SCA Java binding.jms

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<binding.jms>

The Tuscany Java SCA runtime supports the Java Messaging Service using the <binding.jms> SCDL extension. New JMS based service endpoints can be provided using a <binding.jms> element within a SCA <service>, existing JMS queues can be accessed using a <binding.jms> element within a SCA <reference>.

The JMS binding is one of the SCA extensions which is being formalized in the OASIS Open Composite Services Architecture with a published specifications document.

Using the JMS binding

The simplest way to use the JMS binding is to use the URI syntax to configure the binding, for example:

<binding.jms uri="jms:RequestQueue"/>

This tells the binding to use a JMS destination named "RequestQueue", with all the other configuration options using default values.

By default Tuscany will use a JMS connection factory named 'ConnectionFactory', this can be changed by using a query parameter in the URI, for example, to use a connection factory named 'myCF' can be done as follows:

<binding.jms uri="jms:RequestQueue?connectionFactoryName=myCF"/>

When using a SCA reference for RPC style requests and no response destination is defined in the SCDL then a temporary replyTo queue will automatically be created and used.

When using the JMS binding with SCA services then the syntax can be simplified even further by letting the destination name default to the service name. For example, the following SCDL snippet creates a JMS service listening on a JMS destination named "MyService":

<service name="MyService">
   <binding.jms />
</service>

Some examples:

HelloWorld

The helloworld-jms sample demonstrates basic RPC style operations over JMS. The sample has one component exposing a JMS service on a queue name 'HelloWorldService' and another component which invokes the service by sending JMS messages to that queue. A temporary destination is used for the response messages. The .composite file for this is shown below, see the sample README for full details.

<composite xmlns="http://www.osoa.org/xmlns/sca/1.0"
           targetNamespace="http://sample"
           xmlns:sample="http://sample"
           name="HelloWorld">

    <component name="HelloWorldClient">
        <implementation.java class="helloworld.HelloWorldClient"/>
        <reference name="helloWorldRef">
            <binding.jms uri="jms:HelloWorldService"/>
        </reference>
    </component>

    <component name="HelloWorldServiceComponent">
        <implementation.java class="helloworld.HelloWorldServiceImpl" />
	<service name="HelloWorldService">
            <binding.jms />
        </service>
    </component>

</composite>

Configuring JMS resources

Tuscany locates all JMS resources from JNDI so the environment where Tuscany is running needs to have JNDI and JMS correctly configured in order to use the Tuscany JMS binding.

All JNDI lookups are first tried in the java:comp/env namespace so when running Tuscany in a JEE environment resource aliases may be used to map Tuscany JMS resources to actual resources.

The following describes how to configure JMS in some common environments:

Tuscany J2SE standalone environment with ActiveMQ

The Tuscany standalone runtime can use an embedded Apache ActiveMQ message broker. To use ActiveMQ the application needs to include the JMS API and ActiveMQ jars in the classpath and include a jndi.properties file to configure the ActiveMQ resources in JNDI.

An example of this can be seen in the Tuscany JMS itest which uses the ActiveMQ 4.1.1 release and this jndi.properties file.

For more information on using ActiveMQ see the Apache ActiveMQ website and specifically this page for information about configuring JNDI resources.

Apache Tomcat

Tomcat does not include a JMS broker by default so you need to either embed one in each application, install a broker into the tomcat installation, or use an external broker. Once that is done JNDI resources can be defined using the standard Tomcat facilities, see the Tomcat JNDI How-to.

The Tuscany samples that use JMS and Tomcat demonstrate how to embed a JMS broker within the application by including ActiveMQ and its dependencies within the sample WAR, and using the META-INF/context.xml file to define the JMS resources in JNDI.

JEE application servers such as Apache Geronimo, WebSphere etc

Using an external JMS broker

When the Tuscany environment does not include a JMS broker then an external broker may be used by specifying the initialContextFactory and jndiURL attributes on the binding.jms element. Any JMS 1.1 compatible broker should work such as Apache ActiveMQ or any other proprietary broker. The Tuscany application classpath will need to include jars for the initial context factory and all of its dependencies.

An example of using the Tuscany JMS binding with an external ActiveMQ broker is as follows:

<binding.jms initialContextFactory="org.apache.activemq.jndi.ActiveMQInitialContextFactory" jndiURL="tcp://localhost:61616">
   <destination name="DestQueueA"/>
</binding.jms>

JMS binding schema

The complete JMS binding SCDL schema has the following format:

<binding.jms correlationScheme="string"?
             initialContextFactory="xs:anyURI"?
             jndiURL="xs:anyURI"?
             requestConnection="QName"?
             responseConnection="QName"?
             operationProperties="QName"?
             ... >

   <destination name="xs:anyURI" type="string"? create="string"?>
      <property name="NMTOKEN" type="NMTOKEN">*
   </destination>?

   <connectionFactory name="xs:anyURI" create="string"?>
      <property name="NMTOKEN" type="NMTOKEN">*
   </connectionFactory>?

   <activationSpec name="xs:anyURI" create="string"?>
      <property name="NMTOKEN" type="NMTOKEN">*
   </activationSpec>?

   <response>
      <destination name="xs:anyURI" type="string"? create="string"?>
         <property name="NMTOKEN" type="NMTOKEN">*
      </destination>?
      <connectionFactory name="xs:anyURI" create="string"?>
         <property name="NMTOKEN" type="NMTOKEN">*
      </connectionFactory>?
      <activationSpec name="xs:anyURI" create="string"?>
         <property name="NMTOKEN" type="NMTOKEN">*
      </activationSpec>?
   </response>?

   <resourceAdapter name="NMTOKEN">?
      <property name="NMTOKEN" type="NMTOKEN">*
   </resourceAdapter>?

   <headers JMSType="string"?
            JMSCorrelationId="string"?
            JMSDeliveryMode="string"?
            JMSTimeToLive="int"?
            JMSPriority="string"?>
      <property name="NMTOKEN" type="NMTOKEN">*
   </headers>?

   <operationProperties name="string" nativeOperation="string"?>
      <property name="NMTOKEN" type="NMTOKEN">*
      <headers JMSType="string"?
               JMSCorrelationId="string"?
               JMSDeliveryMode="string"?
               JMSTimeToLive="int"?
               JMSPriority="string"?>
         <property name="NMTOKEN" type="NMTOKEN">*
      </headers>?
   </operationProperties>*

</binding.jms>

See the JMS Binding Specification 1.0 for full details of each of these configuration options.

Not all these elements are supported by Tuscany. Specifically, the <activationSpec> and <resourceAdapter> elements are not supported as Tuscany does not use JCA or MDBs for its JMS support. Additionally, support for the requestConnection, responseConnection, and operationProperties attributes has not yet been implemented but this should get done shortly.

The create attribute on the destination element is not supported in most environments and all JMS resources (connection factories, queues and topics) need to be pre-configured. An exception to this is when using Apache ActiveMQ as the JMS broker Tuscany may be able to dynamically create queue and topic resources. This is mainly only useful for unit testing and it is recommended that user applications are designed with the expectation that JMS resources need to be preconfigured.

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