使用地图作为Maven插件参数

问题描述：

是否可以使用地图作为Maven插件参数?

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

@Parameter
private Map<String, Map<String, String>> converters;

然后像

<converters>
  <json>
     <indent>true</indent>
     <strict>true</strict>
  </json>
  <yaml>
      <stripComments>false</stripComments>
  </yaml>
<converters>

如果我以这种方式使用它，则converters仅包含键json和yaml，其值为空.

If I use it like this, converters only contain the keys json and yaml with null as values.

我知道可以将复杂的对象作为值，但是像本例中一样，是否可以将映射用于可变元素值?

I know it is possible to have complex objects as values, but is it also somehow possible to use maps for variable element values like in this example?

答

一种解决方案非常简单，可用于1级嵌套.在替代答案中可以找到一种更复杂的方法，该方法也可能允许对Maps进行更深层的嵌套.

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.

代替使用接口作为类型参数，只需使用像TreeMap

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

 @Parameter
 private Map<String, TreeMap> converters.

原因是在

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.

使用地图作为Maven插件参数

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