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 $Id: ServiceLocator.java,v 1.7 2003/03/04 21:36:38 inder Exp $ */

package com.sun.j2ee.blueprints.servicelocator.web;

import java.util.*;
import java.net.*;
import javax.ejb.*;
import javax.jms.*;
import javax.naming.*;
import javax.rmi.*;
import javax.sql.*;
import javax.transaction.*;

import com.sun.j2ee.blueprints.servicelocator.ServiceLocatorException;

/**
 * This class is an implementation of the Service Locator pattern. It is
 * used to looukup resources such as EJBHomes, JMS Destinations, etc.
 * This implementation uses the "singleton" strategy and also the "caching"
 * strategy.
 * This implementation is intended to be used on the web tier and
 * not on the ejb tier.
 */
public class ServiceLocator {
    
    private InitialContext ic;
    //used to hold references to EJBHomes/JMS Resources for re-use
    private Map cache = Collections.synchronizedMap(new HashMap());
    
    private static ServiceLocator instance = new ServiceLocator();
    
    public static ServiceLocator getInstance() {
        return instance;
    }
    
    private ServiceLocator() throws ServiceLocatorException {
        try {
            ic = new InitialContext();
        } catch (Exception e) {
            throw new ServiceLocatorException(e);
        }
    }
    
    /**
     * will get the ejb Local home factory. If this ejb home factory has already been
     * clients need to cast to the type of EJBHome they desire
     *
     * @return the EJB Home corresponding to the homeName
     */
    public EJBLocalHome getLocalHome(String jndiHomeName) throws ServiceLocatorException {
        EJBLocalHome home = (EJBLocalHome) cache.get(jndiHomeName);
        if (home == null) {
            try {
                home = (EJBLocalHome) ic.lookup(jndiHomeName);
                cache.put(jndiHomeName, home);
            } catch (Exception e) {
                throw new ServiceLocatorException(e);
            }
        }
        return home;
    }
    
    /**
     * will get the ejb Remote home factory. If this ejb home factory has already been
     * clients need to cast to the type of EJBHome they desire
     *
     * @return the EJB Home corresponding to the homeName
     */
    public EJBHome getRemoteHome(String jndiHomeName, Class className) throws ServiceLocatorException {
        EJBHome home = (EJBHome) cache.get(jndiHomeName);
        if (home == null) {
            try {
                Object objref = ic.lookup(jndiHomeName);
                Object obj = PortableRemoteObject.narrow(objref, className);
                home = (EJBHome)obj;
                cache.put(jndiHomeName, home);
            } catch (Exception e) {
                throw new ServiceLocatorException(e);
            }
        }
        return home;
    }
    
    /**
     * @return the factory for the factory to get queue connections from
     */
    public  QueueConnectionFactory getQueueConnectionFactory(String qConnFactoryName)
    throws ServiceLocatorException {
        QueueConnectionFactory factory = (QueueConnectionFactory) cache.get(qConnFactoryName);
        if (factory == null) {
            try {
                factory = (QueueConnectionFactory) ic.lookup(qConnFactoryName);
                cache.put(qConnFactoryName, factory);
            } catch (Exception e) {
                throw new ServiceLocatorException(e);
            }
        }
        return factory;
    }
    
    /**
     * @return the Queue Destination to send messages to
     */
    public  Queue getQueue(String queueName) throws ServiceLocatorException {
        Queue queue = (Queue) cache.get(queueName);
        if (queue == null) {
            try {
                queue =(Queue)ic.lookup(queueName);
                cache.put(queueName, queue);
            } catch (Exception e) {
                throw new ServiceLocatorException(e);
            }
        }
        return queue;
    }
    
    /**
     * This method helps in obtaining the topic factory
     * @return the factory for the factory to get topic connections from
     */
    public  TopicConnectionFactory getTopicConnectionFactory(String topicConnFactoryName) throws ServiceLocatorException {
        TopicConnectionFactory factory = (TopicConnectionFactory) cache.get(topicConnFactoryName);
        if (factory == null) {
            try {
                factory = (TopicConnectionFactory) ic.lookup(topicConnFactoryName);
                cache.put(topicConnFactoryName, factory);
            } catch (Exception e) {
                throw new ServiceLocatorException(e);
            }
        }
        return factory;
    }
    
    /**
     * This method obtains the topc itself for a caller
     * @return the Topic Destination to send messages to
     */
    public  Topic getTopic(String topicName) throws ServiceLocatorException {
        Topic topic = (Topic) cache.get(topicName);
        if (topic == null) {
            try {
                topic = (Topic)ic.lookup(topicName);
                cache.put(topicName, topic);
            } catch (Exception e) {
                throw new ServiceLocatorException(e);
            }
        }
        return topic;
    }
    
    /**
     * This method obtains the datasource itself for a caller
     * @return the DataSource corresponding to the name parameter
     */
    public DataSource getDataSource(String dataSourceName) throws ServiceLocatorException {
        DataSource dataSource = (DataSource) cache.get(dataSourceName);
        if (dataSource == null) {
            try {
                dataSource = (DataSource)ic.lookup(dataSourceName);
                cache.put(dataSourceName, dataSource );
            } catch (Exception e) {
                throw new ServiceLocatorException(e);
            }
        }
        return dataSource;
    }
    
    /**
     * This method obtains the UserTransaction itself for a caller
     * @return the UserTransaction corresponding to the name parameter
     */
    public UserTransaction getUserTransaction(String utName) throws ServiceLocatorException {
        try {
            return (UserTransaction) ic.lookup(utName);
        } catch (Exception e) {
            throw new ServiceLocatorException(e);
        }
    }
    
    
    /**
     * @return the URL value corresponding
     * to the env entry name.
     */
    public URL getUrl(String envName) throws ServiceLocatorException {
        try {
            return (URL)ic.lookup(envName);
        } catch (Exception e) {
            throw new ServiceLocatorException(e);
        }
    }
    
    /**
     * @return the boolean value corresponding
     * to the env entry such as SEND_CONFIRMATION_MAIL property.
     */
    public boolean getBoolean(String envName) throws ServiceLocatorException {
        try {
            return ((Boolean)ic.lookup(envName)).booleanValue();
        } catch (Exception e) {
            throw new ServiceLocatorException(e);
        }
    }
    
    /**
     * @return the String value corresponding
     * to the env entry name.
     */
    public String getString(String envName) throws ServiceLocatorException {
        try {
            return (String)ic.lookup(envName);
        } catch (Exception e) {
            throw new ServiceLocatorException(e);
        }
    }
}