/*
* Copyright (C) 2008 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.service.processor;
import static com.google.auto.common.MoreElements.getAnnotationMirror;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.SortedSet;
import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.Filer;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedOptions;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.PackageElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.DeclaredType;
import javax.lang.model.util.Types;
import javax.tools.Diagnostic.Kind;
import javax.tools.FileObject;
import javax.tools.StandardLocation;
import com.google.auto.service.AutoService;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multimap;
import com.google.common.collect.Sets;
/**
* Processes {@link AutoService} annotations and generates the service provider
* configuration files described in {@link java.util.ServiceLoader}.
* <p>
* Processor Options:<ul>
* <li>debug - turns on debug statements</li>
* </ul>
*/
@SupportedOptions({ "debug", "verify" })
public class AutoServiceProcessor extends AbstractProcessor {
/**
* Maps the class names of service provider interfaces to the
* class names of the concrete classes which implement them.
* <p>
* For example,
* {@code "com.google.apphosting.LocalRpcService" ->
* "com.google.apphosting.datastore.LocalDatastoreService"}
*/
private Multimap<String, String> providers = HashMultimap.create();
@Override
public ImmutableSet<String> getSupportedAnnotationTypes() {
return ImmutableSet.of(AutoService.class.getName());
}
@Override
public SourceVersion getSupportedSourceVersion() {
return SourceVersion.latestSupported();
}
/**
* <ol>
* <li> For each class annotated with {@link AutoService}<ul>
* <li> Verify the {@link AutoService} interface value is correct
* <li> Categorize the class by its service interface
* </ul>
*
* <li> For each {@link AutoService} interface <ul>
* <li> Create a file named {@code META-INF/services/<interface>}
* <li> For each {@link AutoService} annotated class for this interface <ul>
* <li> Create an entry in the file
* </ul>
* </ul>
* </ol>
*/
@Override
public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
try {
return processImpl(annotations, roundEnv);
} catch (Exception e) {
// We don't allow exceptions of any kind to propagate to the compiler
StringWriter writer = new StringWriter();
e.printStackTrace(new PrintWriter(writer));
fatalError(writer.toString());
return true;
}
}
private boolean processImpl(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
if (roundEnv.processingOver()) {
generateConfigFiles();
} else {
processAnnotations(annotations, roundEnv);
}
return true;
}
private void processAnnotations(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) {
Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(AutoService.class);
log(annotations.toString());
log(elements.toString());
for (Element e : elements) {
// TODO(gak): check for error trees?
TypeElement providerImplementer = (TypeElement) e;
AnnotationMirror providerAnnotation = getAnnotationMirror(e, AutoService.class).get();
DeclaredType providerInterface = getProviderInterface(providerAnnotation);
TypeElement providerType = (TypeElement) providerInterface.asElement();
log("provider interface: " + providerType.getQualifiedName());
log("provider implementer: " + providerImplementer.getQualifiedName());
if (!checkImplementer(providerImplementer, providerType)) {
String message = "ServiceProviders must implement their service provider interface. "
+ providerImplementer.getQualifiedName() + " does not implement "
+ providerType.getQualifiedName();
error(message, e, providerAnnotation);
}
String providerTypeName = getBinaryName(providerType);
String providerImplementerName = getBinaryName(providerImplementer);
log("provider interface binary name: " + providerTypeName);
log("provider implementer binary name: " + providerImplementerName);
providers.put(providerTypeName, providerImplementerName);
}
}
private void generateConfigFiles() {
Filer filer = processingEnv.getFiler();
for (String providerInterface : providers.keySet()) {
String resourceFile = "META-INF/services/" + providerInterface;
log("Working on resource file: " + resourceFile);
try {
SortedSet<String> allServices = Sets.newTreeSet();
try {
// would like to be able to print the full path
// before we attempt to get the resource in case the behavior
// of filer.getResource does change to match the spec, but there's
// no good way to resolve CLASS_OUTPUT without first getting a resource.
FileObject existingFile = filer.getResource(StandardLocation.CLASS_OUTPUT, "",
resourceFile);
log("Looking for existing resource file at " + existingFile.toUri());
Set<String> oldServices = ServicesFiles.readServiceFile(existingFile.openInputStream());
log("Existing service entries: " + oldServices);
allServices.addAll(oldServices);
} catch (IOException e) {
// According to the javadoc, Filer.getResource throws an exception
// if the file doesn't already exist. In practice this doesn't
// appear to be the case. Filer.getResource will happily return a
// FileObject that refers to a non-existent file but will throw
// IOException if you try to open an input stream for it.
log("Resource file did not already exist.");
}
Set<String> newServices = new HashSet<String>(providers.get(providerInterface));
if (allServices.containsAll(newServices)) {
log("No new service entries being added.");
return;
}
allServices.addAll(newServices);
log("New service file contents: " + allServices);
FileObject fileObject = filer.createResource(StandardLocation.CLASS_OUTPUT, "",
resourceFile);
OutputStream out = fileObject.openOutputStream();
ServicesFiles.writeServiceFile(allServices, out);
out.close();
log("Wrote to: " + fileObject.toUri());
} catch (IOException e) {
fatalError("Unable to create " + resourceFile + ", " + e);
return;
}
}
}
/**
* Verifies {@link ServiceProvider} constraints on the concrete provider class.
* Note that these constraints are enforced at runtime via the ServiceLoader,
* we're just checking them at compile time to be extra nice to our users.
*/
private boolean checkImplementer(TypeElement providerImplementer, TypeElement providerType) {
String verify = processingEnv.getOptions().get("verify");
if (verify == null || !Boolean.valueOf(verify)) {
return true;
}
// TODO: We're currently only enforcing the subtype relationship
// constraint. It would be nice to enforce them all.
Types types = processingEnv.getTypeUtils();
return types.isSubtype(providerImplementer.asType(), providerType.asType());
}
/**
* Returns the binary name of a reference type. For example,
* {@code com.google.Foo$Bar}, instead of {@code com.google.Foo.Bar}.
*
*/
private String getBinaryName(TypeElement element) {
return getBinaryNameImpl(element, element.getSimpleName().toString());
}
private String getBinaryNameImpl(TypeElement element, String className) {
Element enclosingElement = element.getEnclosingElement();
if (enclosingElement instanceof PackageElement) {
PackageElement pkg = (PackageElement) enclosingElement;
if (pkg.isUnnamed()) {
return className;
}
return pkg.getQualifiedName() + "." + className;
}
TypeElement typeElement = (TypeElement) enclosingElement;
return getBinaryNameImpl(typeElement, typeElement.getSimpleName() + "$" + className);
}
private DeclaredType getProviderInterface(AnnotationMirror providerAnnotation) {
// The very simplest of way of doing this, is also unfortunately unworkable.
// We'd like to do:
// ServiceProvider provider = e.getAnnotation(ServiceProvider.class);
// Class<?> providerInterface = provider.value();
//
// but unfortunately we can't load the arbitrary class at annotation
// processing time. So, instead, we have to use the mirror to get at the
// value (much more painful).
Map<? extends ExecutableElement, ? extends AnnotationValue> valueIndex =
providerAnnotation.getElementValues();
log("annotation values: " + valueIndex);
AnnotationValue value = valueIndex.values().iterator().next();
return (DeclaredType) value.getValue();
}
private void log(String msg) {
if (processingEnv.getOptions().containsKey("debug")) {
processingEnv.getMessager().printMessage(Kind.NOTE, msg);
}
}
private void error(String msg, Element element, AnnotationMirror annotation) {
processingEnv.getMessager().printMessage(Kind.ERROR, msg, element, annotation);
}
private void fatalError(String msg) {
processingEnv.getMessager().printMessage(Kind.ERROR, "FATAL ERROR: " + msg);
}
}