AbstractSpecificationCodec.java

/*
 * Copyright © 2014-2016 Cask Data, 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 co.cask.cdap.proto.codec;

import co.cask.cdap.internal.guava.reflect.TypeParameter;
import co.cask.cdap.internal.guava.reflect.TypeToken;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

import java.lang.reflect.Type;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Abstract base class to provides common methods for all Codec.
 *
 * @param <T> The specification type that this codec handle.
 */
public abstract class AbstractSpecificationCodec<T> implements JsonSerializer<T>, JsonDeserializer<T> {

  protected final <V> JsonElement serializeMap(Map<String, V> map,
                                               JsonSerializationContext context,
                                               Class<V> valueType) {
    Type type = new TypeToken<Map<String, V>>() { }.where(new TypeParameter<V>() { }, valueType).getType();
    return context.serialize(map, type);
  }

  protected final <V> Map<String, V> deserializeMap(JsonElement json,
                                                    JsonDeserializationContext context,
                                                    Class<V> valueType) {
    Type type = new TypeToken<Map<String, V>>() { }.where(new TypeParameter<V>() { }, valueType).getType();
    Map<String, V> map = context.deserialize(json, type);
    return map == null ? Collections.<String, V>emptyMap() : map;
  }

  protected final <V> JsonElement serializeSet(Set<V> set, JsonSerializationContext context, Class<V> valueType) {
    Type type = new TypeToken<Set<V>>() { }.where(new TypeParameter<V>() { }, valueType).getType();
    return context.serialize(set, type);
  }

  protected final <V> Set<V> deserializeSet(JsonElement json, JsonDeserializationContext context, Class<V> valueType) {
    Type type = new TypeToken<Set<V>>() { }.where(new TypeParameter<V>() { }, valueType).getType();
    Set<V> set = context.deserialize(json, type);
    return set == null ? Collections.<V>emptySet() : set;
  }

  protected final <V> JsonElement serializeList(List<V> list, JsonSerializationContext context, Class<V> valueType) {
    Type type = new TypeToken<List<V>>() { }.where(new TypeParameter<V>() { }, valueType).getType();
    return context.serialize(list, type);
  }

  protected final <V> List<V> deserializeList(JsonElement json,
                                              JsonDeserializationContext context, Class<V> valueType) {
    Type type = new TypeToken<List<V>>() { }.where(new TypeParameter<V>() { }, valueType).getType();
    List<V> list = context.deserialize(json, type);
    return list == null ? Collections.<V>emptyList() : list;
  }
}