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# 1 Introduction to JMX Programming for Message Queue Clients

While Message Queue's Administration Console and command line administration utilities allow an administrator to interactively configure and monitor Message Queue resources (such as brokers, connections, and destinations), these tools are not accessible from within a running client application.

To provide programmatic access to such administrative functions, Message Queue also incorporates an application programming interface based on the Java Management Extensions (JMX). Client applications can use this JMX API to programmatically perform the configuration and monitoring operations that are available interactively through the Administration Console and command line utilities.

You can use Message Queue's JMX API in your client applications for a variety of purposes:

- To optimize performance by monitoring the usage of brokers and other Message Queue resources and reconfiguring their parameters based on the results

- To automate regular maintenance tasks, rolling upgrades, and so forth

- To write your own utility applications to replace or enhance standard Message Queue tools such as the Broker utility (`imqbrokerd`) and Command utility (`imqcmd`)

In addition, since JMX is the Java standard for building management applications and is widely used for managing J2EE infrastructure, you can use it to incorporate your Message Queue client as part of a larger J2EE deployment using a standard management framework throughout.

## JMX Architecture

The JMX Specification defines an architecture for the instrumentation and programmatic management of distributed resources. This architecture is based on the notion of a managed bean, or MBean: a Java object, similar to a JavaBean, representing a resource to be managed. Message Queue MBeans may be associated with individual resources such as brokers, connections, or destinations, or with whole categories of resources, such as the set of all destinations on a broker. There are separate configuration MBeans and monitor MBeans for setting a resource's configuration properties and monitoring its runtime state.

Each MBean is identified by an object name, an instance of the JMX class `ObjectName` conforming to the syntax and conventions defined in the JMX Specification. Object names for Message Queue MBeans are either defined as static constants or returned by static methods in the Message Queue utility class `MQObjectName`; see Object Names for further information.

An MBean provides access to its underlying resource through a management interface consisting of the following:

- Attributes holding data values representing static or dynamic properties of the resource

- Operations that can be invoked to perform actions on the resource

- Notifications informing the client application of state changes or other significant events affecting the resource

Client applications obtain MBeans through an MBean server, which serves as a container and registry for MBeans. Each Message Queue broker process contains an MBean server, accessed by means of a JMX connector. The JMX connector is used to obtain an MBean server connection, which in turn provides access to individual MBeans on the server. Configuring or monitoring a Message Queue resource with JMX requires the following steps:

1. Obtain a JMX connector.

2. Get an MBean server connection from the JMX connector.

3. Construct an object name identifying the particular MBean you wish to operate on.

4. Pass the object name to the appropriate methods of the MBean server connection to access the MBean's attributes, operations, and notifications.

5. Close the MBean server connection.

See Using the JMX API for code examples illustrating the technique for various MBean operations.

## Message Queue MBeans

Message Queue's JMX functionality is exposed through MBeans associated with various Message Queue resources. These MBeans are of two kinds: resource MBeans and manager MBeans. The attributes, operations, and notifications available for each type of MBean are described in detail in Message Queue MBean Reference.

### Resource MBeans

Resource MBeans are associated with individual Message Queue resources of the following types:

- Message brokers

- Connection services

- Connections

- Destinations

- Broker clusters

- Logging

- The Java Virtual Machine (JVM)

Configuration and monitoring functions are implemented by separate MBeans. Each managed resource is associated with a configuration MBean for setting the resource's configuration and a monitor MBean for gathering (typically transient) information about its runtime state. For instance, there is a destination configuration MBean for configuring a destination and a destination monitor MBean for obtaining runtime information about it. In general, each instance of a managed resource has its own pair of MBeans: thus there is a separate destination configuration MBean and destination monitor MBean for each individual destination. (In the case of the Java Virtual Machine, there is only a JVM monitor MBean with no corresponding configuration MBean.)

Configuration MBeans are used to perform such tasks as the following:

- Set a broker's port number

- Set a broker's maximum message size

- Pause a connection service

- Set the maximum number of threads for a connection service

- Purge all messages from a destination

- Set the level of logging information to be written to an output channel

Monitor MBeans are used to obtain runtime information such as the following:

- The current number of connections on a service

- The cumulative number of messages received by a destination since the broker was started

- The current state (running or paused) of a queue destination

- The current number of message producers for a topic destination

- The host name and port number of a cluster's master broker

- The current JVM heap size

### Manager MBeans

In addition to the resource MBeans associated with individual resources, there are also manager MBeans for managing some whole categories of resources. These manager MBeans also come in pairs—one for configuration and one for monitoring—for the following resource categories:

- Connection services

- Connections

- Destinations

- Message producers

- Message consumers

- Transactions

Unlike individual resource MBeans, a broker has only one pair of manager MBeans for each whole category of resources: for instance, a single destination manager configuration MBean and a single destination manager monitor MBean. For some categories (connection services, connections, destinations), the manager MBeans exist in addition to the ones for individual resources, and are used to manage the collection of resource MBeans within the category or to perform global tasks that are beyond the scope of individual resource MBeans. Thus, for instance, there is a connection manager configuration MBean and a connection manager monitor MBean in addition to the connection configuration and connection monitor MBeans associated with individual connections. Manager MBeans of this type are used to perform tasks such as the following:

- Get the object names of the connection service monitor MBeans for all available connection services

- Get the total number of current connections

- Destroy a connection

- Create or destroy a destination

- Enable or disable auto-creation of destinations

- Pause message delivery for all destinations

In other cases (message producers, message consumers, transactions), there are no MBeans associated with individual resources and all of the resources in the category are managed through the manager MBeans themselves. The manager MBeans for these categories can be used for such tasks as the following:

- Get the destination name associated with a message producer

- Purge all messages from a durable subscriber

- Commit or roll back a transaction

### Object Names

Each individual MBean is designated by an object name belonging to the JMX class `ObjectName`, which encapsulates a string identifying the MBean. For Message Queue MBeans, the encapsulated name string has the following syntax:

`com.sun.messaging.jms.server:`property`=`value`[,`property`=`value`]*`

Table 1-1 shows the possible properties.

Table 1-1 Object Name Properties

Property | Description | Values
--- | --- | ---
`type` | MBean type | See Table 1-2.
`subtype` | MBean subtype | See Table 1-3.
`desttype` | Destination type Applies only to MBeans of the following types: Destination configuration Destination monitor | See Table 1-4.
`name` | Resource name Applies only to MBeans of the following types: Service configuration Service monitor Destination configuration Destination monitor | For service configuration and service monitor MBeans, see Table 1-5. For destination configuration and destination monitor MBeans, the destination name. Examples: `myTopic` `temporary_destination://queue/129.145.180.99/63008/1`
`id` | Resource identifier Applies only to MBeans of the following types: Connection configuration Connection monitor | Example: `7853717387765338368`

Table 1-2 shows the possible values for the object name's `type` property.

Table 1-2 Message Queue MBean Types

Value | Description
--- | ---
`Broker` | Broker resource MBean
`Service` | Connection service resource MBean
`ServiceManager` | Connection service manager MBean
`Connection` | Connection resource MBean
`ConnectionManager` | Connection manager MBean
`Destination` | Destination resource MBean
`DestinationManager` | Destination manager MBean
`ProducerManager` | Message producer manager MBean
`ConsumerManager` | Message consumer manager MBean
`TransactionManager` | Transaction manager MBean
`Cluster` | Broker cluster resource MBean
`Log` | Logging resource MBean
`JVM` | JVM resource MBean

Table 1-3 shows the possible values for the object name's `subtype` property.

Table 1-3 Message Queue MBean Subtypes

Value | Description
--- | ---
`Config` | Configuration MBean
`Monitor` | Monitor MBean

For destination configuration and destination monitor MBeans, the object name's `desttype` property specifies whether the destination is a point-to-point queue or a publish/subscribe topic. Table 1-4 shows the possible values, which are defined for convenience as static constants in the utility class `DestinationType`.

Table 1-4 Destination Types

Value | Utility Constant | Meaning
--- | --- | ---
`q` | `DestinationType``.``QUEUE` | Queue (point-to-point) destination
`t` | `DestinationType``.``TOPIC` | Topic (publish/subscribe) destination

For service configuration and service monitor MBeans, the object name's `name` property identifies the connection service with which the MBean is associated. Table 1-5 shows the possible values.

Table 1-5 Connection Service Names

Service Name | Service Type | Protocol Type
--- | --- | ---
`jms` | Normal | TCP
`ssljms` | Normal | TLS (SSL-based security)
`httpjms` | Normal | HTTP
`httpsjms` | Normal | HTTPS (SSL-based security)
`admin` | Admin | TCP
`ssladmin` | Admin | TLS (SSL-based security)

Table 1-6 shows some example object names.

Table 1-6 Example Object Names

MBean type | Object Name
--- | ---
Broker configuration | `com.sun.messaging.jms.server:type=Broker,subtype=Config`
Service manager monitor | `com.sun.messaging.jms.server:type=ServiceManager,subtype=Monitor`
Connection configuration | `com.sun.messaging.jms.server:type=Connection,subtype=Config,id=7853717387765338368`
Destination monitor | `com.sun.messaging.jms.server:type=Destination,subtype=Monitor,desttype=t,name="MyQueue"`

The object names for each type of Message Queue MBean are given in the relevant sections of Message Queue MBean Reference. All such names are either defined as static constants or returned by static methods in the utility class `MQObjectName` (see Table 1-7). For instance, the constant

    MQObjectName.BROKER_CONFIG_MBEAN_NAME

is defined as a string representing the object name for a broker configuration MBean, and the method call

    MQObjectName. createDestinationMonitor(DestinationType .TOPIC, "MyQueue");

returns the destination monitor MBean object name shown in Table 1-6. Note that, whereas methods such as `createDestinationMonitor` return an actual object name (that is, an object of class `ObjectName`) that can be assigned directly to a variable of that type

    ObjectNamedestMonitorName
    = MQObjectName. createDestinationMonitor(DestinationType .TOPIC, "Dest");

constants like `BROKER_CONFIG_MBEAN_NAME` instead represent an ordinary string (class `String`) that must then be converted into the corresponding object name itself:

    ObjectNamebrokerConfigName
    = new ObjectName(MQObjectName.BROKER_CONFIG_MBEAN_NAME);

Table 1-7 Utility Constants and Methods for Object Names

MBean Type | Utility Constant or Method
--- | ---
Broker configuration | `MQObjectName``.``BROKER_CONFIG_MBEAN_NAME`
Broker monitor | `MQObjectName``.``BROKER_MONITOR_MBEAN_NAME`
Service configuration | `MQObjectName``.``createServiceConfig`
Service monitor | `MQObjectName``.``createServiceMonitor`
Service manager configuration | `MQObjectName``.``SERVICE_MANAGER_CONFIG_MBEAN_NAME`
Service manager monitor | `MQObjectName``.``SERVICE_MANAGER_MONITOR_MBEAN_NAME`
Connection configuration | `MQObjectName``.``createConnectionConfig`
Connection monitor | `MQObjectName``.` `createConnectionMonitor`
Connection manager configuration | `MQObjectName``.``CONNECTION_MANAGER_CONFIG_MBEAN_NAME`
Connection manager monitor | `MQObjectName``.``CONNECTION_MANAGER_MONITOR_MBEAN_NAME`
Destination configuration | `MQObjectName``.` `createDestinationConfig`
Destination monitor | `MQObjectName``.` `createDestinationMonitor`
Destination manager configuration | `MQObjectName``.``DESTINATION_MANAGER_CONFIG_MBEAN_NAME`
Destination manager monitor | `MQObjectName``.``DESTINATION_MANAGER_MONITOR_MBEAN_NAME`
Producer manager configuration | `MQObjectName``.``PRODUCER_MANAGER_CONFIG_MBEAN_NAME`
Producer manager monitor | `MQObjectName``.``PRODUCER_MANAGER_MONITOR_MBEAN_NAME`
Consumer manager configuration | `MQObjectName``.``CONSUMER_MANAGER_CONFIG_MBEAN_NAME`
Consumer manager monitor | `MQObjectName``.``CONSUMER_MANAGER_MONITOR_MBEAN_NAME`
Transaction manager configuration | `MQObjectName``.``TRANSACTION_MANAGER_CONFIG_MBEAN_NAME`
Transaction manager monitor | `MQObjectName``.``TRANSACTION_MANAGER_MONITOR_MBEAN_NAME`
Cluster configuration | `MQObjectName``.``CLUSTER_CONFIG_MBEAN_NAME`
Cluster monitor | `MQObjectName``.``CLUSTER_MONITOR_MBEAN_NAME`
Log configuration | `MQObjectName``.``LOG_CONFIG_MBEAN_NAME`
Log monitor | `MQObjectName``.``LOG_MONITOR_MBEAN_NAME`
JVM monitor | `MQObjectName``.``JVM_MONITOR_MBEAN_NAME`