CODEWITHSUNDEEP
javaannotationsprocessor
fbiville
fbiville

Reputation: 8970

How to generate a method on an annotated class?

I wanna learn and have fun with annotations. Here is my use case: I have got a bunch of classes who basically have the same role: validate a video URL against a regex (1 method) and return the corresponding embedded HTML (another method).

The thing is the validation method is always the same. I could of course use inheritance, but I would like if it is possible to create an annotation like this:

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.??)
@Inherited
@Documented
public @interface VideoProvider {
        String regex();
        int group() default 1;
}

Processed like that:

//processor class
public boolean process(Set<? extends TypeElement> annotations,
        RoundEnvironment roundEnv) {
    for (TypeElement annotation : annotations) {
        for (Element e :    roundEnv.getElementsAnnotatedWith(annotation)) {
            if (e.getKind().isClass()) {
                //?????
            }
        }
    }
    return false;
}

The idea would be to dynamically change the annotated classes to inject a method that performs the validation. Is that feasible ?

Thanks in advance!

Rolf

Upvotes: 2

Views: 3272

Answers (2)

antlersoft
antlersoft

Reputation: 14751

I think you're doing it wrong---

But if you really want to implement this with annotation processing at compile time, you should look at the Pluggable Annotation Processing API

This is specifically for adding annotation-driven extensions to the compilation process, to do things like automatically adding methods.

Upvotes: 0

Amir Raminfar
Amir Raminfar

Reputation: 34179

Look at using java's Proxy class you cglib Enhancer class. Both solutions allow you to proxy a class and over take any method.

Upvotes: 2

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