cn.ieclipse.af.demo.sample.volley.adapter.CollectionsAdapter.java Source code

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Here is the source code for cn.ieclipse.af.demo.sample.volley.adapter.CollectionsAdapter.java

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/*
 * Copyright (C) 2015-2016 QuickAF
 *
 * 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 cn.ieclipse.af.demo.sample.volley.adapter;

import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.internal.$Gson$Types;
import com.google.gson.internal.ConstructorConstructor;
import com.google.gson.internal.ObjectConstructor;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.Collection;

/**
 * CollectionsAdapter??null
 *
 * @author wangjian
 * @date 2016-08-08.
 */
public class CollectionsAdapter implements TypeAdapterFactory {

    private final ConstructorConstructor constructorConstructor;

    public CollectionsAdapter(ConstructorConstructor constructorConstructor) {
        this.constructorConstructor = constructorConstructor;
    }

    @Override
    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
        Type type = typeToken.getType();

        Class<? super T> rawType = typeToken.getRawType();
        if (!Collection.class.isAssignableFrom(rawType)) {
            return null;
        }

        Type elementType = $Gson$Types.getCollectionElementType(type, rawType);
        TypeAdapter<?> elementTypeAdapter = gson.getAdapter(TypeToken.get(elementType));
        ObjectConstructor<T> constructor = constructorConstructor.get(typeToken);

        @SuppressWarnings({ "unchecked", "rawtypes" }) // create() doesn't define a type parameter
        TypeAdapter<T> result = new Adapter(gson, elementType, elementTypeAdapter, constructor);
        return result;
    }

    private static final class Adapter<E> extends TypeAdapter<Collection<E>> {
        private final TypeAdapter<E> elementTypeAdapter;
        private final ObjectConstructor<? extends Collection<E>> constructor;

        public Adapter(Gson context, Type elementType, TypeAdapter<E> elementTypeAdapter,
                ObjectConstructor<? extends Collection<E>> constructor) {
            this.elementTypeAdapter = new TypeAdapterRuntimeTypeWrapper<E>(context, elementTypeAdapter,
                    elementType);
            this.constructor = constructor;
        }

        @Override
        public Collection<E> read(JsonReader in) throws IOException {
            if (in.peek() == JsonToken.NULL) {
                in.nextNull();
                //?null
                return constructor.construct();
            }

            Collection<E> collection = constructor.construct();
            in.beginArray();
            while (in.hasNext()) {
                E instance = elementTypeAdapter.read(in);
                collection.add(instance);
            }
            in.endArray();
            return collection;
        }

        @Override
        public void write(JsonWriter out, Collection<E> collection) throws IOException {
            if (collection == null) {
                out.nullValue();
                return;
            }

            out.beginArray();
            for (E element : collection) {
                elementTypeAdapter.write(out, element);
            }
            out.endArray();
        }
    }

}