These sections briefly review the different WebLogic JMS concepts and features, and describe how they work with other application components and WebLogic Server.
It is assumed the reader is familiar with Java programming and JMS 1.1 concepts and features.
The WebLogic Server implementation of JMS is an enterprise-class messaging system that is tightly integrated into the WebLogic Server platform. It fully supports theand also provides numerous nsions that go beyond the standard JMS APIs.
An enterprise messaging system enables applications to asynchronously communicate with one another through the exchange of messages. A message is a request, report, and/or event that contains information needed to coordinate communication between different applications. A message provides a level of abstraction, allowing you to separate the details about the destination system from the application code.
The Java Message Service (JMS) is a standard API for accessing enterprise messaging systems that is implemented by industry messaging providers. Specifically, JMS:
WebLogic JMS accepts messages from producer applications and delivers them to consumer applications. For more information on JMS API programming with WebLogic Server, see Programming WebLogic JMS.
The following figure illustrates the WebLogic JMS architecture.
The major components of the WebLogic JMS architecture include:
weblogic-jmsmd.xsdschema. For more information, see What Are JMS Configuration Resources?.
In general, the WebLogic Server domain configuration file (
config.xml) contains the configuration information required for a domain. This configuration information can be further classified into environment-related information and application-related information. Examples of environment-related information are the identification and definition of JMS servers, JDBC data sources, WebLogic persistent stores, and server network addresses. These system resources are usually unique from domain to domain.
The configuration and management of these system resources are the responsibility of a WebLogic administrator, who usually receives this information from an organization’s system administrator or MIS department. To accomplish these tasks, an administrator can use the WebLogic Administration Console, various command-line tools, such as WebLogic Scripting Tool (WLST), or JMX APIs for programmatic administration.
Examples of application-related definitions that are independent of the domain environment are the various Java EE application components configurations, such as EAR, WAR, JAR, RAR files, and JMS and JDBC modules. The application components are originally developed and packaged by an application development team, and may contain optional programs (compiled Java code) and respective configuration information (also called descriptors, which are mostly stored as XML files). In the case of JMS and JDBC modules, however, there are no compiled Java programs involved. These pre-packaged applications are given to WebLogic Server administrators for deployment in a WebLogic domain.
The process of deploying an application links the application components to the environment-specific resource definitions, such as which server instances should host a given application component (targeting), and the WebLogic persistent store to use for persisting JMS messages.
Once the initial deployment is completed, an administrator has only limited control over deployed applications. For example, administrators are only allowed to ensure the proper life cycle of these applications (deploy, undeploy, redeploy, remove, etc.) and to tune the parameters, such as increasing or decreasing the number of instances of any given application to satisfy the client needs. Other than life cycle and tuning, any modification to these applications must be completed by the application development team.
In releases prior to WebLogic Server 9.0, all JMS configuration information was stored in a WebLogic domain’s configuration file. In this release, JMS configuration resources, such as queue and topic destinations and connections factories, are stored outside of the WebLogic domain as module descriptor files, which are defined by XML documents that conform to the
weblogic-jmsmd.xsd schema. JMS modules do not include JMS server definitions, which are still stored in the WebLogic domain configuration file, as described in Overview of JMS Servers.
You create and manage JMS resources either as system modules, similar to the way they were managed prior to this release, or as application modules. JMS application modules are a WebLogic-specific extension of Java EE modules and can be deployed either with a Java EE application (as a packaged resource) or as stand-alone modules that can be made globally available. See Overview of JMS Modules.
JMS servers are environment-related configuration entities that act as management containers for destination resources within JMS modules that are targeted to specific JMS servers. A JMS server’s primary responsibility for its targeted destinations is to maintain information on what persistent store is used for any persistent messages that arrive on the destinations, and to maintain the states of durable subscribers created on the destinations. As a container for targeted destinations, any configuration or run-time changes to a JMS server can affect all of its destinations.
JMS servers are persisted in the domain’s
config.xml file and multiple JMS servers can be configured on the various WebLogic Server instances in a cluster, as long as they are uniquely named. Client applications use either the JNDI tree or the
java:/comp/env naming context to look up a connection factory and create a connection to establish communication with a JMS server. Each JMS server handles requests for all targeted modules’ destinations. Requests for destinations not handled by a JMS server are forwarded to the appropriate server instance.
Beginning in WebLogic Server 9.0, JMS server behavior differs in certain respects from behavior in pre-9.0 releases:
For more information on configuring JMS servers, see JMS Server Configuration.
JMS modules are application-related definitions that are independent of the domain environment. You create and manage JMS resources either as system modules or as application modules. JMS system modules are typically configured using the Administration Console or the WebLogic Scripting Tool (WLST), which adds a reference to the module in the domain’s
config.xml file. JMS application modules are a WebLogic-specific extension of Java EE modules and can be deployed either with a Java EE application (as a packaged resource) or as stand-alone modules that can be made globally available.
The main difference between system modules and application modules comes down to ownership. System modules are owned and modified by the WebLogic administrator and are available to all applications. Application modules are owned and modified by the WebLogic developers, who package the JMS resource modules with the application's EAR file.
With modular deployment of JMS resources, you can migrate your application and the required JMS configuration from environment to environment, such as from a testing environment to a production environment, without opening an enterprise application file (such as an EAR file) or a stand-alone JMS module, and without extensive manual JMS reconfiguration.
These sections describe the different types of JMS module and the resources that they can contain:
WebLogic Administrators typically use the Administration Console or the WebLogic Scripting Tool (WLST) to create and deploy (target) JMS modules, and to configure the module’s configuration resources, such as queues, and topics connection factories.
JMS modules that you configure this way are considered system modules. JMS system modules are owned by the Administrator, who can at any time add, modify, or delete resources. System modules are globally available for targeting to servers and clusters configured in the domain, and therefore are available to all applications deployed on the same targets and to client applications.
When you create a JMS system module WebLogic Server creates a JMS module file in the
config\jms subdirectory of the domain directory, and adds a reference to the module in the domain’s
config.xml file as a
JMSSystemResource element. This reference includes the path to the JMS system module file and a list of target servers and clusters on which the module is deployed.
The JMS module conforms to the
weblogic-jmsmd.xsd schema, as described in JMS Schema. System modules are also accessible through WebLogic Management Extension (JMX) utilities, as a
JMSSystemResourceMBean. The naming convention for JMS system modules is MyJMSModule
Figure 2-2 shows an example of a JMS system module listing in the domain’s
config.xml file and the module that it maps to in the
For more information about configuring JMS system modules, see Configuring Basic JMS System Resources.
JMS configuration resources can also be managed as deployable application modules, similar to standard Java EE descriptor-based modules. JMS Application modules can be deployed either with a Java EE application as a packaged module, where the resources in the module are optionally made available to only the enclosing application (i.e., application-scoped), or as a standalone module that provides global access to the resources defined in that module.
Application developers typically create application modules in an enterprise-level IDE or another development tool that supports editing XML descriptor files, then package the JMS modules with an application and pass the application to a WebLogic Administrator to deploy, manage, and tune.
As discussed in Domain Configuration: Environment-Related Resources versus Application-Related Resources, JMS application modules do not contain compiled Java programs as part of the package, enabling administrators or application developers to create and manage JMS resources on demand.
For more information about configuring JMS application modules, see Configuring JMS Application Modules for Deployment.
A key to understanding WebLogic JMS configuration and management is that who creates a JMS resource and how a JMS resource is created determines how a resource is deployed and modified. Both WebLogic administrators and programmers can configure JMS modules:
In contrast to system modules, deployed application modules are owned by the developer who created and packaged the module, rather than the administrator who deploys the module, which means the administrator has more limited control over deployed resources. When deploying an application module, an administrator can change resource properties that were specified in the module, but the administrator cannot add or delete resources. As with other Java EE modules, deployment configuration changes for a application module are stored in a deployment plan for the module, leaving the original module untouched.
Table 2-1 lists the JMS module types and how they can be configured and modified.
For more information about preparing JMS application modules for deployment, see Configuring JMS Application Modules for Deploymentandin Deploying Applications to WebLogic Server.
The following configuration resources are defined as part of a system module or an application module:
All other JMS environment-related resources must be configured by the administrator as domain configuration resources. This includes:
For more information about configuring JMS system modules, see Configuring Basic JMS System Resources.
In support of the modular configuration model for JMS resources, BEA provides a schema for WebLogic JMS objects:
jmsmd stands for JMS module descriptor. When you create JMS resource modules (descriptors), the modules must conform to the schema. IDEs and other tools can validate JMS resource modules based on this schema.
weblogic-jmsmd.xsd schema is available online at http://www.bea.com/ns/weblogic/920/weblogic-jmsmd.xsd.
A JMS interop module is a special type of JMS system resource module. It is created and managed as a result of a JMS configuration upgrade for this release, and/or through the use of WebLogic JMX MBean APIs from prior releases.
JMS interop modules differ in many ways from JMS system resource modules, as follows.
interop-jms.xmland the file exists in the domain’s
JMSInteropModuleMBean, which is a child MBean of
DomainMBean, and can be looked up from
DomainMBeanlike any other child MBean in a domain.
A JMS interop module can also implement many of the WebLogic Server 9.0 or later features, such as message unit-of-order and destination quota. However, it cannot implement the following WebLogic Server 9.0 or later features:
|Caution:||Use of any new features in the current release in a JMS interop module may possibly break compatibility with JMX clients prior to WebLogic Server 9.0.|
These environment-related resources must be configured by the administrator as domain configuration resources in order to be accessible to JMS Servers and JMS modules.
The WebLogic Persistent Store provides a built-in, high-performance storage solution for all subsystems and services that require persistence. For example, it can store persistent JMS messages or temporarily store messages sent using the Store-and-Forward feature. Each WebLogic Server instance in a domain has a default persistent store that requires no configuration and which can be simultaneously used by subsystems that prefer to use the system’s default storage. However, you can also configure a dedicated file-based store or JDBC database-accessible store to suit your JMS implementation. For more information on configuring a persistent store for JMS, seein Configuring WebLogic Server Environments.
The SAF service enables WebLogic Server to deliver messages reliably between applications that are distributed across WebLogic Server instances. For example, with the SAF service, an application that runs on or connects to a local WebLogic Server instance can reliably send messages to a destination that resides on a remote server. If the destination is not available at the moment the messages are sent, either because of network problems or system failures, then the messages are saved on a local server instance, and are forwarded to the remote destination once it becomes available.
JMS modules utilize the SAF service to enable local JMS message producers to reliably send messages to remote JMS queues or topics. For more information, seein Configuring and Managing WebLogic Store-and-Forward.
The WebLogic Server Path Service is a persistent map that can be used to store the mapping of a group of messages to a messaging resource by pinning messages to a distributed queue member or store-and-forward path. For more information on configuring a path service, see Using the WebLogic Path Service.
The Messaging Bridge allows you to configure a forwarding mechanism between any two messaging products, providing interoperability between separate implementations of WebLogic JMS, or between WebLogic JMS and another messaging product. The messaging bridge instances and bridge source and target destination instances are persisted in the domain’s
config.xml file. For more information, see in Configuring and Managing WebLogic Messaging Bridge.