Spring.NET and MVC3 on IIS7 - session scope behaviour

Question

probably it's a stupid question and I simply did not understand how Spring and IIS work, but lets give it a try.

I'm quite new to ASP.NET and as far as I understand, the session handling is similar to Apache/PHP:

A session is shared between tabs of a browser, but not between different browsers. I.e. if I open my page in Firefox and put something in the cart, the cart will still contain my items in another tab, but opening the very same page in Internet Explorer should show me an empty cart.

However I cannot reproduce this behaviour using Spring.NET.

I made a hello-world with a shopping cart object which is noted in session scope:

<objects xmlns="http://www.springframework.net">
  <object id="shoppingCart" type="DemoShop.Models.Cart.ShoppingCart, DemoShop" singleton="true" scope="session" />
</objects>

If I add something into my cart, it persists across any tab and browser. So this looks to me as if this object is a real singleton and thus persistent during the runtime of the IIS application.

I know, what you are going to say: Why did I use the attribute singleton="true" in my spring config? Well if I remove it or set it to false, then the object will not persist in the session, but will be re-created on every request and thus lose it's data.

The Spring.NET documentation is not speaking about the singleton attribute in MVC context at all and it took me some time to figure out, that it seem to be required using MVC3.

I was able to successfully create application scope objects using

<object id="..." type="..., ..." singleton="true" scope="application" />

and request scope object using either

<object id="..." type="..., ..." scope="request" />

or

<object id="..." type="..., ..." singleton="false" scope="request" />

However leaving the singleton attribute out, always put my object in request scope no matter which scope I actually noted in the scope attribute.

My guess is, that the session is not actually shared between Firefox and IE, but the cart object is simply in application scope, because I'm using spring the wrong way.

Can anyone give me advice or hints what I'm doing wrong or is this a problem in IIS7?

Answer 1

It's a bug.

After some excessive debugging of the spring.net source code we found out:

1. Support for session scoped objects is given by the spring.web dll
2. The spring.web.mvc dll does not depend on spring.web
3. This means, it is impossible to instantiate an MvcApplicationContext that can resolve session scoped objects

The following solution shows a custom MvcApplicationContext that fully enables session scoped objects within MVC3 using spring.net.

The reason why a standard application context cannot resolve web scopes is that it's using the class RootObjectDefinition whis doesn't know about the scope attribute (in the config xml). The WebApplicationContext instead instantiates RootWebObjectDefinition types, which know the scope.

The WebObjectsFactory overrides the method CreateRootObjectDefinition which returns instances of RootWebObjectDefinition. This is the one, we want to return from our application context. This is done by overriding the method CreateObjectsFactory.

Next thing, we have to override is the method CreateXmlObjectDefinitionReader. When spring is reading the metadata from the config, it will not parse additional attributes like scope if we don't take a specific reader. Therefore we will use the WebObjectDefinitionReader in our application context.

For the configuration of your session scoped objects, you can either leave out the singleton attribute or set it explicitly to true. Otherwise with value false the session scope will be disabled for sure.

EXAMPLE:

<objects xmlns="http://www.springframework.net">
    <object id="shoppingCart" type="ShoppingCart, ..." singleton="true" scope="session" />
</objects>

Step-by-Step solution:

1. Create MvcWebApplicationContext inheriting from MvcApplicationContext. You will need to override the two methods mentioned above and create default constructors.
2. Create a MvcWebContextHandler inheriting from MvcContextHandler. This will trigger that our custom application context will be used.
3. Use custom context handler in your web.config.
4. For IIS6 support or visual studio build-in webserver: add WebSupportModule to system.web section.
5. For IIS7 support: Add WebSupportModule to system.webserver section.

web.config:

<configSections>
    <sectionGroup name="spring">
        <section name="context" type="YourNamspace.MvcWebContextHandler, YourAssembly"/>    
        ....
    </sectionGroup>    
    ....
</configSections>

<!-- IIS6 -->
<system.web>
    <httpModules>
        <add name="Spring" type="Spring.Context.Support.WebSupportModule, Spring.Web"/>
    </httpModules>
</system.web>

<!-- IIS7 -->
<system.webServer>
    <validation validateIntegratedModeConfiguration="false"/>
    <modules runAllManagedModulesForAllRequests="true" >
        <add name="Spring" type="Spring.Context.Support.WebSupportModule, Spring.Web"/>
    </modules>
</system.webServer>

Custom application context class:

public class MvcWebApplicationContext: MvcApplicationContext {

    public MvcWebApplicationContext(string name, bool caseSensitive, params string[] configurationLocations)
    : this(new MvcApplicationContextArgs(name, null, configurationLocations, null, caseSensitive))
    { }

    public MvcWebApplicationContext(string name, bool caseSensitive, IApplicationContext parentContext, params string[] configurationLocations)
    : this(new MvcApplicationContextArgs(name, parentContext, configurationLocations, null, caseSensitive))
    { }

    public MvcWebApplicationContext(MvcApplicationContextArgs args)
    : base(args)
    { }

    public MvcWebApplicationContext(string name, bool caseSensitive, string[] configurationLocations, IResource[] configurationResources)
    : this(new MvcApplicationContextArgs(name, null, configurationLocations, configurationResources, caseSensitive))
    { }

    public MvcWebApplicationContext(params string[] configurationLocations)
    : this(new MvcApplicationContextArgs(string.Empty, null, configurationLocations, null, false))
    { }

    protected override XmlObjectDefinitionReader CreateXmlObjectDefinitionReader(DefaultListableObjectFactory objectFactory)
    {
        return new WebObjectDefinitionReader(GetContextPathWithTrailingSlash(), objectFactory, new XmlUrlResolver());
    }

    protected override DefaultListableObjectFactory CreateObjectFactory()
    {
        return new WebObjectFactory(GetContextPathWithTrailingSlash(), IsCaseSensitive);
    }

    private string GetContextPathWithTrailingSlash()
    {
        string contextPath = this.Name;
        if (contextPath == DefaultRootContextName)
        {
            contextPath = "/";
        }
        else 
        {
            contextPath = contextPath + "/";
        }
        return contextPath;
    }
}

Custom context handler class:

public class MvcWebContextHandler : MvcContextHandler {

    protected override Type DefaultApplicationContextType
    {
        get { return typeof(MvcWebApplicationContext); }
    }  
}

We added this bug to Spring.NET's issue tracker: https://jira.springsource.org/browse/SPRNET-1450