Using the Flash scope ( and RedirectAttributes ) without in Spring MVC 3.1

Question

In my Spring MVC 3.1 application, I think I can't use "<mvc:annotation-driven />". Why? Because I want to apply an interceptor to all mappings except to the "<mvc:resources" elements. So I can't use :

<mvc:annotation-driven />

<mvc:resources order="-10" mapping="/public/**" location="/public/" />
<mvc:resources order="-10" mapping="/favicon.ico" location="/public/favicon.ico" />
<mvc:resources order="-10" mapping="/robots.txt" location="/public/robots.txt" />
<mvc:resources order="-10" mapping="/humans.txt" location="/public/humans.txt" />

<mvc:interceptors>  
  <mvc:interceptor>
    <mvc:mapping path="/**"/>
    <bean class="com.my.Interceptor" />
  </mvc:interceptor>
</mvc:interceptors>

Because I don't want the interceptor to apply to the resources and there is no way (I think) to specify a path for the mapping which would apply the interceptor to everything except this and that.

So I have to add my own RequestMappingHandlerMapping to be able to specify the interceptor on it, and not globally. Because of this and this, it seems I can't simply define my own RequestMappingHandlerMapping while keeping the <mvc:annotation-driven /> element!

So... With some help, I've been able to get rid of the <mvc:annotation-driven /> element and pretty much everything works well now. I have my interceptor applied on everything but my resources. Everything works well, except the flash scope!

@RequestMapping(value="/test", method=RequestMethod.POST)
public String test(Model model, RedirectAttributes redirectAttrs) 
{
    redirectAttrs.addFlashAttribute("myKey", "my message");
    return "redirect:test2";
}

@RequestMapping(value="/test2")
public String test2(Model model, HttpServletRequest request) 
{
    Map<String, ?> map = RequestContextUtils.getInputFlashMap(request); // map is NULL
    System.out.println(model.containsAttribute("myKey")); // Prints FALSE
}

The flash map is NULL and my model doesn't contain my variable. When I try with the <mvc:annotation-driven /> element it works well! So my question is: what is missing from my context to make the flash scope work?

I also did try to set "org.springframework.web" to a DEBUG logging level, and after the redirect there is nothing logged related to a FlashMap or FlashMapManager. It seems some required bean is definitely missing.

Here are the interesting parts of my context file:

<!-- commented! -->
<!-- <mvc:annotation-driven /> -->

<bean id="baseInterceptor" class="com.my.Interceptor" />

<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping">
    <property name="order" value="0" />
    <property name="interceptors">
        <list>
            <ref bean="conversionServiceExposingInterceptor" />
            <ref bean="baseInterceptor" />
        </list>
    </property>
</bean>

<bean id="myRequestMappingHandlerAdapter" class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
    <property name="webBindingInitializer">
        <bean class="org.springframework.web.bind.support.ConfigurableWebBindingInitializer">
            <property name="conversionService" ref="conversionService" />
            <property name="validator" ref="validator" />
        </bean> 
    </property>
    <property name="messageConverters">
        <list>
            <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter" />
            <bean class="org.springframework.http.converter.StringHttpMessageConverter" />
            <bean class="org.springframework.http.converter.FormHttpMessageConverter" />
            <bean class="org.springframework.http.converter.xml.SourceHttpMessageConverter" />
        </list>
    </property>
</bean>

<bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean" />
<bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean" />
<bean id="conversionServiceExposingInterceptor" class="org.springframework.web.servlet.handler.ConversionServiceExposingInterceptor">
    <constructor-arg ref="conversionService" />
</bean>

<bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
    <property name="basename" value="classpath:/messages/messages" />
    <property name="defaultEncoding" value="UTF-8" />
</bean>

<bean class="org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver"></bean>

<mvc:resources order="-10" mapping="/public/**" location="/public/" />
<mvc:resources order="-10" mapping="/favicon.ico" location="/public/favicon.ico" />
<mvc:resources order="-10" mapping="/robots.txt" location="/public/robots.txt" />
<mvc:resources order="-10" mapping="/humans.txt" location="/public/humans.txt" />

What is missing for the flash scope to work?

UPDATE : See my answer for the solution... Nothing was missing actually. Only the Session was not working correctly and I found a way to make it work.

Answer 1

I finally found what was missing for the flash scope to work!

In the action where I access the flash variables (on the page the redirect leads to), I have to use this:

public String test2(Model model, HttpServletRequest request, HttpSession session)

instead of this :

public String test2(Model model, HttpServletRequest request)

It seems that this makes the Session to work correctly and therefore makes the flash scope to work correctly too! Why? I don't know...

Answer 2

It looks like all you need to do is to register a flash map manager with a bean name of flashMapManager and it should get automatically initialized and used by your Dispatcher Servlet:

<bean name="flashMapManager" class="org.springframework.web.servlet.support.DefaultFlashMapManager/>