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From conflue...@apache.org
Subject [CONF] Apache Tuscany: SCA Java binding.jms (page edited)
Date Fri, 29 Aug 2008 07:08:00 GMT
SCA Java binding.jms (TUSCANY) edited by ant
      Page: http://cwiki.apache.org/confluence/display/TUSCANY/SCA+Java+binding.jms
   Changes: http://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=57033&originalVersion=34&revisedVersion=35


{include: SCA Java Subproject Menu}
{include: Java SCA Menu New}

h3. <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 |http://www.oasis-opencsa.org/sca-bindings]

(on) Not all function described here as been included in a Tuscany release yet. It will be
included in the next Tuscany SCA release.

h4. Using the JMS binding

The simplest way to use the JMS binding is to use the URI syntax to configure the binding,
for example:
{code}<binding.jms uri="jms:RequestQueue"/>{code}
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:
{code}<binding.jms uri="jms:RequestQueue?connectionFactoryName=myCF"/>{code}

(on) 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 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 />

h3. Some examples:

h4. HelloWorld

The [helloworld-jms|https://svn.apache.org/repos/asf/incubator/tuscany/java/sca/samples/helloworld-jms-webapp/]
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 helloworld sample [README|https://svn.apache.org/repos/asf/incubator/tuscany/java/sca/samples/helloworld-jms-webapp/README]
for full details.

<composite xmlns="http://www.osoa.org/xmlns/sca/1.0"

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

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


h3. Using SCA callbacks with the JMS binding

The Tuscany JMS binding supports using SCA callbacks for creating asynchronous clients and

This is done by using a <callback> element in the SCDL for the service or reference
as shown in the following example. 
See the [callbacks-jms|https://svn.apache.org/repos/asf/tuscany/java/sca/samples/callbacks-jms/]
sample for a complete example of using callbacks

<composite xmlns="http://www.osoa.org/xmlns/sca/1.0"

    <component name="ClientComponent">
        <implementation.java class="callbacks.OrderServiceClient" />
        <reference name="orderService" target="ServiceComponent/OrderService">
            <binding.jms uri="jms:OrderService"/>
                <binding.jms />

    <component name="ServiceComponent">
        <implementation.java class="callbacks.OrderServiceImpl" />
        <service name="OrderService">
            <binding.jms />
                <binding.jms />


(on) When no destination is defined on the callback binding of a <reference> then a
JMS temporary queue will be used.

h3. Setting JMS headers and user properties

JMS headers and user properties can be set on JMS messages sent from Tuscany by using the
<Headers> and <OperationProperties> elements of the JMS binding. The <Headers>
element applies to all messages, the <OperationProperties> applies to individual operations
and may override values set on the <Headers> element.

An example of using these is shown in the following snippet of SCDL:
<binding.jms uri="jms:ServiceQueue">
    <headers JMSType="someTypeValue" />
    <operationProperties name="op2">
        <headers JMSType="op2SpecificTypeValue" />

A complete working example of using <Headers> and <OperationProperties> can be
seen in the [properties itest | https://svn.apache.org/repos/asf/tuscany/java/sca/itest/jms/src/test/java/org/apache/tuscany/sca/binding/jms/PropertiesTestCase.java]

h3. Using JMS message selectors 

Services using the JMS binding to receive messages may only want a subset of the messages
arriving on a queue or topic. This can be done by using the <SubscriptionHeaders> element
which enables defining a [JMS message selector | http://java.sun.com/j2ee/1.4/docs/tutorial/doc/JMS4.html#wp79281]
to filter the messages that will be received.   

An example of using these is shown in the following snippet of SCDL:
<binding.jms uri="jms:ServiceTopic" >
    <SubscriptionHeaders JMSSelector="JMSType = 'type1'"/>

A complete working example of using <SubscriptionHeaders> can be seen in the [jms selectors
itest | https://svn.apache.org/repos/asf/tuscany/java/sca/itest/jms-selectors].

h3. Using a definitions.xml file and the requestConnection/responseConnection attributes

It can be useful to define the details of the JMS resources separately from the SCA composite,
to support this the SCA definitions.xml file can be used to define 'model' <binding.jms>
elements which can then be referred to from the binding within the composite.  

For example, the following shows a definitions.xml file defining a JMS queue and connection
factory which are then used by a JMS binding within a composite.

The definitions.xml file:
<definitions xmlns="http://www.osoa.org/xmlns/sca/1.0"
             targetNamespace="http://jms" >

    <binding.jms name="itest:TestService" >
        <destination name="MyServiceQueue" create="never"/>
        <connectionFactory name="MyConnectionFactory"/>


and a binding which uses the definitions.xml binding:
{code}<binding.jms requestConnection="itest:TestService" />{code}

A complete working example of using the requestConnection/responseConnection attributes can
be seen in the [jms definitions itest | https://svn.apache.org/repos/asf/tuscany/java/sca/itest/jms-definitions].

h3. 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. 

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

h4. Tuscany J2SE standalone environment with ActiveMQ

The Tuscany standalone runtime can use an embedded [Apache ActiveMQ|http://activemq.apache.org/]
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|https://svn.apache.org/repos/asf/tuscany/java/sca/itest/jms/]
which uses the [ActiveMQ 4.1.1|http://repo1.maven.org/maven2/org/apache/activemq/activemq-core/4.1.1/activemq-core-4.1.1.jar]
release and [this|https://svn.apache.org/repos/asf/tuscany/java/sca/itest/jms/src/main/resources/jndi.properties]
jndi.properties file. 

For more information on using ActiveMQ see the Apache ActiveMQ website and specifically [this|http://activemq.apache.org/jndi-support.html]
page for information about configuring JNDI resources. 

h4. Apache Tomcat

Tomcat does not include a JMS broker by default so you need to either embed one in each Tuscany
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|http://tomcat.apache.org/tomcat-6.0-doc/jndi-resources-howto.html]. 

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
webapp META-INF/context.xml file to define the JMS resources in JNDI. 

h4. JEE application servers such as Apache Geronimo, WebSphere etc

JEE Application servers such as Geronimo, WebSphere, WebLogic etc come with their own JMS
broker that can be used by Tuscany. All the JMS resources used by a Tuscany application must
be manually defined in the application server. Usually the application server has some sort
of admin console where the resources can be defined using a web browser. 

The Tuscany helloworld JMS sample [README|https://svn.apache.org/repos/asf/tuscany/java/sca/samples/helloworld-jms-webapp/README]
describes the specific details of how to do this for some common application servers.

{note:title=ClassCastExceptions when using Tuscany applications in an Application Server}
Tuscany applications, specifically the JMS samples, are built to work out of-the-box on Tomcat
by including a JMS broker embedded within the application. This causes incompatibilities with
some Application Servers because the Java class of JMS resources may use different class loaders
in the server and the application. The solution is to delete any JMS API jar included in the
application WAR, for example, the geronimo-jms_1.1_spec-1.1.jar.   

h4. (/) Using JEE resource references

When running Tuscany in a JEE environment it can be useful to use JEE resource references
to map local application resource names to global JNDI names. This can be done by using <resource-ref>
elements in the application deployment descriptor. If a <resource-ref> exists for a
JMS binding resource then Tuscany will use that instead of looking up the resource directly
in the global JNDI.

For example, adding the following definitions to the helloworld JMS sample [web.xml|https://svn.apache.org/repos/asf/incubator/tuscany/java/sca/samples/helloworld-jms-webapp/src/main/webapp/WEB-INF/web.xml]
will enable mapping the 'ConnectionFactory' and 'HelloWorldService' names used by the JMS
binding into names for the actual resources used on the Application Server. This will normally
occur when the application is dployed with the deploy tool asking what real resource names
the resourecs should be mapped to.


h4. 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"
   <destination name="DestQueueA"/>

h4. Using the WebSphere client for JMS

The Tuscany JMS binding now (post Tuscany SCA 1.2) works the [WebSphere client for JMS | http://www-1.ibm.com/support/docview.wss?uid=swg24012804]
which enables Tuscany applications running outside of WebSphere to use JMS resources defined
within WebSphere. You need to include the JMS client jars in the Tuscany classpath and ensure
that the JMS connection factory has the "endpoint providers" field configured in WebSphere.
See this [email thread | http://apache.markmail.org/message/qufruqdwxuvaagev] for more information.

h3. JMS Message types and message body format

The SCA JMS specification only defines how to use JMS TextMessages which contain XML in the
message body, however it is a common requirement to use alternative message types and body
formats. Currently Tuscany defines an additional "messageProcessor" attribute on the binding.jms
element to support additional message types and payload formats. For the time being this should
be considered an interim solution which will be changed in future Tuscany releases.

The messageProcessor attribute value may be "XMLTextMessage", "TextMessage", "ObjectMessage",
or the name of a Java class that implements the org.apache.tuscany.sca.binding.jms.provider.JMSMessageProcessor
interface. For example:

<reference name="serviceA" promote="HelloWorldClient/serviceA">
    <binding.jms messageProcessor="my.TestMessageProcessor" />

For a complete example of using the messageProcessor attribute see the [MessageProcessorTestCase|https://svn.apache.org/repos/asf/tuscany/java/sca/itest/jms/src/test/java/org/apache/tuscany/sca/binding/jms/MessageProcessorTestCase.java]

h3. JMS binding schema

The complete JMS binding SCDL schema has the following format:

<binding.jms correlationScheme="string"?
             ... >

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

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

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

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

   <complexType name="SubscriptionHeaders"> 
      <attribute name="JMSSelector" type="string"/> 

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

   <headers JMSType="string"?
      <property name="NMTOKEN" type="NMTOKEN">*

   <operationProperties name="string" nativeOperation="string"?>
      <headers JMSType="string"?
         <property name="NMTOKEN" type="NMTOKEN">*


(?) See the [JMS Binding Specification 1.0|http://www.osoa.org/download/attachments/35/SCA_JMSBinding_V100.pdf?version=2]
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.

(!) 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 then 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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