{section}
{column}
h1. Features

The Petals JMS component can be used to interact with an external JMS application or server (through a queue or a topic).
When used with the provider role, it allows to post TextMessages to a JMS queue or topic.
When used with the consumer role, it allows to read messages from a queue or receive messages posted on a given topic.
{column}

{column:width=35%}
{panel:title=Table of contents}{toc}{panel}
{panel:title=Contributors}{contributors:order=name|mode=list}{panel}
{column}
{section}

h1. Recommended Usage

This component should be used whenever interactions with a JMS server or application is required.
This component needs a driver (also called a shared library in Petals) so that Petals can interact with the JMS application. This shared library generally contains the JNDI classes, as a JNDI is used to enable communications between both servers.

\\
{note}* Only JMS TextMessage are recognized by the Petals JMS component.
* With the version 3.0, only XML messages can be published and received from a JMS application.
* In Petals, the invoked service operation is mapped to the _operation_ property of the JMS _TextMessage_ (both in consumming and providing mode).
{note}

\\
{note}If you use ActiveMQ as a JMS server, be careful.
ActiveMQ (AMQ) does not provide a complete JNDI server, which results in limitations with Petals.

* There is no problem with AMQ if you rely on dynamic queues and topics (ActiveMQ's specific mechnaism).
* For static queues and topics, there are two solutions.
** Use a separate JNDI server and configure both Petals and ActiveMQ to use it.
** Rely on AMQ's limited JNDI but upgrade the Petals JMS component (meaning it has to be patched).
The patch consist in putting additional properties in the initial context. See [this discussion|http://jira.petalslink.com/browse/PETALSBCJMS-15] for more information.
{note}

h1. Sending a message to a JMS Queue

This use case is similar to [publishing a message on a JMS topic|#Publishing-a-message-to-a-JMS-Topic].

h1. Publishing a message to a JMS Topic

{center}!petals-bc-jms_provide_service.png|width=600px!{center}

h2. Usage

To do that with Petals, you have to create a service associated with the Petals JMS component.
This is achieved by creating a service unit whose jbi.xml contains a *provides* section. When deployed in Petals, the Petals JMS component will emulate a service. When this service is invoked, the received message will be posted as a _TextMessage_ on the topic defined in the service unit configuration.

{note}* All the MEP are allowed. However, due to the JMS paradigm, all exchanges are processed like *InOnly* exchanges. For exemple, an InOut exchange returns a default message if the JMS message is sent succesfully.
* The external Queue or Topic referenced by the Service Unit does not have to be available before the Service Unit is started. But the JNDI server where Queue or Topic are registered must be available before the Service Unit deployment.
* Properties from the Petals message are automatically converted to JMS message properties.
{note}

h2. Configuration

h3. Service Unit descriptor

The Service Unit descriptor file ( jbi.xml ) looks like this:

{code:lang=xml}<?xml version="1.0" encoding="UTF-8"?>
<!--
JBI descriptor for the Petals' "petals-bc-jms" component (JMS).
Originally created for the version 3.1 of the component.
-->
<jbi:jbi version="1.0"
xmlns:generatedNs="http://petals.ow2.org"
xmlns:jbi="http://java.sun.com/xml/ns/jbi"
xmlns:jms="http://petals.ow2.org/components/jms/version-3"
xmlns:petalsCDK="http://petals.ow2.org/components/extensions/version-5"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

<!-- Import a Service into Petals or Expose a Petals Service => use a BC. -->
<jbi:services binding-component="true">

<!-- Import a Service into Petals => provides a Service. -->
<jbi:provides
interface-name="generatedNs:itf"
service-name="generatedNs:srv"
endpoint-name="srvEndpoint">

<!-- CDK specific elements -->
<petalsCDK:timeout>30000</petalsCDK:timeout>
<petalsCDK:validate-wsdl>true</petalsCDK:validate-wsdl>
<petalsCDK:forward-security-subject>false</petalsCDK:forward-security-subject>
<petalsCDK:forward-message-properties>false</petalsCDK:forward-message-properties>
<petalsCDK:forward-attachments>false</petalsCDK:forward-attachments>
<petalsCDK:wsdl xsi:nil="true" />

<!-- Component specific elements -->
<jms:jndi-provider-url>tcp://localhost:61616</jms:jndi-provider-url>
<jms:jndi-initial-context-factory>org.apache.activemq.jndi.ActiveMQInitialContextFactory</jms:jndi-initial-context-factory>
<jms:jndi-destination-name>dynamicQueues/PetalsQueue</jms:jndi-destination-name>
<jms:jndi-connection-factory>QueueConnectionFactory</jms:jndi-connection-factory>
<jms:transacted>false</jms:transacted>
<jms:max-active>10</jms:max-active>
<jms:max-idle>5</jms:max-idle>
<jms:max-wait>10000</jms:max-wait>
<jms:time-between-eviction-runs-millis>30000</jms:time-between-eviction-runs-millis>
<jms:min-evictable-idle-time-millis>600000</jms:min-evictable-idle-time-millis>
<jms:test-while-idle>true</jms:test-while-idle>
</jbi:provides>
</jbi:services>
</jbi:jbi>{code}

\\
{center}{*}Service Unit attributes to provide services*{center}
{table-plus:columnAttributes=,,style="text-align:center;",style="text-align:center;",style="text-align:center;"}

|| {color:#333333}Parameter{color} || {color:#333333}Description{color} || {color:#333333}Default{color} || {color:#333333}Required{color} ||
| provides | Name of the JBI service that will be activated to expose the JMS destination into the JBI environment. Interface (qname), service (qname) and endpoint (string) name are required. | \- | Yes |
| address | Address composed of the URL provider (JNDI access) | \- | Yes |
| destination-name | The JMS destination name where messages will be sent (Queue or Topic JNDI name) | \- | Yes |
| initial-context-factory | The initial-context-factory class name, used to create an InitalContext. | \- | Yes |
| connection-factory | name of the JMS ConnectionFactory registered. | \- | Yes |
| user | User name to access the JMS Destination. | "" | Yes |
| password | Password to access the JMS Destination. | "" | Yes |
| transacted | JMS communication transacted mode. true or false. | false | Yes |
| max-active | Controls the maximum number of JMS connections that can be borrowed from the pool at one time. When non-positive, there is no limit to the number of connections that may be active at one time. When maxActive is exceeded, the pool is said to be exhausted. | 10 | No |
| max-idle | Controls the maximum number of JMS connections that can sit idle in the pool at any time. When negative, there is no limit to the number of connections that may be idle at one time. | 5 | No |
| max-wait | If a positive maxWait value is supplied, the JMS component will wait for at most that many milliseconds to retrieve an available JMS connection. If maxWait is non-positive, the component will wait indefinitely. | 10000 | No |
| time-between-eviction-runs-millis | Indicates how long the eviction thread should sleep before "runs" of examining idle connections. When non-positive, no eviction thread will
be launched. | 10000 | No |
| min-evictable-idle-time-millis | Specifies the minimum amount of time that a connection may sit idle in the pool before it is eligable for eviction due to idle time. When non-positive,
no connections will be dropped from the pool due to idle time alone. | 2000 | No |
| test-while-idle | Indicates whether or not idle connections should be validated. Connections that fail to validate will be dropped from the pool. | true | No |

{table-plus}

{center}{*}Advanced configuration of Service Unit (provides elements)*{center}
{table-plus:columnAttributes=,,style="text-align:center;",style="text-align:center;",style="text-align:center;"}

|| {color:#333333}Parameter{color} || {color:#333333}Description{color} || {color:#333333}Default{color} || {color:#333333}Required{color} ||
| wsdl | Path to a wsdl file describing services and operations offered by an endpoint activated by the SU. This extension is only usable with provides fields. \\
The path can be a url "http" or "file" or relative to the r oot directory of the SU archive. Ex: "file:///user/ofabre/test.wsdl" or "/WSDL/test.wsdl". \\
If no wsdl path is specified, a simplified description will automaticaly be written by the CF. | \- | No |

{table-plus}

h3. Service Unit content

The Service Unit has to contain the following elements, packaged in an archive:
* The META-INF/jbi.xml descriptor file, has described above
* An optional WSDL file describing the related service.

{code}
service-unit.zip
+ META-INF
- jbi.xml (as defined above)
- service.wsdl (optional)
{code}

h1. Consuming a message from a JMS Queue

This use case is similar to [subscribing to a JMS topic|#Subscribing-to-a-JMS-Topic].

h1. Subscribing to a JMS Topic

{center}!petals-bc-jms-consume_service.png|width=600px!{center}
{center}_Consumes a JBI service on JMS message_{center}

h2. Usage

The Petals JMS component can listen to an external JMS Queue or JMS Topic.
When it receives a message, it creates a Petals message and sends to a Petals service (we say that the component consumes the JBI service). This service is specified in the Service Unit.

{note}
* All MEP are allowed. But, due to the JMS paradigm, all exchanges are processed like *InOnly* exchanges.
* The external Queue or Topic referenced by the Service Unit has to be available before you start the Service Unit.
{note}

h2. Configuration

h3. Service Unit Descriptor

The Service Unit descriptor file ( jbi.xml ) looks like this:

{code}<?xml version="1.0" encoding="UTF-8"?>
<!--
JBI descriptor for the Petals' "petals-bc-jms" component (JMS).
Originally created for the version 3.1 of the component.
-->
<jbi:jbi version="1.0"
xmlns:generatedNs="http://petals.ow2.org"
xmlns:jbi="http://java.sun.com/xml/ns/jbi"
xmlns:jms="http://petals.ow2.org/components/jms/version-3"
xmlns:petalsCDK="http://petals.ow2.org/components/extensions/version-5"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

<!-- Import a Service into Petals or Expose a Petals Service => use a BC. -->
<jbi:services binding-component="true">

<!-- Expose a Petals Service => consumes a Service. -->
<jbi:consumes
interface-name="generatedNs:itf"
service-name="generatedNs:srv"
endpoint-name="srvEndpoint">

<!-- CDK specific elements -->
<petalsCDK:timeout>30000</petalsCDK:timeout>
<petalsCDK:operation xmlns:wedontcareNs="http://something">wedontcareNs:wedontcare</petalsCDK:operation>
<petalsCDK:mep>InOnly</petalsCDK:mep>

<!-- Component specific elements -->
<jms:jndi-provider-url>tcp://localhost:61616</jms:jndi-provider-url>
<jms:jndi-initial-context-factory>org.apache.activemq.jndi.ActiveMQInitialContextFactory</jms:jndi-initial-context-factory>
<jms:jndi-destination-name>dynamicTopics/PetalsTopic</jms:jndi-destination-name>
<jms:jndi-connection-factory>ConnectionFactory</jms:jndi-connection-factory>
<jms:transacted>false</jms:transacted>
</jbi:consumes>
</jbi:services>
</jbi:jbi>{code}

{center}{*}Service Unit attributes to consume services*{center}
{table-plus:columnAttributes=,,style="text-align:center;",style="text-align:center;",style="text-align:center;"}

|| {color:#333333}Parameter{color} || {color:#333333}Description{color} || {color:#333333}Default{color} || {color:#333333}Required{color} ||
| consumes | Name of the JBI service that will be called into the JBI environment. When a JMS message is received. Only the interface (qname) name can be provided (the container will choose a ServiceEndpoint for this interface), or you can only set service (qname) and endpoint (string) names, without the interface name. | \- | Yes |
| address | Address composed of the URL provider (JNDI access) and the destination name to listen to | \- | Yes |
| destination-name | The JMS destination name where messages will be sent (Queue or Topic JNDI name) | \- | Yes |
| initial-context-factory | The initial-context-factory class name, used to create an InitalContext. | \- | Yes |
| connection-factory | name of the JMS ConnectionFactory registered. | \- | Yes |
| user | User name to access the JMS Destination. | "" | Yes |
| password | Password to access the JMS Destination. | "" | Yes |
| transacted | JMS communication transacted mode. true or false. | false | No |
| operation | JMS operation property. | \- | Yes |
{table-plus}

Extra attributes:

{center}{*}Advanced configuration of Service Unit (consumes elements)*{center}
{table-plus:columnAttributes=,,style="text-align:center;",style="text-align:center;",style="text-align:center;"}

|| {color:#333333}Parameter{color} || {color:#333333}Description{color} || {color:#333333}Default{color} || {color:#333333}Required{color} ||
| mep | Message exchange pattern abbreviation. This parameter can be used in conjunction with a method of the Listeners: createMessageExchange(Extensions extensions). This method returns
a MessageExchange corresponding to the type of the specified pattern. \\
Admitted values are: {{InOnly}}, {{RobustInOnly}}, {{InOptionalOut}}, {{InOut}}. | \- | Yes |
| operation | Operation to call on a service. This parameter can be used in conjuntcion
with the sendXXX methods of the Listeners. If no operation is specified in the MessageExchange to send, this parameter will be used. | \- | Yes |
| timeout | Timeout in milliseconds in a synchroneous send. This parameter can be used in conjunction with the *sendSync(MessageExchange exchange)* method of the Listeners. With this, a synchroneous send is done with this timeout value. \\
0 for no timeout. \\
int number >= 0 for a timeout. | \- | No |
| operation | JMS operation property. | \- | Yes |
{table-plus}

h3. Service Unit content

The Service Unit has to contain the following elements, packaged in an archive:
* The META-INF/jbi.xml descriptor file, has described above

{code}
service-unit.zip
+ META-INF
- jbi.xml (as defined above)
{code}

h1. Monitoring the component

h2. Using metrics

Several probes providing metrics are included in the component, and are available through the JMX MBean '{{org.ow2.petals:type=custom,name=monitoring_*<component-id>*}}', where {{*<component-id>*}} is the unique JBI identifier of the component.

h3. Common metrics

{include:0 CDK Component Monitoring Metrics 5.6.0}

h3. Dedicated metrics

No dedicated metric is available.

h2. Receiving alerts

Several alerts are notified by the component through notification of the JMX MBean '{{org.ow2.petals:type=custom,name=monitoring_*<component-id>*}}', where {{*<component-id>*}} is the unique JBI identifier of the component.

{tip}To integrate these alerts with Nagios, see [petalsesbsnapshot:Receiving Petals ESB defects in Nagios].{tip}

No dedicated alert is available.