compare.handler.get.MetadataHandler.java Source code

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Here is the source code for compare.handler.get.MetadataHandler.java

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/*
 * This file is part of Compare.
 *
 *  Compare is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  Compare is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with Compare.  If not, see <http://www.gnu.org/licenses/>.
 *  (c) copyright Desmond Schmidt 2015
 */
package compare.handler.get;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import compare.exception.CompareException;
import calliope.core.database.Connection;
import calliope.core.database.Connector;
import calliope.core.constants.Database;
import calliope.core.constants.JSONKeys;
import compare.constants.Params;
import org.json.simple.JSONValue;
import org.json.simple.JSONObject;

/**
 * Get the version1 attribute of a CORTEX
 * @author desmond
 */
public abstract class MetadataHandler extends CompareGetHandler {
    boolean saved;
    String metadataKey;
    String metadataValue;

    public MetadataHandler(String metadataKey) {
        this.metadataKey = metadataKey;
        this.saved = false;
    }

    /**
     * Save the version1 metadata item to the METADATA database
     * @param jObj1 the object retrieved from the metadata database or null
     * @param conn the database connection
     * @throws CompareException if database save failed
     */
    protected void saveToMetadata(JSONObject jObj1, Connection conn) throws CompareException {
        try {
            if (!saved && metadataValue != null && metadataValue.length() > 0) {
                if (jObj1 == null)
                    jObj1 = new JSONObject();
                // update metadata for next time
                jObj1.put(metadataKey, metadataValue);
                if (jObj1.containsKey(JSONKeys._ID))
                    jObj1.remove(JSONKeys._ID);
                conn.putToDb(Database.METADATA, docid, jObj1.toJSONString());
            }
        } catch (Exception e) {
            throw new CompareException(e);
        }
    }

    /**
     * Get the version1 metadata item from the MVD itself
     * @param jObj2 the BSON document from CORTEX
     * @throws CompareException if the metadata was not present
     */
    protected abstract void getMetadataFromObject(JSONObject jObj2) throws CompareException;

    /**
     * Get the version1 metadata item from the CORTEX BSON
     * @param conn the database connection
     * @throws CompareException if the database fetch failed
     */
    public void getMetadataFromCortex(Connection conn) throws CompareException {
        try {
            String res = conn.getFromDb(Database.CORTEX, docid);
            JSONObject jObj2 = (JSONObject) JSONValue.parse(res);
            if (jObj2.containsKey(metadataKey))
                metadataValue = (String) jObj2.get(metadataKey);
            else
                getMetadataFromObject(jObj2);
        } catch (Exception e) {
            throw new CompareException(e);
        }
    }

    /**
     * Handle a request to get some metadata for a document
     * @param request the http request
     * @param response the response
     * @param urn the current urn (ignored)
     * @throws CompareException if the resource could not be found
     */
    public void handle(HttpServletRequest request, HttpServletResponse response, String urn)
            throws CompareException {
        try {
            Connection conn = Connector.getConnection();
            docid = request.getParameter(Params.DOCID);
            if (docid != null && docid.length() > 0) {
                String res = conn.getFromDb(Database.METADATA, docid);
                JSONObject jObj1 = null;
                if (res != null) {
                    jObj1 = (JSONObject) JSONValue.parse(res);
                    if (jObj1.containsKey(metadataKey)) {
                        metadataValue = (String) jObj1.get(metadataKey);
                        saved = true;
                    }
                }
                if (metadataValue == null)
                    getMetadataFromCortex(conn);
                saveToMetadata(jObj1, conn);
            } else
                metadataValue = "";
            response.setContentType("text/plain");
            response.getWriter().write(metadataValue);
        } catch (Exception e) {
            throw new CompareException(e);
        }
    }
}