001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.activemq.web; 018 019import java.util.LinkedList; 020 021import javax.jms.Connection; 022import javax.jms.ConnectionFactory; 023import javax.jms.JMSException; 024import javax.jms.Session; 025 026import org.apache.activemq.ActiveMQSession; 027import org.slf4j.Logger; 028import org.slf4j.LoggerFactory; 029 030/** 031 * A simple pool of JMS Session objects intended for use by Queue browsers. 032 */ 033public class SessionPool { 034 035 private static final Logger LOG = LoggerFactory.getLogger(SessionPool.class); 036 037 private ConnectionFactory connectionFactory; 038 private Connection connection; 039 private final LinkedList<Session> sessions = new LinkedList<Session>(); 040 041 public Connection getConnection() throws JMSException { 042 if (checkConnection()) { 043 return connection; 044 } 045 046 synchronized (this) { 047 try { 048 connection = getConnectionFactory().createConnection(); 049 connection.start(); 050 return connection; 051 } catch (JMSException jmsEx) { 052 LOG.debug("Caught exception while attempting to get a new Connection.", jmsEx); 053 connection.close(); 054 connection = null; 055 throw jmsEx; 056 } 057 } 058 } 059 060 private boolean checkConnection() { 061 if (connection == null) { 062 return false; 063 } 064 065 try { 066 connection.getMetaData(); 067 return true; 068 } catch (JMSException e) { 069 return false; 070 } 071 } 072 073 public void setConnection(Connection connection) { 074 this.connection = connection; 075 } 076 077 public ConnectionFactory getConnectionFactory() { 078 if (connectionFactory == null) { 079 throw new IllegalStateException("No ConnectionFactory has been set for the session pool"); 080 } 081 return connectionFactory; 082 } 083 084 public void setConnectionFactory(ConnectionFactory connectionFactory) { 085 this.connectionFactory = connectionFactory; 086 } 087 088 public Session borrowSession() throws JMSException { 089 Session answer = null; 090 synchronized (sessions) { 091 if (sessions.isEmpty()) { 092 LOG.trace("Creating a new session."); 093 answer = createSession(); 094 } else { 095 LOG.trace("Serving session from the pool."); 096 answer = sessions.removeLast(); 097 } 098 } 099 return answer; 100 } 101 102 public void returnSession(Session session) { 103 if (session != null && !((ActiveMQSession) session).isClosed()) { 104 synchronized (sessions) { 105 LOG.trace("Returning session to the pool."); 106 sessions.add(session); 107 } 108 } else { 109 LOG.debug("Session closed or null, not returning to the pool."); 110 } 111 } 112 113 protected Session createSession() throws JMSException { 114 return getConnection().createSession(false, Session.AUTO_ACKNOWLEDGE); 115 } 116}