Sync.java

package tap.resource;

/*
 * This file is part of TAPLibrary.
 * 
 * TAPLibrary is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * TAPLibrary 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 Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with TAPLibrary.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * Copyright 2012,2014 - UDS/Centre de Données astronomiques de Strasbourg (CDS),
 *                       Astronomisches Rechen Institut (ARI)
 */

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import tap.ServiceConnection;
import tap.TAPException;
import tap.TAPJob;
import tap.TAPSyncJob;
import tap.parameters.TAPParameters;
import uws.UWSException;
import uws.service.log.UWSLog.LogLevel;

/**
 * <p>Synchronous resource of a TAP service.</p>
 * 
 * <p>
 * 	Requests sent to this resource can be either to get the capabilities of the TAP service (which should actually be accessed with the resource /capabilities)
 * 	or to execute synchronously an ADQL query. For the second case, "synchronously" means that result or error is returned immediately when the execution ends.
 * 	Besides, generally, the execution time is much more limited than an asynchronous query. 
 * </p>
 * 
 * @author Gr&eacute;gory Mantelet (CDS;ARI)
 * @version 2.0 (09/2014)
 */
public class Sync implements TAPResource {

	/** Name of this TAP resource. */
	public static final String RESOURCE_NAME = "sync";

	/** Description of the TAP service owning this resource. */
	protected final ServiceConnection service;

	/** List of all capabilities of the TAP service. */
	protected final Capabilities capabilities;

	/**
	 * Build a synchronous resource for the TAP service whose the description and
	 * the capabilities are provided in parameters.
	 * 
	 * @param service		Description of the TAP service which will own this resource.
	 * @param capabilities	Capabilities of the TAP service.
	 */
	public Sync(final ServiceConnection service, final Capabilities capabilities){
		this.service = service;
		this.capabilities = capabilities;
	}

	@Override
	public String getName(){
		return RESOURCE_NAME;
	}

	@Override
	public void setTAPBaseURL(final String baseURL){
		;
	}

	@Override
	public void init(final ServletConfig config) throws ServletException{
		;
	}

	@Override
	public void destroy(){
		;
	}

	@Override
	public boolean executeResource(final HttpServletRequest request, final HttpServletResponse response) throws IOException, TAPException{
		// Retrieve the execution parameters:
		TAPParameters params = service.getFactory().createTAPParameters(request);
		params.check();

		// CASE 1: GET CAPABILITIES
		/* If the user asks for the capabilities through the TAP parameters, execute the corresponding resource. */
		if (params.getRequest().equalsIgnoreCase(TAPJob.REQUEST_GET_CAPABILITIES))
			return capabilities.executeResource(request, response);

		// CASE 2: EXECUTE SYNCHRONOUSLY AN ADQL QUERY
		// Ensure the service is currently available:
		if (!service.isAvailable())
			throw new TAPException("Can not execute a query: this TAP service is not available! " + service.getAvailability(), UWSException.SERVICE_UNAVAILABLE);

		/* Ensure that at least 1 DB connection is available for asynchronous queries.
		 * If yes, just execute synchronously the given job: */
		if (service.getFactory().countFreeConnections() > 1){
			try{
				TAPSyncJob syncJob = new TAPSyncJob(service, params);
				syncJob.start(response);
				return true;
			}catch(TAPException te){
				throw te;
			}catch(Exception t){
				service.getLogger().logTAP(LogLevel.FATAL, params, "SYNC_INIT", "Unexpected error while executing the given ADQL query!", t);
				throw new TAPException("Unexpected error while executing the given ADQL query!");
			}
		}
		// Otherwise, send an error:
		else
			throw new TAPException("TAP service too busy! No connection available for the moment. You should try later or create an asynchronous query (which will be executed when enough resources will be available again).", UWSException.SERVICE_UNAVAILABLE);

	}

}