/*************************************************************************
 *                                                                       *
 *  EJBCA Community: The OpenSource Certificate Authority                *
 *                                                                       *
 *  This software 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 2.1 of the License, or any later version.                    *
 *                                                                       *
 *  See terms of license at gnu.org.                                     *
 *                                                                       *
 *************************************************************************/

package org.ejbca.core.ejb;

import java.net.URL;

import javax.mail.Session;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NameNotFoundException;
import javax.naming.NamingException;
import javax.sql.DataSource;

import org.apache.log4j.Logger;

/**
 * A simple implementation of the ServiceLocator/HomeFactory J2EE Pattern.
 * {@link http://developer.java.sun.com/developer/restricted/patterns/ServiceLocator.html}
 *
 * It is used to look up JNDI related resources such as EJB homes, datasources, ...
 * @version $Id: ServiceLocator.java 22117 2015-10-29 10:53:42Z mikekushner $
 */
public class ServiceLocator {

    private static final Logger log = Logger.getLogger(ServiceLocator.class);
    		
    /** the jndi context */
    private transient Context ctx;

    /** the singleton instance */
    private static transient ServiceLocator instance;

    /**
     * Create a new service locator object.
     * @throws ServiceLocatorException if the context failed to be initialized
     */
    private ServiceLocator() throws ServiceLocatorException {
        try {
            this.ctx = new InitialContext();
        } catch (NamingException e){
            throw new ServiceLocatorException(e);
        }
    }

    /**
     * return the singleton instance
     * @return the singleton instance
     * @throws ServiceLocatorException if the instance could not be initialized the first time
     */
    public static final ServiceLocator getInstance() throws ServiceLocatorException {
        // synchronization is intentionally left out. It 'should' not have dramatic
        // consequences as it is not that destructive.
        if (instance == null){
            instance = new ServiceLocator();
        }
        return instance;
    }

    /**
     * return the datasource object corresponding the the env entry name
     * @return the DataSource corresponding to the env entry name parameter
     * @throws ServiceLocatorException if the lookup fails
     */
    public DataSource getDataSource(String dataSourceName) throws ServiceLocatorException {
        return (DataSource)getObject(dataSourceName);
    }

    /**
     * return the URL object corresponding to the env entry name
     * @param envName the env entry name
     * @return the URL value corresponding to the env entry name.
     * @throws ServiceLocatorException if the lookup fails
     */
    public URL getUrl(String envName) throws ServiceLocatorException {
        return (URL)getObject(envName);
    }

    /**
     * return a boolean value corresponding to the env entry
     * @param envName the env entry name
     * @return the boolean value corresponding to the env entry.
     * @throws ServiceLocatorException if the lookup fails
     */
    public boolean getBoolean(String envName) throws ServiceLocatorException {
        return ((Boolean)getObject(envName)).booleanValue();
    }

    /**
     * return a string value corresponding to the env entry
     * @param envName the env entry name
     * @return the boolean value corresponding to the env entry.
     * @throws ServiceLocatorException if the lookup fails
     */
    public String getString(String envName) throws ServiceLocatorException {
        String ret = null;
        try {
            ret = (String)getObject(envName);        	
        } catch (ServiceLocatorException e) {
        	if (e.getCause() instanceof NameNotFoundException) {
				// ignore this and return null, otherwise we can not have empty values in Glassfish
        		ret = null;
			}
        }
        return ret;
    }

    /**
     * return a mail session corresponding to the env entry
     * @param envName the env entry name
     * @return the mail session corresponding to the env entry.
     * @throws ServiceLocatorException if the lookup fails
     */
    public Session getMailSession(String envName) throws ServiceLocatorException {
        return (Session)getObject(envName);
    }

    /**
     * return a known java object corresponding to the env entry
     * @param envName the env entry name
     * @return the java object corresponding to the env entry
     * @throws ServiceLocatorException if the lookup fails
     */
    public Object getObject(String envName) throws ServiceLocatorException {
        try {
        	if (log.isDebugEnabled()) {
            	log.debug("Doing lookup of '" + envName + "'");
        	}
            return ctx.lookup(envName);
        } catch (NamingException e) {
            throw new ServiceLocatorException(e);
        }
    }
}