| /* |
| * Copyright 2019 Google LLC |
| * |
| * 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.value.processor; |
| |
| import static java.util.stream.Collectors.toList; |
| |
| import com.google.common.collect.ImmutableList; |
| import java.io.BufferedReader; |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.io.InputStreamReader; |
| import java.net.URL; |
| import java.net.URLConnection; |
| import java.nio.charset.StandardCharsets; |
| import java.util.Collections; |
| import java.util.List; |
| import java.util.Optional; |
| import java.util.ServiceConfigurationError; |
| |
| /** |
| * A replacement for {@link java.util.ServiceLoader} that avoids certain long-standing bugs. This |
| * simpler implementation does not bother with lazy loading but returns all the service |
| * implementations in one list. It makes sure that {@link URLConnection#setUseCaches} is called to |
| * turn off jar caching, since that tends to lead to problems in versions before JDK 9. |
| * |
| * @see <a href="https://github.com/google/auto/issues/718">Issue #718</a> |
| * @see <a href="https://bugs.openjdk.java.net/browse/JDK-8156014">JDK-8156014</a> |
| */ |
| public final class SimpleServiceLoader { |
| private SimpleServiceLoader() {} |
| |
| public static <T> ImmutableList<T> load(Class<? extends T> service, ClassLoader loader) { |
| String resourceName = "META-INF/services/" + service.getName(); |
| List<URL> resourceUrls; |
| try { |
| resourceUrls = Collections.list(loader.getResources(resourceName)); |
| } catch (IOException e) { |
| throw new ServiceConfigurationError("Could not look up " + resourceName, e); |
| } |
| ImmutableList.Builder<T> providers = ImmutableList.builder(); |
| for (URL resourceUrl : resourceUrls) { |
| try { |
| providers.addAll(providersFromUrl(resourceUrl, service, loader)); |
| } catch (IOException e) { |
| throw new ServiceConfigurationError("Could not read " + resourceUrl, e); |
| } |
| } |
| return providers.build(); |
| } |
| |
| private static <T> ImmutableList<T> providersFromUrl( |
| URL resourceUrl, Class<T> service, ClassLoader loader) throws IOException { |
| ImmutableList.Builder<T> providers = ImmutableList.builder(); |
| URLConnection urlConnection = resourceUrl.openConnection(); |
| urlConnection.setUseCaches(false); |
| try (InputStream in = urlConnection.getInputStream(); |
| BufferedReader reader = |
| new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8))) { |
| for (String line : reader.lines().collect(toList())) { |
| Optional<String> maybeClassName = parseClassName(line); |
| if (maybeClassName.isPresent()) { |
| String className = maybeClassName.get(); |
| Class<?> c; |
| try { |
| c = Class.forName(className, false, loader); |
| } catch (ClassNotFoundException e) { |
| throw new ServiceConfigurationError("Could not load " + className, e); |
| } |
| if (!service.isAssignableFrom(c)) { |
| throw new ServiceConfigurationError( |
| "Class " + className + " is not assignable to " + service.getName()); |
| } |
| try { |
| Object provider = c.getConstructor().newInstance(); |
| providers.add(service.cast(provider)); |
| } catch (ReflectiveOperationException e) { |
| throw new ServiceConfigurationError("Could not construct " + className, e); |
| } |
| } |
| } |
| return providers.build(); |
| } |
| } |
| |
| private static Optional<String> parseClassName(String line) { |
| int hash = line.indexOf('#'); |
| if (hash >= 0) { |
| line = line.substring(0, hash); |
| } |
| line = line.trim(); |
| return line.isEmpty() ? Optional.empty() : Optional.of(line); |
| } |
| } |