Chapter 2 Quick Start Tutorial

Chapter 2
Quick Start Tutorial

This chapter provides a quick introduction to JMS client programming in a Sun Java System Message Queue environment. It consists of a tutorial-style description of procedures used to create, compile, and run a simple HelloWorldMessage example application.

This chapter covers the following topics:

Setting Up Your Environment

Starting and Testing the Message Server

Developing a Simple Client Application

Compiling and Running a Client Application

Example Application Code

For the purpose of this tutorial it is sufficient to run the Message Queue server in a default configuration. For instructions on configuring a Message Queue server, please refer to the Message Queue Administration Guide.

The minimum JDK level required to compile and run Message Queue clients is 1.2.2.

Setting Up Your Environment

You need to set the CLASSPATH environment variable when compiling and running a JMS client. (The IMQ_HOME variable, where used, refers to the directory where Message Queue is installed on Windows platforms and some Sun Java System Application Server platforms.)

The value of CLASSPATH depends on the following factors:

the platform on which you compile or run

whether you are compiling or running a JMS application

whether your application is a SOAP client or a SOAP servlet

whether your application uses the SOAP/JMS transformer utilities

the JDK version you are using (which affects JNDI support).

Table 2-1 specifies the directories where jar files are to be found on the different platforms:

Table 2-1 jar File Locations
Platform	Directory
Solaris™	/usr/share/lib/
Solaris, using the standalone version of Sun Java System Application Server	IMQ_HOME/lib/
Linux	/opt/imq/lib/
Windows	IMQ_HOME\lib\

Table 2-2 lists the jar files you need to compile and run different kinds of code.

Table 2-2 jar Files Needed in CLASSPATH
Code	To Compile	To Run	Discussion
JMS client	jms.jar imq.jar jndi.jar	jms.jar imq.jar Directory containing compiled Java app or '.'	See discussion of JNDI jar files, following this table.
SOAP Client	saaj-api.jar activation.jar	saaj-api.jar Directory containing compiled Java app or '.'	See Chapter 6, "Working With SOAP Messages"
SOAP Servlet	jaxm-api.jar saaj-api.jar activation.jar		SOAP servlets can run in the App Server 7 without additional runtime support.
code using SOAP/JMS transformer utilities	imqxm.jar (and jars for JMS and SOAP clients)		Also add the appropriate jar files mentioned in this table for the kind of code you are writing.

A client application must be able to access JNDI jar files (jndi.jar) even if the application does not use JNDI directly to look up Message Queue administered objects. This is because JNDI is referenced by methods belonging to the Destination and ConnectionFactory classes.

JNDI jar files are bundled with JDK 1.4. Thus, if you are using this JDK, you do not have to add jndi.jar to your CLASSPATH setting. However, if you are using an earlier version of the JDK, you must include jndi.jar in your classpath.

If you are using JNDI to look up Message Queue administered objects, you must also include the following files in your CLASSPATH setting:

if you are using the file-system context (with any JDK version), you must include the fscontext.jar file.

if you are using the LDAP context

with JDK 1.2 or 1.3, include the ldap.jar, ldabbp.jar, and fscontext.jar files.

with JDK 1.4, all files are already bundled with this JDK.

Starting and Testing the Message Server

This tutorial assumes that you do not have a Message Queue server currently running. A message server consists of one or more brokers—the software component that routes and delivers messages.

(If you run the broker as a UNIX startup process or Windows service, then it is already running and you can skip to To Test a Broker below.)

To Start a Broker

In a terminal window, change to the directory containing Message Queue executables:

Table 2-3 Location of Message Queue Executables
Platform	Location
Solaris	/usr/bin/
Linux	/opt/imq/bin/
Windows	IMQ_HOME/bin/

Run the broker startup command (imqbrokerd) as shown below.

imqbrokerd -tty

The -tty option causes all logged messages to be displayed to the terminal console (in addition to the log file).

The broker will start and display a few messages before displaying the message, “imqbroker@host:7676 ready.” It is now ready and available for clients to use.

To Test a Broker

One simple way to check the broker startup is by using the Message Queue Command (imqcmd) utility to display information about the broker.

In a separate terminal window, change to the directory containing Message Queue executables (see Table 2-3).

Run imqcmd with the arguments shown below.

imqcmd query bkr -u admin -p admin

The output displayed should be similar to what is shown below.


% imqcmd query bkr -u admin -p admin

Querying the broker specified by:

-------------------------
Host Primary Port
-------------------------
localhost 7676

Version 3.5 SP1
Instance Name imqbroker
Primary Port 7676

Current Number of Messages in System 0
Current Total Message Bytes in System 0

Max Number of Messages in System unlimited (-1)
Max Total Message Bytes in System unlimited (-1)
Max Message Size 70m


Auto Create Queues true
Auto Create Topics true
Auto Created Queue Max Number of Active Consumers 1
Auto Created Queue Max Number of Backup Consumers 0

Cluster Broker List (active)
Cluster Broker List (configured)
Cluster Master Broker
Cluster URL

Log Level INFO
Log Rollover Interval (seconds) 604800
Log Rollover Size (bytes) unlimited (-1)

Successfully queried the broker.

Current Number of Messages in System 0

Developing a Simple Client Application

This section leads you through the steps used to create a simple “Hello World” client application that sends a message to a queue destination and then retrieves the same message from the queue. You can find this example, named HelloWorldMessage in the IMQ_HOME/demo/helloworld/helloworldmessage directory.

The following steps describe the HelloWorldMessage example

Import the interfaces and Message Queue implementation classes for the JMS API.

The javax.jms package defines all the JMS interfaces necessary to develop a JMS client.

import javax.jms.*;

Instantiate a Message Queue QueueConnectionFactory administered object.

A QueueConnectionFactory object encapsulates all the Message Queue-specific configuration properties for creating QueueConnection connections to a Message Queue server.

QueueConnectionFactory myQConnFactory =
new com.sun.messaging.QueueConnectionFactory();

ConnectionFactory administered objects can also be accessed through a JNDI lookup (see Looking Up ConnectionFactory Objects). This approach makes the client code JMS-provider independent and also allows for a centrally administered messaging system.

Create a connection to the message server.

A QueueConnection object is the active connection to the message server in the Point-To-Point programming domain.

QueueConnection myQConn =
myQConnFactory.createQueueConnection();

Create a session within the connection.

A QueueSession object is a single-threaded context for producing and consuming messages. It enables clients to create producers and consumers of messages for a queue destination.

QueueSession myQSess = myQConn.createQueueSession(false,
Session.AUTO_ACKNOWLEDGE);

The myQSess object created above is non-transacted and automatically acknowledges messages upon consumption by a consumer.

Instantiate a Message Queue queue administered object that corresponds to a queue destination in the message server.

Destination administered objects encapsulate provider-specific destination naming syntax and behavior. The code below instantiates a queue administered object for a physical queue destination named “world”.

Queue myQueue = new.com.sun.messaging.Queue("world");

Destination administered objects can also be accessed through a JNDI lookup (see Looking Up Destination Objects). This approach makes the client code JMS-provider independent and also allows for a centrally administered messaging system.

Create a QueueSender message producer.

This message producer, associated with myQueue, is used to send messages to the queue destination named “world”.

QueueSender myQueueSender = myQSess.createSender(myQueue);

Create and send a message to the queue.

You create a TextMessage object using the QueueSession object and populate it with a string representing the data of the message. Then you use the QueueSender object to send the message to the “world” queue destination.

TextMessage myTextMsg = myQSess.createTextMessage();
myTextMsg.setText("Hello World");
System.out.println(“Sending Message: “ + myTextMsg.getText());
myQueueSender.send(myTextMsg);

Create a QueueReceiver message consumer.

This message consumer, associated with myQueue, is used to receive messages from the queue destination named “world”.

QueueReceiver myQueueReceiver =
myQSess.createReceiver(myQueue);

Start the QueueConnection you created in Step 3.

Messages for consumption by a client can only be delivered over a connection that has been started (while messages produced by a client can be delivered to a destination without starting a connection, as in Step 7.

myQConn.start();

Receive a message from the queue.

You receive a message from the “world” queue destination using the QueueReceiver object. The code, below, is an example of a synchronous consumption of messages (see Message Consumption: Synchronous and Asynchronous).

Message msg = myQueueReceiver.receive();

Retrieve the contents of the message.

Once the message is received successfully, its contents can be retrieved.

if (msg instanceof TextMessage) {
TextMessage txtMsg = (TextMessage) msg;
System.out.println("Read Message: " + txtMsg.getText());
}

Close the session and connection resources.

myQSess.close();
myQConn.close();

Compiling and Running a Client Application

To compile and run Java clients in a Message Queue environment, it is recommended that you use the Java2 SDK Standard Edition v1.4, though versions 1.3 and 1.2 are also supported. The recommended SDK can be downloaded from the following location:

http://java.sun.com/j2se/1.4

Be sure that you have set the CLASSPATH environment variable correctly, as described in Setting Up Your Environment, before attempting to compile or run a client application.

The following instructions are based on the HelloWorldMessage application, as created in Developing a Simple Client Application, and located in the Message Queue 3.5 SP1 JMS example applications directory (see Table 2-4). Please note that these instructions are furnished as an example. You do not actually need to compile the example; it is shipped precompiled. Of course, if you modify the source for the example, you will need to recompile.

To Compile and Run the HelloWorldMessage Application

Make the directory containing the application your current directory.

The Message Queue 3.5 SP1 example applications directory on Solaris is not writable by users, so copy the HelloWorldMessage application to a writable directory and make that directory your current directory.

Compile the HelloWorldMessage application as shown below.

javac HelloWorldMessage.java

This step results in the HelloWorldMessage.class file being created in the current directory.

Run the HelloWorldMessage application:

java HelloWorldMessage

The following output is displayed when you run HelloWorldMessage.

Sending Message: Hello World

Read Message: Hello World

Example Application Code

The example applications provided by Message Queue 3.5 SP1 consist of both JMS messaging applications as well as JAXM messaging examples (see Working With SOAP Messages for more information).

Directories containing example application code are set as follows:

Solaris: /usr/demo/imq

Linux: /opt/imq/demo

Windows: IMQ_HOME\demo\

Each directory (except for the JMS directory) contains a README file that describes the source files included in that directory. Table 2-4 lists and describes the contents of the directories of interest to Message Queue Java clients.

Table 2-4 Example Programs
Directory	Contents
helloworld	Simple programs that show how a JMS client is created and deployed in Message Queue. These examples include the steps required to create administered objects in Message Queue, and show to use JNDI in the client to look up and use those objects.
jms	Sample programs that demonstrate the use of the JMS API with Message Queue.
jaxm	Sample programs that demonstrate how to use SOAP messages in conjunction with JMS in Message Queue.
applications	Two directories: One contains source for a GUI application that uses the Message Queue JMS monitoring API to get the list of queues from a Message Queue broker and browse their contents using a JMS queue browser. One contains source for a GUI application that uses the JMS API to implement a simple chat application.
monitoring	Sample programs that demonstrate how to use the JMS API for monitoring the broker.
jdbc	Examples for plugging in a PointBase and an Oracle database.
imqobjmgr	Examples of imqobjmgr command files.

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