[MJLINK-83] Implement multiple launcher elements

[pedro-w]

This is a simple change to allow the Maven plugin to generate more than one launcher in a jlink image. The jlink tool itself already supports this, but there was no way to pass the required invocation onto it from Maven.

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[vietj]

I do support this feature that is useful

[olamy]

sounds good. Could you please add a simple test for this new feature?

[pedro-w]

I have added a new test class as requested @olamy

[olamy]

I have added a new test class as requested @olamy

Thanks. I would prefer avoid using the technique of reflection and prefer using something such https://github.com/apache/maven-compiler-plugin/blob/master/src/test/java/org/apache/maven/plugin/compiler/CompilerMojoTestCase.java

[pedro-w]

I will look into that. I based the first attempt on the existing test

[olamy]

I will look into that. I based the first attempt on the existing test

good point. Another technique is available here https://github.com/apache/maven-invoker-plugin/blob/1bd7bb2d009b40d747fad3808458d984c4abde21/src/test/java/org/apache/maven/plugins/invoker/InvokerMojoTest.java#L50

[pedro-w]

I've been able to do it using your second suggested method, i.e. using org.apache.maven.api.plugin.testing.MojoExtension.setVariableValueToObject

The calls now look like this:

        JLinkMojo mojo = new JLinkMojo();
        setVariableValueToObject(mojo, "launcher", "com.example.Launch");

What do you think? I just couldn't get the first method, using the @InjectMojo annotations and associated mechanisms to work at all. It seemed to be a problem with the dependencies and their versions.

[olamy]

I've been able to do it using your second suggested method, i.e. using org.apache.maven.api.plugin.testing.MojoExtension.setVariableValueToObject

The calls now look like this:

        JLinkMojo mojo = new JLinkMojo();
        setVariableValueToObject(mojo, "launcher", "com.example.Launch");

What do you think? I just couldn't get the first method, using the @InjectMojo annotations and associated mechanisms to work at all. It seemed to be a problem with the dependencies and their versions.

Yup sorry I realised I sent a link on plugins now build with Maven 4.
All good

[pedro-w]

OK if I understand correctly we're going back to reflection because setVariableValueToObject is (as far as I can see) only in version 4.0.0-SNAPSHOT of the plugin test harness. When Maven 4 becomes widespread we can revisit.

Also I fixed a warning from plugin:descriptor and force-pushed the branch.

Is that everything?