mirror of https://github.com/grpc/grpc-java.git
core: generifiy ServiceProvider class (#3886)
Moving all the common code among different service provider classes to one place.
This commit is contained in:
zpencer
GitHub
parent
417765b814
commit
2996207c20
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@ -0,0 +1,74 @@
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/*
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* Copyright 2017, gRPC Authors All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package io.grpc;
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import com.google.common.annotations.VisibleForTesting;
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import java.util.List;
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@Internal
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public final class InternalServiceProviders {
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private InternalServiceProviders() {
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}
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/**
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* Accessor for method.
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*/
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public static <T> T load(
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Class<T> klass,
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Iterable<Class<?>> hardcoded,
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ClassLoader classLoader,
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PriorityAccessor<T> priorityAccessor) {
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return ServiceProviders.load(klass, hardcoded, classLoader, priorityAccessor);
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}
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/**
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* Accessor for method.
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*/
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public static <T> List<T> loadAll(
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Class<T> klass,
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Iterable<Class<?>> hardCodedClasses,
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ClassLoader classLoader,
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PriorityAccessor<T> priorityAccessor) {
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return ServiceProviders.loadAll(klass, hardCodedClasses, classLoader, priorityAccessor);
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}
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/**
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* Accessor for method.
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*/
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@VisibleForTesting
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public static <T> Iterable<T> getCandidatesViaServiceLoader(Class<T> klass, ClassLoader cl) {
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return ServiceProviders.getCandidatesViaServiceLoader(klass, cl);
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}
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/**
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* Accessor for method.
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*/
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@VisibleForTesting
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public static <T> Iterable<T> getCandidatesViaHardCoded(
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Class<T> klass, Iterable<Class<?>> hardcoded) {
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return ServiceProviders.getCandidatesViaHardCoded(klass, hardcoded);
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}
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/**
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* Accessor for {@link ServiceProviders#isAndroid}.
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*/
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public static boolean isAndroid(ClassLoader cl) {
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return ServiceProviders.isAndroid(cl);
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}
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public interface PriorityAccessor<T> extends ServiceProviders.PriorityAccessor<T> {}
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}
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@ -0,0 +1,153 @@
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/*
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* Copyright 2017, gRPC Authors All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package io.grpc;
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import com.google.common.annotations.VisibleForTesting;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.List;
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import java.util.ServiceConfigurationError;
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import java.util.ServiceLoader;
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final class ServiceProviders {
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private ServiceProviders() {
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// do not instantiate
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}
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/**
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* If this is not Android, returns the highest priority implementation of the class via
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* {@link ServiceLoader}.
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* If this is Android, returns an instance of the highest priority class in {@code hardcoded}.
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*/
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public static <T> T load(
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Class<T> klass,
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Iterable<Class<?>> hardcoded,
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ClassLoader cl,
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PriorityAccessor<T> priorityAccessor) {
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List<T> candidates = loadAll(klass, hardcoded, cl, priorityAccessor);
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if (candidates.isEmpty()) {
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return null;
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}
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return candidates.get(0);
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}
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/**
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* If this is not Android, returns all available implementations discovered via
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* {@link ServiceLoader}.
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* If this is Android, returns all available implementations in {@code hardcoded}.
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* The list is sorted in descending priority order.
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*/
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public static <T> List<T> loadAll(
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Class<T> klass,
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Iterable<Class<?>> hardcoded,
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ClassLoader cl,
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final PriorityAccessor<T> priorityAccessor) {
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Iterable<T> candidates;
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if (isAndroid(cl)) {
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candidates = getCandidatesViaHardCoded(klass, hardcoded);
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} else {
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candidates = getCandidatesViaServiceLoader(klass, cl);
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}
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List<T> list = new ArrayList<T>();
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for (T current: candidates) {
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if (!priorityAccessor.isAvailable(current)) {
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continue;
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}
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list.add(current);
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}
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// Sort descending based on priority.
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Collections.sort(list, Collections.reverseOrder(new Comparator<T>() {
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@Override
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public int compare(T f1, T f2) {
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return priorityAccessor.getPriority(f1) - priorityAccessor.getPriority(f2);
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}
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}));
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return Collections.unmodifiableList(list);
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}
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/**
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* Returns true if the {@link ClassLoader} is for android.
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*/
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static boolean isAndroid(ClassLoader cl) {
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try {
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// Specify a class loader instead of null because we may be running under Robolectric
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Class.forName("android.app.Application", /*initialize=*/ false, cl);
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return true;
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} catch (Exception e) {
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// If Application isn't loaded, it might as well not be Android.
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return false;
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}
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}
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/**
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* Loads service providers for the {@code klass} service using {@link ServiceLoader}.
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*/
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@VisibleForTesting
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public static <T> Iterable<T> getCandidatesViaServiceLoader(Class<T> klass, ClassLoader cl) {
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Iterable<T> i = ServiceLoader.load(klass, cl);
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// Attempt to load using the context class loader and ServiceLoader.
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// This allows frameworks like http://aries.apache.org/modules/spi-fly.html to plug in.
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if (!i.iterator().hasNext()) {
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i = ServiceLoader.load(klass);
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}
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return i;
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}
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/**
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* Load providers from a hard-coded list. This avoids using getResource(), which has performance
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* problems on Android (see https://github.com/grpc/grpc-java/issues/2037).
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*/
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@VisibleForTesting
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static <T> Iterable<T> getCandidatesViaHardCoded(Class<T> klass, Iterable<Class<?>> hardcoded) {
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List<T> list = new ArrayList<T>();
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for (Class<?> candidate : hardcoded) {
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list.add(create(klass, candidate));
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}
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return list;
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}
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@VisibleForTesting
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static <T> T create(Class<T> klass, Class<?> rawClass) {
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try {
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return rawClass.asSubclass(klass).getConstructor().newInstance();
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} catch (Throwable t) {
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throw new ServiceConfigurationError(
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String.format("Provider %s could not be instantiated %s", rawClass.getName(), t), t);
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}
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}
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/**
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* An interface that allows us to get priority information about a provider.
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*/
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public interface PriorityAccessor<T> {
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/**
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* Checks this provider is available for use, taking the current environment into consideration.
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* If {@code false}, no other methods are safe to be called.
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*/
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boolean isAvailable(T provider);
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/**
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* A priority, from 0 to 10 that this provider should be used, taking the current environment
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* into consideration. 5 should be considered the default, and then tweaked based on environment
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* detection. A priority of 0 does not imply that the provider wouldn't work; just that it
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* should be last in line.
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*/
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int getPriority(T provider);
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}
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}
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@ -0,0 +1,316 @@
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/*
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* Copyright 2015, gRPC Authors All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package io.grpc;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertFalse;
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import static org.junit.Assert.assertNull;
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import static org.junit.Assert.assertSame;
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import static org.junit.Assert.assertTrue;
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import static org.junit.Assert.fail;
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import com.google.common.collect.ImmutableList;
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import io.grpc.InternalServiceProviders.PriorityAccessor;
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import java.util.Collections;
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import java.util.Iterator;
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import java.util.List;
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import java.util.ServiceConfigurationError;
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import org.junit.Test;
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import org.junit.runner.RunWith;
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import org.junit.runners.JUnit4;
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/** Unit tests for {@link ServiceProviders}. */
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@RunWith(JUnit4.class)
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public class ServiceProvidersTest {
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private static final List<Class<?>> NO_HARDCODED = Collections.emptyList();
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private static final PriorityAccessor<FooProvider> ACCESSOR =
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new PriorityAccessor<FooProvider>() {
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@Override
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public boolean isAvailable(FooProvider provider) {
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return provider.isAvailable();
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}
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@Override
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public int getPriority(FooProvider provider) {
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return provider.priority();
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}
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};
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private final String serviceFile = "META-INF/services/io.grpc.ServiceProvidersTest$FooProvider";
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@Test
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public void contextClassLoaderProvider() {
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ClassLoader ccl = Thread.currentThread().getContextClassLoader();
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try {
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ClassLoader cl = new ReplacingClassLoader(
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getClass().getClassLoader(),
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serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-multipleProvider.txt");
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// test that the context classloader is used as fallback
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ClassLoader rcll = new ReplacingClassLoader(
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getClass().getClassLoader(),
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serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-empty.txt");
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Thread.currentThread().setContextClassLoader(rcll);
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assertEquals(
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Available7Provider.class,
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ServiceProviders.load(FooProvider.class, NO_HARDCODED, cl, ACCESSOR).getClass());
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} finally {
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Thread.currentThread().setContextClassLoader(ccl);
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}
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}
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@Test
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public void noProvider() {
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ClassLoader ccl = Thread.currentThread().getContextClassLoader();
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try {
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ClassLoader cl = new ReplacingClassLoader(
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getClass().getClassLoader(),
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serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-doesNotExist.txt");
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Thread.currentThread().setContextClassLoader(cl);
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assertNull(ServiceProviders.load(FooProvider.class, NO_HARDCODED, cl, ACCESSOR));
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} finally {
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Thread.currentThread().setContextClassLoader(ccl);
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}
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}
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@Test
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public void multipleProvider() throws Exception {
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ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-multipleProvider.txt");
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assertSame(
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Available7Provider.class,
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ServiceProviders.load(FooProvider.class, NO_HARDCODED, cl, ACCESSOR).getClass());
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List<FooProvider> providers = ServiceProviders.loadAll(
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FooProvider.class, NO_HARDCODED, cl, ACCESSOR);
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assertEquals(3, providers.size());
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assertEquals(Available7Provider.class, providers.get(0).getClass());
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assertEquals(Available5Provider.class, providers.get(1).getClass());
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assertEquals(Available0Provider.class, providers.get(2).getClass());
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}
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@Test
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public void unavailableProvider() {
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// tries to load Available7 and UnavailableProvider, which has priority 10
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ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-unavailableProvider.txt");
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assertEquals(
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Available7Provider.class,
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ServiceProviders.load(FooProvider.class, NO_HARDCODED, cl, ACCESSOR).getClass());
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}
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@Test
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public void unknownClassProvider() {
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ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-unknownClassProvider.txt");
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try {
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FooProvider ignored = ServiceProviders.load(FooProvider.class, NO_HARDCODED, cl, ACCESSOR);
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fail("Exception expected");
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} catch (ServiceConfigurationError e) {
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// noop
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}
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}
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@Test
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public void exceptionSurfacedToCaller_failAtInit() {
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ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-failAtInitProvider.txt");
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try {
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// Even though there is a working provider, if any providers fail then we should fail
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// completely to avoid returning something unexpected.
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FooProvider ignored = ServiceProviders.load(FooProvider.class, NO_HARDCODED, cl, ACCESSOR);
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fail("Expected exception");
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} catch (ServiceConfigurationError expected) {
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// noop
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}
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}
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@Test
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public void exceptionSurfacedToCaller_failAtPriority() {
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ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-failAtPriorityProvider.txt");
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try {
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// The exception should be surfaced to the caller
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FooProvider ignored = ServiceProviders.load(FooProvider.class, NO_HARDCODED, cl, ACCESSOR);
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fail("Expected exception");
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} catch (FailAtPriorityProvider.PriorityException expected) {
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// noop
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}
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}
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@Test
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public void exceptionSurfacedToCaller_failAtAvailable() {
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ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
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"io/grpc/ServiceProvidersTest$FooProvider-failAtAvailableProvider.txt");
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try {
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// The exception should be surfaced to the caller
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FooProvider ignored = ServiceProviders.load(FooProvider.class, NO_HARDCODED, cl, ACCESSOR);
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fail("Expected exception");
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} catch (FailAtAvailableProvider.AvailableException expected) {
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// noop
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}
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}
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@Test
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public void getCandidatesViaHardCoded_multipleProvider() throws Exception {
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Iterator<FooProvider> candidates = ServiceProviders.getCandidatesViaHardCoded(
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FooProvider.class,
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ImmutableList.<Class<?>>of(
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Available7Provider.class,
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Available0Provider.class))
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.iterator();
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assertEquals(Available7Provider.class, candidates.next().getClass());
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assertEquals(Available0Provider.class, candidates.next().getClass());
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assertFalse(candidates.hasNext());
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}
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@Test
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public void getCandidatesViaHardCoded_failAtInit() throws Exception {
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try {
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Iterable<FooProvider> ignored = ServiceProviders.getCandidatesViaHardCoded(
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FooProvider.class,
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Collections.<Class<?>>singletonList(FailAtInitProvider.class));
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fail("Expected exception");
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} catch (ServiceConfigurationError expected) {
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// noop
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}
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}
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@Test
|
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public void getCandidatesViaHardCoded_failAtInit_moreCandidates() throws Exception {
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try {
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Iterable<FooProvider> ignored = ServiceProviders.getCandidatesViaHardCoded(
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FooProvider.class,
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ImmutableList.<Class<?>>of(FailAtInitProvider.class, Available0Provider.class));
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fail("Expected exception");
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} catch (ServiceConfigurationError expected) {
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// noop
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||||
}
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}
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@Test
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public void create_throwsErrorOnMisconfiguration() throws Exception {
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class PrivateClass {}
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try {
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FooProvider ignored = ServiceProviders.create(FooProvider.class, PrivateClass.class);
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fail("Expected exception");
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} catch (ServiceConfigurationError expected) {
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assertTrue("Expected ClassCastException cause: " + expected.getCause(),
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expected.getCause() instanceof ClassCastException);
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}
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||||
}
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/**
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* A provider class for this unit test.
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*/
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public abstract static class FooProvider {
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abstract boolean isAvailable();
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abstract int priority();
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}
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private static class BaseProvider extends FooProvider {
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private final boolean isAvailable;
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private final int priority;
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public BaseProvider(boolean isAvailable, int priority) {
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this.isAvailable = isAvailable;
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this.priority = priority;
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}
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||||
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@Override
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public boolean isAvailable() {
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return isAvailable;
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}
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||||
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@Override
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public int priority() {
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return priority;
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||||
}
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||||
}
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||||
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public static final class Available0Provider extends BaseProvider {
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public Available0Provider() {
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super(true, 0);
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}
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}
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public static final class Available5Provider extends BaseProvider {
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public Available5Provider() {
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super(true, 5);
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}
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}
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public static final class Available7Provider extends BaseProvider {
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public Available7Provider() {
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super(true, 7);
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}
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}
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||||
|
||||
public static final class UnavailableProvider extends BaseProvider {
|
||||
public UnavailableProvider() {
|
||||
super(false, 10);
|
||||
}
|
||||
}
|
||||
|
||||
public static final class FailAtInitProvider extends FooProvider {
|
||||
public FailAtInitProvider() {
|
||||
throw new RuntimeException("intentionally broken");
|
||||
}
|
||||
|
||||
@Override
|
||||
public boolean isAvailable() {
|
||||
return true;
|
||||
}
|
||||
|
||||
@Override
|
||||
public int priority() {
|
||||
return 0;
|
||||
}
|
||||
}
|
||||
|
||||
public static final class FailAtPriorityProvider extends FooProvider {
|
||||
@Override
|
||||
public boolean isAvailable() {
|
||||
return true;
|
||||
}
|
||||
|
||||
@Override
|
||||
public int priority() {
|
||||
throw new PriorityException();
|
||||
}
|
||||
|
||||
public static final class PriorityException extends RuntimeException {}
|
||||
}
|
||||
|
||||
public static final class FailAtAvailableProvider extends FooProvider {
|
||||
@Override
|
||||
public boolean isAvailable() {
|
||||
throw new AvailableException();
|
||||
}
|
||||
|
||||
@Override
|
||||
public int priority() {
|
||||
return 0;
|
||||
}
|
||||
|
||||
public static final class AvailableException extends RuntimeException {}
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,2 @@
|
|||
io.grpc.ServiceProvidersTest$FailAtAvailableProvider
|
||||
io.grpc.ServiceProvidersTest$Available5Provider
|
||||
|
|
@ -0,0 +1,2 @@
|
|||
io.grpc.ServiceProvidersTest$FailAtInitProvider
|
||||
io.grpc.ServiceProvidersTest$Available5Provider
|
||||
|
|
@ -0,0 +1,2 @@
|
|||
io.grpc.ServiceProvidersTest$FailAtPriorityProvider
|
||||
io.grpc.ServiceProvidersTest$Available5Provider
|
||||
|
|
@ -0,0 +1,3 @@
|
|||
io.grpc.ServiceProvidersTest$Available5Provider
|
||||
io.grpc.ServiceProvidersTest$Available7Provider
|
||||
io.grpc.ServiceProvidersTest$Available0Provider
|
||||
|
|
@ -0,0 +1,2 @@
|
|||
io.grpc.ServiceProvidersTest$UnavailableProvider
|
||||
io.grpc.ServiceProvidersTest$Available7Provider
|
||||
|
|
@ -0,0 +1 @@
|
|||
io.grpc.ServiceProvidersTest$UnknownClassProvider
|
||||
Loading…
Reference in New Issue