components/camel-jms/src/main/docs/jms-component.adoc

= JMS Component
:doctitle: JMS
:shortname: jms
:artifactid: camel-jms
:description: Sent and receive messages to/from a JMS Queue or Topic.
:since: 1.0
:supportlevel: Stable
:tabs-sync-option:
:component-header: Both producer and consumer are supported
//Manually maintained attributes
:camel-spring-boot-name: jms

*Since Camel {since}*

*{component-header}*

This component allows messages to be sent to (or consumed from) a
http://java.sun.com/products/jms/[JMS] Queue or Topic. It uses Spring's
JMS support for declarative transactions, including Spring's
`JmsTemplate` for sending and a `MessageListenerContainer` for
consuming.

Maven users will need to add the following dependency to their `pom.xml`
for this component:

[source,xml]
------------------------------------------------------------
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-jms</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>
------------------------------------------------------------

[TIP]
====
*Using ActiveMQ*

If you are using http://activemq.apache.org/[Apache ActiveMQ], you
should prefer the ActiveMQ component as it has been
optimized for ActiveMQ. All the options and
samples on this page are also valid for the ActiveMQ
component.
====

[NOTE]
====
*Transacted and caching*

See section _Transactions and Cache Levels_ below if you are using
transactions with xref:jms-component.adoc[JMS] as it can impact performance.
====

[NOTE]
====
*Request/Reply over JMS*

Make sure to read the section _Request-reply over JMS_ further below on
this page for important notes about request/reply, as Camel offers a
number of options to configure for performance, and clustered
environments.
====

== URI format

--------------------------------------------
jms:[queue:|topic:]destinationName[?options]
--------------------------------------------

Where `destinationName` is a JMS queue or topic name. By default, the
`destinationName` is interpreted as a queue name. For example, to
connect to the queue, `FOO.BAR` use:

-----------
jms:FOO.BAR
-----------

You can include the optional `queue:` prefix, if you prefer:

-----------------
jms:queue:FOO.BAR
-----------------

To connect to a topic, you _must_ include the `topic:` prefix. For
example, to +
 connect to the topic, `Stocks.Prices`, use:

-----------------------
jms:topic:Stocks.Prices
-----------------------

You append query options to the URI by using the following format,
`?option=value&option=value&...`

== Notes

=== Using ActiveMQ

The JMS component reuses Spring 2's `JmsTemplate` for sending messages.
This is not ideal for use in a non-J2EE container and typically requires
some caching in the JMS provider to avoid
http://activemq.apache.org/jmstemplate-gotchas.html[poor performance].

If you intend to use http://activemq.apache.org/[Apache ActiveMQ] as
your message broker, the recommendation is that you do one of the
following: 

* Use the ActiveMQ component, which is already
optimized to use ActiveMQ efficiently
* Use the `PoolingConnectionFactory` in ActiveMQ.

=== Transactions and Cache Levels

If you are consuming messages and using transactions
(`transacted=true`) then the default settings for cache level can impact
performance.

If you are using XA transactions, then you cannot cache as it can cause
the XA transaction to not work properly.

If you are *not* using XA, then you should consider caching as it speeds
up performance, such as setting `cacheLevelName=CACHE_CONSUMER`.

The default setting for `cacheLevelName` is
`CACHE_AUTO`. This default auto-detects the mode and sets the cache
level accordingly to:

* `CACHE_CONSUMER` if `transacted=false`
* `CACHE_NONE` if `transacted=true`

So you can say the default setting is conservative. Consider using
`cacheLevelName=CACHE_CONSUMER` if you are using non-XA transactions.

=== Durable Subscriptions

==== Durable Subscriptions with JMS 2.0

If you wish to use durable topic subscriptions, you need to specify the `durableSubscriptionName`.

==== Durable Subscriptions with JMS 1.1

If you wish to use durable topic subscriptions, you need to specify both
`clientId` and `durableSubscriptionName`. The value of the `clientId`
must be unique and can only be used by a single JMS connection instance
in your entire network.

[NOTE]
====
If you are using the https://activemq.apache.org/components/classic/[Apache ActiveMQ Classic] or https://activemq.apache.org/components/artemis/[Apache ActiveMQ Artemis],
you may prefer to use a feature called Virtual Topic. This should remove the necessity of having a unique `clientId`.

You can consult the specific documentation for https://activemq.apache.org/components/artemis/migration-documentation/VirtualTopics.html[Artemis]
or for https://activemq.apache.org/virtual-destinations.html[ActiveMQ Classic] for details about how to leverage this feature.

You can find more details about durable messaging for ActiveMQ Classic http://activemq.apache.org/how-do-durable-queues-and-topics-work.html[here].
====

=== Message Header Mapping

When using message headers, the JMS specification states that header
names must be valid Java identifiers. So try to name your headers to be
valid Java identifiers. One benefit of doing this is that you can then
use your headers inside a JMS Selector (whose SQL92 syntax mandates Java
identifier syntax for headers).

A simple strategy for mapping header names is used by default. The
strategy is to replace any dots and hyphens in the header name as shown
below and to reverse the replacement when the header name is restored
from a JMS message sent over the wire. What does this mean? No more
losing method names to invoke on a bean component, no more losing the
filename header for the File Component, and so on.

The current header name strategy for accepting header names in Camel is
as follows:

* Dots are replaced by `\_DOT_` and the replacement is reversed when
Camel consume the message
* Hyphen is replaced by `\_HYPHEN_` and the replacement is reversed when
Camel consumes the message

You can configure many different properties on the JMS endpoint, which
map to properties on the `JMSConfiguration` object. 

[WARNING]
====
*Mapping to Spring JMS*

Many of these properties map to properties on Spring JMS, which Camel
uses for sending and receiving messages. So you can get more information
about these properties by consulting the relevant Spring documentation.
====


// component-configure options: START

// component-configure options: END

// component options: START
include::partial$component-configure-options.adoc[]
include::partial$component-endpoint-options.adoc[]
// component options: END

// endpoint options: START

// endpoint options: END

// component headers: START
include::partial$component-endpoint-headers.adoc[]
// component headers: END

== Samples

JMS is used in many examples for other components as well. But we
provide a few samples below to get started.

=== Receiving from JMS

In the following sample, we configure a route that receives JMS messages
and routes the message to a POJO:

[source,java]
--------------------------------
from("jms:queue:foo").
   to("bean:myBusinessLogic");
--------------------------------

You can use any of the EIP patterns so the route can be
context based. For example, here's how to filter an order topic for the
big spenders:

[source,java]
----------------------------------------------
from("jms:topic:OrdersTopic").
  filter().method("myBean", "isGoldCustomer").
  to("jms:queue:BigSpendersQueue");
----------------------------------------------

=== Sending to JMS

In the sample below, we poll a file folder and send the file content to a
JMS topic. As we want the content of the file as a `TextMessage` instead
of a `BytesMessage`, we need to convert the body to a `String`:

[source,java]
------------------------------
from("file://orders").
  convertBodyTo(String.class).
  to("jms:topic:OrdersTopic");
------------------------------

=== Using Annotations

Camel also has annotations, so you can use xref:manual::pojo-consuming.adoc[POJO Consuming] and xref:manual::pojo-producing.adoc[POJO Producing].

=== Spring DSL sample

The preceding examples use the Java DSL. Camel also supports Spring XML
DSL. Here is the big spender sample using Spring DSL:

[source,xml]
---------------------------------------------------
<route>
  <from uri="jms:topic:OrdersTopic"/>
  <filter>
    <method ref="myBean" method="isGoldCustomer"/>
    <to uri="jms:queue:BigSpendersQueue"/>
  </filter>
</route>
---------------------------------------------------

=== Other samples

JMS appears in many of the examples for other components and EIP
patterns, as well in this Camel documentation. So feel free to browse
the documentation. 

=== Using JMS as a Dead Letter Queue storing Exchange

Normally, when using xref:jms-component.adoc[JMS] as the transport, it only
transfers the body and headers as the payload. If you want to use
xref:jms-component.adoc[JMS] with a xref:eips:dead-letter-channel.adoc[Dead Letter
Channel], using a JMS queue as the Dead Letter Queue, then normally the
caused Exception is not stored in the JMS message. You can, however, use
the `transferExchange` option on the JMS dead letter queue to instruct
Camel to store the entire Exchange in the queue as a
`javax.jms.ObjectMessage` that holds a
`org.apache.camel.support.DefaultExchangeHolder`. This allows you to
consume from the Dead Letter Queue and retrieve the caused exception
from the Exchange property with the key `Exchange.EXCEPTION_CAUGHT`. The
demo below illustrates this:

[source,java]
------------------------------------------------------------------------
// setup error handler to use JMS as queue and store the entire Exchange
errorHandler(deadLetterChannel("jms:queue:dead?transferExchange=true"));
------------------------------------------------------------------------

Then you can consume from the JMS queue and analyze the problem:

[source,java]
-----------------------------------------------------------------------------------
from("jms:queue:dead").to("bean:myErrorAnalyzer");

// and in our bean
String body = exchange.getIn().getBody();
Exception cause = exchange.getProperty(Exchange.EXCEPTION_CAUGHT, Exception.class);
// the cause message is
String problem = cause.getMessage();
-----------------------------------------------------------------------------------

=== Using JMS as a Dead Letter Channel storing error only

You can use JMS to store the cause error message or to store a custom
body, which you can initialize yourself. The following example uses the
Message Translator EIP to do a
transformation on the failed exchange before it is moved to the
xref:jms-component.adoc[JMS] dead letter queue:

[source,java]
--------------------------------------------------------------------------------------------------
// we sent it to a seda dead queue first
errorHandler(deadLetterChannel("seda:dead"));

// and on the seda dead queue we can do the custom transformation before its sent to the JMS queue
from("seda:dead").transform(exceptionMessage()).to("jms:queue:dead");
--------------------------------------------------------------------------------------------------

Here we only store the original cause error message in the transform.
You can, however, use any Expression to send
whatever you like. For example, you can invoke a method on a Bean or use
a custom processor.


== Message Mapping between JMS and Camel

Camel automatically maps messages between `javax.jms.Message` and
`org.apache.camel.Message`.

When sending a JMS message, Camel converts the message body to the
following JMS message types:

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Body Type |JMS Message |Comment
|`String` |`javax.jms.TextMessage` | 

|`org.w3c.dom.Node` |`javax.jms.TextMessage` |The DOM will be converted
to `String`.

|`Map` |`javax.jms.MapMessage` | 

|`java.io.Serializable` |`javax.jms.ObjectMessage` | 

|`byte[]` |`javax.jms.BytesMessage` | 

|`java.io.File` |`javax.jms.BytesMessage` | 

|`java.io.Reader` |`javax.jms.BytesMessage` | 

|`java.io.InputStream` |`javax.jms.BytesMessage` | 

|`java.nio.ByteBuffer` |`javax.jms.BytesMessage` | 
|=======================================================================

When receiving a JMS message, Camel converts the JMS message to the
following body type:

[width="100%",cols="50%,50%",options="header",]
|=============================================
|JMS Message |Body Type
|`javax.jms.TextMessage` |`String`
|`javax.jms.BytesMessage` |`byte[]`
|`javax.jms.MapMessage` |`Map<String, Object>`
|`javax.jms.ObjectMessage` |`Object`
|=============================================

=== Disabling auto-mapping of JMS messages

You can use the `mapJmsMessage` option to disable the auto-mapping
above. If disabled, Camel will not try to map the received JMS message,
but instead uses it directly as the payload. This allows you to avoid
the overhead of mapping and let Camel just pass through the JMS message.
For instance, it even allows you to route `javax.jms.ObjectMessage` JMS
messages with classes you do *not* have on the classpath.

=== Using a custom MessageConverter

You can use the `messageConverter` option to do the mapping yourself in
a Spring `org.springframework.jms.support.converter.MessageConverter`
class.

For example, in the route below, we use a custom message converter when
sending a message to the JMS order queue:

[source,java]
----------------------------------------------------------------------------------------
from("file://inbox/order").to("jms:queue:order?messageConverter=#myMessageConverter");
----------------------------------------------------------------------------------------

You can also use a custom message converter when consuming from a JMS
destination.

=== Controlling the mapping strategy selected

You can use the `jmsMessageType` option on the endpoint URL to force a
specific message type for all messages.

In the route below, we poll files from a folder and send them as
`javax.jms.TextMessage` as we have forced the JMS producer endpoint to
use text messages:

[source,java]
-----------------------------------------------------------------------
from("file://inbox/order").to("jms:queue:order?jmsMessageType=Text");
-----------------------------------------------------------------------

You can also specify the message type to use for each message by setting
the header with the key `CamelJmsMessageType`. For example:

[source,java]
---------------------------------------------------------------------------------------------------------
from("file://inbox/order").setHeader("CamelJmsMessageType", JmsMessageType.Text).to("jms:queue:order");
---------------------------------------------------------------------------------------------------------

The possible values are defined in the `enum` class,
`org.apache.camel.jms.JmsMessageType`.

== Message format when sending

The exchange sent over the JMS wire must conform to the
http://java.sun.com/j2ee/1.4/docs/api/javax/jms/Message.html[JMS Message
spec].

For the `exchange.in.header` the following rules apply for the header
**keys**:

* Keys starting with `JMS` or `JMSX` are reserved.
* `exchange.in.headers` keys must be literals and all be valid Java
identifiers (do not use dots in the key name).
* Camel replaces dots & hyphens and the reverse when consuming JMS
messages: +
 `.` is replaced by `_DOT_` and the reverse replacement when Camel
consumes the message. +
 `-` is replaced by `_HYPHEN_` and the reverse replacement when Camel
consumes the message.
* See also the option `jmsKeyFormatStrategy`, which allows use of your
own custom strategy for formatting keys.

For the `exchange.in.header`, the following rules apply for the header
**values**:

* The values must be primitives or their counter-objects (such as
`Integer`, `Long`, `Character`). The types, `String`, `CharSequence`,
`Date`, `BigDecimal` and `BigInteger` are all converted to their
`toString()` representation. All other types are dropped.

Camel will log with category `org.apache.camel.component.jms.JmsBinding`
at *DEBUG* level if it drops a given header value. For example:

----------------------------------------------------------------------------------------------------------------------------------------------------------------
2008-07-09 06:43:04,046 [main           ] DEBUG JmsBinding
  - Ignoring non primitive header: order of class: org.apache.camel.component.jms.issues.DummyOrder with value: DummyOrder{orderId=333, itemId=4444, quantity=2}
----------------------------------------------------------------------------------------------------------------------------------------------------------------

== Message format when receiving

Camel adds the following properties to the `Exchange` when it receives a
message:

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Property |Type |Description
|`org.apache.camel.jms.replyDestination` |`javax.jms.Destination` |The
reply destination.
|=======================================================================

Camel adds the following JMS properties to the In message headers when
it receives a JMS message:

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Header |Type |Description
|`JMSCorrelationID` |`String` |The JMS correlation ID.

|`JMSDeliveryMode` |`int` |The JMS delivery mode.

|`JMSDestination` |`javax.jms.Destination` |The JMS destination.

|`JMSExpiration` |`long` |The JMS expiration.

|`JMSMessageID` |`String` |The JMS unique message ID.

|`JMSPriority` |`int` |The JMS priority (with 0 as the lowest priority
and 9 as the highest).

|`JMSRedelivered` |`boolean` |Whether the JMS message is redelivered.

|`JMSReplyTo` |`javax.jms.Destination` |The JMS reply-to destination.

|`JMSTimestamp` |`long` |The JMS timestamp.

|`JMSType` |`String` |The JMS type.

|`JMSXGroupID` |`String` |The JMS group ID.
|=======================================================================

As all the above information is standard JMS, you can check the
http://java.sun.com/javaee/5/docs/api/javax/jms/Message.html[JMS
documentation] for further details.

== About using Camel to send and receive messages and JMSReplyTo

The JMS component is complex, and you have to pay close attention to how
it works in some cases. So this is a short summary of some
areas/pitfalls to look for.

When Camel sends a message using its `JMSProducer`, it checks the
following conditions:

* The message exchange pattern.
* Whether a `JMSReplyTo` was set in the endpoint or in the message
headers.
* Whether any of the following options have been set on the JMS
endpoint: `disableReplyTo`, `preserveMessageQos`, `explicitQosEnabled`.

All this can be a tad complex to understand and configure to support
your use case.

=== JmsProducer

The `JmsProducer` behaves as follows, depending on configuration:

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Exchange Pattern |Other options |Description
|_InOut_ |- |Camel will expect a reply, set a temporary `JMSReplyTo`,
and after sending the message, it will start to listen for the reply
message on the temporary queue.

|_InOut_ |`JMSReplyTo` is set |Camel will expect a reply and, after
sending the message, it will start to listen for the reply message on
the specified `JMSReplyTo` queue.

|_InOnly_ |- |Camel will send the message and *not* expect a reply.

|_InOnly_ |`JMSReplyTo` is set |By default, Camel discards the
`JMSReplyTo` destination and clears the `JMSReplyTo` header before
sending the message. Camel then sends the message and does *not* expect
a reply. Camel logs this in the log at `WARN` level (changed to `DEBUG`
level from *Camel 2.6* onwards. You can use `preserveMessageQuo=true` to
instruct Camel to keep the `JMSReplyTo`. In all situations the
`JmsProducer` does *not* expect any reply and thus continue after
sending the message.
|=======================================================================

=== JmsConsumer

The `JmsConsumer` behaves as follows, depending on configuration:

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Exchange Pattern |Other options |Description
|_InOut_ |- |Camel will send the reply back to the `JMSReplyTo` queue.

|_InOnly_ |- |Camel will not send a reply back, as the pattern is
__InOnly__.

|- |`disableReplyTo=true` |This option suppress replies.
|=======================================================================

So pay attention to the message exchange pattern set on your exchanges.

If you send a message to a JMS destination in the middle of your route,
you can specify the exchange pattern to use, see more at
Request Reply. +
 This is useful if you want to send an `InOnly` message to a JMS topic:

[source,java]
------------------------------------------------------
from("activemq:queue:in")
   .to("bean:validateOrder")
   .to(ExchangePattern.InOnly, "activemq:topic:order")
   .to("bean:handleOrder");
------------------------------------------------------

== Reuse endpoint and send to different destinations computed at runtime

If you need to send messages to a lot of different JMS destinations, it
makes sense to reuse a JMS endpoint and specify the real destination in
a message header. This allows Camel to reuse the same endpoint, but send
to different destinations. This greatly reduces the number of endpoints
created and economizes on memory and thread resources.

You can specify the destination in the following headers:

[width="100%",cols="10%,10%,80%",options="header",]
|=====================================================================
|Header |Type |Description
|`CamelJmsDestination` |`javax.jms.Destination` |A destination object.
|`CamelJmsDestinationName` |`String` |The destination name.
|=====================================================================

For example, the following route shows how you can compute a destination
at run time and use it to override the destination appearing in the JMS
URL:

[source,java]
--------------------------------
from("file://inbox")
  .to("bean:computeDestination")
  .to("activemq:queue:dummy");
--------------------------------

The queue name, `dummy`, is just a placeholder. It must be provided as
part of the JMS endpoint URL, but it will be ignored in this example.

In the `computeDestination` bean, specify the real destination by
setting the `CamelJmsDestinationName` header as follows:

[source,java]
-------------------------------------------------------------------------
public void setJmsHeader(Exchange exchange) {
   String id = ....
   exchange.getIn().setHeader("CamelJmsDestinationName", "order:" + id");
}
-------------------------------------------------------------------------

Then Camel will read this header and use it as the destination instead
of the one configured on the endpoint. So, in this example Camel sends
the message to `activemq:queue:order:2`, assuming the `id` value was 2.

If both the `CamelJmsDestination` and the `CamelJmsDestinationName`
headers are set, `CamelJmsDestination` takes priority. Keep in mind that
the JMS producer removes both `CamelJmsDestination` and
`CamelJmsDestinationName` headers from the exchange and do not propagate
them to the created JMS message to avoid the accidental loops
in the routes (in scenarios when the message will be forwarded to
another JMS endpoint).

== Configuring different JMS providers

You can configure your JMS provider in Spring XML as
follows:

You can configure as many JMS component instances as you wish
and give them *a unique name using the* `id` **attribute**. The
preceding example configures an `activemq` component. You could do the
same to configure MQSeries, TibCo, BEA, Sonic and so on.

Once you have a named JMS component, you can then refer to endpoints
within that component using URIs. For example, for the component name,
`activemq`, you can then refer to destinations using the URI format,
`activemq:[queue:|topic:]destinationName`. You can use the same approach
for all other JMS providers.

This works by the SpringCamelContext lazily fetching components from the
spring context for the scheme name you use for
Endpoint URIs and having the
Component resolve the endpoint URIs.

=== Using JNDI to find the ConnectionFactory

If you are using a J2EE container, you might need to look up JNDI to
find the JMS `ConnectionFactory` rather than use the usual `<bean>`
mechanism in Spring. You can do this using Spring's factory bean or the
new Spring XML namespace. For example:

[source,xml]
-----------------------------------------------------------------------------
<bean id="weblogic" class="org.apache.camel.component.jms.JmsComponent">
  <property name="connectionFactory" ref="myConnectionFactory"/>
</bean>

<jee:jndi-lookup id="myConnectionFactory" jndi-name="jms/connectionFactory"/>
-----------------------------------------------------------------------------

See
http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/xsd-config.html#xsd-config-body-schemas-jee[The
jee schema] in the Spring reference documentation for more details about
JNDI lookup.

== Concurrent Consuming

A common requirement with JMS is to consume messages concurrently in
multiple threads to make an application more responsive. You
can set the `concurrentConsumers` option to specify the number of
threads servicing the JMS endpoint, as follows:

[source,java]
---------------------------------------------
from("jms:SomeQueue?concurrentConsumers=20").
  bean(MyClass.class);
---------------------------------------------

You can configure this option in one of the following ways:

* On the `JmsComponent`,
* On the endpoint URI or,
* By invoking `setConcurrentConsumers()` directly on the `JmsEndpoint`.

=== Concurrent Consuming with async consumer

Notice that each concurrent consumer will only pick up the next available
message from the JMS broker, when the current message has been fully
processed. You can set the option `asyncConsumer=true` to let the
consumer pick up the next message from the JMS queue, while the previous
message is being processed asynchronously (by the
Asynchronous Routing Engine). See
more details in the table on top of the page about the `asyncConsumer`
option.

[source,java]
----------------------------------------------------------------
from("jms:SomeQueue?concurrentConsumers=20&asyncConsumer=true").
  bean(MyClass.class);
----------------------------------------------------------------

== Request-reply over JMS

Camel supports Request Reply over JMS. In
essence the MEP of the Exchange should be `InOut` when you send a
message to a JMS queue.

Camel offers a number of options to configure request/reply over JMS
that influence performance and clustered environments. The table below
summaries the options.

[width="100%",cols="10%,10%,10%,70%",options="header",]
|=======================================================================
|Option |Performance |Cluster |Description
|`Temporary` |Fast |Yes |A temporary queue is used as reply queue, and
automatic created by Camel. To use this, do *not* specify a `replyTo` queue
name. And you can optionally configure `replyToType=Temporary` to make
it stand out that temporary queues are in use.

|`Shared` |Slow |Yes |A shared persistent queue is used as reply queue.
The queue must be created beforehand, although some brokers can create
them on the fly, such as Apache ActiveMQ. To use this, you must specify
the replyTo queue name. And you can optionally configure
`replyToType=Shared` to make it stand out that shared queues are in use.
A shared queue can be used in a clustered environment with multiple
nodes running this Camel application at the same time. All of them using the
same shared reply queue. This is possible because JMS Message selectors
are used to correlate expected reply messages; this impacts performance
though. JMS Message selectors are slower, and therefore not as fast as
`Temporary` or `Exclusive` queues. See further below how to tweak this
for better performance.

|`Exclusive` |Fast |No (*Yes) |An exclusive persistent queue is used as
reply queue. The queue must be created beforehand, although some brokers
can create them on the fly, such as Apache ActiveMQ. To use this, you must
specify the replyTo queue name. And you *must* configure
`replyToType=Exclusive` to instruct Camel to use exclusive queues, as
`Shared` is used by default, if a `replyTo` queue name was configured.
When using exclusive reply queues, then JMS Message selectors are *not*
in use, and therefore other applications must not use this queue as
well. An exclusive queue *cannot* be used in a clustered environment
with multiple nodes running this Camel application at the same time; as
we do not have control if the reply queue comes back to the same node
that sent the request message; that is why shared queues use JMS Message
selectors to make sure of this. *Though* if you configure each Exclusive
reply queue with a unique name per node, then you can run this in a
clustered environment. As then the reply message will be sent back to
that queue for the given node that awaits the reply message.

|`concurrentConsumers` |Fast |Yes |Allows processing
reply messages concurrently using concurrent message listeners in use.
You can specify a range using the `concurrentConsumers` and
`maxConcurrentConsumers` options. *Notice:* That using `Shared` reply
queues may not work as well with concurrent listeners, so use this
option with care.

|`maxConcurrentConsumers` |Fast |Yes |Allows processing
reply messages concurrently using concurrent message listeners in use.
You can specify a range using the `concurrentConsumers` and
`maxConcurrentConsumers` options. *Notice:* That using `Shared` reply
queues may not work as well with concurrent listeners, so use this
option with care.
|=======================================================================

The `JmsProducer` detects the `InOut` and provides a `JMSReplyTo` header
with the reply destination to be used. By default, Camel uses a temporary
queue, but you can use the `replyTo` option on the endpoint to specify a
fixed reply queue (see more below about fixed reply queue).

Camel will automatically set up a consumer that listens to on the reply queue,
so you should *not* do anything. +
 This consumer is a Spring `DefaultMessageListenerContainer` which
listen for replies. However, it's fixed to one concurrent consumer. +
 That means replies will be processed in sequence as there is only one
thread to process the replies. You can configure the listener to use
concurrent threads using the `concurrentConsumers` and
`maxConcurrentConsumers` options. This allows you to easier configure
this in Camel as shown below:

[source,java]
-------------------------------------------------------
from(xxx)
.inOut().to("activemq:queue:foo?concurrentConsumers=5")
.to(yyy)
.to(zzz);
-------------------------------------------------------

In this route, we instruct Camel to route replies
asynchronously using a thread pool with five threads.

=== Request-reply over JMS and using a shared fixed reply queue

If you use a fixed reply queue when doing
Request Reply over JMS as shown in the example
below, then pay attention.

[source,java]
---------------------------------------------
from(xxx)
.inOut().to("activemq:queue:foo?replyTo=bar")
.to(yyy)
---------------------------------------------

In this example, the fixed reply queue named "bar" is used. By default,
Camel assumes the queue is shared when using fixed reply queues, and
therefore it uses a `JMSSelector` to only pick up the expected reply
messages (e.g., based on the `JMSCorrelationID`). See the next section for
exclusive fixed reply queues. That means it's not as fast as temporary
queues. You can speed up how often Camel will pull for reply messages
using the `receiveTimeout` option. By default, its 1000 milliseconds. So to
make it faster, you can set it to 250 millis to pull 4 times per second
as shown:

[source,java]
----------------------------------------------------------------
from(xxx)
.inOut().to("activemq:queue:foo?replyTo=bar&receiveTimeout=250")
.to(yyy)
----------------------------------------------------------------

Notice this will cause the Camel to send pull requests to the message
broker more frequently, and thus require more network traffic. +
 It is generally recommended to use temporary queues if possible.

=== Request-reply over JMS and using an exclusive fixed reply queue

In the previous example, Camel would anticipate the fixed reply queue
named "bar" was shared, and thus it uses a `JMSSelector` to only consume
reply messages which it expects. However, there is a drawback to doing this
as the JMS selector is slower. Also, the consumer on the reply queue is
slower to update with new JMS selector ids. In fact, it only updates when
the `receiveTimeout` option times out, which by default is 1 second. So
in theory, the reply messages could take up till about 1 sec to be
detected. On the other hand, if the fixed reply queue is exclusive to the
Camel reply consumer, then we can avoid using the JMS selectors, and
thus be more performant. In fact, as fast as using temporary queues. There is
the `ReplyToType` option which you can configure to `Exclusive` +
 to tell Camel that the reply queue is exclusive as shown in the example
below:

[source,java]
-------------------------------------------------------------------
from(xxx)
.inOut().to("activemq:queue:foo?replyTo=bar&replyToType=Exclusive")
.to(yyy)
-------------------------------------------------------------------

Mind that the queue must be exclusive to each and every endpoint. So if
you have two routes, then they each need a unique reply queue as shown
in the next example:

[source,java]
-----------------------------------------------------------------------------
from(xxx)
.inOut().to("activemq:queue:foo?replyTo=bar&replyToType=Exclusive")
.to(yyy)

from(aaa)
.inOut().to("activemq:queue:order?replyTo=order.reply&replyToType=Exclusive")
.to(bbb)
-----------------------------------------------------------------------------

The same applies if you run in a clustered environment. Then each node
in the cluster must use a unique reply queue name. As otherwise, each
node in the cluster may pick up messages intended as a reply on
another node. For clustered environments, it's recommended to use shared
reply queues instead.

== Synchronizing clocks between senders and receivers

When doing messaging between systems, it is desirable that the systems
have synchronized clocks. For example, when sending a xref:jms-component.adoc[JMS]
message, then you can set a time to live value on the message. Then the
receiver can inspect this value and determine if the message is already
expired, and thus drop the message instead of consume and process it.
However, this requires that both sender and receiver have synchronized
clocks.

[NOTE]
====
If you are using http://activemq.apache.org/[ActiveMQ], then you
can use the http://activemq.apache.org/timestampplugin.html[timestamp
plugin] to synchronize clocks.
====

== About time to live

Read first above about synchronized clocks.

When you do request/reply (InOut) over xref:jms-component.adoc[JMS] with Camel,
then Camel uses a timeout on the sender side, which is default 20
seconds from the `requestTimeout` option. You can control this by
setting a higher/lower value. However, the time to live value is still
set on the xref:jms-component.adoc[JMS] message being sent. So that requires the
clocks to be synchronized between the systems. If they are not, then you
may want to disable the time to live value being set. This is now
possible using the `disableTimeToLive` option from *Camel 2.8* onwards.
So if you set this option to `disableTimeToLive=true`, then Camel does
*not* set any time to live value when sending xref:jms-component.adoc[JMS]
messages. *But* the request timeout is still active. So for example, if
you do request/reply over xref:jms-component.adoc[JMS] and have disabled time to
live, then Camel will still use a timeout by 20 seconds (the
`requestTimeout` option). That option can also be configured.
So the two options `requestTimeout` and `disableTimeToLive` gives you
Fine-grained control when doing request/reply.

You can provide a header in the message
to override and use as the request timeout value instead of the endpoint
configured value. For example:

[source,java]
--------------------------------------------------------
   from("direct:someWhere")
     .to("jms:queue:foo?replyTo=bar&requestTimeout=30s")
     .to("bean:processReply");
--------------------------------------------------------

In the route above we have an endpoint configured `requestTimeout` of 30
seconds. So Camel will wait up till 30 seconds for that reply message to
come back on the bar queue. If no reply message is received then a
`org.apache.camel.ExchangeTimedOutException` is set on the
Exchange, and Camel continues routing the message,
which would then fail due the exception, and Camel's error handler
reacts.

If you want to use a per message timeout value, you can set the header
with key
`org.apache.camel.component.jms.JmsConstants#JMS_REQUEST_TIMEOUT` which
has constant value `"CamelJmsRequestTimeout"` with a timeout value as
a long type.

For example, we can use a bean to compute the timeout value per
individual message, such as calling the `"whatIsTheTimeout"` method on
the service bean as shown below:

[source,java]
----------------------------------------------------------------------------------------
from("direct:someWhere")
  .setHeader("CamelJmsRequestTimeout", method(ServiceBean.class, "whatIsTheTimeout"))
  .to("jms:queue:foo?replyTo=bar&requestTimeout=30s")
  .to("bean:processReply");
----------------------------------------------------------------------------------------

When you do fire and forget (InOut) over xref:jms-component.adoc[JMS] with Camel,
then Camel by default does *not* set any time to live value on the
message. You can configure a value by using the `timeToLive` option. For
example, to indicate a 5 sec., you set `timeToLive=5000`. The option
`disableTimeToLive` can be used to force disabling the time to live,
also for InOnly messaging. The `requestTimeout` option is not being used
for InOnly messaging.

== Enabling Transacted Consumption

A common requirement is to consume from a queue in a transaction and
then process the message using the Camel route. To do this, just ensure
that you set the following properties on the component/endpoint:

* `transacted` = true
* `transactionManager` = a _Transsaction Manager_ - typically the
`JmsTransactionManager`

See the Transactional Client EIP pattern
for further details.

Transactions and [Request Reply] over JMS

When using Request Reply over JMS, you cannot
use a single transaction; JMS will not send any messages until a commit
is performed, so the server side won't receive anything at all until the
transaction commits. Therefore, to use xref:eips:requestReply-eip.adoc[Request
Reply], you must commit a transaction after sending the request and then
use a separate transaction for receiving the response.

To address this issue, the JMS component uses different properties to
specify transaction use for oneway messaging and request reply
messaging:

The `transacted` property applies *only* to the InOnly message
Exchange Pattern (MEP).

You can leverage the
http://static.springsource.org/spring/docs/3.0.x/javadoc-api/org/springframework/jms/listener/AbstractPollingMessageListenerContainer.html#setSessionTransacted(boolean)[DMLC
transacted session API] using the following properties on
component/endpoint:

* `transacted` = true
* `lazyCreateTransactionManager` = false

The benefit of doing so is that the cacheLevel setting will be honored
when using local transactions without a configured TransactionManager.
When a TransactionManager is configured, no caching happens at DMLC
level, and it is necessary to rely on a pooled connection factory. For more
details about this kind of setup, see
http://tmielke.blogspot.com/2012/03/camel-jms-with-transactions-lessons.html[here]
and
http://forum.springsource.org/showthread.php?123631-JMS-DMLC-not-caching%20connection-when-using-TX-despite-cacheLevel-CACHE_CONSUMER&p=403530&posted=1#post403530[here].

== Using JMSReplyTo for late replies

When using Camel as a JMS listener, it sets an Exchange property with
the value of the ReplyTo `javax.jms.Destination` object, having the key
`ReplyTo`. You can obtain this `Destination` as follows:

[source,java]
-----------------------------------------------------------------------------------------------------------------
Destination replyDestination = exchange.getIn().getHeader(JmsConstants.JMS_REPLY_DESTINATION, Destination.class);
-----------------------------------------------------------------------------------------------------------------

And then later use it to send a reply using regular JMS or Camel.

[source,java]
----------------------------------------------------------------------------------------
// we need to pass in the JMS component, and in this sample we use ActiveMQ
JmsEndpoint endpoint = JmsEndpoint.newInstance(replyDestination, activeMQComponent);
// now we have the endpoint we can use regular Camel API to send a message to it
template.sendBody(endpoint, "Here is the late reply.");
----------------------------------------------------------------------------------------

A different solution to sending a reply is to provide the
`replyDestination` object in the same Exchange property when sending.
Camel will then pick up this property and use it for the real
destination. The endpoint URI must include a dummy destination, however.
For example:

[source,java]
----------------------------------------------------------------------------------------------------------------------------------------
// we pretend to send it to some non-existing dummy queue
template.send("activemq:queue:dummy, new Processor() {
   public void process(Exchange exchange) throws Exception {
      // and here we override the destination with the ReplyTo destination object so the message is sent to there instead of dummy
      exchange.getIn().setHeader(JmsConstants.JMS_DESTINATION, replyDestination);
      exchange.getIn().setBody("Here is the late reply.");
    }
}
----------------------------------------------------------------------------------------------------------------------------------------

== Using a request timeout

In the sample below we send a Request Reply
style message Exchange (we use the `requestBody`
method = `InOut`) to the slow queue for further processing in Camel, and
we wait for a return reply:


== Sending an InOnly message and keeping the JMSReplyTo header

When sending to a xref:jms-component.adoc[JMS] destination using *camel-jms*, the
producer will use the MEP to detect if its _InOnly_ or _InOut_ messaging.
However, there can be times when you want to send an _InOnly_ message but
keeping the `JMSReplyTo` header. To do so, you have to instruct Camel to
keep it, otherwise the `JMSReplyTo` header will be dropped.

For example, to send an _InOnly_ message to the foo queue, but with a
`JMSReplyTo` with bar queue you can do as follows:

[source,java]
-------------------------------------------------------------------------------------
template.send("activemq:queue:foo?preserveMessageQos=true", new Processor() {
   public void process(Exchange exchange) throws Exception {
      exchange.getIn().setBody("World");
      exchange.getIn().setHeader("JMSReplyTo", "bar");
    }
});
-------------------------------------------------------------------------------------

Notice we use `preserveMessageQos=true` to instruct Camel to keep the
`JMSReplyTo` header.

== Setting JMS provider options on the destination

Some JMS providers, like IBM's WebSphere MQ, need options to be set on
the JMS destination. For example, you may need to specify the
`targetClient` option. Since `targetClient` is a WebSphere MQ option and not
a Camel URI option, you need to set that on the JMS destination name
like so:

[source,java]
-----------------------------------------------------------------------------------
// ...
.setHeader("CamelJmsDestinationName", constant("queue:///MY_QUEUE?targetClient=1"))
.to("wmq:queue:MY_QUEUE?useMessageIDAsCorrelationID=true");
-----------------------------------------------------------------------------------

Some versions of WMQ won't accept this option on the destination name,
and you will get an exception like:

----------------------------------------------------------------------------------------------------------------------------------
com.ibm.msg.client.jms.DetailedJMSException: JMSCC0005: The specified
value 'MY_QUEUE?targetClient=1' is not allowed for
'XMSC_DESTINATION_NAME'
----------------------------------------------------------------------------------------------------------------------------------

A workaround is to use a custom DestinationResolver:

[source,java]
----------------------------------------------------------------------------------------------------------------------------------
JmsComponent wmq = new JmsComponent(connectionFactory);

wmq.setDestinationResolver(new DestinationResolver() {
    public Destination resolveDestinationName(Session session, String destinationName, boolean pubSubDomain) throws JMSException {
        MQQueueSession wmqSession = (MQQueueSession) session;
        return wmqSession.createQueue("queue:///" + destinationName + "?targetClient=1");
    }
});
----------------------------------------------------------------------------------------------------------------------------------



include::spring-boot:partial$starter.adoc[]