
/* 
 * Copyright 2001-2009 Terracotta, Inc. 
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not 
 * use this file except in compliance with the License. You may obtain a copy 
 * of the License at 
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0 
 *   
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 
 * License for the specific language governing permissions and limitations 
 * under the License.
 * 
 */

package org.quartz.ee.jta;

import javax.naming.InitialContext;
import javax.transaction.HeuristicMixedException;
import javax.transaction.HeuristicRollbackException;
import javax.transaction.NotSupportedException;
import javax.transaction.RollbackException;
import javax.transaction.SystemException;
import javax.transaction.UserTransaction;

import org.quartz.SchedulerException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * <p>
 * A helper for obtaining a handle to a UserTransaction...
 * </p>
 * <p>
 * To ensure proper cleanup of the InitalContext used to create/lookup
 * the UserTransaction, be sure to always call returnUserTransaction() when
 * you are done with the UserTransaction. 
 * </p>
 * 
 * @author James House
 */
public class UserTransactionHelper {
    
    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Constants.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    public static final String DEFAULT_USER_TX_LOCATION = "java:comp/UserTransaction";
    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Data members.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    private static String userTxURL = DEFAULT_USER_TX_LOCATION;
    
    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Constructors.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    /**
     * Do not allow the creation of an all static utility class.
     */
    private UserTransactionHelper() {
    }

    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Interface.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    public static String getUserTxLocation() {
        return userTxURL;
    }

    /**
     * Set the JNDI URL at which the Application Server's UserTransaction can
     * be found. If not set, the default value is "java:comp/UserTransaction" -
     * which works for nearly all application servers.
     */
    public static void setUserTxLocation(String userTxURL) {
        if (userTxURL != null) {
            UserTransactionHelper.userTxURL = userTxURL;
        }
    }

    /**
     * Create/Lookup a UserTransaction in the InitialContext via the
     * name set in setUserTxLocation().
     */
    public static UserTransaction lookupUserTransaction() throws SchedulerException {
        return new UserTransactionWithContext();
    }
    
    /**
     * Return a UserTransaction that was retrieved via getUserTransaction().
     * This will make sure that the InitalContext used to lookup/create the 
     * UserTransaction is properly cleaned up.
     */
    public static void returnUserTransaction(UserTransaction userTransaction) {
        if ((userTransaction != null) && 
            (userTransaction instanceof UserTransactionWithContext)) {
            UserTransactionWithContext userTransactionWithContext = 
                (UserTransactionWithContext)userTransaction;
            
            userTransactionWithContext.closeContext();
        }
    }


    /**
     * This class wraps a UserTransaction with the InitialContext that was used
     * to look it up, so that when the UserTransaction is returned to the 
     * UserTransactionHelper the InitialContext can be closed.
     */
    private static class UserTransactionWithContext implements UserTransaction {
        InitialContext context;
        UserTransaction userTransaction;
        
        public UserTransactionWithContext() throws SchedulerException {
            try {
                context = new InitialContext();
            } catch (Throwable t) {
                throw new SchedulerException(
                    "UserTransactionHelper failed to create InitialContext to lookup/create UserTransaction.", t);
            }
            
            try {
                userTransaction = (UserTransaction)context.lookup(userTxURL);
            } catch (Throwable t) {
                closeContext();
                throw new SchedulerException(
                    "UserTransactionHelper could not lookup/create UserTransaction.",
                    t);
            }
            
            if (userTransaction == null) {
                closeContext();
                throw new SchedulerException(
                    "UserTransactionHelper could not lookup/create UserTransaction from the InitialContext.");
            }
        }

        /**
         * Close the InitialContext that was used to lookup/create the
         * underlying UserTransaction.
         */
        public void closeContext() {
            try {
                if (context != null) {
                    context.close();
                }
            } catch (Throwable t) {
                getLog().warn("Failed to close InitialContext used to get a UserTransaction.", t);
            }
            context = null;
        }

        /**
         * When we are being garbage collected, make sure we were properly
         * returned to the UserTransactionHelper.
         */
        @Override
        protected void finalize() throws Throwable {
            try {
                if (context != null) {
                    getLog().warn("UserTransaction was never returned to the UserTransactionHelper.");
                    closeContext();
                }
            } finally {
                super.finalize();
            }
        }

        private static Logger getLog() {
            return LoggerFactory.getLogger(UserTransactionWithContext.class);
        }
        
        // Wrapper methods that just delegate to the underlying UserTransaction
        
        public void begin() throws NotSupportedException, SystemException {
            userTransaction.begin();
        }

        public void commit() throws RollbackException, HeuristicMixedException, HeuristicRollbackException, SecurityException, IllegalStateException, SystemException {
            userTransaction.commit();        
        }

        public void rollback() throws IllegalStateException, SecurityException, SystemException {
            userTransaction.rollback();
        }

        public void setRollbackOnly() throws IllegalStateException, SystemException {
            userTransaction.setRollbackOnly();
        }

        public int getStatus() throws SystemException {
            return userTransaction.getStatus();
        }

        public void setTransactionTimeout(int seconds) throws SystemException {
            userTransaction.setTransactionTimeout(seconds);
        }
    }
}
