ConnectionPool.java
/*
* Copyright (c) 2002-2022, City of Paris
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright notice
* and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice
* and the following disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* 3. Neither the name of 'Mairie de Paris' nor 'Lutece' nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* License 1.0
*/
package fr.paris.lutece.util.pool.service;
import fr.paris.lutece.portal.service.util.AppException;
import org.apache.commons.collections.CollectionUtils;
import org.apache.logging.log4j.Logger;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import javax.sql.DataSource;
/**
* This class manages a database connection pool. <br>
* Connections are wrapped by a {@link LuteceConnection} to avoid explicit calls to {@link Connection#close()}. Connections are released to this pool when
* {@link Connection#close()} is called, and are not actually closed until {@link #release()} call.
*
* @see LuteceConnection
*/
public class ConnectionPool implements DataSource
{
private static final String DEFAULT_CHECK_VALID_CONNECTION_SQL = "SELECT 1";
private String _strUrl;
private String _strUser;
private String _strPassword;
private int _nMaxConns;
private int _nTimeOut;
private Logger _logger;
private int _nCheckedOut;
private List<Connection> _freeConnections = new ArrayList<>( );
private String _strCheckValidConnectionSql; // Added in v1.4
private PrintWriter _logWriter;
/**
* Constructor.
*
* @param strName
* Nom du pool
* @param strUrl
* JDBC Data source URL
* @param strUser
* SQL User
* @param strPassword
* SQL Password
* @param nMaxConns
* Max connections
* @param nInitConns
* Initials connections
* @param nTimeOut
* Timeout to get a connection
* @param logger
* the Logger object
* @param strCheckValidConnectionSql
* The SQL syntax used for check connexion validatation
*/
public ConnectionPool( String strName, String strUrl, String strUser, String strPassword, int nMaxConns, int nInitConns, int nTimeOut, Logger logger,
String strCheckValidConnectionSql )
{
_strUrl = strUrl;
_strUser = strUser;
_strPassword = strPassword;
_nMaxConns = nMaxConns;
_nTimeOut = ( nTimeOut > 0 ) ? nTimeOut : 5;
_logger = logger;
initPool( nInitConns );
_logger.info( "New pool created : {}", strName );
_strCheckValidConnectionSql = ( ( strCheckValidConnectionSql != null ) && !strCheckValidConnectionSql.equals( "" ) ) ? strCheckValidConnectionSql
: DEFAULT_CHECK_VALID_CONNECTION_SQL;
String lf = System.getProperty( "line.separator" );
_logger.debug( "{} url={}{} user= {}{} password= {}{} initconns= {}{} maxConns={}{} logintimeout={}", lf, strUrl, lf, _strUser, lf, _strPassword, lf,
nInitConns, lf, _nMaxConns, lf, _nTimeOut );
_logger.debug( ( ) -> getStats( ) );
}
/**
* Initializes the pool
*
* @param initConns
* Number of connections to create at the initialisation
*/
private void initPool( int initConns )
{
for ( int i = 0; i < initConns; i++ )
{
try
{
Connection pc = newConnection( );
_freeConnections.add( pc );
}
catch( SQLException e )
{
throw new AppException( "SQL Error executing command : " + e.toString( ), e );
}
}
}
/**
* Returns a connection from the pool.
*
* @return An open connection
* @throws SQLException
* The SQL exception
*/
@Override
public Connection getConnection( ) throws SQLException
{
_logger.debug( "Request for connection received" );
try
{
return getConnection( _nTimeOut * 1000L );
}
catch( SQLException e )
{
_logger.error( "Exception getting connection", e );
throw e;
}
}
/**
* Returns a connection from the pool.
*
* @param timeout
* The maximum time to wait for a connection
* @return An open connection
* @throws SQLException
* The SQL exception
*/
private synchronized Connection getConnection( long timeout ) throws SQLException
{
// Get a pooled Connection from the cache or a new one.
// Wait if all are checked out and the max limit has
// been reached.
long startTime = System.currentTimeMillis( );
long remaining = timeout;
Connection conn = null;
while ( ( conn = getPooledConnection( ) ) == null )
{
try
{
_logger.debug( "Waiting for connection. Timeout= {}", remaining );
wait( remaining );
}
catch( InterruptedException e )
{
_logger.debug( "A connection has been released by another thread.", e );
}
remaining = timeout - ( System.currentTimeMillis( ) - startTime );
if ( remaining <= 0 )
{
// Timeout has expired
_logger.debug( "Time-out while waiting for connection" );
throw new SQLException( "getConnection() timed-out" );
}
}
// Check if the Connection is still OK
if ( !isConnectionOK( conn ) )
{
// It was bad. Try again with the remaining timeout
_logger.error( "Removed selected bad connection from pool" );
return getConnection( remaining );
}
_nCheckedOut++;
_logger.debug( "Delivered connection from pool" );
_logger.debug( getStats( ) );
return conn;
}
/**
* Checks a connection to see if it's still alive
*
* @param conn
* The connection to check
* @return true if the connection is OK, otherwise false.
*/
private boolean isConnectionOK( Connection conn )
{
Statement testStmt = null;
try
{
if ( !conn.isClosed( ) )
{
// Try to createStatement to see if it's really alive
testStmt = conn.createStatement( );
testStmt.executeQuery( _strCheckValidConnectionSql );
testStmt.close( );
}
else
{
return false;
}
}
catch( SQLException e )
{
if ( testStmt != null )
{
try
{
testStmt.close( );
}
catch( SQLException se )
{
throw new AppException( "ConnectionService : SQL Error executing command : " + se.toString( ) );
}
}
_logger.error( "Pooled Connection was not okay", e );
return false;
}
return true;
}
/**
* Gets a connection from the pool
*
* @return An opened connection
* @throws SQLException
* The exception
*/
private Connection getPooledConnection( ) throws SQLException
{
Connection conn = null;
if ( CollectionUtils.isNotEmpty( _freeConnections ) )
{
// Pick the first Connection in the Vector
// to get round-robin usage
conn = _freeConnections.get( 0 );
_freeConnections.remove( 0 );
}
else
if ( ( _nMaxConns == 0 ) || ( _nCheckedOut < _nMaxConns ) )
{
conn = newConnection( );
}
return conn;
}
/**
* Creates a new connection. <br>
* The connection is wrapped by {@link LuteceConnection}
*
* @return The new created connection
* @throws SQLException
* The SQL exception
*/
private Connection newConnection( ) throws SQLException
{
Connection conn;
if ( _strUser == null )
{
conn = DriverManager.getConnection( _strUrl );
}
else
{
conn = DriverManager.getConnection( _strUrl, _strUser, _strPassword );
}
// wrap connection so this connection pool is used when conn.close() is called
conn = LuteceConnectionFactory.newInstance( this, conn );
_logger.info( "New connection created. Connections count is : " + ( getConnectionCount( ) + 1 ) );
return conn;
}
/**
* Returns a connection to pool.
*
* @param conn
* The released connection to return to pool
*/
public synchronized void freeConnection( Connection conn )
{
// Put the connection at the end of the Vector
_freeConnections.add( conn );
_nCheckedOut--;
notifyAll( );
_logger.debug( "Returned connection to pool" );
_logger.debug( ( ) -> getStats( ) );
}
/**
* Releases the pool by closing all its connections.
*/
public synchronized void release( )
{
for ( Connection connection : _freeConnections )
{
try
{
if ( connection instanceof LuteceConnection )
{
( (LuteceConnection) connection ).closeConnection( );
}
else
{
connection.close( );
}
_logger.debug( "Closed connection" );
}
catch( SQLException e )
{
_logger.error( "Couldn't close connection", e );
}
}
_freeConnections.clear( );
}
/**
* Returns stats on pool's connections
*
* @return Stats as String.
*/
private String getStats( )
{
return "Total connections: " + getConnectionCount( ) + " Available: " + getFreeConnectionCount( ) + " Checked-out: " + getBusyConnectionCount( );
}
/**
* Returns the number of connections opened by the pool (available or busy)
*
* @return A connection count
*/
public int getConnectionCount( )
{
return getFreeConnectionCount( ) + getBusyConnectionCount( );
}
/**
* Returns the number of free connections of the pool (available or busy)
*
* @return A connection count
*/
public int getFreeConnectionCount( )
{
return _freeConnections.size( );
}
/**
* Returns the number of busy connections of the pool (available or busy)
*
* @return A connection count
*/
public int getBusyConnectionCount( )
{
return _nCheckedOut;
}
/**
* Returns the maximum number of connections of the pool
*
* @return A connection count
*/
public int getMaxConnectionCount( )
{
return _nMaxConns;
}
/**
* Returns the connection of the pool.
*
* @param username
* the username
* @param password
* the password
* @return A connection
* @throws SQLException
* the sQL exception
*/
@Override
public Connection getConnection( String username, String password ) throws SQLException
{
return getConnection( );
}
/**
* Get the log.
*
* @return A log writer
* @throws SQLException
* the sQL exception
*/
@Override
public PrintWriter getLogWriter( ) throws SQLException
{
_logger.debug( "ConnectionPool : DataSource getLogWriter called" );
return _logWriter;
}
/**
* Set the log.
*
* @param out
* the new log writer
* @throws SQLException
* the sQL exception
*/
@Override
public void setLogWriter( PrintWriter out ) throws SQLException
{
_logger.debug( "ConnectionPool : DataSource setLogWriter called" );
_logWriter = out;
}
/**
* Set Login Timeout.
*
* @param seconds
* the new login timeout
* @throws SQLException
* the sQL exception
*/
@Override
public void setLoginTimeout( int seconds ) throws SQLException
{
// Do nothing
}
/**
* Get loging timeout.
*
* @return A time out
* @throws SQLException
* the sQL exception
*/
@Override
public int getLoginTimeout( ) throws SQLException
{
return _nTimeOut;
}
/**
* Get the unwrap.
*
* @param <T>
* the generic type
* @param iface
* the iface
* @return null
* @throws SQLException
* the sQL exception
*/
@Override
public <T> T unwrap( Class<T> iface ) throws SQLException
{
return null;
}
/**
* Get the wrapper.
*
* @param iface
* the iface
* @return false
* @throws SQLException
* the sQL exception
*/
@Override
public boolean isWrapperFor( Class<?> iface ) throws SQLException
{
return false;
}
/**
* Implementation of JDBC 4.1's getParentLogger method (Java 7)
*
* @return the parent logger
*/
public java.util.logging.Logger getParentLogger( )
{
return java.util.logging.Logger.getLogger( java.util.logging.Logger.GLOBAL_LOGGER_NAME );
}
}