/*
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*
* Licensed 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.
Sample Application
Writing a Basic JMS Application using Publish and Subscribe using
Message Selectors
This sample publishes messages and sets a property in the message header when
publishing messages. The subscriber set a message selector to select these
messages. In this sample we name the property "Department"
Usage:
java SelectorChat -b <broker:port> -u <username> -p <password> -v <property> -s <selector>
-b broker:port points to your message broker
Default: tcp://localhost:61616
-u username must be unique (but is not checked)
-p password (optional) password for user (not checked)
Default: password
-s selection required, selection value to set to message property
Suggested demonstration:
- In separate console windows with the environment set,
start instances of the application
under unique user names.
For example:
java SelectorChat -u BOB -s MARKETING
java SelectorChat -u JANE -s MARKETING
- Enter text and then press Enter to publish the message.
- See messages appear under the various user names as you
enter messages in each console window.
- Try starting a new instance with a different message selector
- Stop a session by pressing CTRL+C in its console window.
*/
import org.apache.activemq.*;
public class SelectorChat
implements javax.jms.MessageListener
{
private static final String APP_TOPIC = "jms.samples.chat";
private static final String PROPERTY_NAME = "Department";
private static final String DEFAULT_BROKER_NAME = "tcp://localhost:61616";
private static final String DEFAULT_PASSWORD = "password";
private javax.jms.Connection connect = null;
private javax.jms.Session pubSession = null;
private javax.jms.Session subSession = null;
private javax.jms.MessageProducer publisher = null;
/** Create JMS client for publishing and subscribing to messages. */
private void chatter( String broker, String username, String password, String selection)
{
// Create a connection.
try
{
javax.jms.ConnectionFactory factory;
factory = new ActiveMQConnectionFactory(username, password, broker);
connect = factory.createConnection (username, password);
pubSession = connect.createSession(false,javax.jms.Session.AUTO_ACKNOWLEDGE);
subSession = connect.createSession(false,javax.jms.Session.AUTO_ACKNOWLEDGE);
}
catch (javax.jms.JMSException jmse)
{
System.err.println("error: Cannot connect to Broker - " + broker);
jmse.printStackTrace();
System.exit(1);
}
// Create Publisher and Subscriber to 'chat' topics
try
{
javax.jms.Topic topic = pubSession.createTopic (APP_TOPIC);
// NOTE: The subscriber's message selector will now be set:
javax.jms.MessageConsumer subscriber = subSession.createConsumer(topic, PROPERTY_NAME + " = \'" + selection +"\'", false);
subscriber.setMessageListener(this);
publisher = pubSession.createProducer(topic);
// Now that setup is complete, start the Connection
connect.start();
}
catch (javax.jms.JMSException jmse)
{
jmse.printStackTrace();
System.exit(1);
}
try
{
// Read all standard input and send it as a message.
java.io.BufferedReader stdin =
new java.io.BufferedReader( new java.io.InputStreamReader( System.in ) );
System.out.println ("\nSelectorChat application:\n"
+ "===========================\n"
+ "The application user " + username + " connects to the broker at " + DEFAULT_BROKER_NAME + ".\n"
+ "The application will publish messages with " + PROPERTY_NAME + " set to " + selection + " to the " + APP_TOPIC + " topic .\n"
+ "The application also subscribes to that topic, selecting only messages where " + PROPERTY_NAME + " is " + selection + ".\n"
+ "Type some text, and then press Enter to publish it as a TextMesssage from " + username + ".\n");
while ( true )
{
String s = stdin.readLine();
if ( s == null )
exit();
else if ( s.length() > 0 )
{
javax.jms.TextMessage msg = pubSession.createTextMessage();
msg.setText( username + ": " + s );
// NOTE: here we set a property on messages to be published:
msg.setStringProperty(PROPERTY_NAME, selection);
publisher.send( msg );
}
}
}
catch ( java.io.IOException ioe )
{
ioe.printStackTrace();
}
catch ( javax.jms.JMSException jmse )
{
jmse.printStackTrace();
}
}
/**
* Handle the message
* (as specified in the javax.jms.MessageListener interface).
*/
public void onMessage( javax.jms.Message aMessage)
{
try
{
// Cast the message as a text message.
javax.jms.TextMessage textMessage = (javax.jms.TextMessage) aMessage;
// This handler reads a single String from the
// message and prints it to the standard output.
try
{
String string = textMessage.getText();
System.out.println( string );
}
catch (javax.jms.JMSException jmse)
{
jmse.printStackTrace();
}
}
catch (java.lang.RuntimeException rte)
{
rte.printStackTrace();
}
}
/** Cleanup resources and then exit. */
private void exit()
{
try
{
connect.close();
}
catch (javax.jms.JMSException jmse)
{
jmse.printStackTrace();
}
System.exit(0);
}
//
// NOTE: the remainder of this sample deals with reading arguments
// and does not utilize any JMS classes or code.
//
/** Main program entry point. */
public static void main(String argv[]) {
// Is there anything to do?
if (argv.length == 0) {
printUsage();
System.exit(1);
}
// Values to be read from parameters
String broker = DEFAULT_BROKER_NAME;
String username = null;
String password = DEFAULT_PASSWORD;
String selection = null;
// Check parameters
for (int i = 0; i < argv.length; i++) {
String arg = argv[i];
// Options
if (!arg.startsWith("-")) {
System.err.println ("error: unexpected argument - "+arg);
printUsage();
System.exit(1);
}
else {
if (arg.equals("-b")) {
if (i == argv.length - 1 || argv[i+1].startsWith("-")) {
System.err.println("error: missing broker name:port");
System.exit(1);
}
broker = argv[++i];
continue;
}
if (arg.equals("-u")) {
if (i == argv.length - 1 || argv[i+1].startsWith("-")) {
System.err.println("error: missing user name");
System.exit(1);
}
username = argv[++i];
continue;
}
if (arg.equals("-p")) {
if (i == argv.length - 1 || argv[i+1].startsWith("-")) {
System.err.println("error: missing password");
System.exit(1);
}
password = argv[++i];
continue;
}
if (arg.equals("-s")) {
if (i == argv.length - 1 || argv[i+1].startsWith("-")) {
System.err.println("error: missing selection");
System.exit(1);
}
selection = argv[++i];
continue;
}
if (arg.equals("-h")) {
printUsage();
System.exit(1);
}
}
}
// Check values read in.
if (username == null) {
System.err.println ("error: user name must be supplied");
printUsage();
}
if (selection == null) {
System.err.println ("error: selection must be supplied");
printUsage();
System.exit(1);
}
// Start the JMS client for the "chat".
SelectorChat chat = new SelectorChat();
chat.chatter (broker, username, password, selection);
}
/** Prints the usage. */
private static void printUsage() {
StringBuffer use = new StringBuffer();
use.append("usage: java SelectorChat (options) ...\n\n");
use.append("options:\n");
use.append(" -b name:port Specify name:port of broker.\n");
use.append(" Default broker: "+DEFAULT_BROKER_NAME+"\n");
use.append(" -u name Specify unique user name. (Required)\n");
use.append(" -p password Specify password for user.\n");
use.append(" Default password: "+DEFAULT_PASSWORD+"\n");
use.append(" -s selection Message selector value. (Required)\n");
use.append(" -h This help screen\n");
System.err.println (use);
}
}