1 /* 2 * Copyright (C) 2016 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.collect; 18 19 import com.google.common.annotations.GwtCompatible; 20 21 /** 22 * A dummy superclass to support GWT serialization of the element type of an {@link 23 * ImmutableMultiset}. The GWT supersource for this class contains a field of type {@code E}. 24 * 25 * <p>For details about this hack, see {@code GwtSerializationDependencies}, which takes the same 26 * approach but with a subclass rather than a superclass. 27 * 28 * <p>TODO(cpovirk): Consider applying this subclass approach to our other types. 29 * 30 * <p>For {@code ImmutableMultiset} in particular, I ran into a problem with the {@code 31 * GwtSerializationDependencies} approach: When autogenerating a serializer for the new class, GWT 32 * tries to refer to our dummy serializer for the superclass, 33 * ImmutableMultiset_CustomFieldSerializer. But that type has no methods (since it's never actually 34 * used). We could probably fix the problem by adding dummy methods to that class, but that is 35 * starting to sound harder than taking the superclass approach, which I've been coming to like, 36 * anyway, since it doesn't require us to declare dummy methods (though occasionally constructors) 37 * and make types non-final. 38 */ 39 @GwtCompatible(emulated = true) 40 abstract class ImmutableMultisetGwtSerializationDependencies<E> extends ImmutableCollection<E> {} 41