uk.ac.ncl.aries.entanglement.player.spi.CreateNodeIfNotExistsPlayer.java Source code

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Here is the source code for uk.ac.ncl.aries.entanglement.player.spi.CreateNodeIfNotExistsPlayer.java

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/*
 * 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: 27-Nov-2012, 11:56:00
 */

package uk.ac.ncl.aries.entanglement.player.spi;

import com.mongodb.BasicDBObject;
import com.torrenttamer.util.UidGenerator;
import uk.ac.ncl.aries.entanglement.graph.EdgeDAO;
import uk.ac.ncl.aries.entanglement.player.LogPlayerException;
import uk.ac.ncl.aries.entanglement.graph.NodeDAO;
import uk.ac.ncl.aries.entanglement.revlog.commands.CreateNodeIfNotExists;
import uk.ac.ncl.aries.entanglement.revlog.data.RevisionItem;

/**
 * Creates a graph node if it does not already exist by UID or [type|name].
 * 
 * @author Keith Flanagan
 */
public class CreateNodeIfNotExistsPlayer extends AbstractLogItemPlayer {
    @Override
    public String getSupportedLogItemType() {
        return CreateNodeIfNotExists.class.getSimpleName();
    }

    @Override
    public void playItem(NodeDAO nodeDao, EdgeDAO edgeDao, RevisionItem item) throws LogPlayerException {
        try {
            /******************
             * TODO: instead of just returning if the node already exists, we might 
             *       want to update its contents.
             */

            /*
             * Nodes MUST have a UID, and a type. A 'well known name' may also optionally
             * be set. 
             * 
             * However, the DBObject that we receive in the <code>RevisionItem<code>
             * here may not have one or more of these required items set. For example,
             * if the process that created the RevisionItem only cares about the 
             * 'well known name', then it may not have specified a UID. In this case,
             * we need to generate a UID here.
             * 
             * Here, we need to set any required values that don't currently have values
             * specified for them by the incoming RevisionItem and check that others
             * exist.
             */
            CreateNodeIfNotExists cn = (CreateNodeIfNotExists) item.getOp();

            BasicDBObject serializedNode = cn.getNode();

            // Find out whether this node already exists by UID
            String nodeUid = null;
            boolean exists;
            if (serializedNode.containsField(NodeDAO.FIELD_UID)) {
                nodeUid = serializedNode.getString(NodeDAO.FIELD_UID);
                exists = nodeDao.existsByUid(nodeUid);
                if (exists) {
                    return; // For now, do nothing if a node with the same UID already exists
                }
            }

            // Node type is a required property
            if (!serializedNode.containsField(NodeDAO.FIELD_TYPE)) {
                throw new LogPlayerException("Can't play operation: " + item.getOp() + ". Property "
                        + NodeDAO.FIELD_TYPE + " was not set.");
            }

            // Find out whether this node already exists by type|name
            String nodeType = serializedNode.getString(NodeDAO.FIELD_TYPE);
            String nodeName = serializedNode.getString(NodeDAO.FIELD_NAME);
            if (serializedNode.containsField(NodeDAO.FIELD_NAME)) {
                exists = nodeDao.existsByName(nodeType, nodeName);
                if (exists) {
                    return; // For now, do nothing if a node with the same type and name combo already exists
                }
            }

            /*
             * If we get here, then the node does not currently exist.
             */

            // Generate a UID for this node, if one does not already exist
            if (!serializedNode.containsField(NodeDAO.FIELD_UID)) {
                serializedNode.put(NodeDAO.FIELD_UID, UidGenerator.generateUid());
            }

            nodeDao.store(serializedNode);
        } catch (Exception e) {
            throw new LogPlayerException("Failed to play command", e);
        }
    }
}