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Maps MongoDB objects to POJOs using Jackson
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/*
 * Copyright 2011 VZ Netzwerke Ltd
 *
 * 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 org.mongojack.internal.util;

import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.mongodb.MongoException;
import org.mongojack.internal.object.BsonObjectGenerator;
import org.mongojack.internal.object.BsonObjectTraversingParser;

import java.io.IOException;

/**
 * Handler for ids.  Converts them between the objects type and the database type
 *
 * @author James Roper
 * @since 1.0
 */
public interface IdHandler {
    
    /**
     * Convert the given database id to the java objects id
     *
     * @param dbId The database id to convert from
     * @return The converted id
     */
    K fromDbId(D dbId);

    /**
     * Convert the given java object id to the databases id
     *
     * @param id The java object id to convert from
     * @return The converted database id
     */
    D toDbId(K id);

    public static class NoopIdHandler implements IdHandler {
        public K fromDbId(K dbId) {
            return dbId;
        }

        public K toDbId(K id) {
            return id;
        }
    }

    public static class JacksonIdHandler implements IdHandler {
        private final JsonSerializer jsonSerializer;
        private final JsonDeserializer jsonDeserializer;
        private final ObjectMapper objectMapper;

        public JacksonIdHandler(JsonSerializer jsonSerializer, JsonDeserializer jsonDeserializer, ObjectMapper objectMapper) {
            this.jsonSerializer = jsonSerializer;
            this.jsonDeserializer = jsonDeserializer;
            this.objectMapper = objectMapper;
        }

        /**
         * Convert the given database id to the java objects id
         *
         * @param dbId The database id to convert from
         * @return The converted id
         */
        public K fromDbId(D dbId) {
            try {
                return jsonDeserializer.deserialize(new BsonObjectTraversingParser(null, dbId, objectMapper), null);
            } catch (IOException e) {
                throw new MongoException("Error deserializing ID", e);
            }
        }

        /**
         * Convert the given java object id to the databases id
         *
         * @param id The java object id to convert from
         * @return The converted database id
         */
        public D toDbId(K id) {
            BsonObjectGenerator generator = new BsonObjectGenerator();
            try {
                jsonSerializer.serialize(id, generator, null);
            } catch (IOException e) {
                throw new MongoException("Error serializing ID", e);
            }
            return (D) generator.getValue();
        }
    }
}