Fix issue #1438 by generalizing the usage of the ServiceHelper class.

Also add test to check the behavior of the `ServiceHelper` when using different classloaders.

Signed-off-by: Clement Escoffier <clement.escoffier@gmail.com>

src/main/java/io/vertx/core/Future.java

@@ -305,6 +305,6 @@ default Handler<AsyncResult<T>> completer() {
     };
   }
 
-  static FutureFactory factory = ServiceHelper.loadFactory(FutureFactory.class);
+  FutureFactory factory = ServiceHelper.loadFactory(FutureFactory.class);
 
 }

src/main/java/io/vertx/core/ServiceHelper.java

@@ -16,7 +16,7 @@
 
 package io.vertx.core;
 
-import java.util.ServiceLoader;
+import java.util.*;
 
 /**
  * A helper class for loading factories from the classpath and from the vert.x OSGi bundle.
@@ -26,18 +26,50 @@
 public class ServiceHelper {
 
   public static <T> T loadFactory(Class<T> clazz) {
-    ServiceLoader<T> factories = ServiceLoader.load(clazz);
+    T factory = loadFactoryOrNull(clazz);
+    if (factory == null) {
+      throw new IllegalStateException("Cannot find META-INF/services/" + clazz.getName() + " on classpath");
+    }
+    return factory;
+  }
+
+  public static <T> T loadFactoryOrNull(Class<T> clazz) {
+    Collection<T> collection = loadFactories(clazz);
+    if (!collection.isEmpty()) {
+      return collection.iterator().next();
+    } else {
+      return null;
+    }
+  }
+
+
+  public static <T> Collection<T> loadFactories(Class<T> clazz) {
+    return loadFactories(clazz, null);
+  }
+
+  public static <T> Collection<T> loadFactories(Class<T> clazz, ClassLoader classLoader) {
+    List<T> list = new ArrayList<>();
+    ServiceLoader<T> factories;
+    if (classLoader != null) {
+      factories = ServiceLoader.load(clazz, classLoader);
+    } else {
+      // this is equivalent to:
+      // ServiceLoader.load(clazz, TCCL);
+      factories = ServiceLoader.load(clazz);
+    }
     if (factories.iterator().hasNext()) {
-      return factories.iterator().next();
+      factories.iterator().forEachRemaining(list::add);
+      return list;
     } else {
-      // By default ServiceLoader.load uses the TCCL, this may not be enough in environment deading with
+      // By default ServiceLoader.load uses the TCCL, this may not be enough in environment dealing with
       // classloaders differently such as OSGi. So we should try to use the  classloader having loaded this
       // class. In OSGi it would be the bundle exposing vert.x and so have access to all its classes.
       factories = ServiceLoader.load(clazz, ServiceHelper.class.getClassLoader());
       if (factories.iterator().hasNext()) {
-        return factories.iterator().next();
+        factories.iterator().forEachRemaining(list::add);
+        return list;
       } else {
-        throw new IllegalStateException("Cannot find META-INF/services/" + clazz.getName() + " on classpath");
+        return Collections.emptyList();
       }
     }
   }

src/main/java/io/vertx/core/Vertx.java

@@ -521,5 +521,5 @@ static void clusteredVertx(VertxOptions options, Handler<AsyncResult<Vertx>> res
    */
   @Nullable @GenIgnore Handler<Throwable> exceptionHandler();
 
-  static final VertxFactory factory = ServiceHelper.loadFactory(VertxFactory.class);
+  VertxFactory factory = ServiceHelper.loadFactory(VertxFactory.class);
 }

src/main/java/io/vertx/core/buffer/Buffer.java

@@ -697,6 +697,6 @@ static Buffer buffer(ByteBuf byteBuf) {
   @GenIgnore
   ByteBuf getByteBuf();
 
-  static final BufferFactory factory = ServiceHelper.loadFactory(BufferFactory.class);
+  BufferFactory factory = ServiceHelper.loadFactory(BufferFactory.class);
 
 }

src/main/java/io/vertx/core/http/WebSocketFrame.java

@@ -106,5 +106,5 @@ static WebSocketFrame continuationFrame(Buffer data, boolean isFinal) {
    */
   boolean isFinal();
 
-  static final WebSocketFrameFactory factory = ServiceHelper.loadFactory(WebSocketFrameFactory.class);
+  WebSocketFrameFactory factory = ServiceHelper.loadFactory(WebSocketFrameFactory.class);
 }

src/main/java/io/vertx/core/impl/DeploymentManager.java

@@ -52,10 +52,8 @@ public DeploymentManager(VertxInternal vertx) {
   }
 
   private void loadVerticleFactories() {
-    ServiceLoader<VerticleFactory> factories = ServiceLoader.load(VerticleFactory.class);
-    for (VerticleFactory factory: factories) {
-      registerVerticleFactory(factory);
-    }
+    Collection<VerticleFactory> factories = ServiceHelper.loadFactories(VerticleFactory.class);
+    factories.forEach(this::registerVerticleFactory);
     VerticleFactory defaultFactory = new JavaVerticleFactory();
     defaultFactory.init(vertx);
     defaultFactories.add(defaultFactory);

src/main/java/io/vertx/core/impl/VertxImpl.java

@@ -365,10 +365,8 @@ private VertxMetrics initialiseMetrics(VertxOptions options) {
     if (options.getMetricsOptions() != null && options.getMetricsOptions().isEnabled()) {
       VertxMetricsFactory factory = options.getMetricsOptions().getFactory();
       if (factory == null) {
-        ServiceLoader<VertxMetricsFactory> factories = ServiceLoader.load(VertxMetricsFactory.class);
-        if (factories.iterator().hasNext()) {
-          factory = factories.iterator().next();
-        } else {
+        factory = ServiceHelper.loadFactoryOrNull(VertxMetricsFactory.class);
+        if (factory == null) {
           log.warn("Metrics has been set to enabled but no VertxMetricsFactory found on classpath");
         }
       }
@@ -392,16 +390,15 @@ private ClusterManager getClusterManager(VertxOptions options) {
           // We allow specify a sys prop for the cluster manager factory which overrides ServiceLoader
           try {
             Class<?> clazz = Class.forName(clusterManagerClassName);
-            mgr = (ClusterManager)clazz.newInstance();
+            mgr = (ClusterManager) clazz.newInstance();
           } catch (Exception e) {
             throw new IllegalStateException("Failed to instantiate " + clusterManagerClassName, e);
           }
         } else {
-          ServiceLoader<ClusterManager> mgrs = ServiceLoader.load(ClusterManager.class);
-          if (!mgrs.iterator().hasNext()) {
+          mgr = ServiceHelper.loadFactoryOrNull(ClusterManager.class);
+          if (mgr == null) {
             throw new IllegalStateException("No ClusterManagerFactory instances found on classpath");
           }
-          mgr = mgrs.iterator().next();
         }
         return mgr;
       }
@@ -424,7 +421,7 @@ private long scheduleTimeout(ContextImpl context, Handler<Long> handler, long de
   public static Context context() {
     Thread current = Thread.currentThread();
     if (current instanceof VertxThread) {
-      return ((VertxThread)current).getContext();
+      return ((VertxThread) current).getContext();
     }
     return null;
   }
@@ -450,7 +447,7 @@ private void closeClusterManager(Handler<AsyncResult<Void>> completionHandler) {
     if (clusterManager != null) {
       // Workaround fo Hazelcast bug https://github.com/hazelcast/hazelcast/issues/5220
       if (clusterManager instanceof ExtendedClusterManager) {
-        ExtendedClusterManager ecm = (ExtendedClusterManager)clusterManager;
+        ExtendedClusterManager ecm = (ExtendedClusterManager) clusterManager;
         ecm.beforeLeave();
       }
       clusterManager.leave(ar -> {

src/main/java/io/vertx/core/impl/launcher/ServiceCommandFactoryLoader.java

@@ -15,13 +15,13 @@
  */
 package io.vertx.core.impl.launcher;
 
+import io.vertx.core.ServiceHelper;
 import io.vertx.core.spi.launcher.CommandFactory;
 import io.vertx.core.spi.launcher.CommandFactoryLookup;
 
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
-import java.util.ServiceLoader;
 
 /**
  * Looks for command factories using a service loader.
@@ -30,28 +30,28 @@
  */
 public class ServiceCommandFactoryLoader implements CommandFactoryLookup {
 
-  private ServiceLoader<CommandFactory> loader;
+  private Collection<CommandFactory> commands;
 
   /**
    * Creates a new instance of {@link ServiceCommandFactoryLoader} using the classloader having loaded the
    * {@link ServiceCommandFactoryLoader} class.
    */
   public ServiceCommandFactoryLoader() {
-    this.loader = ServiceLoader.load(CommandFactory.class, getClass().getClassLoader());
+    this.commands = ServiceHelper.loadFactories(CommandFactory.class, getClass().getClassLoader());
   }
 
   /**
    * Creates a new instance of {@link ServiceCommandFactoryLoader} using specified classloader.
    */
   public ServiceCommandFactoryLoader(ClassLoader loader) {
-    this.loader = ServiceLoader.load(CommandFactory.class, loader);
+    this.commands = ServiceHelper.loadFactories(CommandFactory.class, loader);
   }
 
   @Override
   public Collection<CommandFactory<?>> lookup() {
-    List<CommandFactory<?>> commands = new ArrayList<>();
-    loader.forEach(commands::add);
-    return commands;
+    List<CommandFactory<?>> list = new ArrayList<>();
+    commands.stream().forEach(list::add);
+    return list;
   }
 
 }

src/main/java/io/vertx/core/impl/launcher/commands/BareCommand.java

@@ -15,10 +15,7 @@
  */
 package io.vertx.core.impl.launcher.commands;
 
-import io.vertx.core.AsyncResult;
-import io.vertx.core.Vertx;
-import io.vertx.core.VertxException;
-import io.vertx.core.VertxOptions;
+import io.vertx.core.*;
 import io.vertx.core.cli.annotations.*;
 import io.vertx.core.impl.launcher.VertxLifecycleHooks;
 import io.vertx.core.metrics.MetricsOptions;
@@ -32,7 +29,6 @@
 import java.net.SocketException;
 import java.util.Enumeration;
 import java.util.Properties;
-import java.util.ServiceLoader;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
@@ -231,9 +227,8 @@ protected void beforeStartingVertx(VertxOptions options) {
    */
   protected MetricsOptions getMetricsOptions() {
     MetricsOptions metricsOptions;
-    ServiceLoader<VertxMetricsFactory> factories = ServiceLoader.load(VertxMetricsFactory.class);
-    if (factories.iterator().hasNext()) {
-      VertxMetricsFactory factory = factories.iterator().next();
+    VertxMetricsFactory factory = ServiceHelper.loadFactoryOrNull(VertxMetricsFactory.class);
+    if (factory != null) {
       metricsOptions = factory.newOptions();
     } else {
       metricsOptions = new MetricsOptions();

src/main/java/io/vertx/core/streams/Pump.java

@@ -101,7 +101,7 @@ static <T> Pump pump(ReadStream<T> rs, WriteStream<T> ws, int writeQueueMaxSize)
    */
   int numberPumped();
 
-  static final PumpFactory factory = ServiceHelper.loadFactory(PumpFactory.class);
+  PumpFactory factory = ServiceHelper.loadFactory(PumpFactory.class);
 
 
 }

src/test/externals/META-INF/services/io.vertx.test.spi.SomeFactory

@@ -0,0 +1,16 @@
+#
+#  Copyright (c) 2011-2015 The original author or authors
+#  ------------------------------------------------------
+#  All rights reserved. This program and the accompanying materials
+#  are made available under the terms of the Eclipse Public License v1.0
+#  and Apache License v2.0 which accompanies this distribution.
+#
+#       The Eclipse Public License is available at
+#       http://www.eclipse.org/legal/epl-v10.html
+#
+#       The Apache License v2.0 is available at
+#       http://www.opensource.org/licenses/apache2.0.php
+#
+#  You may elect to redistribute this code under either of these licenses.
+#
+io.vertx.core.externals.SomeFactoryImplA

src/test/externals/SomeFactoryImplA.java

@@ -0,0 +1,34 @@
+/*
+ *  Copyright (c) 2011-2015 The original author or authors
+ *  ------------------------------------------------------
+ *  All rights reserved. This program and the accompanying materials
+ *  are made available under the terms of the Eclipse Public License v1.0
+ *  and Apache License v2.0 which accompanies this distribution.
+ *
+ *       The Eclipse Public License is available at
+ *       http://www.eclipse.org/legal/epl-v10.html
+ *
+ *       The Apache License v2.0 is available at
+ *       http://www.opensource.org/licenses/apache2.0.php
+ *
+ *  You may elect to redistribute this code under either of these licenses.
+ */
+
+package io.vertx.core.externals;
+
+import io.vertx.test.spi.SomeFactory;
+
+/**
+ * @author <a href="http://escoffier.me">Clement Escoffier</a>
+ */
+public class SomeFactoryImplA implements SomeFactory {
+  @Override
+  public String name() {
+    return "A";
+  }
+
+  @Override
+  public ClassLoader classloader() {
+    return this.getClass().getClassLoader();
+  }
+}

src/test/java/io/vertx/core/FakeFactoryImplA.java

@@ -0,0 +1,34 @@
+/*
+ *  Copyright (c) 2011-2015 The original author or authors
+ *  ------------------------------------------------------
+ *  All rights reserved. This program and the accompanying materials
+ *  are made available under the terms of the Eclipse Public License v1.0
+ *  and Apache License v2.0 which accompanies this distribution.
+ *
+ *       The Eclipse Public License is available at
+ *       http://www.eclipse.org/legal/epl-v10.html
+ *
+ *       The Apache License v2.0 is available at
+ *       http://www.opensource.org/licenses/apache2.0.php
+ *
+ *  You may elect to redistribute this code under either of these licenses.
+ */
+
+package io.vertx.core;
+
+import io.vertx.test.spi.FakeFactory;
+
+/**
+ * @author <a href="http://escoffier.me">Clement Escoffier</a>
+ */
+public class FakeFactoryImplA implements FakeFactory {
+  @Override
+  public String name() {
+    return "A";
+  }
+
+  @Override
+  public ClassLoader classloader() {
+    return this.getClass().getClassLoader();
+  }
+}

src/test/java/io/vertx/core/FakeFactoryImplB.java

@@ -0,0 +1,34 @@
+/*
+ *  Copyright (c) 2011-2015 The original author or authors
+ *  ------------------------------------------------------
+ *  All rights reserved. This program and the accompanying materials
+ *  are made available under the terms of the Eclipse Public License v1.0
+ *  and Apache License v2.0 which accompanies this distribution.
+ *
+ *       The Eclipse Public License is available at
+ *       http://www.eclipse.org/legal/epl-v10.html
+ *
+ *       The Apache License v2.0 is available at
+ *       http://www.opensource.org/licenses/apache2.0.php
+ *
+ *  You may elect to redistribute this code under either of these licenses.
+ */
+
+package io.vertx.core;
+
+import io.vertx.test.spi.FakeFactory;
+
+/**
+ * @author <a href="http://escoffier.me">Clement Escoffier</a>
+ */
+public class FakeFactoryImplB implements FakeFactory {
+  @Override
+  public String name() {
+    return "B";
+  }
+
+  @Override
+  public ClassLoader classloader() {
+    return this.getClass().getClassLoader();
+  }
+}