Maven plugin loading classes - class

Question

I have an application which has legacy Struts actions extending org.apache.struts.StrutsActions. I would like to be sure that all my classes which are extending StrutsActions have a custom annotation.
In order to provide this I have written a small maven enforcer rule to validate my requirement. However I dont know how to load my classes at my mojo to validate them.
Actually I have done something not fancy which is injection outputDirectory and with a custom class loader I have recursively loaded all classes at my build folder.
Thanks

Answer 1

All classes ? What do you mean by that ? Maybe you mean target/classes/** (which is the default output place for classes) or maybe you mean a list of multiple directory tree locations ?
Can you better explain what your Mojo does and which phase and goals you want it to bind with.
I think maybe you are thinking about how to apply Maven's build cycle to your project incorrectly. Could you explain better what your plugin does, maybe it is does "packaging" work ?
But if I understand you correctly you want the plugin's execution to pickup the additional classpath entry for target/classes/** ? So it can load code and resources from the project itself to change some dynamic behaviour inside the maven-plugin ?
The default way to do this is <dependency> however of course this requires a fixed unit.
Other plugins that allow for this behavior (like maven-antrun-plugin) provide a mechansism to change classpath inside the Mojo and use something from <configuration> section of their pom.xml to do it. It is not clear if the plugin you are using is a Maven one or one you have written ?
.
Validation and packaging that is a valid use case. But I question why on the "classpath" ? I would guess you are binding on process-classes phase.
i.e. the classpath is for the purpose of providing code/resources to the runtime to execute. But in your case you have an input directory rather than a class path requirement.
It is possible in a Mojo to setup a directory scanner on an input directory */.class and then it is possible to (using some library) open each file and inspect the annotation without loading it.
This is also a good kind of separation between unreliable input data and the consistent behaviour of the plugin code itself. What happens if a project decides it wants to implement the same package and/or class as used in the implementation of the plugin itself.
UPDATE: If you really are loading the classes you are checkig into the JVM from your Mojo, then at least implement your own ClassLoader to do it. This is not necessarily a simple problem to solve. You make this ClassLoader find things specified from configuration in the input directory.

Answer 2

I have done it with the help of reflections
<dependency>
<groupId>org.reflections</groupId>
<artifactId>reflections</artifactId>
<version>0.9.5</version>
</dependency>
my implementation is like this:
public void execute(EnforcerRuleHelper helper) throws EnforcerRuleException {
URL url = getURL(helper.evaluate("${project.build.outputDirectory}"));
Predicate<String> filter = new FilterBuilder().include(getTargetSuperTypeForSubtypes());
Predicate<String> filter2 = new FilterBuilder().include(getMustHaveAnnotation());
Reflections reflections = new Reflections(new ConfigurationBuilder()
.setScanners(
new TypeAnnotationsScanner().filterResultsBy(filter2),
new SubTypesScanner().filterResultsBy(filter))
.setUrls(url));
validate(reflections);
}