How to change configs in Spring.Net

Question

An advantage of an IoC container is that you can swap in a mock service at the bottom of your object graph. However this seems much harder to do in Spring.Net than in other

Answer 1

That's a bit apples and oranges comparison as the unit test uses code configuration for Unity and XML (app.config) configuration for Spring.NET.

If you go the XML route, then you can either comment out old implementation A and define the B implementation as the one to use - that what's configuration is all about right? Other option is to have dedicated XML files for each scenario (configuration setup) and include them via context's resource definitions (you have inline resource now). Other options include file system and assembly, see the web configuration section in Spring.NET's manual for a nice example.

If you go the code configuration route I would suggest to check Spring.NET Recoil and upcoming CodeConfig.

Answer 2

Adding as new answer trying to address the open points...

I want to integrate this technique into existing code that uses the usual container. Why do I have to use a different container type, GenericApplicationContext in this case? What if I want to read data into this object from the existing spring config in app.config or web.config? Would it work as the usual context? Could I then write data over these registrations with code?

Spring has concrete application context implementations for different kind of initialization tactics. The most common ones to use are GenericApplicationContext (manual), XmlApplicationContext (XML files) and WebApplicationContext (very much like XmlApplicationContext but tailored for web use). They all implement common interface: IApplicationContext which is the preferred way to access these containers.

Unfortonately altering registrations with code usually means that you need to use the specific sub-class directly. With GenericApplicationContext and StaticApplicationContext this is quite natural but XmlApplicationContext is usually considered to be XML only and this ways "fixed" to XML definition.

How can I specify that ISomeService is to be created as a singleton? I don't mean supply a singleton instance to the container, but the container to create the instance, resolving its constructor, and use it when that type is needed.

Your SpringHelper does just that, by default all objects in Spring are singletons. You could alter this behavior by calling ObjectDefinitionBuilder's SetSingleton method with false.

how can I do the equivalent of container.RegisterType(); ? I want to register type mappings to use in all cases where that type is needed by a constructor.

Spring uses object names (ids) to distinct between different implementations. So if you want to get specific type to serve a specific instance in case that there are many alternatives you should refer to this specific instance by name. If you are using autowiring and your object has dependency to interface ISomeService and there's only one object registered that implements it, the autowiring can set it without ambiguity.

What exactly does container.RegisterType("service"); do? It seems to register ServiceImplementationA as the implementation of ISomeService but ISomeServiceis never mentioned, so there could be ambiguity. e.g. what if ServiceImplementationA implemented more than one interface.

Continuing from previous answer, this registers singleton of type ServiceImplementationA with name "service". This object comes autowiring candidate with all it's implemented interfaces (and with it's concrete type of course).

What is the string name given to the registration for? It won't work with en empty string, but it doesn't seem to matter what it is.

It matters a great deal as explained earlier. The name is unique id within that context (parent context could have object with same name) and can be used to access specific object registrations. In short where other frameworks may associate a type as key to object registration, Spring uses name.