org.dswarm.graph.json.deserializer.ResourceDeserializer.java Source code

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Here is the source code for org.dswarm.graph.json.deserializer.ResourceDeserializer.java

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/**
 * Copyright (C) 2013  2015 SLUB Dresden & Avantgarde Labs GmbH (<code@dswarm.org>)
 *
 * 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.dswarm.graph.json.deserializer;

import java.io.IOException;
import java.util.Iterator;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.ObjectCodec;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ArrayNode;

import org.dswarm.graph.json.Resource;
import org.dswarm.graph.json.Statement;

/**
 *
 * @author tgaengler
 *
 */
public class ResourceDeserializer extends JsonDeserializer<Resource> {

    @Override
    public Resource deserialize(final JsonParser jp, final DeserializationContext ctxt)
            throws IOException, JsonProcessingException {

        final ObjectCodec oc = jp.getCodec();

        if (oc == null) {

            return null;
        }

        final JsonNode node = oc.readTree(jp);

        if (node == null) {

            return null;
        }

        final Iterator<String> resourceUriFieldNames = node.fieldNames();

        if (resourceUriFieldNames == null || !resourceUriFieldNames.hasNext()) {

            return null;
        }

        final String resourceUri = resourceUriFieldNames.next();

        if (resourceUri == null) {

            return null;
        }

        final JsonNode resourceNode = node.get(resourceUri);

        if (resourceNode == null) {

            return null;
        }

        if (!ArrayNode.class.isInstance(resourceNode)) {

            throw new JsonParseException("expected a JSON array full of statement objects of the resource",
                    jp.getCurrentLocation());
        }

        final Resource resource = new Resource(resourceUri);

        if (resourceNode.size() <= 0) {

            return resource;
        }

        for (final JsonNode statementNode : resourceNode) {

            final Statement statement = statementNode.traverse(oc).readValueAs(Statement.class);
            resource.addStatement(statement);
        }

        return resource;
    }
}