Question

I have an enum CommandType with all possible commands. And I have a lot of classes having the same base class Command.

Then I can configure specific objects using the code like this:

<object type="Example.Command.MoveCommand">
    <property name="StepSize" value="10" />
</object>

Now I would like to create Command instances (each time a new one; not singleton) by CommandType value. How to configure such a mapping using Spring.NET?

Answer 1

I think you are looking for ServiceLocator functionality, which I don’t think you can achieve with spring.net by only changing the configuration. Note that the ServiceLocator pattern is generally discouraged from a dependency-injection point of view, because it makes your object aware of its di container.

If you do need a ServiceLocator and don’t mind tying your object to the Spring DI container, following could be a solution.

I assume your current code is something like this:

public class CommandManager
{
  Dictionary<CommandType, Command> { get; set; } // set using DI

  public Command GetBy(CommandType cmdKey)
  {
    return Dictionary[cmdKey];
  } 
}

Map the enum values to names of objects in you spring config by replacing your current Dictionary<CommandType, Command> with a Dictionary<CommandType, string>. Then use the current spring context to get the desired object:

using Spring.Context;
using Spring.Context.Support;

public class CommandManager
{
  Dictionary<CommandType, string> { get; set; } // set using DI; values are object names

  public Command GetBy(CommandType cmdKey)
  {
    string objName = Dictionary[cmdKey];
    IApplicationContext ctx = ContextRegistry.GetContext();

    return (Command)ctx.GetObject(objName);
  } 
}

Don’t forget to set the scope of your command objects to prototype:

<object name="moveCommand" 
        type="Example.Command.MoveCommand, CommandLib"
        scope="prototype">
    <property name="StepSize" value="10" />
</object>

Now every time CommandManager.GetBy(myKey) is called, a new instance is created.