/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2006, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This 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 (at your option) any later version.
 *
 * This software 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 this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.resource.adapter.jdbc.vendor;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.ResultSet;

import org.jboss.logging.Logger;
import org.jboss.resource.adapter.jdbc.ValidConnectionChecker;

/**
 * Implements check valid connection sql Requires MySQL driver 3.1.8 or later.
 * This should work on just about any version of the database itself but will
 * only be "fast" on version 3.22.1 and later. Prior to that version it just
 * does "SELECT 1" anyhow.
 * 
 * @author <a href="mailto:adrian@jboss.org">Adrian Brock</a>
 * @author <a href="mailto:acoliver ot jbosss dat org">Andrew C. Oliver</a>
 * @author <a href="mailto:jim.moran@jboss.org">Jim Moran</a>
 * @version $Revision: 78074 $
 */
public class MySQLValidConnectionChecker implements ValidConnectionChecker, Serializable {


   private static transient Logger log;
    
   private static final long serialVersionUID = 1323747853035005642L;

   private boolean driverHasPingMethod;

   // The timeout (apparently the timeout is ignored?)
   private static Object[] params = new Object[] {};
   
   private transient Method ping;
   
   public MySQLValidConnectionChecker()
   {
      try
      {
         initPing();
      }
      catch (Exception e)
      {
         log.warn("Cannot resolve com.mysq.jdbc.Connection.ping method.  Will use 'SELECT 1' instead.", e);
      }
   }

   public SQLException isValidConnection(Connection c)
   {
      //if there is a ping method then use it, otherwise just use a 'SELECT 1' statement
      if (driverHasPingMethod)
      {
         try
         {
            ping.invoke(c, params);
         }
         catch (Exception e)
         {
            if (e instanceof SQLException)
            {
               return (SQLException) e;
            }
            else
            {
               log.warn("Unexpected error in ping", e);
               return new SQLException("ping failed: " + e.toString());
            }
         }
      }
      else
      {
         Statement stmt = null;
         ResultSet rs = null;
         try
         {
            stmt = c.createStatement();
            rs = stmt.executeQuery("SELECT 1");
         }
         catch (Exception e)
         {
            if (e instanceof SQLException)
            {
               return (SQLException) e;
            }
            else
            {
               log.warn("Unexpected error in ping (SELECT 1)", e);
               return new SQLException("ping (SELECT 1) failed: " + e.toString());
            }
         }
         finally
         {
            //cleanup the Statment
            try
            {
               if (rs != null)
                  rs.close();
               
               if (stmt != null)
                  stmt.close();
            }
            catch (SQLException ignore)
            {
            
            }
         }
      }
      return null;
   }

   private void initPing() throws ClassNotFoundException, NoSuchMethodException
   {
      log = Logger.getLogger(MySQLValidConnectionChecker.class);
      driverHasPingMethod = false;

      Class mysqlConnection = Thread.currentThread().getContextClassLoader().loadClass("com.mysql.jdbc.Connection");
      ping = mysqlConnection.getMethod("ping", new Class[] {});
      if (ping != null)
      {
         driverHasPingMethod = true;
      }
   }

   private void writeObject(ObjectOutputStream stream) throws IOException
   {
      // nothing
   }

   private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException
   {
      try
      {
         initPing();
      }
      catch (Exception e)
      {
         IOException ioe = new IOException("Unable to resolve ping method: " + e.getMessage());
         ioe.initCause(e);
         throw ioe;
      }
   }
}