Java tutorial
/** * The contents of this file are subject to the OpenMRS Public License * Version 1.0 (the "License"); you may not use this file except in * compliance with the License. You may obtain a copy of the License at * http://license.openmrs.org * * Software distributed under the License is distributed on an "AS IS" * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the * License for the specific language governing rights and limitations * under the License. * * Copyright (C) OpenMRS, LLC. All Rights Reserved. */ package org.openmrs.event; import java.io.File; import java.io.Serializable; import java.io.UnsupportedEncodingException; import java.net.URLEncoder; import java.util.HashMap; import java.util.Map; import javax.jms.Destination; import javax.jms.JMSException; import javax.jms.MapMessage; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.Session; import javax.jms.Topic; import javax.jms.TopicConnection; import javax.jms.TopicSession; import javax.jms.TopicSubscriber; import org.apache.activemq.ActiveMQConnectionFactory; import org.apache.commons.lang.StringUtils; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.openmrs.OpenmrsObject; import org.openmrs.api.APIException; import org.openmrs.util.OpenmrsUtil; import org.springframework.jms.connection.SingleConnectionFactory; import org.springframework.jms.core.JmsTemplate; import org.springframework.jms.core.MessageCreator; /** * Used by {@link Event}. */ public class EventEngine { protected final static String DELIMITER = ":"; protected static Log log = LogFactory.getLog(Event.class); protected JmsTemplate jmsTemplate = null; protected Map<String, TopicSubscriber> subscribers = new HashMap<String, TopicSubscriber>(); protected SingleConnectionFactory connectionFactory; /** * @see Event#fireAction(String, OpenmrsObject) */ public void fireAction(String action, final Object object) { Destination key = getDestination(object.getClass(), action); fireEvent(key, object); } /** * @see Event#fireEvent(Destination, OpenmrsObject) */ public void fireEvent(final Destination dest, final Object object) { EventMessage eventMessage = new EventMessage(); if (object instanceof OpenmrsObject) { eventMessage.put("uuid", ((OpenmrsObject) object).getUuid()); } eventMessage.put("classname", object.getClass().getName()); eventMessage.put("action", getAction(dest)); doFireEvent(dest, eventMessage); } /** * @see Event#fireEvent(String, EventMessage) */ public void fireEvent(String topicName, EventMessage eventMessage) { if (StringUtils.isBlank(topicName)) { throw new APIException("Topic name cannot be null or blank"); } doFireEvent(getDestination(topicName), eventMessage); } /** * @param dest * @param eventMessage */ private void doFireEvent(final Destination dest, final EventMessage eventMessage) { initializeIfNeeded(); jmsTemplate.send(dest, new MessageCreator() { @Override public Message createMessage(Session session) throws JMSException { if (log.isInfoEnabled()) log.info("Sending data " + eventMessage); MapMessage mapMessage = session.createMapMessage(); if (eventMessage != null) { for (Map.Entry<String, Serializable> entry : eventMessage.entrySet()) { mapMessage.setObject(entry.getKey(), entry.getValue()); } } return mapMessage; } }); } private synchronized void initializeIfNeeded() { if (jmsTemplate == null) { log.info("creating connection factory"); String dataDirectory = new File(OpenmrsUtil.getApplicationDataDirectory(), "activemq-data") .getAbsolutePath(); try { dataDirectory = URLEncoder.encode(dataDirectory, "UTF-8"); } catch (UnsupportedEncodingException e) { throw new RuntimeException("Failed to encode URI", e); } String brokerURL = "vm://localhost?broker.persistent=true&broker.useJmx=false&broker.dataDirectory=" + dataDirectory; ActiveMQConnectionFactory cf = new ActiveMQConnectionFactory(brokerURL); connectionFactory = new SingleConnectionFactory(cf); // or CachingConnectionFactory ? jmsTemplate = new JmsTemplate(connectionFactory); } else { log.trace("messageListener already defined"); } } /** * @see Event#subscribe(Class, String, EventListener) */ public void subscribe(Class<?> clazz, String action, EventListener listener) { if (action != null) { Destination dest = getDestination(clazz, action); subscribe(dest, listener); } else { for (Event.Action a : Event.Action.values()) { subscribe(getDestination(clazz, a.toString()), listener); } } } /** * @see Event#subscribe(String, EventListener) */ public void subscribe(String topicName, EventListener listener) { if (StringUtils.isBlank(topicName)) { throw new APIException("Topic name cannot be null or blank"); } subscribe(getDestination(topicName), listener); } /** * @see Event#unsubscribe(Class, org.openmrs.event.Event.Action, EventListener) */ public void unsubscribe(Class<?> clazz, Event.Action action, EventListener listener) { if (action != null) { unsubscribe(getDestination(clazz, action.toString()), listener); } else { for (Event.Action a : Event.Action.values()) { unsubscribe(getDestination(clazz, a.toString()), listener); } } } /** * @see Event#unsubscribe(String, EventListener) */ public void unsubscribe(String topicName, EventListener listener) { if (StringUtils.isBlank(topicName)) { throw new APIException("Topic name cannot be null or blank"); } unsubscribe(getDestination(topicName), listener); } /** * @see Event#getDestination(Class, String) */ public Destination getDestination(final Class<?> clazz, final String action) { return getDestination(action.toString() + DELIMITER + clazz.getName()); } /** * @see Event#getDestination(String) */ public Destination getDestination(final String topicName) { return new Topic() { @Override public String getTopicName() throws JMSException { return topicName; } }; } /** * @see Event#subscribe(Destination, EventListener) */ public void subscribe(Destination destination, final EventListener listenerToRegister) { initializeIfNeeded(); TopicConnection conn; Topic topic = (Topic) destination; try { conn = (TopicConnection) jmsTemplate.getConnectionFactory().createConnection(); TopicSession session = conn.createTopicSession(false, TopicSession.AUTO_ACKNOWLEDGE); TopicSubscriber subscriber = session.createSubscriber(topic); subscriber.setMessageListener(new MessageListener() { @Override public void onMessage(Message message) { listenerToRegister.onMessage(message); } }); //Check if this is a duplicate and remove it String key = topic.getTopicName() + DELIMITER + listenerToRegister.getClass().getName(); if (subscribers.containsKey(key)) { unsubscribe(destination, listenerToRegister); } subscribers.put(key, subscriber); conn.start(); } catch (JMSException e) { // TODO Auto-generated catch block. Do something smarter here. e.printStackTrace(); } // List<EventListener> currentListeners = listeners.get(key); // // if (currentListeners == null) { // currentListeners = new ArrayList<EventListener>(); // currentListeners.add(listenerToRegister); // listeners.put(key, currentListeners); // if (log.isInfoEnabled()) // log.info("subscribed: " + listenerToRegister + " to key: " // + key); // // } else { // // prevent duplicates because of weird spring loading // String listernToRegisterName = listenerToRegister.getClass() // .getName(); // Iterator<EventListener> iterator = currentListeners.iterator(); // while (iterator.hasNext()) { // EventListener lstnr = iterator.next(); // if (lstnr.getClass().getName().equals(listernToRegisterName)) // iterator.remove(); // } // // if (log.isInfoEnabled()) // log.info("subscribing: " + listenerToRegister + " to key: " // + key); // // currentListeners.add(listenerToRegister); // } } /** * @see Event#unsubscribe(Destination, EventListener) */ public void unsubscribe(Destination dest, EventListener listener) { initializeIfNeeded(); if (dest != null) { Topic topic = (Topic) dest; try { String key = topic.getTopicName() + DELIMITER + listener.getClass().getName(); if (subscribers.get(key) != null) subscribers.get(key).close(); subscribers.remove(key); } catch (JMSException e) { log.error("Failed to unsubscribe from the specified destination:", e); } } } /** * @see Event#setSubscription(SubscribableEventListener) */ public void setSubscription(SubscribableEventListener listenerToRegister) { // loop over each object and each action to register for (Class<? extends OpenmrsObject> objectClass : listenerToRegister.subscribeToObjects()) { for (String action : listenerToRegister.subscribeToActions()) { Destination key = getDestination(objectClass, action); subscribe(key, listenerToRegister); } } } /** * @see Event#unsetSubscription(SubscribableEventListener) */ public void unsetSubscription(SubscribableEventListener listenerToRegister) { for (Class<? extends OpenmrsObject> objectClass : listenerToRegister.subscribeToObjects()) { for (String action : listenerToRegister.subscribeToActions()) { Destination key = getDestination(objectClass, action); unsubscribe(key, listenerToRegister); } } } protected String getAction(final Destination dest) { if (dest instanceof Topic) { // look for delimiter and get string before that String topicName; try { topicName = ((Topic) dest).getTopicName(); } catch (JMSException e) { // TODO fail hard here? document this in javadoc too return null; } int index = topicName.indexOf(DELIMITER); if (index < 0) { // uh, what? TODO: document this return null; } return topicName.substring(0, index); } else { // what kind of Destination is this if not a Topic?? // TODO: document this return null; } } /** * Closes the underlying shared connection which will close the broker too under the hood */ public void shutdown() { if (log.isDebugEnabled()) log.debug("Shutting down JMS shared connection..."); if (connectionFactory != null) { connectionFactory.destroy(); } } }