如何使Kotlin Library像Java Library？

Question

我正在使用 Android Studio 中的 Java模块编写自定义@Builder注释处理库（类似于Project Lombok）。我不想用Java编写 Java模块，而是想用Kotlin编写。

由于 Android Studio 中没有 Kotlin模块选项，因此我启动了一个新的 Java模块并用Java编写。

@AutoService(Processor.class)
public class BuilderProcessor extends AbstractProcessor {

    private Filer filer;
    @Override
    public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
        for (Element element : roundEnvironment.getElementsAnnotatedWith(Builder.class)){
            TypeSpec binder = createClass(element.getSimpleName().toString());
            TypeElement typeElement = (TypeElement) element;
            JavaFile javaFile = JavaFile.builder(getPackage(typeElement.getQualifiedName().toString()), binder).build();
            try {
                javaFile.writeTo(filer);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return false;
    }

    @Override
    public Set<String> getSupportedAnnotationTypes() {
        Set<String> annotations = new LinkedHashSet<>();
        for (Class<? extends Annotation> annotation : Collections.singleton(Builder.class)) {
            annotations.add(annotation.getCanonicalName());
        }
        return annotations;
    }

    @Override
    public synchronized void init(ProcessingEnvironment processingEnvironment) {
        super.init(processingEnvironment);
        this.filer = processingEnvironment.getFiler();
    }

    private String getPackage(String s){
        return s.substring(0, s.lastIndexOf('.'));
    }

    private TypeSpec createClass(String className){
        return TypeSpec.classBuilder(className + "Builder")
                .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
                .build();
    }
}

如果在UserBuilder.java类之上有注释@Builder，则上面的代码可以很好地工作并创建类User。

现在我想在Kotlin中进行转换。因此，我将代码转换为Kotlin

@AutoService(Processor::class)
class BuilderProcessor : AbstractProcessor() {

    private var filer: Filer? = null
    override fun process(set: Set<TypeElement>, roundEnvironment: RoundEnvironment): Boolean {
        for (element in roundEnvironment.getElementsAnnotatedWith(Builder::class.java)) {
            val binder = createClass(element.simpleName.toString())
            val typeElement = element as TypeElement
            val javaFile = JavaFile.builder(getPackage(typeElement.qualifiedName.toString()), binder).build()
            try {
                javaFile.writeTo(filer!!)
            } catch (e: IOException) {
                e.printStackTrace()
            }

        }
        return false
    }

    override fun getSupportedAnnotationTypes(): Set<String> {
        val annotations = LinkedHashSet<String>()
        for (annotation in setOf(Builder::class.java)) {
            annotations.add(annotation.canonicalName)
        }
        return annotations
    }

    @Synchronized
    override fun init(processingEnvironment: ProcessingEnvironment) {
        super.init(processingEnvironment)
        this.filer = processingEnvironment.filer
    }

    private fun getPackage(s: String): String {
        return s.substring(0, s.lastIndexOf('.'))
    }

    private fun createClass(className: String): TypeSpec {
        return TypeSpec.classBuilder(className + "Builder")
            .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
            .build()
    }
}

并使用Kotlin配置成绩

plugins {
    id 'org.jetbrains.kotlin.jvm'
}
apply plugin: 'java-library'

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    api 'com.google.guava:guava:27.0.1-android'
    implementation 'com.squareup:javapoet:1.9.0'
    implementation 'com.google.auto.service:auto-service:1.0-rc2'
    implementation project(':builder')
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
}

sourceCompatibility = "7"
targetCompatibility = "7"
repositories {
    mavenCentral()
}
compileKotlin {
    kotlinOptions {
        jvmTarget = "1.8"
    }
}
compileTestKotlin {
    kotlinOptions {
        jvmTarget = "1.8"
    }
}

但是，不幸的是，当我构建它时，它不起作用。它会生成，但不会生成UserBuilder.java类。我做错了还是应该采取任何步骤？

有reference的 Project Lombok 的Kotlin版本。