/mongodb-util/src/main/java/com/torrenttamer/mongodb/gson/GsonDBObjectMarshaller.java

/*
 * Copyright 2012 Keith Flanagan
 * 
 * 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.
 * 
 * File created: 28-Nov-2012, 14:08:22
 */

package com.torrenttamer.mongodb.gson;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.util.JSON;
import com.torrenttamer.mongodb.dbobject.DbObjectMarshaller;
import com.torrenttamer.mongodb.dbobject.DbObjectMarshallerException;
import java.lang.reflect.Type;
import java.util.Map;

/**
 *
 * @author Keith Flanagan
 */
public class GsonDBObjectMarshaller
    implements DbObjectMarshaller
{
  private final Gson gson;
  
  public GsonDBObjectMarshaller()
  {
    this.gson = new Gson();
    
  }

  public GsonDBObjectMarshaller(Map<Type, Object> typeToTypeAdaptors)
  {
    GsonBuilder builder = new GsonBuilder();
    for (Type type : typeToTypeAdaptors.keySet()) {
      builder.registerTypeAdapter(type, typeToTypeAdaptors.get(type));  
    }
    
    this.gson = builder.create();
  }
  
  
  @Override
  public BasicDBObject serialize(Object bean) throws DbObjectMarshallerException {
    try {
      return (BasicDBObject) JSON.parse(gson.toJson(bean));
    } catch (Exception ex) {
      throw new DbObjectMarshallerException(
              "Failed to serialize bean type: "+bean.getClass().getName()
              + ", content: "+bean.toString(), ex);
    }
  }
  
  @Override
  public String serializeToString(Object bean) throws DbObjectMarshallerException {
    try {
      StringBuilder sb = new StringBuilder(gson.toJson(bean));
      /*
       * The serializer seems to but double-quote characters at each end.
       * Remove these since they cause problems and are not consistent with the
       * serialization produced by JSON.parse(...).
       */
      if (sb.length() > 0 && sb.charAt(0) == '\"') {
        sb.deleteCharAt(sb.length()-1);
        sb.deleteCharAt(0);
      }
      return sb.toString();
    } catch (Exception ex) {
      throw new DbObjectMarshallerException(
              "Failed to serialize bean type: "+bean.getClass().getName()
              + ", content: "+bean.toString(), ex);
    }
  }
  
  @Override
  public <T> T deserialize(DBObject dbObject, Class<T> type)
      throws DbObjectMarshallerException
  {
    try {
      T item = gson.fromJson(dbObject.toString(), type);
      return item;
    }
    catch(Exception e) {
      throw new RuntimeException(
        "Failed to deserialise object from JSON. Target type: "
        + type + ". Document: " + dbObject, e);
    }
  }

  @Override
  public <T> T deserialize(String jsonString, Class<T> type)
      throws DbObjectMarshallerException
  {
    try {
      T item = gson.fromJson(jsonString, type);
      return item;
    }
    catch(Exception e) {
      throw new RuntimeException(
          "Failed to deserialise object from JSON. Target type: "
              + type + ". Document: " + jsonString, e);
    }
  }

  public Gson getGson() {
    return gson;
  }

}