Overview: Initial IT configuration

A company uses an existing IT configuration provided by IBM MQ Version 8.0 installed on a server with a Windows operating system. This scenario describes migrating the initial IT configuration to an equivalent IT configuration provided by IBM MQ Version 9.0 on the same server.

The initial IT configuration includes several components that an administrator configures or uses, as shown in Figure 1:

JMS application

A stand-alone application that business users interact with, for example to register an order. The application uses the Java Message Service (JMS) for asynchronous messaging.

• JMS is the Java EE messaging standard that is widely supported. JMS-based applications are therefore portable across many messaging products.
• JMS provides a level of abstraction from the details of the messaging layer, simplifying the application development process.
• JMS provides asynchronous communication, enabling applications to run without having to wait for a reply, unlike tightly coupled systems such as remote procedure call (RPC).
• Applications that use JMS do not directly specify details to access resources. Instead, they look up and use administered JMS objects such as a connection factory and a destination.

For some situations, other messaging standards might be more suitable than JMS. For example IBM Message Service Clients for C, C++ and .NET, also known as XMS, are APIs that provide similar benefits to JMS for non-Java applications. XMS is therefore more suitable if you are using the .NET platform, or you want to integrate existing C++ applications with newer Java EE applications.

The application uses point-to-point messaging to send messages to a queue in the infrastructure and processes reply messages, to provide the business user with an appropriate response.

In this messaging model, an application sends a message to a queue, and another application receives the message from the queue and acknowledges receipt of the message. This model is the simplest form of messaging because it involves only two endpoints. This model is also the most appropriate for the scenario sample application: a single client requests information from a single server.

In the alternative messaging model, publish/subscribe, a publisher publishes a message to a message topic. Subscribers subscribe to the topic to receive messages. The publisher and subscriber do not have any information about each other, and the message is received by zero or more recipients.

Queue manager sampleQM

The IBM MQ queue manager that provides the initial messaging infrastructure. It hosts the queue that the JMS application works with.

Q1 [Message queue]

The IBM MQ queue that the JMS application sends messages to.

JNDI namespace

A Java Naming Directory Interface JNDI namespace is used to hold JMS administered objects, which applications can use to connect to IBM MQ and access destinations to send or receive messages.

JNDI is part of Java EE, and provides a standard way for applications to access various types of naming and directory services, for the retrieval of application components. For example, we can use JNDI to access a naming service on a file system to retrieve the location of a printer object, or to access a directory service on an LDAP server to retrieve a user object which contains ID and password information. JNDI therefore enhances the portability of JMS-based applications, and makes it easier to integrate those applications with each other and into existing systems. For JMS messaging, we use JNDI to store objects that represent the target destination of a message, or the connection factory that creates the connection between our application and its messaging destination.

Any application or process with access to the JNDI namespace can use the same administered objects. The properties of the administered objects can be changed in JNDI, with all the applications or processes able to benefit from those same changes.

Initial context

An initial context defines the root of the JNDI namespace. To use IBM MQ Explorer to create and configure administered objects, you first add an initial context that defines the root of the JNDI namespace. Similarly, a JMS application first obtains an initial context, before it can retrieve administered objects from the JNDI namespace.

Connection factory, myCF

A JMS connection factory object defines a set of standard configuration properties for connections. An application uses a connection factory to create a connection to IBM MQ.

Destination, myQueue

A JMS destination can be a topic or a queue. In this scenario, the destination is a queue, and identifies the IBM MQ queue that applications send messages to, or from which an application receives messages, or both. An application looks up the destination in the JNDI namespace to create a connection to the IBM MQ queue.