POST request.
*/
protected boolean shouldRedirect(Map model, HttpServletRequest request) {
return "POST".equals(request.getMethod());
}
/**
* Store the given model into the session.
* @param model the model to store.
* @param request the HTTP request.
*/
protected void storeModel(Map model, HttpServletRequest request) {
if (model == null) {
return;
}
Map modelToStore = new HashMap();
if (hasNamesToStore()) {
for (Iterator iter = namesToStore_.iterator(); iter.hasNext();) {
Object key = iter.next();
Object value = model.get(key);
modelToStore.put(key, value);
model.remove(key);
}
} else {
modelToStore.putAll(model);
model.clear();
}
HttpSession session = request.getSession();
if (log.isInfoEnabled()) {
log.info("store [" + modelToStore + "]");
}
session.setAttribute(getSessionAttributeName(), modelToStore);
}
/**
* Restore a previously stored model from the session into the given model.
* @param model the model to restore the stored model into.
* @param request the HTTP request.
*/
protected Map restoreModel(Map model, HttpServletRequest request) {
HttpSession session = request.getSession();
Map modelToRestore = (Map) session.getAttribute(getSessionAttributeName());
if (modelToRestore != null) {
if (hasNamesToStore()) {
for (Iterator iter = namesToStore_.iterator(); iter.hasNext();) {
Object key = iter.next();
Object value = modelToRestore.get(key);
if (model == null) {
model = new HashMap();
}
model.put(key, value);
}
} else {
if (model == null) {
model = new HashMap();
}
model.putAll(modelToRestore);
}
}
if (log.isInfoEnabled()) {
log.info("restore [" + modelToRestore + "]");
}
session.removeAttribute(getSessionAttributeName()) ;
return model;
}
protected String getSessionAttributeName() {
return "" + redirectView_.getBeanName() + "redirect.model";
}
private boolean hasNamesToStore() {
return namesToStore_ != null && namesToStore_.size() > 0;
}
// accessors hidden
This RedirectAfterPostView can be used for example with the SimpleFormController for both the formView and the successView. For example:
--------- ------------ ------------
|Web | |Form | |View |
|Browser| |Controller| |Controller|
--------- ------------ -------- ------------
|-------GET form------->| | Form | |
| |--------> | View | |
| | -------- |
|<------------OK form------------------| |
|---POST form (error)-->| | |
| |------------->| |
|<------------REDIRECT-----------------| |
|---GET form----------->| |
| |------------->| |
|<------------OK form------------------| | ---------
|-------POST form ----->| | | |Success|
| |-------------------------------->|View |
| | | | ---------
|<------------------------REDIRECT----------------------------|
|--------------------GET success view-------------->| |
| | | |-------->|
|<-----------OK success---------------------------------------|
| | | | |
With the namesToStore List one can define which elements of the model are stored into the session. If namesToStore is empty, the whole model is stored into the session.
In my example I configured it with an XmlViewResolver to declare the views:
<beans>
<bean name="newPersonForm" class="example.RedirectAfterPostView">
<property name="delegatingView">
<bean class="org.springframework.web.servlet.view.JstlView">
<property name="url" value="/WEB-INF/jsp/newPerson.jsp"/>
</bean>
</property>
<property name="redirectView">
<bean class="org.springframework.web.servlet.view.RedirectView">
<property name="url" value="/example/person"/>
<property name="contextRelative" value="true"/>
</bean>
</property>
</bean>
<bean name="newPersonSuccess" class="example.RedirectAfterPostView">
<property name="delegatingView">
<bean class="org.springframework.web.servlet.view.JstlView">
<property name="url" value="/WEB-INF/jsp/newPersonSuccess.jsp"/>
</bean>
</property>
<property name="redirectView">
<bean class="org.springframework.web.servlet.view.RedirectView">
<property name="url" value="/example/personSuccess"/>
<property name="contextRelative" value="true"/>
</bean>
</property>
</bean>
</beans>
As already mentioned the view can be used for both the formView and the successView. The advantage of using it as well for the formView is, that pressing browser's back-buttons or refresh-buttons does not result in a pop-up for re-posting.
Please let me know if you have an opinion about this proposal. I think it is a nicer solution than the one I proposed in an other thread before: http://forum.springframework.org/showthread.php?t=23346&highlight=redirect+post