Java tutorial
/** * 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. */ package org.fusesource.jms.pool; import java.util.Iterator; import java.util.List; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.CopyOnWriteArrayList; import java.util.concurrent.atomic.AtomicBoolean; import javax.jms.Connection; import javax.jms.ExceptionListener; import javax.jms.JMSException; import javax.jms.Session; import org.apache.commons.pool.ObjectPoolFactory; /** * Holds a real JMS connection along with the session pools associated with it. * * */ public class ConnectionPool { private Connection connection; private ConcurrentHashMap<SessionKey, SessionPool> cache; private List<PooledSession> loanedSessions = new CopyOnWriteArrayList<PooledSession>(); private AtomicBoolean started = new AtomicBoolean(false); private int referenceCount; private ObjectPoolFactory poolFactory; private long lastUsed = System.currentTimeMillis(); private long firstUsed = lastUsed; private boolean hasFailed; private boolean hasExpired; private int idleTimeout = 30 * 1000; private long expiryTimeout = 0l; public ConnectionPool(Connection connection, ObjectPoolFactory poolFactory) throws JMSException { this(connection, new ConcurrentHashMap<SessionKey, SessionPool>(), poolFactory); /* TODO: activemq specific // Add a transport Listener so that we can notice if this connection // should be expired due to a connection failure. connection.addTransportListener(new TransportListener() { public void onCommand(Object command) { } public void onException(IOException error) { synchronized (ConnectionPool.this) { hasFailed = true; } } public void transportInterupted() { } public void transportResumed() { } }); // make sure that we set the hasFailed flag, in case the transport already failed // prior to the addition of our new TransportListener if(connection.isTransportFailed()) { hasFailed = true; } */ connection.setExceptionListener(new ExceptionListener() { public void onException(JMSException exception) { synchronized (ConnectionPool.this) { hasFailed = true; } } }); } public ConnectionPool(Connection connection, ConcurrentHashMap<SessionKey, SessionPool> cache, ObjectPoolFactory poolFactory) { this.connection = connection; this.cache = cache; this.poolFactory = poolFactory; } public void start() throws JMSException { if (started.compareAndSet(false, true)) { try { connection.start(); } catch (JMSException e) { started.set(false); throw (e); } } } public synchronized javax.jms.Connection getConnection() { return connection; } public Session createSession(boolean transacted, int ackMode) throws JMSException { SessionKey key = new SessionKey(transacted, ackMode); SessionPool pool = null; pool = cache.get(key); if (pool == null) { SessionPool newPool = createSessionPool(key); SessionPool prevPool = cache.putIfAbsent(key, newPool); if (prevPool != null && prevPool != newPool) { // newPool was not the first one to be associated with this // key... close created session pool try { newPool.close(); } catch (Exception e) { throw new JMSException(e.getMessage()); } } pool = cache.get(key); // this will return a non-null value... } PooledSession session = pool.borrowSession(); this.loanedSessions.add(session); return session; } public Session createXaSession(boolean transacted, int ackMode) throws JMSException { SessionKey key = new SessionKey(transacted, ackMode); SessionPool pool = null; pool = cache.get(key); if (pool == null) { SessionPool newPool = createSessionPool(key); SessionPool prevPool = cache.putIfAbsent(key, newPool); if (prevPool != null && prevPool != newPool) { // newPool was not the first one to be associated with this // key... close created session pool try { newPool.close(); } catch (Exception e) { throw new JMSException(e.getMessage()); } } pool = cache.get(key); // this will return a non-null value... } PooledSession session = pool.borrowSession(); this.loanedSessions.add(session); return session; } public synchronized void close() { if (connection != null) { try { Iterator<SessionPool> i = cache.values().iterator(); while (i.hasNext()) { SessionPool pool = i.next(); i.remove(); try { pool.close(); } catch (Exception e) { } } } finally { try { connection.close(); } catch (Exception e) { } finally { connection = null; } } } } public synchronized void incrementReferenceCount() { referenceCount++; lastUsed = System.currentTimeMillis(); } public synchronized void decrementReferenceCount() { referenceCount--; lastUsed = System.currentTimeMillis(); if (referenceCount == 0) { expiredCheck(); for (PooledSession session : this.loanedSessions) { try { session.close(); } catch (Exception e) { } } this.loanedSessions.clear(); // only clean up temp destinations when all users // of this connection have called close if (getConnection() != null) { /* TODO: activemq specific getConnection().cleanUpTempDestinations(); */ } } } /** * @return true if this connection has expired. */ public synchronized boolean expiredCheck() { if (connection == null) { return true; } if (hasExpired) { if (referenceCount == 0) { close(); } return true; } if (hasFailed || (idleTimeout > 0 && System.currentTimeMillis() > lastUsed + idleTimeout) || expiryTimeout > 0 && System.currentTimeMillis() > firstUsed + expiryTimeout) { hasExpired = true; if (referenceCount == 0) { close(); } return true; } return false; } public int getIdleTimeout() { return idleTimeout; } public void setIdleTimeout(int idleTimeout) { this.idleTimeout = idleTimeout; } protected SessionPool createSessionPool(SessionKey key) { return new SessionPool(this, key, poolFactory.createPool()); } public void setExpiryTimeout(long expiryTimeout) { this.expiryTimeout = expiryTimeout; } public long getExpiryTimeout() { return expiryTimeout; } void onSessionReturned(PooledSession session) { this.loanedSessions.remove(session); } void onSessionInvalidated(PooledSession session) { this.loanedSessions.remove(session); } }