EnumMap_CustomFieldSerializer.java

/*
 * Copyright 2012 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.user.client.rpc.core.java.util;

import com.google.gwt.core.client.GwtScriptOnly;
import com.google.gwt.user.client.rpc.CustomFieldSerializer;
import com.google.gwt.user.client.rpc.SerializationException;
import com.google.gwt.user.client.rpc.SerializationStreamReader;
import com.google.gwt.user.client.rpc.SerializationStreamWriter;

import java.util.EnumMap;
import java.util.EnumSet;

/**
 * Custom field serializer for {@link java.util.EnumMap}.
 */
@GwtScriptOnly
@SuppressWarnings({"unchecked", "rawtypes"})
public final class EnumMap_CustomFieldSerializer extends CustomFieldSerializer<EnumMap> {

  public static void deserialize(SerializationStreamReader streamReader, EnumMap instance)
      throws SerializationException {
    Map_CustomFieldSerializerBase.deserialize(streamReader, instance);
  }

  /**
   * EnumMap has no empty constructor; you must provide the class literal to the constructor.
   * However GWT doesn't emulate java.lang.Class.forName() nor is java.util.Class GWT-RPC
   * serializable. In order to get the type across the wire, one enum of the appropriate class is
   * serialized at the beginning of the stream. Upon deserialization this enum's type is
   * introspected and used in the constructor for the new EnumMap.
   */
  public static EnumMap instantiate(SerializationStreamReader streamReader)
      throws SerializationException {
    Object exemplar = streamReader.readObject();
    Class clazz = exemplar.getClass();
    return new EnumMap(clazz);
  }
  
  public static native <E> E[] getKeyUniverse(EnumMap<?, ?> map) /*-{
    return map.@java.util.EnumMap::keySet.@java.util.EnumSet$EnumSetImpl::all;
  }-*/;

  /**
   * A jsni method is used to access the private keySet field of the EnumMap instance.
   * This EnumSet field is filled with the universe of allowed enums even if the instance is empty.
   * The first enum is pulled from the set and serialized to the stream in order to allow the other
   * side to instantiate the correct type of EnumMap.
   */
  public static void serialize(SerializationStreamWriter streamWriter, EnumMap instance)
      throws SerializationException {
    Object exemplar;
    Object [] keyUniverse = getKeyUniverse(instance);
    exemplar = keyUniverse[0];  
    streamWriter.writeObject(exemplar);
    Map_CustomFieldSerializerBase.serialize(streamWriter, instance);
  }

  @Override
  public void deserializeInstance(SerializationStreamReader streamReader, EnumMap instance)
      throws SerializationException {
    deserialize(streamReader, instance);
  }

  @Override
  public boolean hasCustomInstantiateInstance() {
    return true;
  }

  @Override
  public EnumMap instantiateInstance(SerializationStreamReader streamReader)
      throws SerializationException {
    return instantiate(streamReader);
  }

  @Override
  public void serializeInstance(SerializationStreamWriter streamWriter, EnumMap instance)
      throws SerializationException {
    serialize(streamWriter, instance);
  }
}