tajo-catalog/tajo-catalog-common/src/main/java/org/apache/tajo/catalog/json/CatalogGsonHelper.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.tajo.catalog.json;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.apache.hadoop.fs.Path;
import org.apache.tajo.catalog.Schema;
import org.apache.tajo.catalog.TableMeta;
import org.apache.tajo.common.TajoDataTypes.DataType;
import org.apache.tajo.datum.Datum;
import org.apache.tajo.function.Function;
import org.apache.tajo.json.*;

import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

public class CatalogGsonHelper {
  private static Gson gson;
  private static Gson gsonPretty;

  private CatalogGsonHelper() {
  }

  private static Map<Type, GsonSerDerAdapter<?>> registerAdapters() {
    Map<Type, GsonSerDerAdapter<?>> adapters = new HashMap<>();
    adapters.put(Class.class, new ClassNameSerializer());
    adapters.put(Path.class, new PathSerializer());
    adapters.put(TableMeta.class, new TableMetaAdapter());
    adapters.put(Function.class, new FunctionAdapter());
    adapters.put(Datum.class, new DatumAdapter());
    adapters.put(DataType.class, new DataTypeAdapter());
    adapters.put(Schema.class, new SchemaAdapter());
    return adapters;
  }

  public static Gson getInstance() {
    if (gson == null ) {
      GsonHelper helper = new GsonHelper(registerAdapters());
      gson = helper.getGson();
    }
    return gson;
  }

  public static Gson getPrettyInstance() {
    if (gsonPretty == null) {
      GsonBuilder prettyBuilder = new GsonBuilder()
          .setPrettyPrinting()
          .excludeFieldsWithoutExposeAnnotation();
      GsonHelper.registerAdapters(prettyBuilder, registerAdapters());
      gsonPretty = prettyBuilder.create();
    }

    return gsonPretty;
  }

  public static String toJson(GsonObject object, Class<? extends GsonObject> clazz) {
    return getInstance().toJson(object, clazz);
  }

  public static <T extends GsonObject> T fromJson(String json, Class<T> clazz) {
    return getInstance().fromJson(json, clazz);
  }
}