| /** |
| * 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.json; |
| |
| import com.google.gson.Gson; |
| import com.google.gson.GsonBuilder; |
| import com.google.gson.JsonElement; |
| import com.google.gson.JsonNull; |
| import com.google.gson.JsonObject; |
| import com.google.gson.JsonParseException; |
| import org.apache.tajo.datum.Datum; |
| |
| import java.lang.reflect.Type; |
| import java.util.HashMap; |
| import java.util.Map; |
| |
| public class CommonGsonHelper { |
| private static Gson gson; |
| private static Gson gsonPretty; |
| |
| private CommonGsonHelper() { |
| } |
| |
| private static Map<Type, GsonSerDerAdapter<?>> registerAdapters() { |
| Map<Type, GsonSerDerAdapter<?>> adapters = new HashMap<>(); |
| adapters.put(Datum.class, new DatumAdapter()); |
| adapters.put(Type.class, new TypeAdapter()); |
| |
| 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); |
| } |
| |
| /** |
| * A helper method that gets a JSON object member value after making sure it exists and has a valid value. Useful when |
| * a member value should present to proceed. |
| * @param object A JSON object to get a member value from |
| * @param memberName The name of a member to get value of |
| * @return {@link JsonElement} value read from the given member |
| * @throws JsonParseException When the specified member does not exist or have a value. |
| */ |
| public static JsonElement getOrDie(JsonObject object, String memberName) throws JsonParseException { |
| if (object.has(memberName)) { |
| JsonElement element = object.get(memberName); |
| if (!JsonNull.INSTANCE.equals(element)) { |
| return element; |
| } |
| } |
| throw new JsonParseException("Field '" + memberName + "' not found in JSON object '" + object + "'"); |
| } |
| } |