import java.util.Stack;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.concurrent.TimeUnit;
import javax.sql.ConnectionPoolDataSource;
import javax.sql.ConnectionEvent;
import javax.sql.ConnectionEventListener;
import javax.sql.PooledConnection;
/**
* A simple standalone JDBC connection pool manager.
*
* The public methods of this class are thread-safe.
*
* Author: Christian d'Heureuse ( * href="http://www.source-code.biz">www.source-code.biz)
* License: LGPL.
*
* 2007-06-21: Constructor with a timeout parameter added.
*/
public class MiniConnectionPoolManager {
private ConnectionPoolDataSource dataSource;
private int maxConnections;
private int timeout;
private PrintWriter logWriter;
private Semaphore semaphore;
private Stack
private int activeConnections;
private PoolConnectionEventListener poolConnectionEventListener;
private boolean isDisposed;
/**
* Thrown in {@link #getConnection()} when no free connection becomes available
* within timeout seconds.
*/
public static class TimeoutException extends RuntimeException {
private static final long serialVersionUID = 1;
public TimeoutException () {
super ("Timeout while waiting for a free database connection."); }}
/**
* Constructs a MiniConnectionPoolManager object with a timeout of 60 seconds.
*
* @param dataSource
* the data source for the connections.
* @param maxConnections
* the maximum number of connections.
*/
public MiniConnectionPoolManager (ConnectionPoolDataSource dataSource, int maxConnections) {
this (dataSource, maxConnections, 60); }
/**
* Constructs a MiniConnectionPoolManager object.
*
* @param dataSource
* the data source for the connections.
* @param maxConnections
* the maximum number of connections.
* @param timeout
* the maximum time in seconds to wait for a free connection.
*/
public MiniConnectionPoolManager (ConnectionPoolDataSource dataSource, int maxConnections, int timeout) {
this.dataSource = dataSource;
this.maxConnections = maxConnections;
this.timeout = timeout;
try {
logWriter = dataSource.getLogWriter(); }
catch (SQLException e) {}
if (maxConnections < 1) throw new IllegalArgumentException("Invalid maxConnections value.");
semaphore = new Semaphore(maxConnections,true);
recycledConnections = new Stack
poolConnectionEventListener = new PoolConnectionEventListener(); }
/**
* Closes all unused pooled connections.
*/
public synchronized void dispose() throws SQLException {
if (isDisposed) return;
isDisposed = true;
SQLException e = null;
while (!recycledConnections.isEmpty()) {
PooledConnection pconn = recycledConnections.pop();
try {
pconn.close(); }
catch (SQLException e2) {
if (e == null) e = e2; }}
if (e != null) throw e; }
/**
* Retrieves a connection from the connection pool. If
* maxConnections connections are already in use, the method
* waits until a connection becomes available or timeout seconds
* elapsed. When the application is finished using the connection, it must close
* it in order to return it to the pool.
*
* @return a new Connection object.
* @throws TimeoutException
* when no connection becomes available within timeout
* seconds.
*/
public Connection getConnection() throws SQLException {
// This routine is unsynchronized, because semaphore.acquire() may block.
synchronized (this) {
if (isDisposed) throw new IllegalStateException("Connection pool has been disposed."); }
try {
if (!semaphore.tryAcquire(timeout,TimeUnit.SECONDS))
throw new TimeoutException(); }
catch (InterruptedException e) {
throw new RuntimeException("Interrupted while waiting for a database connection.",e); }
boolean ok = false;
try {
Connection conn = getConnection2();
ok = true;
return conn; }
finally {
if (!ok) semaphore.release(); }}
private synchronized Connection getConnection2() throws SQLException {
if (isDisposed) throw new IllegalStateException("Connection pool has been disposed."); // test
// again
// with
// lock
PooledConnection pconn;
if (!recycledConnections.empty()) {
pconn = recycledConnections.pop(); }
else {
pconn = dataSource.getPooledConnection(); }
Connection conn = pconn.getConnection();
activeConnections++;
pconn.addConnectionEventListener (poolConnectionEventListener);
assertInnerState();
return conn; }
private synchronized void recycleConnection (PooledConnection pconn) {
if (isDisposed) { disposeConnection (pconn); return; }
if (activeConnections <= 0) throw new AssertionError();
activeConnections--;
semaphore.release();
recycledConnections.push (pconn);
assertInnerState(); }
private synchronized void disposeConnection (PooledConnection pconn) {
if (activeConnections <= 0) throw new AssertionError();
activeConnections--;
semaphore.release();
closeConnectionNoEx (pconn);
assertInnerState(); }
private void closeConnectionNoEx (PooledConnection pconn) {
try {
pconn.close(); }
catch (SQLException e) {
log ("Error while closing database connection: "+e.toString()); }}
private void log (String msg) {
String s = "MiniConnectionPoolManager: "+msg;
try {
if (logWriter == null)
System.err.println (s);
else
logWriter.println (s); }
catch (Exception e) {}}
private void assertInnerState() {
if (activeConnections < 0) throw new AssertionError();
if (activeConnections+recycledConnections.size() > maxConnections) throw new AssertionError();
if (activeConnections+semaphore.availablePermits() > maxConnections) throw new AssertionError(); }
private class PoolConnectionEventListener implements ConnectionEventListener {
public void connectionClosed (ConnectionEvent event) {
PooledConnection pconn = (PooledConnection)event.getSource();
pconn.removeConnectionEventListener (this);
recycleConnection (pconn); }
public void connectionErrorOccurred(ConnectionEvent event) {
PooledConnection pconn = (PooledConnection)event.getSource();
pconn.removeConnectionEventListener (this);
disposeConnection (pconn); }}
/**
* Returns the number of active (open) connections of this pool. This is the
* number of Connection objects that have been issued by
* {@link #getConnection()} for which Connection.close() has not
* yet been called.
*
* @return the number of active connections.
*/
public synchronized int getActiveConnections() {
return activeConnections; }
} // end class MiniConnectionPoolManager
// Test program for the MiniConnectionPoolManager class.
import java.io.PrintWriter;
import java.lang.Thread;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Random;
import javax.sql.ConnectionPoolDataSource;
import com.oval.research.connpool.MiniConnectionPoolManager;
public class TestMiniConnectionPoolManager {
private static final int maxConnections = 8; // number of connections
private static final int noOfThreads = 50; // number of worker threads
private static final int processingTime = 30; // total processing time of
// the test program in
// seconds
private static final int threadPauseTime1 = 100; // max. thread pause
// time in microseconds,
// without a connection
private static final int threadPauseTime2 = 100; // max. thread pause
// time in microseconds,
// with a connection
private static MiniConnectionPoolManager poolMgr;
private static WorkerThread[] threads;
private static boolean shutdownFlag;
private static Object shutdownObj = new Object();
private static Random random = new Random();
private static class WorkerThread extends Thread {
public int threadNo;
public void run() {
threadMain(threadNo);
}
};
private static ConnectionPoolDataSource createDataSource() throws Exception {
// Version for H2:
/*
* org.h2.jdbcx.JdbcDataSource dataSource = new
* org.h2.jdbcx.JdbcDataSource(); dataSource.setURL
* ("jdbc:h2:file:c:/temp/temp_TestMiniConnectionPoolManagerDB;DB_CLOSE_DELAY=-1");
*/
// Version for Apache Derby:
org.apache.derby.jdbc.EmbeddedConnectionPoolDataSource dataSource = new org.apache.derby.jdbc.EmbeddedConnectionPoolDataSource();
dataSource
.setDatabaseName("e:/mimiConnection/temp_TestMiniConnectionPoolManagerDB");
dataSource.setCreateDatabase("create");
dataSource.setLogWriter(new PrintWriter(System.out));
// Versioo for JTDS:
/*
* net.sourceforge.jtds.jdbcx.JtdsDataSource dataSource = new
* net.sourceforge.jtds.jdbcx.JtdsDataSource(); dataSource.setAppName
* ("TestMiniConnectionPoolManager"); dataSource.setDatabaseName
* ("Northwind"); dataSource.setServerName ("localhost");
* dataSource.setUser ("sa"); dataSource.setPassword
* (System.getProperty("saPassword"));
*/
// Version for the Microsoft SQL Server driver (sqljdbc.jar):
/*
* // The sqljdbc 1.1 documentation, chapter "Using Connection Pooling",
* recommends to use // SQLServerXADataSource instead of
* SQLServerConnectionPoolDataSource, even when no // distributed
* transactions are used.
* com.microsoft.sqlserver.jdbc.SQLServerXADataSource dataSource = new
* com.microsoft.sqlserver.jdbc.SQLServerXADataSource();
* dataSource.setApplicationName ("TestMiniConnectionPoolManager");
* dataSource.setDatabaseName ("Northwind"); dataSource.setServerName
* ("localhost"); dataSource.setUser ("sa"); dataSource.setPassword
* (System.getProperty("saPassword")); dataSource.setLogWriter (new
* PrintWriter(System.out));
*/
return dataSource;
}
public static void main(String[] args) throws Exception {
System.out.println("Program started.");
ConnectionPoolDataSource dataSource = createDataSource();
poolMgr = new MiniConnectionPoolManager(dataSource, maxConnections);
initDb();
startWorkerThreads();
pause(processingTime * 1000000);
System.out.println("\nStopping threads.");
stopWorkerThreads();
System.out.println("\nAll threads stopped.");
poolMgr.dispose();
System.out.println("Program completed.");
}
private static void startWorkerThreads() {
threads = new WorkerThread[noOfThreads];
for (int threadNo = 0; threadNo < noOfThreads; threadNo++) {
WorkerThread thread = new WorkerThread();
threads[threadNo] = thread;
thread.threadNo = threadNo;
thread.start();
}
}
private static void stopWorkerThreads() throws Exception {
setShutdownFlag();
for (int threadNo = 0; threadNo < noOfThreads; threadNo++) {
threads[threadNo].join();
}
}
private static void setShutdownFlag() {
synchronized (shutdownObj) {
shutdownFlag = true;
shutdownObj.notifyAll();
}
}
private static void threadMain(int threadNo) {
try {
threadMain2(threadNo);
} catch (Throwable e) {
System.out.println("\nException in thread " + threadNo + ": " + e);
e.printStackTrace(System.out);
setShutdownFlag();
}
}
private static void threadMain2(int threadNo) throws Exception {
// System.out.println ("Thread "+threadNo+" started.");
while (true) {
if (!pauseRandom(threadPauseTime1))
return;
threadTask(threadNo);
}
}
private static void threadTask(int threadNo) throws Exception {
Connection conn = null;
try {
conn = poolMgr.getConnection();
if (shutdownFlag)
return;
System.out.print(threadNo + " ");
incrementThreadCounter(conn, threadNo);
pauseRandom(threadPauseTime2);
} finally {
if (conn != null)
conn.close();
}
}
private static boolean pauseRandom(int maxPauseTime) throws Exception {
return pause(random.nextInt(maxPauseTime));
}
private static boolean pause(int pauseTime) throws Exception {
synchronized (shutdownObj) {
if (shutdownFlag)
return false;
if (pauseTime <= 0)
return true;
int ms = pauseTime / 1000;
int ns = (pauseTime % 1000) * 1000;
shutdownObj.wait(ms, ns);
}
return true;
}
private static void initDb() throws SQLException {
Connection conn = null;
try {
conn = poolMgr.getConnection();
System.out.println("initDb connected");
initDb2(conn);
} finally {
if (conn != null)
conn.close();
}
System.out.println("initDb done");
}
private static void initDb2(Connection conn) throws SQLException {
execSqlNoErr(conn, "drop table temp");
execSql(conn, "create table temp (threadNo integer, ctr integer)");
for (int i = 0; i < noOfThreads; i++)
execSql(conn, "insert into temp values(" + i + ",0)");
}
private static void incrementThreadCounter(Connection conn, int threadNo)
throws SQLException {
execSql(conn, "update temp set ctr = ctr + 1 where threadNo="
+ threadNo);
}
private static void execSqlNoErr(Connection conn, String sql) {
try {
execSql(conn, sql);
} catch (SQLException e) {
}
}
private static void execSql(Connection conn, String sql)
throws SQLException {
Statement st = null;
try {
st = conn.createStatement();
st.executeUpdate(sql);
} finally {
if (st != null)
st.close();
}
}
} // end class TestMiniConnectionPoolManager