JMS
Since Camel 1.0
Both producer and consumer are supported
This component allows messages to be sent to (or consumed from) a
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:
<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>|
Using ActiveMQ If you are using Apache ActiveMQ, you should prefer the ActiveMQ component as it has been optimized for ActiveMQ. All of the options and samples on this page are also valid for the ActiveMQ component. |
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Transacted and caching See section Transactions and Cache Levels below if you are using transactions with JMS as it can impact performance. |
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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
poor performance.
If you intend to use 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
PoolingConnectionFactoryin 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_CONSUMERiftransacted=false -
CACHE_NONEiftransacted=true
So you can say the default setting is conservative. Consider using
cacheLevelName=CACHE_CONSUMER if you are using non-XA transactions.
Durable Subscriptions
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. You may prefer to use
Virtual Topics
instead to avoid this limitation. More background on durable messaging
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
DOTand the replacement is reversed when Camel consume the message -
Hyphen is replaced by
HYPHENand 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.
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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. |
Configuring Options
Camel components are configured on two separate levels:
-
component level
-
endpoint level
Configuring Component Options
The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.
Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.
Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.
Configuring Endpoint Options
Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.
Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL as a type safe way of configuring endpoints.
A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.
The following two sections lists all the options, firstly for the component followed by the endpoint.
Component Options
The JMS component supports 99 options, which are listed below.
Endpoint Options
The JMS endpoint is configured using URI syntax:
jms:destinationType:destinationName
with the following path and query parameters:
Path Parameters (2 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
The kind of destination to use. Enum values:
|
queue |
String |
|
Required Name of the queue or topic to use as destination. |
String |
Query Parameters (96 parameters)
Message Headers
The JMS component supports 17 message header(s), which is/are listed below:
| Name | Description | Default | Type |
|---|---|---|---|
CamelJmsDestination (producer) Constant: |
The destination. |
Destination |
|
CamelJmsDestinationName (producer) Constant: |
The name of the queue or topic to use as destination. |
String |
|
|
Constant: |
The JMS group ID. |
String |
|
|
Constant: |
The JMS unique message ID. |
String |
|
|
Constant: |
The JMS correlation ID. |
String |
|
JMSCorrelationIDAsBytes (common) Constant: |
The JMS correlation ID as bytes. |
String |
|
|
Constant: |
The JMS delivery mode. |
int |
|
|
Constant: |
The JMS destination. |
Destination |
|
|
Constant: |
The JMS expiration. |
long |
|
|
Constant: |
The JMS priority (with 0 as the lowest priority and 9 as the highest). |
int |
|
|
Constant: |
Is the JMS message redelivered. |
boolean |
|
|
Constant: |
The JMS timestamp. |
long |
|
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Constant: |
The JMS reply-to destination. |
Destination |
|
|
Constant: |
The JMS type. |
String |
|
|
Constant: |
The XUser id. |
String |
|
|
Constant: |
The message type. Enum values:
|
JmsMessageType |
|
CamelJmsRequestTimeout (producer) Constant: |
The timeout for waiting for a reply when using the InOut Exchange Pattern (in milliseconds). |
20_000 |
long |
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:
from("jms:queue:foo").
to("bean:myBusinessLogic");You can of course 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:
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:
from("file://orders").
convertBodyTo(String.class).
to("jms:topic:OrdersTopic");Using Annotations
Camel also has annotations so you can use POJO Consuming and 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:
<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 JMS as the transport, it only
transfers the body and headers as the payload. If you want to use
JMS with a 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:
// 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:
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 JMS dead letter queue:
// 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:
| Body Type | JMS Message | Comment |
|---|---|---|
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The DOM will be converted
to |
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When receiving a JMS message, Camel converts the JMS message to the following body type:
| JMS Message | Body Type |
|---|---|
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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:
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:
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:
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 that is sent over the JMS wire must conform to the JMS Message spec.
For the exchange.in.header the following rules apply for the header
keys:
-
Keys starting with
JMSorJMSXare reserved. -
exchange.in.headerskeys 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 when consuming JMS messages:
.is replaced byDOTand the reverse replacement when Camel consumes the message.
-is replaced byHYPHENand 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,BigDecimalandBigIntegerare all converted to theirtoString()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:
| Property | Type | Description |
|---|---|---|
|
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The reply destination. |
Camel adds the following JMS properties to the In message headers when it receives a JMS message:
| Header | Type | Description |
|---|---|---|
|
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The JMS correlation ID. |
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The JMS delivery mode. |
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The JMS destination. |
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The JMS expiration. |
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The JMS unique message ID. |
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The JMS priority (with 0 as the lowest priority and 9 as the highest). |
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Is the JMS message redelivered. |
|
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The JMS reply-to destination. |
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The JMS timestamp. |
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The JMS type. |
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The JMS group ID. |
As all the above information is standard JMS you can check the 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 of the areas/pitfalls to look for.
When Camel sends a message using its JMSProducer, it checks the
following conditions:
-
The message exchange pattern,
-
Whether a
JMSReplyTowas 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:
| Exchange Pattern | Other options | Description |
|---|---|---|
InOut |
- |
Camel will expect a reply, set a temporary |
InOut |
|
Camel will expect a reply and, after
sending the message, it will start to listen for the reply message on
the specified |
InOnly |
- |
Camel will send the message and not expect a reply. |
InOnly |
|
By default, Camel discards the
|
JmsConsumer
The JmsConsumer behaves as follows, depending on configuration:
| Exchange Pattern | Other options | Description |
|---|---|---|
InOut |
- |
Camel will send the reply back to the |
InOnly |
- |
Camel will not send a reply back, as the pattern is InOnly. |
- |
|
This option suppresses 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:
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:
| Header | Type | Description |
|---|---|---|
|
|
A destination object. |
|
|
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:
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:
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 in order to avoid the accidental loops
in the routes (in scenarios when the message will be forwarded to the
another JMS endpoint).
Configuring different JMS providers
You can configure your JMS provider in Spring XML as follows:
Basically, 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:
<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 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 in order to make an application more responsive. You
can set the concurrentConsumers option to specify the number of
threads servicing the JMS endpoint, as follows:
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 theJmsEndpoint.
Concurrent Consuming with async consumer
Notice that each concurrent consumer will only pickup 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 pickup 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.
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.
| Option | Performance | Cluster | Description |
|---|---|---|---|
|
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 |
|
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
|
|
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
|
|
Fast |
Yes |
Allows to process
reply messages concurrently using concurrent message listeners in use.
You can specify a range using the |
|
Fast |
Yes |
Allows to process
reply messages concurrently using concurrent message listeners in use.
You can specify a range using the |
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 setup a consumer which listen 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 1 concurrent consumer.
That means replies will be processed in sequence as there are only 1
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:
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 5 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.
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 pickup the expected reply
messages (eg based on the JMSCorrelationID). See next section for
exclusive fixed reply queues. That means its not as fast as temporary
queues. You can speedup how often Camel will pull for reply messages
using the receiveTimeout option. By default its 1000 millis. So to
make it faster you can set it to 250 millis to pull 4 times per second
as shown:
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 frequent, 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 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:
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 an unique reply queue as shown in the next example:
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 an unique reply queue name. As otherwise each node in the cluster may pickup messages which was intended as a reply on another node. For clustered environments its recommended to use shared reply queues instead.
Synchronizing clocks between senders and receivers
When doing messaging between systems, its desirable that the systems have synchronized clocks. For example when sending a 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. If you are using ActiveMQ then you can use the timestamp plugin to synchronize clocks.
About time to live
Read first above about synchronized clocks.
When you do request/reply (InOut) over 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 JMS message being send. 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 JMS
messages. But the request timeout is still active. So for example if
you do request/reply over JMS and have disabled time to
live, then Camel will still use a timeout by 20 seconds (the
requestTimeout option). That option can of course 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:
from("direct:someWhere")
.to("jms:queue:foo?replyTo=bar&requestTimeout=30s")
.to("bean:processReply");In the route above we have a 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
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:
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 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 theJmsTransactionManager
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 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 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 here and 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:
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.
// 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:
// 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 JMS destination using camel-jms the
producer will use the MEP to detect if its InOnly or InOut messaging.
However there can be times where 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:
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:
// ...
.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:
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");
}
});