protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
                               // TODO Auto-generated method stub
                               response.getWriter().append("Served at: ").append(request.getContextPath());
                               mSc = getServletContext();
 
                               MySingleton mySingleton = MySingleton.newInstance();
                              
                               ArrayList<MyModel> models = mySingleton.getModels();
                               for (MyModel model: models){
                                               mSc.log("string is " + model.getString() + ", int is " + model.getInt());
                               }
                              
                }

public class MySingleton {
 
                                                                                                //jms/MyEnvFactory
                //@Resource(mappedName = "jms/MyEnvFactory")
                private ConnectionFactory connectionFactory;
               
                //@Resource(mappedName = "jms/MyEnvQueue")
                private Queue queue;
 
                JMSContext mJmsContext;
                JMSConsumer mJmsConsumer;
               
                ArrayList<MyModel> mModel;
                private static MySingleton mMySingleton;
               
                private MySingleton() {
                               // TODO Auto-generated constructor stub
                               try {
                                               Context context = new InitialContext();
                                               connectionFactory = (ConnectionFactory) context.lookup("jms/MyEnvFactory");
                                               queue = (Queue) context.lookup("jms/MyEnvQueue");
                                                                             
                               } catch (NamingException e) {
                                               // TODO Auto-generated catch block
                                               e.printStackTrace();
                               }
                              
                              
                               mJmsContext = connectionFactory.createContext();
                               mJmsConsumer = mJmsContext.createConsumer(queue);
                              
                               mModel = new ArrayList<>();
 
                               mJmsConsumer.setMessageListener(new MyAsynchMessageListener());
                }
               
                public static MySingleton newInstance(){
                               if (mMySingleton == null){
                                               mMySingleton = new MySingleton();
                               }
                               return mMySingleton;
                }
 
                public void addModel(MyModel model) {
                               // TODO Auto-generated method stub
                               mModel.add(model);
                }
               
                public ArrayList<MyModel> getModels(){
                               return mModel;
                }
               
 
}
 

public class MyModel implements Serializable{
 
                private String mString;
                private int mInt;
               
                public MyModel() {
                               // TODO Auto-generated constructor stub
                }
 
                public String getString() {
                               return mString;
                }
 
                public void setString(String string) {
                               mString = string;
                }
 
                public int getInt() {
                               return mInt;
                }
 
                public void setInt(int i) {
                               mInt = i;
                }
               
               
 
}
 

public class MyAsynchMessageListener implements MessageListener {
 
                MySingleton mMySingleton;
               
                public MyAsynchMessageListener() {
                               // TODO Auto-generated constructor stub
                               mMySingleton = MySingleton.newInstance();
                }
 
                @Override
                public void onMessage(Message message) {
                               // TODO Auto-generated method stub
                               //MyModel model = (MyModel) message;
                               //mMySingleton.addModel(model);
                }
               
}
 

com.sun.messaging.jms.MQRuntimeException: MQRA:DCF:allocation failure:createConnection:Error in allocating a connection. Cause: In-use connections equal max-pool-size and expired max-wait-time. Cannot allocate more connections