Question

I have the following three components defined in the Caste-Windsor XML configuration for my application:

<component id="StringFactory"
           service="IStringFactory, MyApp"
           type="DefaultStringFactory, MyApp"
           lifestyle="singleton"
           />

<component id="TheString"
           type="System.String"
           factoryId="StringFactory"
           factoryCreate="CreateString"
           >
  <parameters>
    <name>SomeString</name>
  </parameters>
</component>

<component id="TheTarget"
           service="ITarget, MyApp"
           type="TheTarget, MyApp"
           lifestyle="transient"
           >
  <parameters>
    <aString>${TheString}</aString>
  </parameters>
</component>

And the following facility defined:

<facility id="factory.support"
          type="Castle.Facilities.FactorySupport.FactorySupportFacility, Castle.MicroKernel"
          />

When I run the application and set a breakpoint in the constructor of the TheObject class, the value passed in as the aString parameter is “${TheString}” when I expect it to resolve to the value of the component with that name.

Also, I have a breakpoint in the StringFactory constructor and CreateString method, neither of which are hit. I know the configuration is being used as other components are resolving correctly.

What am I missing or doing wrong here?

UPDATE

In light of the huge tangient this topic has taken, I’ve refactored the code above to remove anything to do with connection strings. The original intent of this post was about injecting a property with the value returned from a method on another object. Somehow that point was lost in a discussion about why I’m using XML versus code-based configuration and if this is a good way to inject a connection string.

The above approach is far from an original idea and it was pulled from several other discussions on this topic and our requirements are what they are. I’d like help understanding why the configuration as it is in place (whether the right approach or not) isn’t working as expected.

I did verify that the first two components are being instantiated correctly. When I call Container.Resolve(“TheString”), I get the correct value back. For whatever reason, The parameter syntax is not working correctly.

Any ideas?

Answer 1

While not a definitive solution to what I need to do in my application, I believe I’ve figured out what is wrong with the code. Or at least I’ve found a way to make it work which hints at the original problem.

I replaced the String type for TheString with a custom class. That’s it. Once I did that, everything worked fine.

My guess is that it has something to do with the fact that I was trying to use a ValueType (primitive) as a component. I guess Castle doesn’t support it.

So, knowing that’s the case, I can now move on to figuring out if this approach is really going to work or if we need to change direction.

UPDATE

For the sake of completeness, I thought I’d go ahead and explain what I did to solve my problem AND satisfy my requirements.

As before, I have access to my configuration settings through an IConfigurationService defined as:

<component id="ConfigurationService"
           service="MyApp.IConfigurationService, MyApp"
           type="MyApp.RuntimeConfigurationService, MyApp"
           lifestyle="singleton"
           />

This is automatically injected into my (new) IConnectionFactory which is responsible for generating IDbConnection objects based on the connection strings defined in the application’s configuration file. The factory is declared as:

<component id="ConnectionFactory"
           service="MyApp.Factories.IConnectionFactory, MyApp"
           type="MyApp.Factories.DefaultConnectionFactory, MyApp"
           lifestyle="singleton"
           />

In order to resolve what connection is used by my repository, I declare each connection as a component using the ConnectionFactory to create each instance:

<component id="MyDbConnection"
           type="System.Data.IDbConnection,
                 System.Data, Version=2.0.0.0, Culture=neutral,
                 PublicKeyToken=b77a5c561934e089"
           factoryId="ConnectionFactory"
           factoryCreate="CreateConnection"
           lifestyle="transient"
           >
  <parameters>
    <connectionStringName>MyDB</connectionStringName>
  </parameters>
</component>

Notice the fully described reference to System.Data. I found this is necessary whenever referencing assemblies in the GAC.

Finally, my repository is defined as:

<component id="MyRepository"
           service="MyApp.Repositories.IMyRepository, MyApp"
           type="MyApp.Sql.SqlMyRepository, MyApp.Sql"
           lifestyle="transient"
           >
  <parameters>
    <connection>${MyDbConnection}</connection>
  </parameters>
</component>

Now everything resolves correctly and I don’t have ANY hard-coded strings compiled into my code. No connection string names, app setting keys or whatever. The app is completely reconfigurable from the XML files which is a requirement I must satisfy. Plus, other devs that will be working with the solution can manage the actual connection strings in the way they are used to. Win-win.

Hope this helps anyone else that runs into a similar scenario.