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Xalan-Java is an XSLT processor for transforming XML documents into HTML, text, or other XML document types. It implements XSL Transformations (XSLT) Version 1.0 and XML Path Language (XPath) Version 1.0 and can be used from the command line, in an applet or a servlet, or as a module in other program.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.
 */
/*
 * $Id: ConnectionPool.java 468638 2006-10-28 06:52:06Z minchau $
 */

package org.apache.xalan.lib.sql;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

/**
 * An interface used to build wrapper classes around existing
 * Connection Pool libraries.
 * Title:     ConnectionPool
 * @author John Gentilin
 * @version 1.0
 */
public interface ConnectionPool
{

  /**
   * Determine if a Connection Pool has been disabled. If a Connection pool
   * is disabled, then it will only manage connections that are in use.
   *
   */
  public boolean isEnabled( );

  /**
   * The Driver and URL are the only required parmeters.
   * @param d
   *
   */
  public void setDriver( String d );

  /**
   * @param url
   *
   */
  public void setURL( String url );

  /**
   * Start downsizeing the pool, this usally happens right after the
   * pool has been marked as Inactive and we are removing connections
   * that are not currently inuse.
   *
   */
  public void freeUnused( );


  /**
   * Provide an indicator to the PoolManager when the Pool can be removed
   * from the Pool Table.
   *
   */
  public boolean hasActiveConnections( );

  /**
   * The rest of the protocol parameters can eiter be passed in as
   * just Username and Password or as a property collection. If the
   * property collection is used, then the sperate username and password
   * may be ignored, it is up to the wrapper implementation to handle
   * the situation. If the connection information changes while after the
   * pool has been established, the wrapper implementation should ignore
   * the change and throw an error.
   * @param p
   *
   */
  public void setPassword( String p );

  /**
   * @param u
   *
   */
  public void setUser( String u );


  /**
   * Set tne minimum number of connections that are to be maintained in the
   * pool.
   * @param n
   *
   */
  public void setMinConnections( int n );

  /**
   * Test to see if the connection info is valid to make a real connection
   * to the database. This method may cause the pool to be crated and filled
   * with min connections.
   *
   */
  public boolean testConnection( );

  /**
   * Retrive a database connection from the pool
   *
   * @throws SQLException
   */
  public Connection getConnection( )throws SQLException;

   /**
   * Return a connection to the pool, the connection may be closed if the
   * pool is inactive or has exceeded the max number of free connections
   * @param con
   *
   * @throws SQLException
   */
  public void releaseConnection( Connection con )throws SQLException;

   /**
   * Provide a mechinism to return a connection to the pool on Error.
   * A good default behaviour is to close this connection and build
   * a new one to replace it. Some JDBC impl's won't allow you to
   * reuse a connection after an error occurs.
   * @param con
   *
   * @throws SQLException
   */
  public void releaseConnectionOnError( Connection con )throws SQLException;


  /**
   * The Pool can be Enabled and Disabled. Disabling the pool
   * closes all the outstanding Unused connections and any new
   * connections will be closed upon release.
   * @param flag Control the Connection Pool. If it is enabled
   * then Connections will actuall be held around. If disabled
   * then all unused connections will be instantly closed and as
   * connections are released they are closed and removed from the pool.
   *
   */
  public void setPoolEnabled( final boolean flag );

  /**
   * Used to pass in extra configuration options during the
   * database connect phase.
   */
  public void setProtocol(Properties p);


}