Custom Eclipse warning on an annotation

Question

Let's say I have an internal method, which should be used only in certain situations.

Is there any possibility, in Eclipse, to mark it as internal and show a warning when used to prevent me or people who will use my API to use it by mistake not knowing what they're doing. I can't change its visibility as it might be used in other packages/non-extending classes too.

Something like this:

@Internal
public void doSomeInternalStuff()
{
    // ...
}

And then, a warning in Eclipse:

You get the point.

Any hope?

Answer 1

JSR269 ( Pluggable Annotation Processor API ) allows you to write custom annotation processors that can handle custom annotations and enable you to print errors or warning using a javax.annotation.processing.Messager . Below is an example.

import java.util.Set;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.tools.Diagnostic;

@SupportedAnnotationTypes("fully.qualified.name.of.InternalAnnotationType")
@SupportedSourceVersion(SourceVersion.RELEASE_6)
public class CustomAnnotationProcessor extends AbstractProcessor {

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        for (Element element : roundEnv.getElementsAnnotatedWith(InternalAnnotationType.class)) {
            InternalAnnotationType internalAnnotation = element.getAnnotation(InternalAnnotationType.class);
            String message = "The method " + element.getSimpleName()
                       + " is marked internal and its use is discouraged";
            processingEnv.getMessager().printMessage(Diagnostic.Kind.WARNING, message);
        }
        return true;
    }
}

In Eclipse, you can register annotation processors in your Java Compiler by right-clicking on your project, then selecting Properties -> Java Compiler -> Annotation Processing -> Factory Path and adding the Jar that contains your custom annotation processor. Here is an interesting post that explains the details.

Alternatively , you can put all of your "internal" method API inside a dedicated class, and add an access rule for that class in your Eclipse build path, so that any code in your project that depends on this class would display a warning.

Answer 2

阅读关于内部方法的内容Herbert Schildt的书“Java：beginers guide”在这里的链接： http ：//www.amazon.com/Java-Beginners-Guide-5th-Edition/dp/0071606327