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* 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.apache.cayenne.event;
import java.io.Serializable;
import java.util.Collection;
import org.jgroups.Channel;
import org.jgroups.JChannel;
import org.jgroups.Message;
import org.jgroups.MessageListener;
import org.jgroups.blocks.PullPushAdapter;
/**
* Implementation of EventBridge that passes and receives events via JavaGroups
* communication software.
*
* @since 1.1
*/
public class JavaGroupsBridge extends EventBridge implements MessageListener {
// TODO: Meaning of "state" in JGroups is not yet clear to me
protected byte[] state;
protected Channel channel;
protected PullPushAdapter adapter;
protected String multicastAddress;
protected String multicastPort;
protected String configURL;
/**
* Creates new instance of JavaGroupsBridge.
*/
public JavaGroupsBridge(EventSubject localSubject, String externalSubject) {
super(localSubject, externalSubject);
}
/**
* @since 1.2
*/
public JavaGroupsBridge(Collection<EventSubject> localSubjects, String externalSubject) {
super(localSubjects, externalSubject);
}
public String getConfigURL() {
return configURL;
}
public void setConfigURL(String configURL) {
this.configURL = configURL;
}
public String getMulticastAddress() {
return multicastAddress;
}
public void setMulticastAddress(String multicastAddress) {
this.multicastAddress = multicastAddress;
}
public String getMulticastPort() {
return multicastPort;
}
public void setMulticastPort(String multicastPort) {
this.multicastPort = multicastPort;
}
public byte[] getState() {
return state;
}
public void setState(byte[] state) {
this.state = state;
}
/**
* Implementation of org.javagroups.MessageListener - a callback method to process
* incoming messages.
*/
public void receive(Message message) {
try {
CayenneEvent event = messageObjectToEvent((Serializable) message.getObject());
if (event != null) {
onExternalEvent(event);
}
}
catch (Exception ex) {
// TODO: Andrus, 2/8/2006 logging... Log4J was removed to make this usable on
// the client
}
}
@Override
protected void startupExternal() throws Exception {
// TODO: need to do more research to figure out the best default transport
// settings
// to avoid fragmentation, etc.
// if config file is set, use it, otherwise use a default
// set of properties, trying to configure multicast address and port
if (configURL != null) {
channel = new JChannel(configURL);
}
else {
String configString = buildConfigString();
channel = new JChannel(configString);
}
// Important - discard messages from self
channel.setOpt(Channel.LOCAL, Boolean.FALSE);
channel.connect(externalSubject);
if (receivesExternalEvents()) {
adapter = new PullPushAdapter(channel, this);
}
}
/**
* Creates JavaGroups configuration String, using preconfigured multicast port and
* address.
*/
protected String buildConfigString() {
if (multicastAddress == null) {
throw new IllegalStateException("'multcastAddress' is not set");
}
if (multicastPort == null) {
throw new IllegalStateException("'multcastPort' is not set");
}
return "UDP(mcast_addr="
+ multicastAddress
+ ";mcast_port="
+ multicastPort
+ ";ip_ttl=32):"
+ "PING(timeout=3000;num_initial_members=6):"
+ "FD(timeout=3000):"
+ "VERIFY_SUSPECT(timeout=1500):"
+ "pbcast.NAKACK(gc_lag=10;retransmit_timeout=600,1200,2400,4800):"
+ "pbcast.STABLE(desired_avg_gossip=10000):"
+ "FRAG:"
+ "pbcast.GMS(join_timeout=5000;join_retry_timeout=2000;"
+ "shun=true;print_local_addr=false)";
}
@Override
protected void shutdownExternal() throws Exception {
try {
if (adapter != null) {
adapter.stop();
}
channel.close();
}
finally {
adapter = null;
channel = null;
}
}
@Override
protected void sendExternalEvent(CayenneEvent localEvent) throws Exception {
Message message = new Message(null, null, eventToMessageObject(localEvent));
channel.send(message);
}
/**
* Converts CayenneEvent to a serializable object that will be sent via JMS. Default
* implementation simply returns the event, but subclasses can customize this
* behavior.
*/
protected Serializable eventToMessageObject(CayenneEvent event) throws Exception {
return event;
}
/**
* Converts a Serializable instance to CayenneEvent. Returns null if the object is not
* supported. Default implementation simply tries to cast the object to CayenneEvent,
* but subclasses can customize this behavior.
*/
protected CayenneEvent messageObjectToEvent(Serializable object) throws Exception {
return (object instanceof CayenneEvent) ? (CayenneEvent) object : null;
}
}