Required parameters of self written Mojo configured in execution part of POM are ignored and causing error

Required parameters configured in execution part of POM are ignored if:

the parameter ist set as required AND
(no default value is set OR
default-Value is set to "") AND
configuration of parameter values are done in the execution element.

Example:

Parameter definition in Mojo:

	/** 
	 * @parameter  default-value="ATTENTION DEFAULT"
	 * @required
	 */	
	private File dummy1;

and snip from POM:

    <plugins>
      <plugin>
        <groupId>myownartifact.plugin</groupId>
        <artifactId>maven-myownartifact-plugin</artifactId>
        <extensions>true</extensions>
        <executions>
          <execution>
             <id>extract</id>
             <configuration>
              <dummy1>c:/my files/test/dummy1</dummy1>
             </configuration>
             <goals>
               <goal>extract</goal>
             </goals>
          </execution>
        </executions>
      </plugin>     
    </plugins>

runs fine.

If I change the definition of the parameter to

	/** 
	 * @parameter 
	 * @required
	 */	
	private File dummy1;

or

      * @parameter default-value=""

then I got an error:

[0] inside the definition for plugin: 'maven-myownartifact-plugin'specify the following:

<configuration>
...
<dummy2>VALUE</dummy2>
</configuration>.

In my opinion this is a bug because with @required I have already tagged this parameter as mandatory. So I'm already forced to configure it.

BTW, if I configure the parameters outside the execution element evrything works fine as expected!

More info:

• the plugin is bind to the package phase

If a runable example is needed it's possible to provide one.