Using map of maps as Maven plugin parameters

Question

Is it possible to use a map of maps as a Maven plugin parameter?, e.g.

@Parameter
private Map

        

Answer 1

One solution is quite simple and works for 1-level nesting. A more sophisticated approach can be found in the alternative answer which possibly also allows for deeper nesting of Maps.

Instead of using an interface as type parameter, simply use a concrete class like TreeMap

 @Parameter
 private Map converters.

The reason is this check in MapConverter which fails for an interface but suceeds for a concrete class:

   private static Class findElementType( final Type[] typeArguments )
   {
       if ( null != typeArguments && typeArguments.length > 1 
            && typeArguments[1] instanceof Class )
       {
           return (Class) typeArguments[1];
       }
       return Object.class;
   }

As a side-note, an as it is also related to this answer for Maven > 3.3.x it also works to install a custom converter by subclassing BasicComponentConfigurator and using it as a Plexus component. BasicComponentConfigurator has the DefaultConverterLookup as a protected member variable and is hence easily accessible for registering custom converters.