/*
* Copyright 2004-2023 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: Christian d'Heureuse, www.source-code.biz
*
* This class is multi-licensed under LGPL, MPL 2.0, and EPL 1.0.
*
* This module 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 3 of the License, or (at your option) any later version.
* See https://www.gnu.org/licenses/lgpl-3.0.html
*
* This program 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.
*/
package org.h2.jdbcx;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.logging.Logger;
import javax.sql.ConnectionEvent;
import javax.sql.ConnectionEventListener;
import javax.sql.ConnectionPoolDataSource;
import javax.sql.DataSource;
import javax.sql.PooledConnection;
import org.h2.message.DbException;
/**
* A simple standalone JDBC connection pool.
* It is based on the
* <a href="http://www.source-code.biz/snippets/java/8.htm">
* MiniConnectionPoolManager written by Christian d'Heureuse (Java 1.5)
* </a>. It is used as follows:
* <pre>
* import java.sql.*;
* import org.h2.jdbcx.JdbcConnectionPool;
* public class Test {
* public static void main(String... args) throws Exception {
* JdbcConnectionPool cp = JdbcConnectionPool.create(
* "jdbc:h2:~/test", "sa", "sa");
* for (String sql : args) {
* Connection conn = cp.getConnection();
* conn.createStatement().execute(sql);
* conn.close();
* }
* cp.dispose();
* }
* }
* </pre>
*
* @author Christian d'Heureuse
* (<a href="http://www.source-code.biz">www.source-code.biz</a>)
* @author Thomas Mueller
*/
public final class JdbcConnectionPool
implements DataSource, ConnectionEventListener, JdbcConnectionPoolBackwardsCompat {
private static final int DEFAULT_TIMEOUT = 30;
private static final int DEFAULT_MAX_CONNECTIONS = 10;
private final ConnectionPoolDataSource dataSource;
private final Queue<PooledConnection> recycledConnections = new ConcurrentLinkedQueue<>();
private PrintWriter logWriter;
private volatile int maxConnections = DEFAULT_MAX_CONNECTIONS;
private volatile int timeout = DEFAULT_TIMEOUT;
private AtomicInteger activeConnections = new AtomicInteger();
private AtomicBoolean isDisposed = new AtomicBoolean();
private JdbcConnectionPool(ConnectionPoolDataSource dataSource) {
this.dataSource = dataSource;
if (dataSource != null) {
try {
logWriter = dataSource.getLogWriter();
} catch (SQLException e) {
// ignore
}
}
}
/**
* Constructs a new connection pool.
*
* @param dataSource the data source to create connections
* @return the connection pool
*/
public static JdbcConnectionPool create(ConnectionPoolDataSource dataSource) {
return new JdbcConnectionPool(dataSource);
}
/**
* Constructs a new connection pool for H2 databases.
*
* @param url the database URL of the H2 connection
* @param user the user name
* @param password the password
* @return the connection pool
*/
public static JdbcConnectionPool create(String url, String user,
String password) {
JdbcDataSource ds = new JdbcDataSource();
ds.setURL(url);
ds.setUser(user);
ds.setPassword(password);
return new JdbcConnectionPool(ds);
}
/**
* Sets the maximum number of connections to use from now on.
* The default value is 10 connections.
*
* @param max the maximum number of connections
*/
public void setMaxConnections(int max) {
if (max < 1) {
throw new IllegalArgumentException("Invalid maxConnections value: " + max);
}
this.maxConnections = max;
}
/**
* Gets the maximum number of connections to use.
*
* @return the max the maximum number of connections
*/
public int getMaxConnections() {
return maxConnections;
}
/**
* Gets the maximum time in seconds to wait for a free connection.
*
* @return the timeout in seconds
*/
@Override
public int getLoginTimeout() {
return timeout;
}
/**
* Sets the maximum time in seconds to wait for a free connection.
* The default timeout is 30 seconds. Calling this method with the
* value 0 will set the timeout to the default value.
*
* @param seconds the timeout, 0 meaning the default
*/
@Override
public void setLoginTimeout(int seconds) {
if (seconds == 0) {
seconds = DEFAULT_TIMEOUT;
}
this.timeout = seconds;
}
/**
* Closes all unused pooled connections.
* Exceptions while closing are written to the log stream (if set).
*/
public void dispose() {
isDisposed.set(true);
PooledConnection pc;
while ((pc = recycledConnections.poll()) != null) {
closeConnection(pc);
}
}
/**
* Retrieves a connection from the connection pool. If
* <code>maxConnections</code> connections are already in use, the method
* waits until a connection becomes available or <code>timeout</code>
* seconds elapsed. When the application is finished using the connection,
* it must close it in order to return it to the pool.
* If no connection becomes available within the given timeout, an exception
* with SQL state 08001 and vendor code 8001 is thrown.
*
* @return a new Connection object.
* @throws SQLException when a new connection could not be established,
* or a timeout occurred
*/
@Override
public Connection getConnection() throws SQLException {
long max = System.nanoTime() + timeout * 1_000_000_000L;
int spin = 0;
do {
if (activeConnections.incrementAndGet() <= maxConnections) {
try {
return getConnectionNow();
} catch (Throwable t) {
activeConnections.decrementAndGet();
throw t;
}
} else {
activeConnections.decrementAndGet();
}
if (--spin >= 0) {
continue;
}
try {
spin = 3;
Thread.sleep(1);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
} while (System.nanoTime() - max <= 0);
throw new SQLException("Login timeout", "08001", 8001);
}
/**
* INTERNAL
*/
@Override
public Connection getConnection(String user, String password) {
throw new UnsupportedOperationException();
}
private Connection getConnectionNow() throws SQLException {
if (isDisposed.get()) {
throw new IllegalStateException("Connection pool has been disposed.");
}
PooledConnection pc = recycledConnections.poll();
if (pc == null) {
pc = dataSource.getPooledConnection();
}
Connection conn = pc.getConnection();
pc.addConnectionEventListener(this);
return conn;
}
/**
* This method usually puts the connection back into the pool. There are
* some exceptions: if the pool is disposed, the connection is disposed as
* well. If the pool is full, the connection is closed.
*
* @param pc the pooled connection
*/
private void recycleConnection(PooledConnection pc) {
int active = activeConnections.decrementAndGet();
if (active < 0) {
activeConnections.incrementAndGet();
throw new AssertionError();
}
if (!isDisposed.get() && active < maxConnections) {
recycledConnections.add(pc);
if (isDisposed.get()) {
dispose();
}
} else {
closeConnection(pc);
}
}
private void closeConnection(PooledConnection pc) {
try {
pc.close();
} catch (SQLException e) {
if (logWriter != null) {
e.printStackTrace(logWriter);
}
}
}
/**
* INTERNAL
*/
@Override
public void connectionClosed(ConnectionEvent event) {
PooledConnection pc = (PooledConnection) event.getSource();
pc.removeConnectionEventListener(this);
recycleConnection(pc);
}
/**
* INTERNAL
*/
@Override
public void connectionErrorOccurred(ConnectionEvent event) {
// not used
}
/**
* Returns the number of active (open) connections of this pool. This is the
* number of <code>Connection</code> objects that have been issued by
* getConnection() for which <code>Connection.close()</code> has
* not yet been called.
*
* @return the number of active connections.
*/
public int getActiveConnections() {
return activeConnections.get();
}
/**
* INTERNAL
*/
@Override
public PrintWriter getLogWriter() {
return logWriter;
}
/**
* INTERNAL
*/
@Override
public void setLogWriter(PrintWriter logWriter) {
this.logWriter = logWriter;
}
/**
* Return an object of this class if possible.
*
* @param iface the class
* @return this
*/
@Override
@SuppressWarnings("unchecked")
public <T> T unwrap(Class<T> iface) throws SQLException {
try {
if (isWrapperFor(iface)) {
return (T) this;
}
throw DbException.getInvalidValueException("iface", iface);
} catch (Exception e) {
throw DbException.toSQLException(e);
}
}
/**
* Checks if unwrap can return an object of this class.
*
* @param iface the class
* @return whether or not the interface is assignable from this class
*/
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return iface != null && iface.isAssignableFrom(getClass());
}
/**
* [Not supported]
*/
@Override
public Logger getParentLogger() {
return null;
}
}