WFLY-7802 Add externalizers for empty and singleton collections.

clustering/marshalling/spi/src/main/java/org/wildfly/clustering/marshalling/spi/util/CollectionExternalizer.java

@@ -31,6 +31,7 @@
 import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.LinkedList;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedDeque;
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.function.IntFunction;
@@ -98,6 +99,13 @@ public ArrayListExternalizer() {
         }
     }
 
+    @MetaInfServices(Externalizer.class)
+    public static class ConcurrentHashSetExternalizer extends CollectionExternalizer<ConcurrentHashMap.KeySetView<Object, Boolean>> {
+        public ConcurrentHashSetExternalizer() {
+            super(ConcurrentHashMap.KeySetView.class, capacity -> ConcurrentHashMap.newKeySet(capacity));
+        }
+    }
+
     @MetaInfServices(Externalizer.class)
     public static class ConcurrentLinkedDequeExternalizer extends CollectionExternalizer<ConcurrentLinkedDeque<Object>> {
         public ConcurrentLinkedDequeExternalizer() {

clustering/marshalling/spi/src/main/java/org/wildfly/clustering/marshalling/spi/util/EmptyCollectionExternalizer.java

@@ -0,0 +1,140 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2016, Red Hat, Inc., and individual contributors
+ * as indicated by the @author tags. See the copyright.txt file in the
+ * distribution for a full listing of individual contributors.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+ */
+
+package org.wildfly.clustering.marshalling.spi.util;
+
+import java.io.IOException;
+import java.io.ObjectInput;
+import java.io.ObjectOutput;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.Map;
+import java.util.NavigableMap;
+import java.util.NavigableSet;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+import java.util.function.Supplier;
+
+import org.kohsuke.MetaInfServices;
+import org.wildfly.clustering.marshalling.Externalizer;
+
+/**
+ * @author Paul Ferraro
+ */
+public class EmptyCollectionExternalizer<T> implements Externalizer<T> {
+
+    private final Supplier<T> factory;
+
+    EmptyCollectionExternalizer(Supplier<T> factory) {
+        this.factory = factory;
+    }
+
+    @Override
+    public void writeObject(ObjectOutput output, T object) throws IOException {
+        // Nothing to write
+    }
+
+    @Override
+    public T readObject(ObjectInput input) throws IOException, ClassNotFoundException {
+        return this.factory.get();
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public Class<? extends T> getTargetClass() {
+        return (Class<? extends T>) this.factory.get().getClass();
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptyEnumerationExternalizer extends EmptyCollectionExternalizer<Enumeration<Object>> {
+        public EmptyEnumerationExternalizer() {
+            super(() -> Collections.emptyEnumeration());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptyIteratorExternalizer extends EmptyCollectionExternalizer<Iterator<Object>> {
+        public EmptyIteratorExternalizer() {
+            super(() -> Collections.emptyIterator());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptyListExternalizer extends EmptyCollectionExternalizer<List<Object>> {
+        public EmptyListExternalizer() {
+            super(() -> Collections.emptyList());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptyListIteratorExternalizer extends EmptyCollectionExternalizer<ListIterator<Object>> {
+        public EmptyListIteratorExternalizer() {
+            super(() -> Collections.emptyListIterator());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptyMapExternalizer extends EmptyCollectionExternalizer<Map<Object, Object>> {
+        public EmptyMapExternalizer() {
+            super(() -> Collections.emptyMap());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptyNavigableMapExternalizer extends EmptyCollectionExternalizer<NavigableMap<Object, Object>> {
+        public EmptyNavigableMapExternalizer() {
+            super(() -> Collections.emptyNavigableMap());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptyNavigableSetExternalizer extends EmptyCollectionExternalizer<NavigableSet<Object>> {
+        public EmptyNavigableSetExternalizer() {
+            super(() -> Collections.emptyNavigableSet());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptySetExternalizer extends EmptyCollectionExternalizer<Set<Object>> {
+        public EmptySetExternalizer() {
+            super(() -> Collections.emptySet());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptySortedMapExternalizer extends EmptyCollectionExternalizer<SortedMap<Object, Object>> {
+        public EmptySortedMapExternalizer() {
+            super(() -> Collections.emptySortedMap());
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class EmptySortedSetExternalizer extends EmptyCollectionExternalizer<SortedSet<Object>> {
+        public EmptySortedSetExternalizer() {
+            super(() -> Collections.emptySortedSet());
+        }
+    }
+}

clustering/marshalling/spi/src/main/java/org/wildfly/clustering/marshalling/spi/util/SingletonCollectionExternalizer.java

@@ -0,0 +1,77 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2016, Red Hat, Inc., and individual contributors
+ * as indicated by the @author tags. See the copyright.txt file in the
+ * distribution for a full listing of individual contributors.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+ */
+
+package org.wildfly.clustering.marshalling.spi.util;
+
+import java.io.IOException;
+import java.io.ObjectInput;
+import java.io.ObjectOutput;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+import java.util.function.Function;
+
+import org.kohsuke.MetaInfServices;
+import org.wildfly.clustering.marshalling.Externalizer;
+
+/**
+ * @author Paul Ferraro
+ */
+public class SingletonCollectionExternalizer<T extends Collection<Object>> implements Externalizer<T> {
+
+    private final Function<Object, T> factory;
+
+    SingletonCollectionExternalizer(Function<Object, T> factory) {
+        this.factory = factory;
+    }
+
+    @Override
+    public void writeObject(ObjectOutput output, T collection) throws IOException {
+        output.writeObject(collection.stream().findFirst().get());
+    }
+
+    @Override
+    public T readObject(ObjectInput input) throws IOException, ClassNotFoundException {
+        return this.factory.apply(input.readObject());
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public Class<? extends T> getTargetClass() {
+        return (Class<? extends T>) this.factory.apply(null).getClass();
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class SingletonListExternalizer extends SingletonCollectionExternalizer<List<Object>> {
+        public SingletonListExternalizer() {
+            super(Collections::singletonList);
+        }
+    }
+
+    @MetaInfServices(Externalizer.class)
+    public static class SingletonSetExternalizer extends SingletonCollectionExternalizer<Set<Object>> {
+        public SingletonSetExternalizer() {
+            super(Collections::singleton);
+        }
+    }
+}