Java tutorial
/* * Copyright (C) 2013 Google, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.google.auto.factory.processor; import static com.google.common.base.Preconditions.checkArgument; import static com.google.common.base.Preconditions.checkNotNull; import static javax.lang.model.element.Modifier.ABSTRACT; import static javax.lang.model.element.Modifier.PUBLIC; import static javax.tools.Diagnostic.Kind.ERROR; import javax.annotation.processing.Messager; import javax.inject.Inject; import javax.lang.model.element.AnnotationMirror; import javax.lang.model.element.Element; import javax.lang.model.element.ElementKind; import javax.lang.model.element.ExecutableElement; import javax.lang.model.element.Name; import javax.lang.model.element.TypeElement; import javax.lang.model.element.VariableElement; import javax.lang.model.util.ElementKindVisitor6; import javax.lang.model.util.Elements; import com.google.auto.factory.AutoFactory; import com.google.auto.factory.Provided; import com.google.common.base.Function; import com.google.common.base.Functions; import com.google.common.base.Optional; import com.google.common.base.Predicate; import com.google.common.collect.FluentIterable; import com.google.common.collect.ImmutableListMultimap; import com.google.common.collect.ImmutableSet; import com.google.common.collect.Multimaps; /** * A service that traverses an element and returns the set of factory methods defined therein. * * @author Gregory Kick */ final class FactoryDescriptorGenerator { private final Messager messager; private final Elements elements; private final AutoFactoryDeclaration.Factory declarationFactory; @Inject FactoryDescriptorGenerator(Messager messager, Elements elements, AutoFactoryDeclaration.Factory declarationFactory) { this.messager = messager; this.elements = elements; this.declarationFactory = declarationFactory; } ImmutableSet<FactoryMethodDescriptor> generateDescriptor(Element element) { final AnnotationMirror mirror = Mirrors.getAnnotationMirror(element, AutoFactory.class).get(); final Optional<AutoFactoryDeclaration> declaration = declarationFactory.createIfValid(element); if (!declaration.isPresent()) { return ImmutableSet.of(); } return element.accept(new ElementKindVisitor6<ImmutableSet<FactoryMethodDescriptor>, Void>() { @Override protected ImmutableSet<FactoryMethodDescriptor> defaultAction(Element e, Void p) { throw new AssertionError("@AutoFactory applied to an impossible element"); } @Override public ImmutableSet<FactoryMethodDescriptor> visitTypeAsClass(TypeElement type, Void p) { if (type.getModifiers().contains(ABSTRACT)) { // applied to an abstract factory messager.printMessage(ERROR, "Auto-factory doesn't support being applied to abstract classes.", type, mirror); return ImmutableSet.of(); } else { // applied to the type to be created ImmutableSet<ExecutableElement> constructors = Elements2.getConstructors(type); if (constructors.isEmpty()) { return generateDescriptorForDefaultConstructor(declaration.get(), type); } else { return FluentIterable.from(constructors) .transform(new Function<ExecutableElement, FactoryMethodDescriptor>() { @Override public FactoryMethodDescriptor apply(ExecutableElement constructor) { return generateDescriptorForConstructor(declaration.get(), constructor); } }).toSet(); } } } @Override public ImmutableSet<FactoryMethodDescriptor> visitTypeAsInterface(TypeElement type, Void p) { // applied to the factory interface messager.printMessage(ERROR, "Auto-factory doesn't support being applied to interfaces.", type, mirror); return ImmutableSet.of(); } @Override public ImmutableSet<FactoryMethodDescriptor> visitExecutableAsConstructor(ExecutableElement e, Void p) { // applied to a constructor of a type to be created return ImmutableSet.of(generateDescriptorForConstructor(declaration.get(), e)); } }, null); } FactoryMethodDescriptor generateDescriptorForConstructor(final AutoFactoryDeclaration declaration, ExecutableElement constructor) { checkNotNull(constructor); checkArgument(constructor.getKind() == ElementKind.CONSTRUCTOR); Element classElement = constructor.getEnclosingElement(); Name returnType = classElement.accept(new ElementKindVisitor6<Name, Void>() { @Override protected Name defaultAction(Element e, Void p) { throw new AssertionError(); } @Override public Name visitTypeAsClass(TypeElement e, Void p) { if (!e.getTypeParameters().isEmpty()) { messager.printMessage(ERROR, "AutoFactory does not support generic types", e); } return e.getQualifiedName(); } }, null); ImmutableListMultimap<Boolean, ? extends VariableElement> parameterMap = Multimaps .index(constructor.getParameters(), Functions.forPredicate(new Predicate<VariableElement>() { @Override public boolean apply(VariableElement parameter) { return parameter.getAnnotation(Provided.class) != null; } })); ImmutableSet<Parameter> providedParameters = Parameter.forParameterList(parameterMap.get(true)); ImmutableSet<Parameter> passedParameters = Parameter.forParameterList(parameterMap.get(false)); return new FactoryMethodDescriptor.Builder(declaration) .factoryName(declaration.getFactoryName(elements.getPackageOf(constructor).getQualifiedName(), classElement.getSimpleName())) .name("create").returnType(returnType.toString()) .publicMethod(constructor.getEnclosingElement().getModifiers().contains(PUBLIC)) .providedParameters(providedParameters).passedParameters(passedParameters) .creationParameters(Parameter.forParameterList(constructor.getParameters())).build(); } private ImmutableSet<FactoryMethodDescriptor> generateDescriptorForDefaultConstructor( AutoFactoryDeclaration declaration, TypeElement type) { return ImmutableSet.of(new FactoryMethodDescriptor.Builder(declaration) .factoryName(declaration.getFactoryName(elements.getPackageOf(type).getQualifiedName(), type.getSimpleName())) .name("create").returnType(type.getQualifiedName().toString()) .publicMethod(type.getModifiers().contains(PUBLIC)).passedParameters(ImmutableSet.<Parameter>of()) .creationParameters(ImmutableSet.<Parameter>of()).providedParameters(ImmutableSet.<Parameter>of()) .build()); } }