Issue #4340 - ServiceLoader stream which doesn't break if hasNext throws

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-alpn/jetty-alpn-client/src/main/java/org/eclipse/jetty/alpn/client/ALPNClientConnectionFactory.java

@@ -54,7 +54,7 @@ public ALPNClientConnectionFactory(Executor executor, ClientConnectionFactory co
         IllegalStateException failure = new IllegalStateException("No Client ALPNProcessors!");
 
         // Use a for loop on iterator so load exceptions can be caught and ignored
-        ServiceLoader.load(Client.class).stream().flatMap(TypeUtil::providerMap).forEach((processor) ->
+        TypeUtil.serviceLoaderStream(ServiceLoader.load(Client.class)).flatMap(TypeUtil::providerMap).forEach((processor) ->
         {
             try
             {

jetty-alpn/jetty-alpn-server/src/main/java/org/eclipse/jetty/alpn/server/ALPNServerConnectionFactory.java

@@ -51,7 +51,7 @@ public ALPNServerConnectionFactory(@Name("protocols") String... protocols)
 
         IllegalStateException failure = new IllegalStateException("No Server ALPNProcessors!");
         // Use a for loop on iterator so load exceptions can be caught and ignored
-        ServiceLoader.load(Server.class).stream().flatMap(TypeUtil::providerMap).forEach((processor) ->
+        TypeUtil.serviceLoaderStream(ServiceLoader.load(Server.class)).flatMap(TypeUtil::providerMap).forEach((processor) ->
         {
             try
             {

jetty-annotations/src/main/java/org/eclipse/jetty/annotations/AnnotationConfiguration.java

@@ -812,7 +812,7 @@ public List<ServletContainerInitializer> getNonExcludedInitializers(WebAppContex
         long start = 0;
         if (LOG.isDebugEnabled())
             start = System.nanoTime();
-        List<ServletContainerInitializer> scis = ServiceLoader.load(ServletContainerInitializer.class).stream()
+        List<ServletContainerInitializer> scis = TypeUtil.serviceLoaderStream(ServiceLoader.load(ServletContainerInitializer.class))
             .flatMap(TypeUtil::providerMap)
             .collect(Collectors.toList());
         if (LOG.isDebugEnabled())

jetty-http/src/main/java/org/eclipse/jetty/http/PreEncodedHttpField.java

@@ -43,7 +43,7 @@ public class PreEncodedHttpField extends HttpField
 
     static
     {
-        List<HttpFieldPreEncoder> encoders = ServiceLoader.load(HttpFieldPreEncoder.class).stream()
+        List<HttpFieldPreEncoder> encoders = TypeUtil.serviceLoaderStream(ServiceLoader.load(HttpFieldPreEncoder.class))
             .flatMap(TypeUtil::providerMap)
             .filter(encoder -> index(encoder.getHttpVersion()) >= 0)
             .collect(Collectors.toList());

jetty-security/src/main/java/org/eclipse/jetty/security/SecurityHandler.java

@@ -77,7 +77,7 @@ public abstract class SecurityHandler extends HandlerWrapper implements Authenti
 
     static
     {
-        ServiceLoader.load(Authenticator.Factory.class).stream()
+        TypeUtil.serviceLoaderStream(ServiceLoader.load(Authenticator.Factory.class))
             .flatMap(TypeUtil::providerMap)
             .forEach(__knownAuthenticatorFactories::add);
         __knownAuthenticatorFactories.add(new DefaultAuthenticatorFactory());

jetty-util/src/main/java/org/eclipse/jetty/util/ServiceLoaderSpliterator.java

@@ -0,0 +1,103 @@
+//
+// ========================================================================
+// Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
+//
+// This program and the accompanying materials are made available under
+// the terms of the Eclipse Public License 2.0 which is available at
+// https://www.eclipse.org/legal/epl-2.0
+//
+// This Source Code may also be made available under the following
+// Secondary Licenses when the conditions for such availability set
+// forth in the Eclipse Public License, v. 2.0 are satisfied:
+// the Apache License v2.0 which is available at
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+// ========================================================================
+//
+
+package org.eclipse.jetty.util;
+
+import java.util.Iterator;
+import java.util.ServiceConfigurationError;
+import java.util.ServiceLoader;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+
+class ServiceLoaderSpliterator<T> implements Spliterator<ServiceLoader.Provider<T>>
+{
+    private final Iterator<T> iterator;
+
+    public ServiceLoaderSpliterator(ServiceLoader<T> serviceLoader)
+    {
+        iterator = serviceLoader.iterator();
+    }
+
+    @Override
+    public boolean tryAdvance(Consumer<? super ServiceLoader.Provider<T>> action)
+    {
+        Provider<T> next = new Provider<>();
+        try
+        {
+            if (!iterator.hasNext())
+                return false;
+            next.setServiceProvider(iterator.next());
+        }
+        catch (Throwable t)
+        {
+            next.setError(t);
+        }
+
+        action.accept(next);
+        return true;
+    }
+
+    @Override
+    public Spliterator<ServiceLoader.Provider<T>> trySplit()
+    {
+        return null;
+    }
+
+    @Override
+    public long estimateSize()
+    {
+        return Long.MAX_VALUE;
+    }
+
+    @Override
+    public int characteristics()
+    {
+        return Spliterator.ORDERED;
+    }
+
+    private static class Provider<T> implements ServiceLoader.Provider<T>
+    {
+        private T serviceProvider;
+        private Throwable error;
+
+        public void setServiceProvider(T serviceProvider)
+        {
+            this.serviceProvider = serviceProvider;
+        }
+
+        public void setError(Throwable error)
+        {
+            this.error = error;
+        }
+
+        @Override
+        @SuppressWarnings("unchecked")
+        public Class<? extends T> type()
+        {
+            return (Class<? extends T>)get().getClass();
+        }
+
+        @Override
+        public T get()
+        {
+            if (error != null)
+                throw new ServiceConfigurationError("", error);
+            return serviceProvider;
+        }
+    }
+}

jetty-util/src/main/java/org/eclipse/jetty/util/TypeUtil.java

@@ -46,6 +46,7 @@
 import java.util.ServiceLoader;
 import java.util.function.Function;
 import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 import org.eclipse.jetty.util.log.Log;
 import org.eclipse.jetty.util.log.Logger;
@@ -778,4 +779,17 @@ public static <T> Stream<T> providerMap(ServiceLoader.Provider<T> provider)
             return Stream.empty();
         }
     }
+
+    /**
+     * Utility to create a stream which provides the same functionality as {@link ServiceLoader#stream()}.
+     * However this also guards the case in which {@link Iterator#hasNext()} throws. Any exceptions
+     * from the underlying iterator will be cached until the {@link ServiceLoader.Provider#get()} is called.
+     * @param serviceLoader the ServiceLoader instance to use.
+     * @param <T> the type of the service to load.
+     * @return A stream that lazily loads providers for this loader's service
+     */
+    public static <T> Stream<ServiceLoader.Provider<T>> serviceLoaderStream(ServiceLoader<T> serviceLoader)
+    {
+        return StreamSupport.stream(new ServiceLoaderSpliterator<T>(serviceLoader), false);
+    }
 }

jetty-util/src/main/java/org/eclipse/jetty/util/security/Credential.java

@@ -44,7 +44,7 @@ public abstract class Credential implements Serializable
 {
     private static final long serialVersionUID = -7760551052768181572L;
     private static final Logger LOG = Log.getLogger(Credential.class);
-    private static final List<CredentialProvider> CREDENTIAL_PROVIDERS = ServiceLoader.load(CredentialProvider.class).stream().flatMap(TypeUtil::providerMap).collect(Collectors.toList());
+    private static final List<CredentialProvider> CREDENTIAL_PROVIDERS = TypeUtil.serviceLoaderStream(ServiceLoader.load(CredentialProvider.class)).flatMap(TypeUtil::providerMap).collect(Collectors.toList());
 
     /**
      * Check a credential

jetty-webapp/src/main/java/org/eclipse/jetty/webapp/Configurations.java

@@ -75,7 +75,7 @@ public static synchronized List<Configuration> getKnown()
     {
         if (__known.isEmpty())
         {
-            ServiceLoader.load(Configuration.class).stream().flatMap(TypeUtil::providerMap).forEach(configuration ->
+            TypeUtil.serviceLoaderStream(ServiceLoader.load(Configuration.class)).flatMap(TypeUtil::providerMap).forEach(configuration ->
             {
                 if (!configuration.isAvailable())
                 {

jetty-xml/src/main/java/org/eclipse/jetty/xml/XmlConfiguration.java

@@ -96,8 +96,8 @@ public class XmlConfiguration
         {
             ArrayList.class, HashSet.class, Queue.class, List.class, Set.class, Collection.class
         };
-    private static final List<ConfigurationProcessorFactory> PROCESSOR_FACTORIES = ServiceLoader.load(ConfigurationProcessorFactory.class)
-        .stream().flatMap(TypeUtil::providerMap).collect(Collectors.toList());
+    private static final List<ConfigurationProcessorFactory> PROCESSOR_FACTORIES = TypeUtil.serviceLoaderStream(ServiceLoader.load(ConfigurationProcessorFactory.class))
+        .flatMap(TypeUtil::providerMap).collect(Collectors.toList());
     private static final XmlParser PARSER = initParser();
     private static final Comparator<Executable> EXECUTABLE_COMPARATOR = (o1, o2) ->
     {