com.merakianalytics.datapipelines.sinks.PutProcessor Maven / Gradle / Ivy

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package com.merakianalytics.datapipelines.sinks;

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.ElementKind;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.ExecutableType;
import javax.lang.model.type.MirroredTypeException;
import javax.lang.model.type.TypeKind;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.Elements;
import javax.lang.model.util.Types;

import com.merakianalytics.datapipelines.PipelineContext;

/**
 * A compile-time Annotation Processor to verify that {@link com.merakianalytics.datapipelines.sinks.Put} annotations are placed only on methods that have the
 * proper signature
 *
 * @see com.merakianalytics.datapipelines.sinks.Put
 * @see com.merakianalytics.datapipelines.sinks.AbstractDataSink#put(Class, Object, PipelineContext)
 */
@SupportedAnnotationTypes("com.merakianalytics.datapipelines.sinks.Put")
@SupportedSourceVersion(SourceVersion.RELEASE_7)
public class PutProcessor extends AbstractProcessor {
    @Override
    public boolean process(final Set annotations, final RoundEnvironment environment) {
        for(final Element element : environment.getElementsAnnotatedWith(Put.class)) {
            final Put annotation = element.getAnnotation(Put.class);

            if(ElementKind.METHOD != element.getKind()) {
                throw new DataSinkDefinitionException(
                    "Must use @Put with methods only! Tried to use with " + element.getSimpleName()
                        + ", which is not a method.");
            }

            final Set modifiers = element.getModifiers();
            if(!modifiers.contains(Modifier.PUBLIC)) {
                throw new DataSinkDefinitionException(
                    "Must use @Put with public methods only! Tried to use with " + element.getSimpleName()
                        + ", which is not public.");
            }
            if(modifiers.contains(Modifier.STATIC)) {
                throw new DataSinkDefinitionException(
                    "Must use @Put with non-static methods only! Tried to use with " + element.getSimpleName()
                        + ", which is static.");
            }

            final ExecutableType method = (ExecutableType)element.asType();
            final Types types = processingEnv.getTypeUtils();
            final Elements elements = processingEnv.getElementUtils();

            // annotation.value() will throw the exception because it doesn't have compiled class information yet, and is of type Class.
            TypeMirror annotatedType = null;
            try {
                annotation.value();
            } catch(final MirroredTypeException e) {
                annotatedType = e.getTypeMirror();
            }

            if(TypeKind.VOID != method.getReturnType().getKind()) {
                throw new DataSinkDefinitionException(
                    "@Put method must have void return! Tried to use with " + element.getSimpleName() + ", which returns "
                        + method.getReturnType() + ".");
            }
            if(method.getParameterTypes().size() != 2) {
                throw new DataSinkDefinitionException("@Put methods must take 2 arguments: T item, PipelineContext context. Tried to use with "
                    + element.getSimpleName() + ", which has a different signature.");
            }

            final TypeMirror contextType = elements.getTypeElement(PipelineContext.class.getName()).asType();

            if(!types.isAssignable(annotatedType, method.getParameterTypes().get(0))) {
                throw new DataSinkDefinitionException(
                    "@Put method annotated value type must be assignable from the method's first argument type. Tried to use with "
                        + element.getSimpleName() + ", which takes " + method.getParameterTypes().get(0) + ".");
            }
            if(!types.isAssignable(method.getParameterTypes().get(1), contextType)) {
                throw new DataSinkDefinitionException("@Put method second argument must be assignable from " + contextType + ". Tried to use with "
                    + element.getSimpleName() + ", which takes " + method.getParameterTypes().get(1) + ".");
            }
        }

        return true;
    }
}