org.wikidata.wdtk.datamodel.json.jackson.datavalues.JacksonValueDeserializer.java Source code

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Here is the source code for org.wikidata.wdtk.datamodel.json.jackson.datavalues.JacksonValueDeserializer.java

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package org.wikidata.wdtk.datamodel.json.jackson.datavalues;

/*
 * #%L
 * Wikidata Toolkit Data Model
 * %%
 * Copyright (C) 2014 Wikidata Toolkit Developers
 * %%
 * 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.
 * #L%
 */

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;

/**
 * Custom Jackson deserializer that maps the JSON representation of Wikibase
 * values to WDTK classes. In most cases, the class to use is defined by the
 * value of the "type" field, but for entities one has to look deeper into the
 * structure to get the "entity-type" field as well. This is not possible using
 * simpler mechanisms.
 *
 * @author Markus Kroetzsch
 *
 */
public class JacksonValueDeserializer extends StdDeserializer<JacksonValue> {

    /**
     *
     */
    private static final long serialVersionUID = -2851517075035995962L;

    /**
     * Constructor.
     */
    public JacksonValueDeserializer() {
        super(JacksonValue.class);
    }

    @Override
    public JacksonValue deserialize(JsonParser jsonParser, DeserializationContext ctxt)
            throws IOException, JsonProcessingException {

        ObjectMapper mapper = (ObjectMapper) jsonParser.getCodec();
        JsonNode root = mapper.readTree(jsonParser);
        Class<? extends JacksonValue> valueClass = getValueClass(root);

        return mapper.treeToValue(root, valueClass);
    }

    /**
     * Finds the Java class to use for deserializing the JSON structure
     * represented by the given node.
     *
     * @param jsonNode
     *            the JSON node that represents the value to deserialize
     * @return the Java class to use for deserialization
     * @throws JsonMappingException
     *             if we do not have a class for the given JSON
     */
    private Class<? extends JacksonValue> getValueClass(JsonNode jsonNode) throws JsonMappingException {
        String jsonType = jsonNode.get("type").asText();

        switch (jsonType) {
        case JacksonValue.JSON_VALUE_TYPE_ENTITY_ID:
            JsonNode valueNode = jsonNode.get("value");
            if (valueNode != null) {
                String entityType = valueNode.get("entity-type").asText();
                switch (entityType) {
                case JacksonInnerEntityId.JSON_ENTITY_TYPE_ITEM:
                    return JacksonValueItemId.class;
                case JacksonInnerEntityId.JSON_ENTITY_TYPE_PROPERTY:
                    return JacksonValuePropertyId.class;
                default:
                    throw new JsonMappingException(
                            "Entities of type \"" + entityType + "\" are not supported as property values yet.");
                }
            }
        case JacksonValue.JSON_VALUE_TYPE_STRING:
            return JacksonValueString.class;
        case JacksonValue.JSON_VALUE_TYPE_TIME:
            return JacksonValueTime.class;
        case JacksonValue.JSON_VALUE_TYPE_GLOBE_COORDINATES:
            return JacksonValueGlobeCoordinates.class;
        case JacksonValue.JSON_VALUE_TYPE_QUANTITY:
            return JacksonValueQuantity.class;
        case JacksonValue.JSON_VALUE_TYPE_MONOLINGUAL_TEXT:
            return JacksonValueMonolingualText.class;
        default:
            throw new JsonMappingException("Property values of type \"" + jsonType + "\" are not supported yet.");
        }
    }
}