通过配置实现统一-通用基类中的属性依赖注入

Question

I got lost searching for solution to this problem:

I have interface:

public interface ITestService
{
    ...
}

Then, I have base class with that implements that interface and has other service as property:

public class BaseTestServiceImpl<T> : ITestService, IDisposable where T : class
{
    protected T GenericProperty;

    public IOtherService OtherService;

    public void ExampleMethodFromBase()
    {
        OtherService.DoSomething();
    }

    public void Dispose()
    {
        ....
    }
}

Finally, I have several classes that inherit that base class. Example for one of them:

public class SpecificTestServiceImpl : BaseTestServiceImpl<SomeType>
{
    public void ExampleMethodFromSpecific()
    {
        OtherService.DoSomethingElse();
    }
}

Controller that calls methods from SpecificTestServiceImpl looks like this:

public class TestController : Controller
{
    [Dependency("TestService")]
    public BaseTestServiceImpl<SomeType> TestService { get; set; }

    public JsonResult TestAction()
    {
        TestService.ExampleMethodFromSpecific();
    }
}

Unity configuration looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>

    <configSections>
    <section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection, Microsoft.Practices.Unity.Configuration"/>
    </configSections>

    <unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
    <container>
        <alias alias="transient" type="Microsoft.Practices.Unity.TransientLifetimeManager, Microsoft.Practices.Unity" />
        <alias alias="MyType" type="SomeType" />
        <register name="otherService" type="IOtherService" mapTo="OtherServiceImpl">
            <lifetime type="singleton" />
        </register>
        <register type="ITestService" mapTo="BaseTestServiceImpl`1[]">
            <lifetime type="transient" />
            <property name="OtherService" dependencyName="otherService" />
        </register>
        <register name="TestService" type="BaseTestServiceImpl`1[MyType]" mapTo="SpecificTestServiceImpl">
            <lifetime type="singleton" />
        </register>
    </container>
    </unity>
</configuration>

Everything is resolved just fine, until the moment TestAction from TestController is called. Then I get NullPointerException in this line:

OtherService.DoSomethingElse();

in ExampleMethodFromSpecific method from SpecificTestServiceImpl .

It looks like Unity skips parent property injection in child classes.

Can this be done? I've tried setting other lifetime managers to BaseTestServiceImpl registration, but it failed the same way.

Please, help. I'm lost. :(

Thanx in advance.

Answer 1

Now it's been a while since I used unity, and I do prefer to have the config fully in code, but: The requested type in the controller is [Dependency("TestService")] which is configured as a SpecificTestServiceImpl which in turn has not been configured. I would have thought that Unity would have told you that SpecificTestServiceImpl is not configured, but perhaps it does use the mapped type, which is concrete

I just have to add that this mix of public members, interfaces, injected concrete types is rather poorly encapsulated logic and removes quite a lot of the value that a proper design would. The test controller should preferably request an interface ISomeTypeTestService (or similar), which in turn could be mapped to the BaseTestServiceImpl, or it could be a named ITestService which could be requested as it is now