How to check package existence from inside annotation processor when annotating?

Bartek Lipinski ：

I'm building an annotation processor for Android (let's call it that for future explanation TestProcessor).

The plan is for the processor to operate in two modes:

  • Mode 1: code generationA

  • Mode 2: generate code andAB

Mode 2Should only be selected if there are additional (optional) packages in the environment for which the processor generates code.

Is there a way to find out if an optional package exists in the annotation processor's methods?process

Edit 1:

Some small notes on "(optional) packaging". By an add-on package, I mean a Java package that may ( but does not necessarily) exist in the project (i.e. use the processor). Optional packages can, for example, represent content as external libraries. External libraries can but do not have to be included in the project.

Let me give a small example:

  • Suppose we have a (single module) project Sample.
  • Sampleis using mine TestProcessor.
  • Let's Square's Picassotake an external library as an example
  • Operates and generates code sum if SampleHAS Square's Picassois one of its dependencies . In other words: if you can use the class in (in ) without problems , the processor should run in .TestProcessorMode 2ABcom.square.picassoSampleMode 2
  • If not Square's Picassoin Sample'sdependencies, TestProcessorwork in and generate unique code .Mode 1A

Edit 2:

I thought of two solutions to this problem:

  1. Use two types of annotations for both (eg: , )processor Modes@DoStuffModeOne@DoStuffModeTwo
  2. Use a second type of annotation (that should be used e.g. in Applicationthe trigger's use) (e.g.: )Mode 2@TriggerModeTwo

As far as I'm concerned, the second workaround is preferable, but much worse than a situation where it's possible to decide which one to choose .TestProcessorMode

JBirdVegas ：

You can check a ButterKnifeclass in your application's classpath . Then execute logic based on the check result.

Class butterKnifeClass = null;
try {
    butterKnifeClass = Class.forName("butterknife.ButterKnife");
} catch (ClassNotFoundException e) {
    // no butterknife present
}
if (butterKnifeClass != null) {
    // blah... stuff with butterknife
}

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