[TAP] Add a TAP servlet which loads a TAP configuration file and start a TAP service automatically.

package tap.config;

/*

 * 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 2014-2015 - Astronomisches Rechen Institut (ARI)

 */

import static tap.config.TAPConfiguration.DEFAULT_TAP_CONF_FILE;

import static tap.config.TAPConfiguration.TAP_CONF_PARAMETER;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.util.Properties;

import javax.servlet.ServletConfig;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import tap.ServiceConnection;

import tap.resource.TAP;

public class ConfigurableTAPServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	private TAP tap = null;

	@Override

	public void init(final ServletConfig config) throws ServletException{

		// Nothing to do, if TAP is already initialized:

		if (tap != null)

			return;

		/* 1. GET THE FILE PATH OF THE TAP CONFIGURATION FILE */

		String tapConfPath = config.getInitParameter(TAP_CONF_PARAMETER);

		if (tapConfPath == null || tapConfPath.trim().length() == 0)

			tapConfPath = null;

		//throw new ServletException("Configuration file path missing! You must set a servlet init parameter whose the name is \"" + TAP_CONF_PARAMETER + "\".");

		/* 2. OPEN THE CONFIGURATION FILE */

		InputStream input = null;

		// CASE: No file specified => search in the classpath for a file having the default name "tap.properties".

		if (tapConfPath == null)

			input = searchFile(DEFAULT_TAP_CONF_FILE, config);

		else{

			File f = new File(tapConfPath);

			// CASE: The given path matches to an existing local file.

			if (f.exists()){

				try{

					input = new FileInputStream(f);

				}catch(IOException ioe){

					throw new ServletException("Impossible to read the TAP configuration file (" + tapConfPath + ")!", ioe);

				}

			}

			// CASE: The given path seems to be relative to the servlet root directory.

			else

				input = searchFile(tapConfPath, config);

		}

		// If no file has been found, cancel the servlet loading:

		if (input == null)

			throw new ServletException("Configuration file not found with the path: \"" + tapConfPath + "\"! Please provide a correct file path for the TAP configuration file.");

		/* 3. PARSE IT INTO A PROPERTIES SET */

		Properties tapConf = new Properties();

		try{

			tapConf.load(input);

		}catch(IOException ioe){

			throw new ServletException("Impossible to read the TAP configuration file (" + tapConfPath + ")!", ioe);

		}finally{

			try{

				input.close();

			}catch(IOException ioe2){}

		}

		/* 4. CREATE THE TAP SERVICE */

		try{

			// Create the service connection:

			ServiceConnection serviceConn = new ConfigurableServiceConnection(tapConf);

			// Create all the TAP resources:

			tap = new TAP(serviceConn);

		}catch(Exception ex){

			tap = null;

			throw new ServletException("Impossible to initialize the TAP service!", ex);

		}

		// TODO Set the home page file, if any:

		super.init(config);

	}

	protected final InputStream searchFile(final String filePath, final ServletConfig config){

		InputStream input = null;

		// Try to search in the classpath (with just a file name or a relative path):

		input = Thread.currentThread().getContextClassLoader().getResourceAsStream(filePath);

		// If not found, try searching in the WebContent directory (as this fileName is a file path relative to WebContent):

		if (input == null)

			input = config.getServletContext().getResourceAsStream(filePath);

		// LAST CHANCE: Only if it is not a path...

		if (input == null && filePath.indexOf(File.separatorChar) < 0){

			// ...try at the root of WEB-INF:

			input = config.getServletContext().getResourceAsStream("/WEB-INF/" + filePath);

			// ...and at the root of META-INF:

			if (input == null)

				input = config.getServletContext().getResourceAsStream("/META-INF/" + filePath);

		}

		return input;

	}

	@Override

	public void destroy(){

		// Free all resources used by TAP:

		if (tap != null){

			tap.destroy();

			tap = null;

		}

		super.destroy();

	}

	@Override

	protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{

		if (tap != null){

			try{

				tap.executeRequest(req, resp);

			}catch(Throwable t){

				System.err.println("Request aborted !");

				t.printStackTrace(System.err);

				resp.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, t.getMessage());

			}

		}else

			resp.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE, "TAP service not yet initialized!");

	}

}

public final class TAPConfiguration {

	public final static String TAP_CONF_PARAMETER = "tapconf";

	public final static String DEFAULT_TAP_CONF_FILE = "tap.properties";

	/* FILE MANAGER KEYS */

	public final static String KEY_FILE_MANAGER = "file_manager";

	public final static String VALUE_LOCAL = "local";